1 /* Global common subexpression elimination/Partial redundancy elimination
2 and global constant/copy propagation for GNU compiler.
3 Copyright (C) 1997, 1998, 1999, 2000 Free Software Foundation, Inc.
5 This file is part of GNU CC.
7 GNU CC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 GNU CC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GNU CC; see the file COPYING. If not, write to
19 the Free Software Foundation, 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
23 - reordering of memory allocation and freeing to be more space efficient
24 - do rough calc of how many regs are needed in each block, and a rough
25 calc of how many regs are available in each class and use that to
26 throttle back the code in cases where RTX_COST is minimal.
27 - dead store elimination
28 - a store to the same address as a load does not kill the load if the
29 source of the store is also the destination of the load. Handling this
30 allows more load motion, particularly out of loops.
31 - ability to realloc sbitmap vectors would allow one initial computation
32 of reg_set_in_block with only subsequent additions, rather than
33 recomputing it for each pass
37 /* References searched while implementing this.
39 Compilers Principles, Techniques and Tools
43 Global Optimization by Suppression of Partial Redundancies
45 communications of the acm, Vol. 22, Num. 2, Feb. 1979
47 A Portable Machine-Independent Global Optimizer - Design and Measurements
49 Stanford Ph.D. thesis, Dec. 1983
51 A Fast Algorithm for Code Movement Optimization
53 SIGPLAN Notices, Vol. 23, Num. 10, Oct. 1988
55 A Solution to a Problem with Morel and Renvoise's
56 Global Optimization by Suppression of Partial Redundancies
57 K-H Drechsler, M.P. Stadel
58 ACM TOPLAS, Vol. 10, Num. 4, Oct. 1988
60 Practical Adaptation of the Global Optimization
61 Algorithm of Morel and Renvoise
63 ACM TOPLAS, Vol. 13, Num. 2. Apr. 1991
65 Efficiently Computing Static Single Assignment Form and the Control
67 R. Cytron, J. Ferrante, B.K. Rosen, M.N. Wegman, and F.K. Zadeck
68 ACM TOPLAS, Vol. 13, Num. 4, Oct. 1991
71 J. Knoop, O. Ruthing, B. Steffen
72 ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI
74 What's In a Region? Or Computing Control Dependence Regions in Near-Linear
75 Time for Reducible Flow Control
77 ACM Letters on Programming Languages and Systems,
78 Vol. 2, Num. 1-4, Mar-Dec 1993
80 An Efficient Representation for Sparse Sets
81 Preston Briggs, Linda Torczon
82 ACM Letters on Programming Languages and Systems,
83 Vol. 2, Num. 1-4, Mar-Dec 1993
85 A Variation of Knoop, Ruthing, and Steffen's Lazy Code Motion
86 K-H Drechsler, M.P. Stadel
87 ACM SIGPLAN Notices, Vol. 28, Num. 5, May 1993
89 Partial Dead Code Elimination
90 J. Knoop, O. Ruthing, B. Steffen
91 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
93 Effective Partial Redundancy Elimination
94 P. Briggs, K.D. Cooper
95 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
97 The Program Structure Tree: Computing Control Regions in Linear Time
98 R. Johnson, D. Pearson, K. Pingali
99 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
101 Optimal Code Motion: Theory and Practice
102 J. Knoop, O. Ruthing, B. Steffen
103 ACM TOPLAS, Vol. 16, Num. 4, Jul. 1994
105 The power of assignment motion
106 J. Knoop, O. Ruthing, B. Steffen
107 ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
109 Global code motion / global value numbering
111 ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
113 Value Driven Redundancy Elimination
115 Rice University Ph.D. thesis, Apr. 1996
119 Massively Scalar Compiler Project, Rice University, Sep. 1996
121 High Performance Compilers for Parallel Computing
125 Advanced Compiler Design and Implementation
127 Morgan Kaufmann, 1997
129 Building an Optimizing Compiler
133 People wishing to speed up the code here should read:
134 Elimination Algorithms for Data Flow Analysis
135 B.G. Ryder, M.C. Paull
136 ACM Computing Surveys, Vol. 18, Num. 3, Sep. 1986
138 How to Analyze Large Programs Efficiently and Informatively
139 D.M. Dhamdhere, B.K. Rosen, F.K. Zadeck
140 ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI
142 People wishing to do something different can find various possibilities
143 in the above papers and elsewhere.
153 #include "hard-reg-set.h"
156 #include "insn-config.h"
158 #include "basic-block.h"
160 #include "function.h"
164 #define obstack_chunk_alloc gmalloc
165 #define obstack_chunk_free free
167 /* Maximum number of passes to perform. */
170 /* Propagate flow information through back edges and thus enable PRE's
171 moving loop invariant calculations out of loops.
173 Originally this tended to create worse overall code, but several
174 improvements during the development of PRE seem to have made following
175 back edges generally a win.
177 Note much of the loop invariant code motion done here would normally
178 be done by loop.c, which has more heuristics for when to move invariants
179 out of loops. At some point we might need to move some of those
180 heuristics into gcse.c. */
181 #define FOLLOW_BACK_EDGES 1
183 /* We support GCSE via Partial Redundancy Elimination. PRE optimizations
184 are a superset of those done by GCSE.
186 We perform the following steps:
188 1) Compute basic block information.
190 2) Compute table of places where registers are set.
192 3) Perform copy/constant propagation.
194 4) Perform global cse.
196 5) Perform another pass of copy/constant propagation.
198 Two passes of copy/constant propagation are done because the first one
199 enables more GCSE and the second one helps to clean up the copies that
200 GCSE creates. This is needed more for PRE than for Classic because Classic
201 GCSE will try to use an existing register containing the common
202 subexpression rather than create a new one. This is harder to do for PRE
203 because of the code motion (which Classic GCSE doesn't do).
205 Expressions we are interested in GCSE-ing are of the form
206 (set (pseudo-reg) (expression)).
207 Function want_to_gcse_p says what these are.
209 PRE handles moving invariant expressions out of loops (by treating them as
210 partially redundant).
212 Eventually it would be nice to replace cse.c/gcse.c with SSA (static single
213 assignment) based GVN (global value numbering). L. T. Simpson's paper
214 (Rice University) on value numbering is a useful reference for this.
216 **********************
218 We used to support multiple passes but there are diminishing returns in
219 doing so. The first pass usually makes 90% of the changes that are doable.
220 A second pass can make a few more changes made possible by the first pass.
221 Experiments show any further passes don't make enough changes to justify
224 A study of spec92 using an unlimited number of passes:
225 [1 pass] = 1208 substitutions, [2] = 577, [3] = 202, [4] = 192, [5] = 83,
226 [6] = 34, [7] = 17, [8] = 9, [9] = 4, [10] = 4, [11] = 2,
227 [12] = 2, [13] = 1, [15] = 1, [16] = 2, [41] = 1
229 It was found doing copy propagation between each pass enables further
232 PRE is quite expensive in complicated functions because the DFA can take
233 awhile to converge. Hence we only perform one pass. Macro MAX_PASSES can
234 be modified if one wants to experiment.
236 **********************
238 The steps for PRE are:
240 1) Build the hash table of expressions we wish to GCSE (expr_hash_table).
242 2) Perform the data flow analysis for PRE.
244 3) Delete the redundant instructions
246 4) Insert the required copies [if any] that make the partially
247 redundant instructions fully redundant.
249 5) For other reaching expressions, insert an instruction to copy the value
250 to a newly created pseudo that will reach the redundant instruction.
252 The deletion is done first so that when we do insertions we
253 know which pseudo reg to use.
255 Various papers have argued that PRE DFA is expensive (O(n^2)) and others
256 argue it is not. The number of iterations for the algorithm to converge
257 is typically 2-4 so I don't view it as that expensive (relatively speaking).
259 PRE GCSE depends heavily on the second CSE pass to clean up the copies
260 we create. To make an expression reach the place where it's redundant,
261 the result of the expression is copied to a new register, and the redundant
262 expression is deleted by replacing it with this new register. Classic GCSE
263 doesn't have this problem as much as it computes the reaching defs of
264 each register in each block and thus can try to use an existing register.
266 **********************
268 A fair bit of simplicity is created by creating small functions for simple
269 tasks, even when the function is only called in one place. This may
270 measurably slow things down [or may not] by creating more function call
271 overhead than is necessary. The source is laid out so that it's trivial
272 to make the affected functions inline so that one can measure what speed
273 up, if any, can be achieved, and maybe later when things settle things can
276 Help stamp out big monolithic functions! */
278 /* GCSE global vars. */
281 static FILE *gcse_file;
283 /* Note whether or not we should run jump optimization after gcse. We
284 want to do this for two cases.
286 * If we changed any jumps via cprop.
288 * If we added any labels via edge splitting. */
290 static int run_jump_opt_after_gcse;
292 /* Bitmaps are normally not included in debugging dumps.
293 However it's useful to be able to print them from GDB.
294 We could create special functions for this, but it's simpler to
295 just allow passing stderr to the dump_foo fns. Since stderr can
296 be a macro, we store a copy here. */
297 static FILE *debug_stderr;
299 /* An obstack for our working variables. */
300 static struct obstack gcse_obstack;
302 /* Non-zero for each mode that supports (set (reg) (reg)).
303 This is trivially true for integer and floating point values.
304 It may or may not be true for condition codes. */
305 static char can_copy_p[(int) NUM_MACHINE_MODES];
307 /* Non-zero if can_copy_p has been initialized. */
308 static int can_copy_init_p;
314 /* Hash table of expressions. */
318 /* The expression (SET_SRC for expressions, PATTERN for assignments). */
320 /* Index in the available expression bitmaps. */
322 /* Next entry with the same hash. */
323 struct expr *next_same_hash;
324 /* List of anticipatable occurrences in basic blocks in the function.
325 An "anticipatable occurrence" is one that is the first occurrence in the
326 basic block, the operands are not modified in the basic block prior
327 to the occurrence and the output is not used between the start of
328 the block and the occurrence. */
329 struct occr *antic_occr;
330 /* List of available occurrence in basic blocks in the function.
331 An "available occurrence" is one that is the last occurrence in the
332 basic block and the operands are not modified by following statements in
333 the basic block [including this insn]. */
334 struct occr *avail_occr;
335 /* Non-null if the computation is PRE redundant.
336 The value is the newly created pseudo-reg to record a copy of the
337 expression in all the places that reach the redundant copy. */
341 /* Occurrence of an expression.
342 There is one per basic block. If a pattern appears more than once the
343 last appearance is used [or first for anticipatable expressions]. */
347 /* Next occurrence of this expression. */
349 /* The insn that computes the expression. */
351 /* Non-zero if this [anticipatable] occurrence has been deleted. */
353 /* Non-zero if this [available] occurrence has been copied to
355 /* ??? This is mutually exclusive with deleted_p, so they could share
360 /* Expression and copy propagation hash tables.
361 Each hash table is an array of buckets.
362 ??? It is known that if it were an array of entries, structure elements
363 `next_same_hash' and `bitmap_index' wouldn't be necessary. However, it is
364 not clear whether in the final analysis a sufficient amount of memory would
365 be saved as the size of the available expression bitmaps would be larger
366 [one could build a mapping table without holes afterwards though].
367 Someday I'll perform the computation and figure it out.
370 /* Total size of the expression hash table, in elements. */
371 static int expr_hash_table_size;
373 This is an array of `expr_hash_table_size' elements. */
374 static struct expr **expr_hash_table;
376 /* Total size of the copy propagation hash table, in elements. */
377 static int set_hash_table_size;
379 This is an array of `set_hash_table_size' elements. */
380 static struct expr **set_hash_table;
382 /* Mapping of uids to cuids.
383 Only real insns get cuids. */
384 static int *uid_cuid;
386 /* Highest UID in UID_CUID. */
389 /* Get the cuid of an insn. */
390 #define INSN_CUID(INSN) (uid_cuid[INSN_UID (INSN)])
392 /* Number of cuids. */
395 /* Mapping of cuids to insns. */
396 static rtx *cuid_insn;
398 /* Get insn from cuid. */
399 #define CUID_INSN(CUID) (cuid_insn[CUID])
401 /* Maximum register number in function prior to doing gcse + 1.
402 Registers created during this pass have regno >= max_gcse_regno.
403 This is named with "gcse" to not collide with global of same name. */
404 static int max_gcse_regno;
406 /* Maximum number of cse-able expressions found. */
408 /* Maximum number of assignments for copy propagation found. */
411 /* Table of registers that are modified.
412 For each register, each element is a list of places where the pseudo-reg
415 For simplicity, GCSE is done on sets of pseudo-regs only. PRE GCSE only
416 requires knowledge of which blocks kill which regs [and thus could use
417 a bitmap instead of the lists `reg_set_table' uses].
419 `reg_set_table' and could be turned into an array of bitmaps
421 [however perhaps it may be useful to keep the data as is].
422 One advantage of recording things this way is that `reg_set_table' is
423 fairly sparse with respect to pseudo regs but for hard regs could be
424 fairly dense [relatively speaking].
425 And recording sets of pseudo-regs in lists speeds
426 up functions like compute_transp since in the case of pseudo-regs we only
427 need to iterate over the number of times a pseudo-reg is set, not over the
428 number of basic blocks [clearly there is a bit of a slow down in the cases
429 where a pseudo is set more than once in a block, however it is believed
430 that the net effect is to speed things up]. This isn't done for hard-regs
431 because recording call-clobbered hard-regs in `reg_set_table' at each
432 function call can consume a fair bit of memory, and iterating over hard-regs
433 stored this way in compute_transp will be more expensive. */
435 typedef struct reg_set {
436 /* The next setting of this register. */
437 struct reg_set *next;
438 /* The insn where it was set. */
441 static reg_set **reg_set_table;
442 /* Size of `reg_set_table'.
443 The table starts out at max_gcse_regno + slop, and is enlarged as
445 static int reg_set_table_size;
446 /* Amount to grow `reg_set_table' by when it's full. */
447 #define REG_SET_TABLE_SLOP 100
449 /* Bitmap containing one bit for each register in the program.
450 Used when performing GCSE to track which registers have been set since
451 the start of the basic block. */
452 static sbitmap reg_set_bitmap;
454 /* For each block, a bitmap of registers set in the block.
455 This is used by expr_killed_p and compute_transp.
456 It is computed during hash table computation and not by compute_sets
457 as it includes registers added since the last pass (or between cprop and
458 gcse) and it's currently not easy to realloc sbitmap vectors. */
459 static sbitmap *reg_set_in_block;
461 /* For each block, non-zero if memory is set in that block.
462 This is computed during hash table computation and is used by
463 expr_killed_p and compute_transp.
464 ??? Handling of memory is very simple, we don't make any attempt
465 to optimize things (later).
466 ??? This can be computed by compute_sets since the information
468 static char *mem_set_in_block;
470 /* Various variables for statistics gathering. */
472 /* Memory used in a pass.
473 This isn't intended to be absolutely precise. Its intent is only
474 to keep an eye on memory usage. */
475 static int bytes_used;
476 /* GCSE substitutions made. */
477 static int gcse_subst_count;
478 /* Number of copy instructions created. */
479 static int gcse_create_count;
480 /* Number of constants propagated. */
481 static int const_prop_count;
482 /* Number of copys propagated. */
483 static int copy_prop_count;
485 /* These variables are used by classic GCSE.
486 Normally they'd be defined a bit later, but `rd_gen' needs to
487 be declared sooner. */
489 /* A bitmap of all ones for implementing the algorithm for available
490 expressions and reaching definitions. */
491 /* ??? Available expression bitmaps have a different size than reaching
492 definition bitmaps. This should be the larger of the two, however, it
493 is not currently used for reaching definitions. */
494 static sbitmap u_bitmap;
496 /* Each block has a bitmap of each type.
497 The length of each blocks bitmap is:
499 max_cuid - for reaching definitions
500 n_exprs - for available expressions
502 Thus we view the bitmaps as 2 dimensional arrays. i.e.
503 rd_kill[block_num][cuid_num]
504 ae_kill[block_num][expr_num]
507 /* For reaching defs */
508 static sbitmap *rd_kill, *rd_gen, *reaching_defs, *rd_out;
510 /* for available exprs */
511 static sbitmap *ae_kill, *ae_gen, *ae_in, *ae_out;
513 /* Objects of this type are passed around by the null-pointer check
515 struct null_pointer_info {
516 /* The basic block being processed. */
518 /* The first register to be handled in this pass. */
520 /* One greater than the last register to be handled in this pass. */
522 sbitmap *nonnull_local;
523 sbitmap *nonnull_killed;
526 static void compute_can_copy PARAMS ((void));
528 static char *gmalloc PARAMS ((unsigned int));
529 static char *grealloc PARAMS ((char *, unsigned int));
530 static char *gcse_alloc PARAMS ((unsigned long));
531 static void alloc_gcse_mem PARAMS ((rtx));
532 static void free_gcse_mem PARAMS ((void));
533 static void alloc_reg_set_mem PARAMS ((int));
534 static void free_reg_set_mem PARAMS ((void));
535 static int get_bitmap_width PARAMS ((int, int, int));
536 static void record_one_set PARAMS ((int, rtx));
537 static void record_set_info PARAMS ((rtx, rtx, void *));
538 static void compute_sets PARAMS ((rtx));
540 static void hash_scan_insn PARAMS ((rtx, int, int));
541 static void hash_scan_set PARAMS ((rtx, rtx, int));
542 static void hash_scan_clobber PARAMS ((rtx, rtx));
543 static void hash_scan_call PARAMS ((rtx, rtx));
544 static int want_to_gcse_p PARAMS ((rtx));
545 static int oprs_unchanged_p PARAMS ((rtx, rtx, int));
546 static int oprs_anticipatable_p PARAMS ((rtx, rtx));
547 static int oprs_available_p PARAMS ((rtx, rtx));
548 static void insert_expr_in_table PARAMS ((rtx, enum machine_mode,
550 static void insert_set_in_table PARAMS ((rtx, rtx));
551 static unsigned int hash_expr PARAMS ((rtx, enum machine_mode,
553 static unsigned int hash_expr_1 PARAMS ((rtx, enum machine_mode, int *));
554 static unsigned int hash_set PARAMS ((int, int));
555 static int expr_equiv_p PARAMS ((rtx, rtx));
556 static void record_last_reg_set_info PARAMS ((rtx, int));
557 static void record_last_mem_set_info PARAMS ((rtx));
558 static void record_last_set_info PARAMS ((rtx, rtx, void *));
559 static void compute_hash_table PARAMS ((int));
560 static void alloc_set_hash_table PARAMS ((int));
561 static void free_set_hash_table PARAMS ((void));
562 static void compute_set_hash_table PARAMS ((void));
563 static void alloc_expr_hash_table PARAMS ((int));
564 static void free_expr_hash_table PARAMS ((void));
565 static void compute_expr_hash_table PARAMS ((void));
566 static void dump_hash_table PARAMS ((FILE *, const char *,
567 struct expr **, int, int));
568 static struct expr *lookup_expr PARAMS ((rtx));
569 static struct expr *lookup_set PARAMS ((int, rtx));
570 static struct expr *next_set PARAMS ((int, struct expr *));
571 static void reset_opr_set_tables PARAMS ((void));
572 static int oprs_not_set_p PARAMS ((rtx, rtx));
573 static void mark_call PARAMS ((rtx));
574 static void mark_set PARAMS ((rtx, rtx));
575 static void mark_clobber PARAMS ((rtx, rtx));
576 static void mark_oprs_set PARAMS ((rtx));
578 static void alloc_cprop_mem PARAMS ((int, int));
579 static void free_cprop_mem PARAMS ((void));
580 static void compute_transp PARAMS ((rtx, int, sbitmap *, int));
581 static void compute_transpout PARAMS ((void));
582 static void compute_local_properties PARAMS ((sbitmap *, sbitmap *,
584 static void compute_cprop_data PARAMS ((void));
585 static void find_used_regs PARAMS ((rtx));
586 static int try_replace_reg PARAMS ((rtx, rtx, rtx));
587 static struct expr *find_avail_set PARAMS ((int, rtx));
588 static int cprop_jump PARAMS ((rtx, rtx, struct reg_use *, rtx));
590 static int cprop_cc0_jump PARAMS ((rtx, struct reg_use *, rtx));
592 static int cprop_insn PARAMS ((rtx, int));
593 static int cprop PARAMS ((int));
594 static int one_cprop_pass PARAMS ((int, int));
596 static void alloc_pre_mem PARAMS ((int, int));
597 static void free_pre_mem PARAMS ((void));
598 static void compute_pre_data PARAMS ((void));
599 static int pre_expr_reaches_here_p PARAMS ((int, struct expr *, int));
600 static void insert_insn_end_bb PARAMS ((struct expr *, int, int));
601 static void pre_insert_copy_insn PARAMS ((struct expr *, rtx));
602 static void pre_insert_copies PARAMS ((void));
603 static int pre_delete PARAMS ((void));
604 static int pre_gcse PARAMS ((void));
605 static int one_pre_gcse_pass PARAMS ((int));
607 static void add_label_notes PARAMS ((rtx, rtx));
609 static void alloc_code_hoist_mem PARAMS ((int, int));
610 static void free_code_hoist_mem PARAMS ((void));
611 static void compute_code_hoist_vbeinout PARAMS ((void));
612 static void compute_code_hoist_data PARAMS ((void));
613 static int hoist_expr_reaches_here_p PARAMS ((int, int, int, char *));
614 static void hoist_code PARAMS ((void));
615 static int one_code_hoisting_pass PARAMS ((void));
617 static void alloc_rd_mem PARAMS ((int, int));
618 static void free_rd_mem PARAMS ((void));
619 static void handle_rd_kill_set PARAMS ((rtx, int, int));
620 static void compute_kill_rd PARAMS ((void));
621 static void compute_rd PARAMS ((void));
622 static void alloc_avail_expr_mem PARAMS ((int, int));
623 static void free_avail_expr_mem PARAMS ((void));
624 static void compute_ae_gen PARAMS ((void));
625 static int expr_killed_p PARAMS ((rtx, int));
626 static void compute_ae_kill PARAMS ((sbitmap *, sbitmap *));
627 static int expr_reaches_here_p PARAMS ((struct occr *, struct expr *,
629 static rtx computing_insn PARAMS ((struct expr *, rtx));
630 static int def_reaches_here_p PARAMS ((rtx, rtx));
631 static int can_disregard_other_sets PARAMS ((struct reg_set **, rtx, int));
632 static int handle_avail_expr PARAMS ((rtx, struct expr *));
633 static int classic_gcse PARAMS ((void));
634 static int one_classic_gcse_pass PARAMS ((int));
635 static void invalidate_nonnull_info PARAMS ((rtx, rtx, void *));
636 static void delete_null_pointer_checks_1 PARAMS ((int *, sbitmap *, sbitmap *,
637 struct null_pointer_info *));
638 static rtx process_insert_insn PARAMS ((struct expr *));
639 static int pre_edge_insert PARAMS ((struct edge_list *, struct expr **));
640 static int expr_reaches_here_p_work PARAMS ((struct occr *, struct expr *,
642 static int pre_expr_reaches_here_p_work PARAMS ((int, struct expr *,
645 /* Entry point for global common subexpression elimination.
646 F is the first instruction in the function. */
654 /* Bytes used at start of pass. */
655 int initial_bytes_used;
656 /* Maximum number of bytes used by a pass. */
658 /* Point to release obstack data from for each pass. */
659 char *gcse_obstack_bottom;
661 /* We do not construct an accurate cfg in functions which call
662 setjmp, so just punt to be safe. */
663 if (current_function_calls_setjmp)
666 /* Assume that we do not need to run jump optimizations after gcse. */
667 run_jump_opt_after_gcse = 0;
669 /* For calling dump_foo fns from gdb. */
670 debug_stderr = stderr;
673 /* Identify the basic block information for this function, including
674 successors and predecessors. */
675 max_gcse_regno = max_reg_num ();
676 find_basic_blocks (f, max_gcse_regno, file, 1);
679 dump_flow_info (file);
681 /* Return if there's nothing to do. */
682 if (n_basic_blocks <= 1)
684 /* Free storage allocated by find_basic_blocks. */
685 free_basic_block_vars (0);
689 /* Trying to perform global optimizations on flow graphs which have
690 a high connectivity will take a long time and is unlikely to be
693 In normal circumstances a cfg should have about twice has many edges
694 as blocks. But we do not want to punish small functions which have
695 a couple switch statements. So we require a relatively large number
696 of basic blocks and the ratio of edges to blocks to be high. */
697 if (n_basic_blocks > 1000 && n_edges / n_basic_blocks >= 20)
699 /* Free storage allocated by find_basic_blocks. */
700 free_basic_block_vars (0);
704 /* See what modes support reg/reg copy operations. */
705 if (! can_copy_init_p)
711 gcc_obstack_init (&gcse_obstack);
714 /* Record where pseudo-registers are set.
715 This data is kept accurate during each pass.
716 ??? We could also record hard-reg information here
717 [since it's unchanging], however it is currently done during
718 hash table computation.
720 It may be tempting to compute MEM set information here too, but MEM
721 sets will be subject to code motion one day and thus we need to compute
722 information about memory sets when we build the hash tables. */
724 alloc_reg_set_mem (max_gcse_regno);
728 initial_bytes_used = bytes_used;
730 gcse_obstack_bottom = gcse_alloc (1);
732 while (changed && pass < MAX_PASSES)
736 fprintf (file, "GCSE pass %d\n\n", pass + 1);
738 /* Initialize bytes_used to the space for the pred/succ lists,
739 and the reg_set_table data. */
740 bytes_used = initial_bytes_used;
742 /* Each pass may create new registers, so recalculate each time. */
743 max_gcse_regno = max_reg_num ();
747 /* Don't allow constant propagation to modify jumps
749 changed = one_cprop_pass (pass + 1, 0);
752 changed |= one_classic_gcse_pass (pass + 1);
755 changed |= one_pre_gcse_pass (pass + 1);
757 alloc_reg_set_mem (max_reg_num ());
759 run_jump_opt_after_gcse = 1;
762 if (max_pass_bytes < bytes_used)
763 max_pass_bytes = bytes_used;
765 /* Free up memory, then reallocate for code hoisting. We can
766 not re-use the existing allocated memory because the tables
767 will not have info for the insns or registers created by
768 partial redundancy elimination. */
771 /* It does not make sense to run code hoisting unless we optimizing
772 for code size -- it rarely makes programs faster, and can make
773 them bigger if we did partial redundancy elimination (when optimizing
774 for space, we use a classic gcse algorithm instead of partial
775 redundancy algorithms). */
778 max_gcse_regno = max_reg_num ();
780 changed |= one_code_hoisting_pass ();
783 if (max_pass_bytes < bytes_used)
784 max_pass_bytes = bytes_used;
789 fprintf (file, "\n");
792 obstack_free (&gcse_obstack, gcse_obstack_bottom);
796 /* Do one last pass of copy propagation, including cprop into
797 conditional jumps. */
799 max_gcse_regno = max_reg_num ();
801 /* This time, go ahead and allow cprop to alter jumps. */
802 one_cprop_pass (pass + 1, 1);
807 fprintf (file, "GCSE of %s: %d basic blocks, ",
808 current_function_name, n_basic_blocks);
809 fprintf (file, "%d pass%s, %d bytes\n\n",
810 pass, pass > 1 ? "es" : "", max_pass_bytes);
813 /* Free our obstack. */
814 obstack_free (&gcse_obstack, NULL_PTR);
815 /* Free reg_set_table. */
817 /* Free storage allocated by find_basic_blocks. */
818 free_basic_block_vars (0);
819 return run_jump_opt_after_gcse;
822 /* Misc. utilities. */
824 /* Compute which modes support reg/reg copy operations. */
830 #ifndef AVOID_CCMODE_COPIES
833 char *free_point = (char *) oballoc (1);
835 bzero (can_copy_p, NUM_MACHINE_MODES);
838 for (i = 0; i < NUM_MACHINE_MODES; i++)
840 switch (GET_MODE_CLASS (i))
843 #ifdef AVOID_CCMODE_COPIES
846 reg = gen_rtx_REG ((enum machine_mode) i, LAST_VIRTUAL_REGISTER + 1);
847 insn = emit_insn (gen_rtx_SET (VOIDmode, reg, reg));
848 if (recog (PATTERN (insn), insn, NULL_PTR) >= 0)
859 /* Free the objects we just allocated. */
863 /* Cover function to xmalloc to record bytes allocated. */
870 return xmalloc (size);
873 /* Cover function to xrealloc.
874 We don't record the additional size since we don't know it.
875 It won't affect memory usage stats much anyway. */
882 return xrealloc (ptr, size);
885 /* Cover function to obstack_alloc.
886 We don't need to record the bytes allocated here since
887 obstack_chunk_alloc is set to gmalloc. */
893 return (char *) obstack_alloc (&gcse_obstack, size);
896 /* Allocate memory for the cuid mapping array,
897 and reg/memory set tracking tables.
899 This is called at the start of each pass. */
908 /* Find the largest UID and create a mapping from UIDs to CUIDs.
909 CUIDs are like UIDs except they increase monotonically, have no gaps,
910 and only apply to real insns. */
912 max_uid = get_max_uid ();
913 n = (max_uid + 1) * sizeof (int);
914 uid_cuid = (int *) gmalloc (n);
915 bzero ((char *) uid_cuid, n);
916 for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
918 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
919 INSN_CUID (insn) = i++;
921 INSN_CUID (insn) = i;
924 /* Create a table mapping cuids to insns. */
927 n = (max_cuid + 1) * sizeof (rtx);
928 cuid_insn = (rtx *) gmalloc (n);
929 bzero ((char *) cuid_insn, n);
930 for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
932 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
934 CUID_INSN (i) = insn;
939 /* Allocate vars to track sets of regs. */
941 reg_set_bitmap = (sbitmap) sbitmap_alloc (max_gcse_regno);
943 /* Allocate vars to track sets of regs, memory per block. */
945 reg_set_in_block = (sbitmap *) sbitmap_vector_alloc (n_basic_blocks,
947 mem_set_in_block = (char *) gmalloc (n_basic_blocks);
950 /* Free memory allocated by alloc_gcse_mem. */
958 free (reg_set_bitmap);
960 free (reg_set_in_block);
961 free (mem_set_in_block);
964 /* Many of the global optimization algorithms work by solving dataflow
965 equations for various expressions. Initially, some local value is
966 computed for each expression in each block. Then, the values
967 across the various blocks are combined (by following flow graph
968 edges) to arrive at global values. Conceptually, each set of
969 equations is independent. We may therefore solve all the equations
970 in parallel, solve them one at a time, or pick any intermediate
973 When you're going to need N two-dimensional bitmaps, each X (say,
974 the number of blocks) by Y (say, the number of expressions), call
975 this function. It's not important what X and Y represent; only
976 that Y correspond to the things that can be done in parallel. This
977 function will return an appropriate chunking factor C; you should
978 solve C sets of equations in parallel. By going through this
979 function, we can easily trade space against time; by solving fewer
980 equations in parallel we use less space. */
983 get_bitmap_width (n, x, y)
988 /* It's not really worth figuring out *exactly* how much memory will
989 be used by a particular choice. The important thing is to get
990 something approximately right. */
991 size_t max_bitmap_memory = 10 * 1024 * 1024;
993 /* The number of bytes we'd use for a single column of minimum
995 size_t column_size = n * x * sizeof (SBITMAP_ELT_TYPE);
997 /* Often, it's reasonable just to solve all the equations in
999 if (column_size * SBITMAP_SET_SIZE (y) <= max_bitmap_memory)
1002 /* Otherwise, pick the largest width we can, without going over the
1004 return SBITMAP_ELT_BITS * ((max_bitmap_memory + column_size - 1)
1009 /* Compute the local properties of each recorded expression.
1010 Local properties are those that are defined by the block, irrespective
1013 An expression is transparent in a block if its operands are not modified
1016 An expression is computed (locally available) in a block if it is computed
1017 at least once and expression would contain the same value if the
1018 computation was moved to the end of the block.
1020 An expression is locally anticipatable in a block if it is computed at
1021 least once and expression would contain the same value if the computation
1022 was moved to the beginning of the block.
1024 We call this routine for cprop, pre and code hoisting. They all
1025 compute basically the same information and thus can easily share
1028 TRANSP, COMP, and ANTLOC are destination sbitmaps for recording
1029 local properties. If NULL, then it is not necessary to compute
1030 or record that particular property.
1032 SETP controls which hash table to look at. If zero, this routine
1033 looks at the expr hash table; if nonzero this routine looks at
1034 the set hash table. Additionally, TRANSP is computed as ~TRANSP,
1035 since this is really cprop's ABSALTERED. */
1038 compute_local_properties (transp, comp, antloc, setp)
1044 int i, hash_table_size;
1045 struct expr **hash_table;
1047 /* Initialize any bitmaps that were passed in. */
1051 sbitmap_vector_zero (transp, n_basic_blocks);
1053 sbitmap_vector_ones (transp, n_basic_blocks);
1056 sbitmap_vector_zero (comp, n_basic_blocks);
1058 sbitmap_vector_zero (antloc, n_basic_blocks);
1060 /* We use the same code for cprop, pre and hoisting. For cprop
1061 we care about the set hash table, for pre and hoisting we
1062 care about the expr hash table. */
1063 hash_table_size = setp ? set_hash_table_size : expr_hash_table_size;
1064 hash_table = setp ? set_hash_table : expr_hash_table;
1066 for (i = 0; i < hash_table_size; i++)
1070 for (expr = hash_table[i]; expr != NULL; expr = expr->next_same_hash)
1073 int indx = expr->bitmap_index;
1075 /* The expression is transparent in this block if it is not killed.
1076 We start by assuming all are transparent [none are killed], and
1077 then reset the bits for those that are. */
1080 compute_transp (expr->expr, indx, transp, setp);
1082 /* The occurrences recorded in antic_occr are exactly those that
1083 we want to set to non-zero in ANTLOC. */
1087 for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
1089 int bb = BLOCK_NUM (occr->insn);
1090 SET_BIT (antloc[bb], indx);
1092 /* While we're scanning the table, this is a good place to
1094 occr->deleted_p = 0;
1098 /* The occurrences recorded in avail_occr are exactly those that
1099 we want to set to non-zero in COMP. */
1103 for (occr = expr->avail_occr; occr != NULL; occr = occr->next)
1105 int bb = BLOCK_NUM (occr->insn);
1106 SET_BIT (comp[bb], indx);
1108 /* While we're scanning the table, this is a good place to
1114 /* While we're scanning the table, this is a good place to
1116 expr->reaching_reg = 0;
1122 /* Register set information.
1124 `reg_set_table' records where each register is set or otherwise
1127 static struct obstack reg_set_obstack;
1130 alloc_reg_set_mem (n_regs)
1135 reg_set_table_size = n_regs + REG_SET_TABLE_SLOP;
1136 n = reg_set_table_size * sizeof (struct reg_set *);
1137 reg_set_table = (struct reg_set **) gmalloc (n);
1138 bzero ((char *) reg_set_table, n);
1140 gcc_obstack_init (®_set_obstack);
1146 free (reg_set_table);
1147 obstack_free (®_set_obstack, NULL_PTR);
1150 /* Record REGNO in the reg_set table. */
1153 record_one_set (regno, insn)
1157 /* allocate a new reg_set element and link it onto the list */
1158 struct reg_set *new_reg_info, *reg_info_ptr1, *reg_info_ptr2;
1160 /* If the table isn't big enough, enlarge it. */
1161 if (regno >= reg_set_table_size)
1163 int new_size = regno + REG_SET_TABLE_SLOP;
1164 reg_set_table = (struct reg_set **)
1165 grealloc ((char *) reg_set_table,
1166 new_size * sizeof (struct reg_set *));
1167 bzero ((char *) (reg_set_table + reg_set_table_size),
1168 (new_size - reg_set_table_size) * sizeof (struct reg_set *));
1169 reg_set_table_size = new_size;
1172 new_reg_info = (struct reg_set *) obstack_alloc (®_set_obstack,
1173 sizeof (struct reg_set));
1174 bytes_used += sizeof (struct reg_set);
1175 new_reg_info->insn = insn;
1176 new_reg_info->next = NULL;
1177 if (reg_set_table[regno] == NULL)
1178 reg_set_table[regno] = new_reg_info;
1181 reg_info_ptr1 = reg_info_ptr2 = reg_set_table[regno];
1182 /* ??? One could keep a "last" pointer to speed this up. */
1183 while (reg_info_ptr1 != NULL)
1185 reg_info_ptr2 = reg_info_ptr1;
1186 reg_info_ptr1 = reg_info_ptr1->next;
1188 reg_info_ptr2->next = new_reg_info;
1192 /* Called from compute_sets via note_stores to handle one
1193 SET or CLOBBER in an insn. The DATA is really the instruction
1194 in which the SET is occurring. */
1197 record_set_info (dest, setter, data)
1198 rtx dest, setter ATTRIBUTE_UNUSED;
1201 rtx record_set_insn = (rtx) data;
1203 if (GET_CODE (dest) == SUBREG)
1204 dest = SUBREG_REG (dest);
1206 if (GET_CODE (dest) == REG)
1208 if (REGNO (dest) >= FIRST_PSEUDO_REGISTER)
1209 record_one_set (REGNO (dest), record_set_insn);
1213 /* Scan the function and record each set of each pseudo-register.
1215 This is called once, at the start of the gcse pass.
1216 See the comments for `reg_set_table' for further docs. */
1226 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
1227 note_stores (PATTERN (insn), record_set_info, insn);
1228 insn = NEXT_INSN (insn);
1232 /* Hash table support. */
1234 #define NEVER_SET -1
1236 /* For each register, the cuid of the first/last insn in the block to set it,
1237 or -1 if not set. */
1238 static int *reg_first_set;
1239 static int *reg_last_set;
1241 /* While computing "first/last set" info, this is the CUID of first/last insn
1242 to set memory or -1 if not set. `mem_last_set' is also used when
1243 performing GCSE to record whether memory has been set since the beginning
1245 Note that handling of memory is very simple, we don't make any attempt
1246 to optimize things (later). */
1247 static int mem_first_set;
1248 static int mem_last_set;
1250 /* Perform a quick check whether X, the source of a set, is something
1251 we want to consider for GCSE. */
1257 enum rtx_code code = GET_CODE (x);
1275 /* Return non-zero if the operands of expression X are unchanged from the
1276 start of INSN's basic block up to but not including INSN (if AVAIL_P == 0),
1277 or from INSN to the end of INSN's basic block (if AVAIL_P != 0). */
1280 oprs_unchanged_p (x, insn, avail_p)
1288 /* repeat is used to turn tail-recursion into iteration. */
1294 code = GET_CODE (x);
1299 return (reg_last_set[REGNO (x)] == NEVER_SET
1300 || reg_last_set[REGNO (x)] < INSN_CUID (insn));
1302 return (reg_first_set[REGNO (x)] == NEVER_SET
1303 || reg_first_set[REGNO (x)] >= INSN_CUID (insn));
1308 if (mem_last_set != NEVER_SET
1309 && mem_last_set >= INSN_CUID (insn))
1314 if (mem_first_set != NEVER_SET
1315 && mem_first_set < INSN_CUID (insn))
1342 i = GET_RTX_LENGTH (code) - 1;
1343 fmt = GET_RTX_FORMAT (code);
1348 rtx tem = XEXP (x, i);
1350 /* If we are about to do the last recursive call
1351 needed at this level, change it into iteration.
1352 This function is called enough to be worth it. */
1358 if (! oprs_unchanged_p (tem, insn, avail_p))
1361 else if (fmt[i] == 'E')
1364 for (j = 0; j < XVECLEN (x, i); j++)
1366 if (! oprs_unchanged_p (XVECEXP (x, i, j), insn, avail_p))
1375 /* Return non-zero if the operands of expression X are unchanged from
1376 the start of INSN's basic block up to but not including INSN. */
1379 oprs_anticipatable_p (x, insn)
1382 return oprs_unchanged_p (x, insn, 0);
1385 /* Return non-zero if the operands of expression X are unchanged from
1386 INSN to the end of INSN's basic block. */
1389 oprs_available_p (x, insn)
1392 return oprs_unchanged_p (x, insn, 1);
1395 /* Hash expression X.
1396 MODE is only used if X is a CONST_INT.
1397 A boolean indicating if a volatile operand is found or if the expression
1398 contains something we don't want to insert in the table is stored in
1401 ??? One might want to merge this with canon_hash. Later. */
1404 hash_expr (x, mode, do_not_record_p, hash_table_size)
1406 enum machine_mode mode;
1407 int *do_not_record_p;
1408 int hash_table_size;
1412 *do_not_record_p = 0;
1414 hash = hash_expr_1 (x, mode, do_not_record_p);
1415 return hash % hash_table_size;
1418 /* Subroutine of hash_expr to do the actual work. */
1421 hash_expr_1 (x, mode, do_not_record_p)
1423 enum machine_mode mode;
1424 int *do_not_record_p;
1431 /* repeat is used to turn tail-recursion into iteration. */
1437 code = GET_CODE (x);
1442 register int regno = REGNO (x);
1443 hash += ((unsigned) REG << 7) + regno;
1449 unsigned HOST_WIDE_INT tem = INTVAL (x);
1450 hash += ((unsigned) CONST_INT << 7) + (unsigned) mode + tem;
1455 /* This is like the general case, except that it only counts
1456 the integers representing the constant. */
1457 hash += (unsigned) code + (unsigned) GET_MODE (x);
1458 if (GET_MODE (x) != VOIDmode)
1459 for (i = 2; i < GET_RTX_LENGTH (CONST_DOUBLE); i++)
1461 unsigned tem = XWINT (x, i);
1465 hash += ((unsigned) CONST_DOUBLE_LOW (x)
1466 + (unsigned) CONST_DOUBLE_HIGH (x));
1469 /* Assume there is only one rtx object for any given label. */
1471 /* We don't hash on the address of the CODE_LABEL to avoid bootstrap
1472 differences and differences between each stage's debugging dumps. */
1473 hash += ((unsigned) LABEL_REF << 7) + CODE_LABEL_NUMBER (XEXP (x, 0));
1478 /* Don't hash on the symbol's address to avoid bootstrap differences.
1479 Different hash values may cause expressions to be recorded in
1480 different orders and thus different registers to be used in the
1481 final assembler. This also avoids differences in the dump files
1482 between various stages. */
1484 unsigned char *p = (unsigned char *) XSTR (x, 0);
1486 h += (h << 7) + *p++; /* ??? revisit */
1487 hash += ((unsigned) SYMBOL_REF << 7) + h;
1492 if (MEM_VOLATILE_P (x))
1494 *do_not_record_p = 1;
1497 hash += (unsigned) MEM;
1498 hash += MEM_ALIAS_SET (x);
1509 case UNSPEC_VOLATILE:
1510 *do_not_record_p = 1;
1514 if (MEM_VOLATILE_P (x))
1516 *do_not_record_p = 1;
1524 i = GET_RTX_LENGTH (code) - 1;
1525 hash += (unsigned) code + (unsigned) GET_MODE (x);
1526 fmt = GET_RTX_FORMAT (code);
1531 rtx tem = XEXP (x, i);
1533 /* If we are about to do the last recursive call
1534 needed at this level, change it into iteration.
1535 This function is called enough to be worth it. */
1541 hash += hash_expr_1 (tem, 0, do_not_record_p);
1542 if (*do_not_record_p)
1545 else if (fmt[i] == 'E')
1546 for (j = 0; j < XVECLEN (x, i); j++)
1548 hash += hash_expr_1 (XVECEXP (x, i, j), 0, do_not_record_p);
1549 if (*do_not_record_p)
1552 else if (fmt[i] == 's')
1554 register unsigned char *p = (unsigned char *) XSTR (x, i);
1559 else if (fmt[i] == 'i')
1561 register unsigned tem = XINT (x, i);
1571 /* Hash a set of register REGNO.
1573 Sets are hashed on the register that is set.
1574 This simplifies the PRE copy propagation code.
1576 ??? May need to make things more elaborate. Later, as necessary. */
1579 hash_set (regno, hash_table_size)
1581 int hash_table_size;
1586 return hash % hash_table_size;
1589 /* Return non-zero if exp1 is equivalent to exp2.
1590 ??? Borrowed from cse.c. Might want to remerge with cse.c. Later. */
1597 register enum rtx_code code;
1598 register const char *fmt;
1602 if (x == 0 || y == 0)
1605 code = GET_CODE (x);
1606 if (code != GET_CODE (y))
1609 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. */
1610 if (GET_MODE (x) != GET_MODE (y))
1620 return INTVAL (x) == INTVAL (y);
1623 return XEXP (x, 0) == XEXP (y, 0);
1626 return XSTR (x, 0) == XSTR (y, 0);
1629 return REGNO (x) == REGNO (y);
1632 /* Can't merge two expressions in different alias sets, since we can
1633 decide that the expression is transparent in a block when it isn't,
1634 due to it being set with the different alias set. */
1635 if (MEM_ALIAS_SET (x) != MEM_ALIAS_SET (y))
1639 /* For commutative operations, check both orders. */
1647 return ((expr_equiv_p (XEXP (x, 0), XEXP (y, 0))
1648 && expr_equiv_p (XEXP (x, 1), XEXP (y, 1)))
1649 || (expr_equiv_p (XEXP (x, 0), XEXP (y, 1))
1650 && expr_equiv_p (XEXP (x, 1), XEXP (y, 0))));
1656 /* Compare the elements. If any pair of corresponding elements
1657 fail to match, return 0 for the whole thing. */
1659 fmt = GET_RTX_FORMAT (code);
1660 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1665 if (! expr_equiv_p (XEXP (x, i), XEXP (y, i)))
1670 if (XVECLEN (x, i) != XVECLEN (y, i))
1672 for (j = 0; j < XVECLEN (x, i); j++)
1673 if (! expr_equiv_p (XVECEXP (x, i, j), XVECEXP (y, i, j)))
1678 if (strcmp (XSTR (x, i), XSTR (y, i)))
1683 if (XINT (x, i) != XINT (y, i))
1688 if (XWINT (x, i) != XWINT (y, i))
1703 /* Insert expression X in INSN in the hash table.
1704 If it is already present, record it as the last occurrence in INSN's
1707 MODE is the mode of the value X is being stored into.
1708 It is only used if X is a CONST_INT.
1710 ANTIC_P is non-zero if X is an anticipatable expression.
1711 AVAIL_P is non-zero if X is an available expression. */
1714 insert_expr_in_table (x, mode, insn, antic_p, avail_p)
1716 enum machine_mode mode;
1718 int antic_p, avail_p;
1720 int found, do_not_record_p;
1722 struct expr *cur_expr, *last_expr = NULL;
1723 struct occr *antic_occr, *avail_occr;
1724 struct occr *last_occr = NULL;
1726 hash = hash_expr (x, mode, &do_not_record_p, expr_hash_table_size);
1728 /* Do not insert expression in table if it contains volatile operands,
1729 or if hash_expr determines the expression is something we don't want
1730 to or can't handle. */
1731 if (do_not_record_p)
1734 cur_expr = expr_hash_table[hash];
1737 while (cur_expr && ! (found = expr_equiv_p (cur_expr->expr, x)))
1739 /* If the expression isn't found, save a pointer to the end of
1741 last_expr = cur_expr;
1742 cur_expr = cur_expr->next_same_hash;
1747 cur_expr = (struct expr *) gcse_alloc (sizeof (struct expr));
1748 bytes_used += sizeof (struct expr);
1749 if (expr_hash_table[hash] == NULL)
1751 /* This is the first pattern that hashed to this index. */
1752 expr_hash_table[hash] = cur_expr;
1756 /* Add EXPR to end of this hash chain. */
1757 last_expr->next_same_hash = cur_expr;
1759 /* Set the fields of the expr element. */
1761 cur_expr->bitmap_index = n_exprs++;
1762 cur_expr->next_same_hash = NULL;
1763 cur_expr->antic_occr = NULL;
1764 cur_expr->avail_occr = NULL;
1767 /* Now record the occurrence(s). */
1771 antic_occr = cur_expr->antic_occr;
1773 /* Search for another occurrence in the same basic block. */
1774 while (antic_occr && BLOCK_NUM (antic_occr->insn) != BLOCK_NUM (insn))
1776 /* If an occurrence isn't found, save a pointer to the end of
1778 last_occr = antic_occr;
1779 antic_occr = antic_occr->next;
1784 /* Found another instance of the expression in the same basic block.
1785 Prefer the currently recorded one. We want the first one in the
1786 block and the block is scanned from start to end. */
1787 ; /* nothing to do */
1791 /* First occurrence of this expression in this basic block. */
1792 antic_occr = (struct occr *) gcse_alloc (sizeof (struct occr));
1793 bytes_used += sizeof (struct occr);
1794 /* First occurrence of this expression in any block? */
1795 if (cur_expr->antic_occr == NULL)
1796 cur_expr->antic_occr = antic_occr;
1798 last_occr->next = antic_occr;
1799 antic_occr->insn = insn;
1800 antic_occr->next = NULL;
1806 avail_occr = cur_expr->avail_occr;
1808 /* Search for another occurrence in the same basic block. */
1809 while (avail_occr && BLOCK_NUM (avail_occr->insn) != BLOCK_NUM (insn))
1811 /* If an occurrence isn't found, save a pointer to the end of
1813 last_occr = avail_occr;
1814 avail_occr = avail_occr->next;
1819 /* Found another instance of the expression in the same basic block.
1820 Prefer this occurrence to the currently recorded one. We want
1821 the last one in the block and the block is scanned from start
1823 avail_occr->insn = insn;
1827 /* First occurrence of this expression in this basic block. */
1828 avail_occr = (struct occr *) gcse_alloc (sizeof (struct occr));
1829 bytes_used += sizeof (struct occr);
1830 /* First occurrence of this expression in any block? */
1831 if (cur_expr->avail_occr == NULL)
1832 cur_expr->avail_occr = avail_occr;
1834 last_occr->next = avail_occr;
1835 avail_occr->insn = insn;
1836 avail_occr->next = NULL;
1841 /* Insert pattern X in INSN in the hash table.
1842 X is a SET of a reg to either another reg or a constant.
1843 If it is already present, record it as the last occurrence in INSN's
1847 insert_set_in_table (x, insn)
1853 struct expr *cur_expr, *last_expr = NULL;
1854 struct occr *cur_occr, *last_occr = NULL;
1856 if (GET_CODE (x) != SET
1857 || GET_CODE (SET_DEST (x)) != REG)
1860 hash = hash_set (REGNO (SET_DEST (x)), set_hash_table_size);
1862 cur_expr = set_hash_table[hash];
1865 while (cur_expr && ! (found = expr_equiv_p (cur_expr->expr, x)))
1867 /* If the expression isn't found, save a pointer to the end of
1869 last_expr = cur_expr;
1870 cur_expr = cur_expr->next_same_hash;
1875 cur_expr = (struct expr *) gcse_alloc (sizeof (struct expr));
1876 bytes_used += sizeof (struct expr);
1877 if (set_hash_table[hash] == NULL)
1879 /* This is the first pattern that hashed to this index. */
1880 set_hash_table[hash] = cur_expr;
1884 /* Add EXPR to end of this hash chain. */
1885 last_expr->next_same_hash = cur_expr;
1887 /* Set the fields of the expr element.
1888 We must copy X because it can be modified when copy propagation is
1889 performed on its operands. */
1890 /* ??? Should this go in a different obstack? */
1891 cur_expr->expr = copy_rtx (x);
1892 cur_expr->bitmap_index = n_sets++;
1893 cur_expr->next_same_hash = NULL;
1894 cur_expr->antic_occr = NULL;
1895 cur_expr->avail_occr = NULL;
1898 /* Now record the occurrence. */
1900 cur_occr = cur_expr->avail_occr;
1902 /* Search for another occurrence in the same basic block. */
1903 while (cur_occr && BLOCK_NUM (cur_occr->insn) != BLOCK_NUM (insn))
1905 /* If an occurrence isn't found, save a pointer to the end of
1907 last_occr = cur_occr;
1908 cur_occr = cur_occr->next;
1913 /* Found another instance of the expression in the same basic block.
1914 Prefer this occurrence to the currently recorded one. We want
1915 the last one in the block and the block is scanned from start
1917 cur_occr->insn = insn;
1921 /* First occurrence of this expression in this basic block. */
1922 cur_occr = (struct occr *) gcse_alloc (sizeof (struct occr));
1923 bytes_used += sizeof (struct occr);
1924 /* First occurrence of this expression in any block? */
1925 if (cur_expr->avail_occr == NULL)
1926 cur_expr->avail_occr = cur_occr;
1928 last_occr->next = cur_occr;
1929 cur_occr->insn = insn;
1930 cur_occr->next = NULL;
1934 /* Scan pattern PAT of INSN and add an entry to the hash table.
1935 If SET_P is non-zero, this is for the assignment hash table,
1936 otherwise it is for the expression hash table. */
1939 hash_scan_set (pat, insn, set_p)
1943 rtx src = SET_SRC (pat);
1944 rtx dest = SET_DEST (pat);
1946 if (GET_CODE (src) == CALL)
1947 hash_scan_call (src, insn);
1949 if (GET_CODE (dest) == REG)
1951 int regno = REGNO (dest);
1954 /* Only record sets of pseudo-regs in the hash table. */
1956 && regno >= FIRST_PSEUDO_REGISTER
1957 /* Don't GCSE something if we can't do a reg/reg copy. */
1958 && can_copy_p [GET_MODE (dest)]
1959 /* Is SET_SRC something we want to gcse? */
1960 && want_to_gcse_p (src))
1962 /* An expression is not anticipatable if its operands are
1963 modified before this insn. */
1964 int antic_p = oprs_anticipatable_p (src, insn);
1965 /* An expression is not available if its operands are
1966 subsequently modified, including this insn. */
1967 int avail_p = oprs_available_p (src, insn);
1968 insert_expr_in_table (src, GET_MODE (dest), insn, antic_p, avail_p);
1970 /* Record sets for constant/copy propagation. */
1972 && regno >= FIRST_PSEUDO_REGISTER
1973 && ((GET_CODE (src) == REG
1974 && REGNO (src) >= FIRST_PSEUDO_REGISTER
1975 && can_copy_p [GET_MODE (dest)])
1976 || GET_CODE (src) == CONST_INT
1977 || GET_CODE (src) == SYMBOL_REF
1978 || GET_CODE (src) == CONST_DOUBLE)
1979 /* A copy is not available if its src or dest is subsequently
1980 modified. Here we want to search from INSN+1 on, but
1981 oprs_available_p searches from INSN on. */
1982 && (insn == BLOCK_END (BLOCK_NUM (insn))
1983 || ((tmp = next_nonnote_insn (insn)) != NULL_RTX
1984 && oprs_available_p (pat, tmp))))
1985 insert_set_in_table (pat, insn);
1990 hash_scan_clobber (x, insn)
1991 rtx x ATTRIBUTE_UNUSED, insn ATTRIBUTE_UNUSED;
1993 /* Currently nothing to do. */
1997 hash_scan_call (x, insn)
1998 rtx x ATTRIBUTE_UNUSED, insn ATTRIBUTE_UNUSED;
2000 /* Currently nothing to do. */
2003 /* Process INSN and add hash table entries as appropriate.
2005 Only available expressions that set a single pseudo-reg are recorded.
2007 Single sets in a PARALLEL could be handled, but it's an extra complication
2008 that isn't dealt with right now. The trick is handling the CLOBBERs that
2009 are also in the PARALLEL. Later.
2011 If SET_P is non-zero, this is for the assignment hash table,
2012 otherwise it is for the expression hash table.
2013 If IN_LIBCALL_BLOCK nonzero, we are in a libcall block, and should
2014 not record any expressions. */
2017 hash_scan_insn (insn, set_p, in_libcall_block)
2020 int in_libcall_block;
2022 rtx pat = PATTERN (insn);
2024 /* Pick out the sets of INSN and for other forms of instructions record
2025 what's been modified. */
2027 if (GET_CODE (pat) == SET && ! in_libcall_block)
2029 /* Ignore obvious no-ops. */
2030 if (SET_SRC (pat) != SET_DEST (pat))
2031 hash_scan_set (pat, insn, set_p);
2033 else if (GET_CODE (pat) == PARALLEL)
2037 for (i = 0; i < XVECLEN (pat, 0); i++)
2039 rtx x = XVECEXP (pat, 0, i);
2041 if (GET_CODE (x) == SET)
2043 if (GET_CODE (SET_SRC (x)) == CALL)
2044 hash_scan_call (SET_SRC (x), insn);
2046 else if (GET_CODE (x) == CLOBBER)
2047 hash_scan_clobber (x, insn);
2048 else if (GET_CODE (x) == CALL)
2049 hash_scan_call (x, insn);
2052 else if (GET_CODE (pat) == CLOBBER)
2053 hash_scan_clobber (pat, insn);
2054 else if (GET_CODE (pat) == CALL)
2055 hash_scan_call (pat, insn);
2059 dump_hash_table (file, name, table, table_size, total_size)
2062 struct expr **table;
2063 int table_size, total_size;
2066 /* Flattened out table, so it's printed in proper order. */
2067 struct expr **flat_table;
2068 unsigned int *hash_val;
2071 = (struct expr **) xcalloc (total_size, sizeof (struct expr *));
2072 hash_val = (unsigned int *) xmalloc (total_size * sizeof (unsigned int));
2074 for (i = 0; i < table_size; i++)
2078 for (expr = table[i]; expr != NULL; expr = expr->next_same_hash)
2080 flat_table[expr->bitmap_index] = expr;
2081 hash_val[expr->bitmap_index] = i;
2085 fprintf (file, "%s hash table (%d buckets, %d entries)\n",
2086 name, table_size, total_size);
2088 for (i = 0; i < total_size; i++)
2090 struct expr *expr = flat_table[i];
2092 fprintf (file, "Index %d (hash value %d)\n ",
2093 expr->bitmap_index, hash_val[i]);
2094 print_rtl (file, expr->expr);
2095 fprintf (file, "\n");
2098 fprintf (file, "\n");
2105 /* Record register first/last/block set information for REGNO in INSN.
2106 reg_first_set records the first place in the block where the register
2107 is set and is used to compute "anticipatability".
2108 reg_last_set records the last place in the block where the register
2109 is set and is used to compute "availability".
2110 reg_set_in_block records whether the register is set in the block
2111 and is used to compute "transparency". */
2114 record_last_reg_set_info (insn, regno)
2118 if (reg_first_set[regno] == NEVER_SET)
2119 reg_first_set[regno] = INSN_CUID (insn);
2120 reg_last_set[regno] = INSN_CUID (insn);
2121 SET_BIT (reg_set_in_block[BLOCK_NUM (insn)], regno);
2124 /* Record memory first/last/block set information for INSN. */
2127 record_last_mem_set_info (insn)
2130 if (mem_first_set == NEVER_SET)
2131 mem_first_set = INSN_CUID (insn);
2132 mem_last_set = INSN_CUID (insn);
2133 mem_set_in_block[BLOCK_NUM (insn)] = 1;
2136 /* Called from compute_hash_table via note_stores to handle one
2137 SET or CLOBBER in an insn. DATA is really the instruction in which
2138 the SET is taking place. */
2141 record_last_set_info (dest, setter, data)
2142 rtx dest, setter ATTRIBUTE_UNUSED;
2145 rtx last_set_insn = (rtx) data;
2147 if (GET_CODE (dest) == SUBREG)
2148 dest = SUBREG_REG (dest);
2150 if (GET_CODE (dest) == REG)
2151 record_last_reg_set_info (last_set_insn, REGNO (dest));
2152 else if (GET_CODE (dest) == MEM
2153 /* Ignore pushes, they clobber nothing. */
2154 && ! push_operand (dest, GET_MODE (dest)))
2155 record_last_mem_set_info (last_set_insn);
2158 /* Top level function to create an expression or assignment hash table.
2160 Expression entries are placed in the hash table if
2161 - they are of the form (set (pseudo-reg) src),
2162 - src is something we want to perform GCSE on,
2163 - none of the operands are subsequently modified in the block
2165 Assignment entries are placed in the hash table if
2166 - they are of the form (set (pseudo-reg) src),
2167 - src is something we want to perform const/copy propagation on,
2168 - none of the operands or target are subsequently modified in the block
2169 Currently src must be a pseudo-reg or a const_int.
2171 F is the first insn.
2172 SET_P is non-zero for computing the assignment hash table. */
2175 compute_hash_table (set_p)
2180 /* While we compute the hash table we also compute a bit array of which
2181 registers are set in which blocks.
2182 We also compute which blocks set memory, in the absence of aliasing
2183 support [which is TODO].
2184 ??? This isn't needed during const/copy propagation, but it's cheap to
2186 sbitmap_vector_zero (reg_set_in_block, n_basic_blocks);
2187 bzero ((char *) mem_set_in_block, n_basic_blocks);
2189 /* Some working arrays used to track first and last set in each block. */
2190 /* ??? One could use alloca here, but at some size a threshold is crossed
2191 beyond which one should use malloc. Are we at that threshold here? */
2192 reg_first_set = (int *) gmalloc (max_gcse_regno * sizeof (int));
2193 reg_last_set = (int *) gmalloc (max_gcse_regno * sizeof (int));
2195 for (bb = 0; bb < n_basic_blocks; bb++)
2199 int in_libcall_block;
2202 /* First pass over the instructions records information used to
2203 determine when registers and memory are first and last set.
2204 ??? The mem_set_in_block and hard-reg reg_set_in_block computation
2205 could be moved to compute_sets since they currently don't change. */
2207 for (i = 0; i < max_gcse_regno; i++)
2208 reg_first_set[i] = reg_last_set[i] = NEVER_SET;
2209 mem_first_set = NEVER_SET;
2210 mem_last_set = NEVER_SET;
2212 for (insn = BLOCK_HEAD (bb);
2213 insn && insn != NEXT_INSN (BLOCK_END (bb));
2214 insn = NEXT_INSN (insn))
2216 #ifdef NON_SAVING_SETJMP
2217 if (NON_SAVING_SETJMP && GET_CODE (insn) == NOTE
2218 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_SETJMP)
2220 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
2221 record_last_reg_set_info (insn, regno);
2226 if (GET_RTX_CLASS (GET_CODE (insn)) != 'i')
2229 if (GET_CODE (insn) == CALL_INSN)
2231 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
2232 if ((call_used_regs[regno]
2233 && regno != STACK_POINTER_REGNUM
2234 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2235 && regno != HARD_FRAME_POINTER_REGNUM
2237 #if ARG_POINTER_REGNUM != FRAME_POINTER_REGNUM
2238 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2240 #if defined (PIC_OFFSET_TABLE_REGNUM) && !defined (PIC_OFFSET_TABLE_REG_CALL_CLOBBERED)
2241 && ! (regno == PIC_OFFSET_TABLE_REGNUM && flag_pic)
2244 && regno != FRAME_POINTER_REGNUM)
2245 || global_regs[regno])
2246 record_last_reg_set_info (insn, regno);
2247 if (! CONST_CALL_P (insn))
2248 record_last_mem_set_info (insn);
2251 note_stores (PATTERN (insn), record_last_set_info, insn);
2254 /* The next pass builds the hash table. */
2256 for (insn = BLOCK_HEAD (bb), in_libcall_block = 0;
2257 insn && insn != NEXT_INSN (BLOCK_END (bb));
2258 insn = NEXT_INSN (insn))
2260 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
2262 if (find_reg_note (insn, REG_LIBCALL, NULL_RTX))
2263 in_libcall_block = 1;
2264 else if (find_reg_note (insn, REG_RETVAL, NULL_RTX))
2265 in_libcall_block = 0;
2266 hash_scan_insn (insn, set_p, in_libcall_block);
2271 free (reg_first_set);
2272 free (reg_last_set);
2273 /* Catch bugs early. */
2274 reg_first_set = reg_last_set = 0;
2277 /* Allocate space for the set hash table.
2278 N_INSNS is the number of instructions in the function.
2279 It is used to determine the number of buckets to use. */
2282 alloc_set_hash_table (n_insns)
2287 set_hash_table_size = n_insns / 4;
2288 if (set_hash_table_size < 11)
2289 set_hash_table_size = 11;
2290 /* Attempt to maintain efficient use of hash table.
2291 Making it an odd number is simplest for now.
2292 ??? Later take some measurements. */
2293 set_hash_table_size |= 1;
2294 n = set_hash_table_size * sizeof (struct expr *);
2295 set_hash_table = (struct expr **) gmalloc (n);
2298 /* Free things allocated by alloc_set_hash_table. */
2301 free_set_hash_table ()
2303 free (set_hash_table);
2306 /* Compute the hash table for doing copy/const propagation. */
2309 compute_set_hash_table ()
2311 /* Initialize count of number of entries in hash table. */
2313 bzero ((char *) set_hash_table, set_hash_table_size * sizeof (struct expr *));
2315 compute_hash_table (1);
2318 /* Allocate space for the expression hash table.
2319 N_INSNS is the number of instructions in the function.
2320 It is used to determine the number of buckets to use. */
2323 alloc_expr_hash_table (n_insns)
2328 expr_hash_table_size = n_insns / 2;
2329 /* Make sure the amount is usable. */
2330 if (expr_hash_table_size < 11)
2331 expr_hash_table_size = 11;
2332 /* Attempt to maintain efficient use of hash table.
2333 Making it an odd number is simplest for now.
2334 ??? Later take some measurements. */
2335 expr_hash_table_size |= 1;
2336 n = expr_hash_table_size * sizeof (struct expr *);
2337 expr_hash_table = (struct expr **) gmalloc (n);
2340 /* Free things allocated by alloc_expr_hash_table. */
2343 free_expr_hash_table ()
2345 free (expr_hash_table);
2348 /* Compute the hash table for doing GCSE. */
2351 compute_expr_hash_table ()
2353 /* Initialize count of number of entries in hash table. */
2355 bzero ((char *) expr_hash_table, expr_hash_table_size * sizeof (struct expr *));
2357 compute_hash_table (0);
2360 /* Expression tracking support. */
2362 /* Lookup pattern PAT in the expression table.
2363 The result is a pointer to the table entry, or NULL if not found. */
2365 static struct expr *
2369 int do_not_record_p;
2370 unsigned int hash = hash_expr (pat, GET_MODE (pat), &do_not_record_p,
2371 expr_hash_table_size);
2374 if (do_not_record_p)
2377 expr = expr_hash_table[hash];
2379 while (expr && ! expr_equiv_p (expr->expr, pat))
2380 expr = expr->next_same_hash;
2385 /* Lookup REGNO in the set table.
2386 If PAT is non-NULL look for the entry that matches it, otherwise return
2387 the first entry for REGNO.
2388 The result is a pointer to the table entry, or NULL if not found. */
2390 static struct expr *
2391 lookup_set (regno, pat)
2395 unsigned int hash = hash_set (regno, set_hash_table_size);
2398 expr = set_hash_table[hash];
2402 while (expr && ! expr_equiv_p (expr->expr, pat))
2403 expr = expr->next_same_hash;
2407 while (expr && REGNO (SET_DEST (expr->expr)) != regno)
2408 expr = expr->next_same_hash;
2414 /* Return the next entry for REGNO in list EXPR. */
2416 static struct expr *
2417 next_set (regno, expr)
2422 expr = expr->next_same_hash;
2423 while (expr && REGNO (SET_DEST (expr->expr)) != regno);
2427 /* Reset tables used to keep track of what's still available [since the
2428 start of the block]. */
2431 reset_opr_set_tables ()
2433 /* Maintain a bitmap of which regs have been set since beginning of
2435 sbitmap_zero (reg_set_bitmap);
2436 /* Also keep a record of the last instruction to modify memory.
2437 For now this is very trivial, we only record whether any memory
2438 location has been modified. */
2442 /* Return non-zero if the operands of X are not set before INSN in
2443 INSN's basic block. */
2446 oprs_not_set_p (x, insn)
2453 /* repeat is used to turn tail-recursion into iteration. */
2459 code = GET_CODE (x);
2474 if (mem_last_set != 0)
2480 return ! TEST_BIT (reg_set_bitmap, REGNO (x));
2486 fmt = GET_RTX_FORMAT (code);
2487 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2492 /* If we are about to do the last recursive call
2493 needed at this level, change it into iteration.
2494 This function is called enough to be worth it. */
2500 not_set_p = oprs_not_set_p (XEXP (x, i), insn);
2504 else if (fmt[i] == 'E')
2507 for (j = 0; j < XVECLEN (x, i); j++)
2509 int not_set_p = oprs_not_set_p (XVECEXP (x, i, j), insn);
2519 /* Mark things set by a CALL. */
2525 mem_last_set = INSN_CUID (insn);
2528 /* Mark things set by a SET. */
2531 mark_set (pat, insn)
2534 rtx dest = SET_DEST (pat);
2536 while (GET_CODE (dest) == SUBREG
2537 || GET_CODE (dest) == ZERO_EXTRACT
2538 || GET_CODE (dest) == SIGN_EXTRACT
2539 || GET_CODE (dest) == STRICT_LOW_PART)
2540 dest = XEXP (dest, 0);
2542 if (GET_CODE (dest) == REG)
2543 SET_BIT (reg_set_bitmap, REGNO (dest));
2544 else if (GET_CODE (dest) == MEM)
2545 mem_last_set = INSN_CUID (insn);
2547 if (GET_CODE (SET_SRC (pat)) == CALL)
2551 /* Record things set by a CLOBBER. */
2554 mark_clobber (pat, insn)
2557 rtx clob = XEXP (pat, 0);
2559 while (GET_CODE (clob) == SUBREG || GET_CODE (clob) == STRICT_LOW_PART)
2560 clob = XEXP (clob, 0);
2562 if (GET_CODE (clob) == REG)
2563 SET_BIT (reg_set_bitmap, REGNO (clob));
2565 mem_last_set = INSN_CUID (insn);
2568 /* Record things set by INSN.
2569 This data is used by oprs_not_set_p. */
2572 mark_oprs_set (insn)
2575 rtx pat = PATTERN (insn);
2577 if (GET_CODE (pat) == SET)
2578 mark_set (pat, insn);
2579 else if (GET_CODE (pat) == PARALLEL)
2583 for (i = 0; i < XVECLEN (pat, 0); i++)
2585 rtx x = XVECEXP (pat, 0, i);
2587 if (GET_CODE (x) == SET)
2589 else if (GET_CODE (x) == CLOBBER)
2590 mark_clobber (x, insn);
2591 else if (GET_CODE (x) == CALL)
2595 else if (GET_CODE (pat) == CLOBBER)
2596 mark_clobber (pat, insn);
2597 else if (GET_CODE (pat) == CALL)
2602 /* Classic GCSE reaching definition support. */
2604 /* Allocate reaching def variables. */
2607 alloc_rd_mem (n_blocks, n_insns)
2608 int n_blocks, n_insns;
2610 rd_kill = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
2611 sbitmap_vector_zero (rd_kill, n_basic_blocks);
2613 rd_gen = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
2614 sbitmap_vector_zero (rd_gen, n_basic_blocks);
2616 reaching_defs = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
2617 sbitmap_vector_zero (reaching_defs, n_basic_blocks);
2619 rd_out = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
2620 sbitmap_vector_zero (rd_out, n_basic_blocks);
2623 /* Free reaching def variables. */
2630 free (reaching_defs);
2634 /* Add INSN to the kills of BB.
2635 REGNO, set in BB, is killed by INSN. */
2638 handle_rd_kill_set (insn, regno, bb)
2642 struct reg_set *this_reg = reg_set_table[regno];
2646 if (BLOCK_NUM (this_reg->insn) != BLOCK_NUM (insn))
2647 SET_BIT (rd_kill[bb], INSN_CUID (this_reg->insn));
2648 this_reg = this_reg->next;
2652 /* Compute the set of kill's for reaching definitions. */
2660 For each set bit in `gen' of the block (i.e each insn which
2661 generates a definition in the block)
2662 Call the reg set by the insn corresponding to that bit regx
2663 Look at the linked list starting at reg_set_table[regx]
2664 For each setting of regx in the linked list, which is not in
2666 Set the bit in `kill' corresponding to that insn
2669 for (bb = 0; bb < n_basic_blocks; bb++)
2671 for (cuid = 0; cuid < max_cuid; cuid++)
2673 if (TEST_BIT (rd_gen[bb], cuid))
2675 rtx insn = CUID_INSN (cuid);
2676 rtx pat = PATTERN (insn);
2678 if (GET_CODE (insn) == CALL_INSN)
2682 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
2684 if ((call_used_regs[regno]
2685 && regno != STACK_POINTER_REGNUM
2686 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2687 && regno != HARD_FRAME_POINTER_REGNUM
2689 #if ARG_POINTER_REGNUM != FRAME_POINTER_REGNUM
2690 && ! (regno == ARG_POINTER_REGNUM
2691 && fixed_regs[regno])
2693 #if defined (PIC_OFFSET_TABLE_REGNUM) && !defined (PIC_OFFSET_TABLE_REG_CALL_CLOBBERED)
2694 && ! (regno == PIC_OFFSET_TABLE_REGNUM && flag_pic)
2696 && regno != FRAME_POINTER_REGNUM)
2697 || global_regs[regno])
2698 handle_rd_kill_set (insn, regno, bb);
2702 if (GET_CODE (pat) == PARALLEL)
2706 /* We work backwards because ... */
2707 for (i = XVECLEN (pat, 0) - 1; i >= 0; i--)
2709 enum rtx_code code = GET_CODE (XVECEXP (pat, 0, i));
2710 if ((code == SET || code == CLOBBER)
2711 && GET_CODE (XEXP (XVECEXP (pat, 0, i), 0)) == REG)
2712 handle_rd_kill_set (insn,
2713 REGNO (XEXP (XVECEXP (pat, 0, i), 0)),
2717 else if (GET_CODE (pat) == SET)
2719 if (GET_CODE (SET_DEST (pat)) == REG)
2721 /* Each setting of this register outside of this block
2722 must be marked in the set of kills in this block. */
2723 handle_rd_kill_set (insn, REGNO (SET_DEST (pat)), bb);
2726 /* FIXME: CLOBBER? */
2732 /* Compute the reaching definitions as in
2733 Compilers Principles, Techniques, and Tools. Aho, Sethi, Ullman,
2734 Chapter 10. It is the same algorithm as used for computing available
2735 expressions but applied to the gens and kills of reaching definitions. */
2740 int bb, changed, passes;
2742 for (bb = 0; bb < n_basic_blocks; bb++)
2743 sbitmap_copy (rd_out[bb] /*dst*/, rd_gen[bb] /*src*/);
2750 for (bb = 0; bb < n_basic_blocks; bb++)
2752 sbitmap_union_of_preds (reaching_defs[bb], rd_out, bb);
2753 changed |= sbitmap_union_of_diff (rd_out[bb], rd_gen[bb],
2754 reaching_defs[bb], rd_kill[bb]);
2760 fprintf (gcse_file, "reaching def computation: %d passes\n", passes);
2763 /* Classic GCSE available expression support. */
2765 /* Allocate memory for available expression computation. */
2768 alloc_avail_expr_mem (n_blocks, n_exprs)
2769 int n_blocks, n_exprs;
2771 ae_kill = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
2772 sbitmap_vector_zero (ae_kill, n_basic_blocks);
2774 ae_gen = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
2775 sbitmap_vector_zero (ae_gen, n_basic_blocks);
2777 ae_in = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
2778 sbitmap_vector_zero (ae_in, n_basic_blocks);
2780 ae_out = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
2781 sbitmap_vector_zero (ae_out, n_basic_blocks);
2783 u_bitmap = (sbitmap) sbitmap_alloc (n_exprs);
2784 sbitmap_ones (u_bitmap);
2788 free_avail_expr_mem ()
2797 /* Compute the set of available expressions generated in each basic block. */
2804 /* For each recorded occurrence of each expression, set ae_gen[bb][expr].
2805 This is all we have to do because an expression is not recorded if it
2806 is not available, and the only expressions we want to work with are the
2807 ones that are recorded. */
2809 for (i = 0; i < expr_hash_table_size; i++)
2811 struct expr *expr = expr_hash_table[i];
2812 while (expr != NULL)
2814 struct occr *occr = expr->avail_occr;
2815 while (occr != NULL)
2817 SET_BIT (ae_gen[BLOCK_NUM (occr->insn)], expr->bitmap_index);
2820 expr = expr->next_same_hash;
2825 /* Return non-zero if expression X is killed in BB. */
2828 expr_killed_p (x, bb)
2836 /* repeat is used to turn tail-recursion into iteration. */
2842 code = GET_CODE (x);
2846 return TEST_BIT (reg_set_in_block[bb], REGNO (x));
2849 if (mem_set_in_block[bb])
2869 i = GET_RTX_LENGTH (code) - 1;
2870 fmt = GET_RTX_FORMAT (code);
2875 rtx tem = XEXP (x, i);
2877 /* If we are about to do the last recursive call
2878 needed at this level, change it into iteration.
2879 This function is called enough to be worth it. */
2885 if (expr_killed_p (tem, bb))
2888 else if (fmt[i] == 'E')
2891 for (j = 0; j < XVECLEN (x, i); j++)
2893 if (expr_killed_p (XVECEXP (x, i, j), bb))
2902 /* Compute the set of available expressions killed in each basic block. */
2905 compute_ae_kill (ae_gen, ae_kill)
2906 sbitmap *ae_gen, *ae_kill;
2910 for (bb = 0; bb < n_basic_blocks; bb++)
2912 for (i = 0; i < expr_hash_table_size; i++)
2914 struct expr *expr = expr_hash_table[i];
2916 for ( ; expr != NULL; expr = expr->next_same_hash)
2918 /* Skip EXPR if generated in this block. */
2919 if (TEST_BIT (ae_gen[bb], expr->bitmap_index))
2922 if (expr_killed_p (expr->expr, bb))
2923 SET_BIT (ae_kill[bb], expr->bitmap_index);
2929 /* Actually perform the Classic GCSE optimizations. */
2931 /* Return non-zero if occurrence OCCR of expression EXPR reaches block BB.
2933 CHECK_SELF_LOOP is non-zero if we should consider a block reaching itself
2934 as a positive reach. We want to do this when there are two computations
2935 of the expression in the block.
2937 VISITED is a pointer to a working buffer for tracking which BB's have
2938 been visited. It is NULL for the top-level call.
2940 We treat reaching expressions that go through blocks containing the same
2941 reaching expression as "not reaching". E.g. if EXPR is generated in blocks
2942 2 and 3, INSN is in block 4, and 2->3->4, we treat the expression in block
2943 2 as not reaching. The intent is to improve the probability of finding
2944 only one reaching expression and to reduce register lifetimes by picking
2945 the closest such expression. */
2948 expr_reaches_here_p_work (occr, expr, bb, check_self_loop, visited)
2952 int check_self_loop;
2957 for (pred = BASIC_BLOCK(bb)->pred; pred != NULL; pred = pred->pred_next)
2959 int pred_bb = pred->src->index;
2961 if (visited[pred_bb])
2963 /* This predecessor has already been visited.
2967 else if (pred_bb == bb)
2969 /* BB loops on itself. */
2971 && TEST_BIT (ae_gen[pred_bb], expr->bitmap_index)
2972 && BLOCK_NUM (occr->insn) == pred_bb)
2974 visited[pred_bb] = 1;
2976 /* Ignore this predecessor if it kills the expression. */
2977 else if (TEST_BIT (ae_kill[pred_bb], expr->bitmap_index))
2978 visited[pred_bb] = 1;
2979 /* Does this predecessor generate this expression? */
2980 else if (TEST_BIT (ae_gen[pred_bb], expr->bitmap_index))
2982 /* Is this the occurrence we're looking for?
2983 Note that there's only one generating occurrence per block
2984 so we just need to check the block number. */
2985 if (BLOCK_NUM (occr->insn) == pred_bb)
2987 visited[pred_bb] = 1;
2989 /* Neither gen nor kill. */
2992 visited[pred_bb] = 1;
2993 if (expr_reaches_here_p_work (occr, expr, pred_bb, check_self_loop,
2999 /* All paths have been checked. */
3003 /* This wrapper for expr_reaches_here_p_work() is to ensure that any
3004 memory allocated for that function is returned. */
3007 expr_reaches_here_p (occr, expr, bb, check_self_loop)
3011 int check_self_loop;
3014 char * visited = (char *) xcalloc (n_basic_blocks, 1);
3016 rval = expr_reaches_here_p_work(occr, expr, bb, check_self_loop, visited);
3023 /* Return the instruction that computes EXPR that reaches INSN's basic block.
3024 If there is more than one such instruction, return NULL.
3026 Called only by handle_avail_expr. */
3029 computing_insn (expr, insn)
3033 int bb = BLOCK_NUM (insn);
3035 if (expr->avail_occr->next == NULL)
3037 if (BLOCK_NUM (expr->avail_occr->insn) == bb)
3039 /* The available expression is actually itself
3040 (i.e. a loop in the flow graph) so do nothing. */
3043 /* (FIXME) Case that we found a pattern that was created by
3044 a substitution that took place. */
3045 return expr->avail_occr->insn;
3049 /* Pattern is computed more than once.
3050 Search backwards from this insn to see how many of these
3051 computations actually reach this insn. */
3053 rtx insn_computes_expr = NULL;
3056 for (occr = expr->avail_occr; occr != NULL; occr = occr->next)
3058 if (BLOCK_NUM (occr->insn) == bb)
3060 /* The expression is generated in this block.
3061 The only time we care about this is when the expression
3062 is generated later in the block [and thus there's a loop].
3063 We let the normal cse pass handle the other cases. */
3064 if (INSN_CUID (insn) < INSN_CUID (occr->insn))
3066 if (expr_reaches_here_p (occr, expr, bb, 1))
3071 insn_computes_expr = occr->insn;
3075 else /* Computation of the pattern outside this block. */
3077 if (expr_reaches_here_p (occr, expr, bb, 0))
3082 insn_computes_expr = occr->insn;
3087 if (insn_computes_expr == NULL)
3089 return insn_computes_expr;
3093 /* Return non-zero if the definition in DEF_INSN can reach INSN.
3094 Only called by can_disregard_other_sets. */
3097 def_reaches_here_p (insn, def_insn)
3102 if (TEST_BIT (reaching_defs[BLOCK_NUM (insn)], INSN_CUID (def_insn)))
3105 if (BLOCK_NUM (insn) == BLOCK_NUM (def_insn))
3107 if (INSN_CUID (def_insn) < INSN_CUID (insn))
3109 if (GET_CODE (PATTERN (def_insn)) == PARALLEL)
3111 if (GET_CODE (PATTERN (def_insn)) == CLOBBER)
3112 reg = XEXP (PATTERN (def_insn), 0);
3113 else if (GET_CODE (PATTERN (def_insn)) == SET)
3114 reg = SET_DEST (PATTERN (def_insn));
3117 return ! reg_set_between_p (reg, NEXT_INSN (def_insn), insn);
3126 /* Return non-zero if *ADDR_THIS_REG can only have one value at INSN.
3127 The value returned is the number of definitions that reach INSN.
3128 Returning a value of zero means that [maybe] more than one definition
3129 reaches INSN and the caller can't perform whatever optimization it is
3130 trying. i.e. it is always safe to return zero. */
3133 can_disregard_other_sets (addr_this_reg, insn, for_combine)
3134 struct reg_set **addr_this_reg;
3138 int number_of_reaching_defs = 0;
3139 struct reg_set *this_reg = *addr_this_reg;
3143 if (def_reaches_here_p (insn, this_reg->insn))
3145 number_of_reaching_defs++;
3146 /* Ignore parallels for now. */
3147 if (GET_CODE (PATTERN (this_reg->insn)) == PARALLEL)
3150 && (GET_CODE (PATTERN (this_reg->insn)) == CLOBBER
3151 || ! rtx_equal_p (SET_SRC (PATTERN (this_reg->insn)),
3152 SET_SRC (PATTERN (insn)))))
3154 /* A setting of the reg to a different value reaches INSN. */
3157 if (number_of_reaching_defs > 1)
3159 /* If in this setting the value the register is being
3160 set to is equal to the previous value the register
3161 was set to and this setting reaches the insn we are
3162 trying to do the substitution on then we are ok. */
3164 if (GET_CODE (PATTERN (this_reg->insn)) == CLOBBER)
3166 if (! rtx_equal_p (SET_SRC (PATTERN (this_reg->insn)),
3167 SET_SRC (PATTERN (insn))))
3170 *addr_this_reg = this_reg;
3173 /* prev_this_reg = this_reg; */
3174 this_reg = this_reg->next;
3177 return number_of_reaching_defs;
3180 /* Expression computed by insn is available and the substitution is legal,
3181 so try to perform the substitution.
3183 The result is non-zero if any changes were made. */
3186 handle_avail_expr (insn, expr)
3190 rtx pat, insn_computes_expr;
3192 struct reg_set *this_reg;
3193 int found_setting, use_src;
3196 /* We only handle the case where one computation of the expression
3197 reaches this instruction. */
3198 insn_computes_expr = computing_insn (expr, insn);
3199 if (insn_computes_expr == NULL)
3205 /* At this point we know only one computation of EXPR outside of this
3206 block reaches this insn. Now try to find a register that the
3207 expression is computed into. */
3209 if (GET_CODE (SET_SRC (PATTERN (insn_computes_expr))) == REG)
3211 /* This is the case when the available expression that reaches
3212 here has already been handled as an available expression. */
3213 int regnum_for_replacing = REGNO (SET_SRC (PATTERN (insn_computes_expr)));
3214 /* If the register was created by GCSE we can't use `reg_set_table',
3215 however we know it's set only once. */
3216 if (regnum_for_replacing >= max_gcse_regno
3217 /* If the register the expression is computed into is set only once,
3218 or only one set reaches this insn, we can use it. */
3219 || (((this_reg = reg_set_table[regnum_for_replacing]),
3220 this_reg->next == NULL)
3221 || can_disregard_other_sets (&this_reg, insn, 0)))
3230 int regnum_for_replacing = REGNO (SET_DEST (PATTERN (insn_computes_expr)));
3231 /* This shouldn't happen. */
3232 if (regnum_for_replacing >= max_gcse_regno)
3234 this_reg = reg_set_table[regnum_for_replacing];
3235 /* If the register the expression is computed into is set only once,
3236 or only one set reaches this insn, use it. */
3237 if (this_reg->next == NULL
3238 || can_disregard_other_sets (&this_reg, insn, 0))
3244 pat = PATTERN (insn);
3246 to = SET_SRC (PATTERN (insn_computes_expr));
3248 to = SET_DEST (PATTERN (insn_computes_expr));
3249 changed = validate_change (insn, &SET_SRC (pat), to, 0);
3251 /* We should be able to ignore the return code from validate_change but
3252 to play it safe we check. */
3256 if (gcse_file != NULL)
3258 fprintf (gcse_file, "GCSE: Replacing the source in insn %d with reg %d %s insn %d\n",
3259 INSN_UID (insn), REGNO (to),
3260 use_src ? "from" : "set in",
3261 INSN_UID (insn_computes_expr));
3266 /* The register that the expr is computed into is set more than once. */
3267 else if (1 /*expensive_op(this_pattrn->op) && do_expensive_gcse)*/)
3269 /* Insert an insn after insnx that copies the reg set in insnx
3270 into a new pseudo register call this new register REGN.
3271 From insnb until end of basic block or until REGB is set
3272 replace all uses of REGB with REGN. */
3275 to = gen_reg_rtx (GET_MODE (SET_DEST (PATTERN (insn_computes_expr))));
3277 /* Generate the new insn. */
3278 /* ??? If the change fails, we return 0, even though we created
3279 an insn. I think this is ok. */
3281 = emit_insn_after (gen_rtx_SET (VOIDmode, to,
3282 SET_DEST (PATTERN (insn_computes_expr))),
3283 insn_computes_expr);
3284 /* Keep block number table up to date. */
3285 set_block_num (new_insn, BLOCK_NUM (insn_computes_expr));
3286 /* Keep register set table up to date. */
3287 record_one_set (REGNO (to), new_insn);
3289 gcse_create_count++;
3290 if (gcse_file != NULL)
3292 fprintf (gcse_file, "GCSE: Creating insn %d to copy value of reg %d, computed in insn %d,\n",
3293 INSN_UID (NEXT_INSN (insn_computes_expr)),
3294 REGNO (SET_SRC (PATTERN (NEXT_INSN (insn_computes_expr)))),
3295 INSN_UID (insn_computes_expr));
3296 fprintf (gcse_file, " into newly allocated reg %d\n", REGNO (to));
3299 pat = PATTERN (insn);
3301 /* Do register replacement for INSN. */
3302 changed = validate_change (insn, &SET_SRC (pat),
3303 SET_DEST (PATTERN (NEXT_INSN (insn_computes_expr))),
3306 /* We should be able to ignore the return code from validate_change but
3307 to play it safe we check. */
3311 if (gcse_file != NULL)
3313 fprintf (gcse_file, "GCSE: Replacing the source in insn %d with reg %d set in insn %d\n",
3315 REGNO (SET_DEST (PATTERN (NEXT_INSN (insn_computes_expr)))),
3316 INSN_UID (insn_computes_expr));
3325 /* Perform classic GCSE.
3326 This is called by one_classic_gcse_pass after all the dataflow analysis
3329 The result is non-zero if a change was made. */
3337 /* Note we start at block 1. */
3340 for (bb = 1; bb < n_basic_blocks; bb++)
3342 /* Reset tables used to keep track of what's still valid [since the
3343 start of the block]. */
3344 reset_opr_set_tables ();
3346 for (insn = BLOCK_HEAD (bb);
3347 insn != NULL && insn != NEXT_INSN (BLOCK_END (bb));
3348 insn = NEXT_INSN (insn))
3350 /* Is insn of form (set (pseudo-reg) ...)? */
3352 if (GET_CODE (insn) == INSN
3353 && GET_CODE (PATTERN (insn)) == SET
3354 && GET_CODE (SET_DEST (PATTERN (insn))) == REG
3355 && REGNO (SET_DEST (PATTERN (insn))) >= FIRST_PSEUDO_REGISTER)
3357 rtx pat = PATTERN (insn);
3358 rtx src = SET_SRC (pat);
3361 if (want_to_gcse_p (src)
3362 /* Is the expression recorded? */
3363 && ((expr = lookup_expr (src)) != NULL)
3364 /* Is the expression available [at the start of the
3366 && TEST_BIT (ae_in[bb], expr->bitmap_index)
3367 /* Are the operands unchanged since the start of the
3369 && oprs_not_set_p (src, insn))
3370 changed |= handle_avail_expr (insn, expr);
3373 /* Keep track of everything modified by this insn. */
3374 /* ??? Need to be careful w.r.t. mods done to INSN. */
3375 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
3376 mark_oprs_set (insn);
3383 /* Top level routine to perform one classic GCSE pass.
3385 Return non-zero if a change was made. */
3388 one_classic_gcse_pass (pass)
3393 gcse_subst_count = 0;
3394 gcse_create_count = 0;
3396 alloc_expr_hash_table (max_cuid);
3397 alloc_rd_mem (n_basic_blocks, max_cuid);
3398 compute_expr_hash_table ();
3400 dump_hash_table (gcse_file, "Expression", expr_hash_table,
3401 expr_hash_table_size, n_exprs);
3406 alloc_avail_expr_mem (n_basic_blocks, n_exprs);
3408 compute_ae_kill (ae_gen, ae_kill);
3409 compute_available (ae_gen, ae_kill, ae_out, ae_in);
3410 changed = classic_gcse ();
3411 free_avail_expr_mem ();
3414 free_expr_hash_table ();
3418 fprintf (gcse_file, "\n");
3419 fprintf (gcse_file, "GCSE of %s, pass %d: %d bytes needed, %d substs, %d insns created\n",
3420 current_function_name, pass,
3421 bytes_used, gcse_subst_count, gcse_create_count);
3427 /* Compute copy/constant propagation working variables. */
3429 /* Local properties of assignments. */
3431 static sbitmap *cprop_pavloc;
3432 static sbitmap *cprop_absaltered;
3434 /* Global properties of assignments (computed from the local properties). */
3436 static sbitmap *cprop_avin;
3437 static sbitmap *cprop_avout;
3439 /* Allocate vars used for copy/const propagation.
3440 N_BLOCKS is the number of basic blocks.
3441 N_SETS is the number of sets. */
3444 alloc_cprop_mem (n_blocks, n_sets)
3445 int n_blocks, n_sets;
3447 cprop_pavloc = sbitmap_vector_alloc (n_blocks, n_sets);
3448 cprop_absaltered = sbitmap_vector_alloc (n_blocks, n_sets);
3450 cprop_avin = sbitmap_vector_alloc (n_blocks, n_sets);
3451 cprop_avout = sbitmap_vector_alloc (n_blocks, n_sets);
3454 /* Free vars used by copy/const propagation. */
3459 free (cprop_pavloc);
3460 free (cprop_absaltered);
3465 /* For each block, compute whether X is transparent.
3466 X is either an expression or an assignment [though we don't care which,
3467 for this context an assignment is treated as an expression].
3468 For each block where an element of X is modified, set (SET_P == 1) or reset
3469 (SET_P == 0) the INDX bit in BMAP. */
3472 compute_transp (x, indx, bmap, set_p)
3482 /* repeat is used to turn tail-recursion into iteration. */
3488 code = GET_CODE (x);
3494 int regno = REGNO (x);
3498 if (regno < FIRST_PSEUDO_REGISTER)
3500 for (bb = 0; bb < n_basic_blocks; bb++)
3501 if (TEST_BIT (reg_set_in_block[bb], regno))
3502 SET_BIT (bmap[bb], indx);
3506 for (r = reg_set_table[regno]; r != NULL; r = r->next)
3508 bb = BLOCK_NUM (r->insn);
3509 SET_BIT (bmap[bb], indx);
3515 if (regno < FIRST_PSEUDO_REGISTER)
3517 for (bb = 0; bb < n_basic_blocks; bb++)
3518 if (TEST_BIT (reg_set_in_block[bb], regno))
3519 RESET_BIT (bmap[bb], indx);
3523 for (r = reg_set_table[regno]; r != NULL; r = r->next)
3525 bb = BLOCK_NUM (r->insn);
3526 RESET_BIT (bmap[bb], indx);
3536 for (bb = 0; bb < n_basic_blocks; bb++)
3537 if (mem_set_in_block[bb])
3538 SET_BIT (bmap[bb], indx);
3542 for (bb = 0; bb < n_basic_blocks; bb++)
3543 if (mem_set_in_block[bb])
3544 RESET_BIT (bmap[bb], indx);
3564 i = GET_RTX_LENGTH (code) - 1;
3565 fmt = GET_RTX_FORMAT (code);
3570 rtx tem = XEXP (x, i);
3572 /* If we are about to do the last recursive call
3573 needed at this level, change it into iteration.
3574 This function is called enough to be worth it. */
3580 compute_transp (tem, indx, bmap, set_p);
3582 else if (fmt[i] == 'E')
3585 for (j = 0; j < XVECLEN (x, i); j++)
3586 compute_transp (XVECEXP (x, i, j), indx, bmap, set_p);
3591 /* Top level routine to do the dataflow analysis needed by copy/const
3595 compute_cprop_data ()
3597 compute_local_properties (cprop_absaltered, cprop_pavloc, NULL, 1);
3598 compute_available (cprop_pavloc, cprop_absaltered,
3599 cprop_avout, cprop_avin);
3602 /* Copy/constant propagation. */
3604 /* Maximum number of register uses in an insn that we handle. */
3607 /* Table of uses found in an insn.
3608 Allocated statically to avoid alloc/free complexity and overhead. */
3609 static struct reg_use reg_use_table[MAX_USES];
3611 /* Index into `reg_use_table' while building it. */
3612 static int reg_use_count;
3614 /* Set up a list of register numbers used in INSN.
3615 The found uses are stored in `reg_use_table'.
3616 `reg_use_count' is initialized to zero before entry, and
3617 contains the number of uses in the table upon exit.
3619 ??? If a register appears multiple times we will record it multiple
3620 times. This doesn't hurt anything but it will slow things down. */
3630 /* repeat is used to turn tail-recursion into iteration. */
3636 code = GET_CODE (x);
3640 if (reg_use_count == MAX_USES)
3642 reg_use_table[reg_use_count].reg_rtx = x;
3660 case ASM_INPUT: /*FIXME*/
3664 if (GET_CODE (SET_DEST (x)) == MEM)
3665 find_used_regs (SET_DEST (x));
3673 /* Recursively scan the operands of this expression. */
3675 fmt = GET_RTX_FORMAT (code);
3676 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
3680 /* If we are about to do the last recursive call
3681 needed at this level, change it into iteration.
3682 This function is called enough to be worth it. */
3688 find_used_regs (XEXP (x, i));
3690 else if (fmt[i] == 'E')
3693 for (j = 0; j < XVECLEN (x, i); j++)
3694 find_used_regs (XVECEXP (x, i, j));
3699 /* Try to replace all non-SET_DEST occurrences of FROM in INSN with TO.
3700 Returns non-zero is successful. */
3703 try_replace_reg (from, to, insn)
3711 note = find_reg_note (insn, REG_EQUAL, NULL_RTX);
3714 note = find_reg_note (insn, REG_EQUIV, NULL_RTX);
3716 /* If this fails we could try to simplify the result of the
3717 replacement and attempt to recognize the simplified insn.
3719 But we need a general simplify_rtx that doesn't have pass
3720 specific state variables. I'm not aware of one at the moment. */
3723 success = validate_replace_src (from, to, insn);
3724 set = single_set (insn);
3726 /* We've failed to do replacement. Try to add REG_EQUAL note to not loose
3728 if (!success && !note)
3732 note = REG_NOTES (insn) = gen_rtx_EXPR_LIST (REG_EQUAL,
3733 copy_rtx (SET_SRC (set)),
3737 /* Always do the replacement in REQ_EQUAL and REG_EQUIV notes. Also
3738 try to simplify them. */
3742 src = XEXP (note, 0);
3743 replace_rtx (src, from, to);
3745 /* Try to simplify resulting note. */
3746 simplified = simplify_rtx (src);
3750 XEXP (note, 0) = src;
3753 /* REG_EQUAL may get simplified into register.
3754 We don't allow that. Remove that note. This code ought
3755 not to hapen, because previous code ought to syntetize
3756 reg-reg move, but be on the safe side. */
3757 else if (REG_P (src))
3758 remove_note (insn, note);
3762 /* Find a set of REGNO that is available on entry to INSN's block.
3763 Returns NULL if not found. */
3765 static struct expr *
3766 find_avail_set (regno, insn)
3770 /* SET1 contains the last set found that can be returned to the caller for
3771 use in a substitution. */
3772 struct expr *set1 = 0;
3774 /* Loops are not possible here. To get a loop we would need two sets
3775 available at the start of the block containing INSN. ie we would
3776 need two sets like this available at the start of the block:
3778 (set (reg X) (reg Y))
3779 (set (reg Y) (reg X))
3781 This can not happen since the set of (reg Y) would have killed the
3782 set of (reg X) making it unavailable at the start of this block. */
3786 struct expr *set = lookup_set (regno, NULL_RTX);
3788 /* Find a set that is available at the start of the block
3789 which contains INSN. */
3792 if (TEST_BIT (cprop_avin[BLOCK_NUM (insn)], set->bitmap_index))
3794 set = next_set (regno, set);
3797 /* If no available set was found we've reached the end of the
3798 (possibly empty) copy chain. */
3802 if (GET_CODE (set->expr) != SET)
3805 src = SET_SRC (set->expr);
3807 /* We know the set is available.
3808 Now check that SRC is ANTLOC (i.e. none of the source operands
3809 have changed since the start of the block).
3811 If the source operand changed, we may still use it for the next
3812 iteration of this loop, but we may not use it for substitutions. */
3813 if (CONSTANT_P (src) || oprs_not_set_p (src, insn))
3816 /* If the source of the set is anything except a register, then
3817 we have reached the end of the copy chain. */
3818 if (GET_CODE (src) != REG)
3821 /* Follow the copy chain, ie start another iteration of the loop
3822 and see if we have an available copy into SRC. */
3823 regno = REGNO (src);
3826 /* SET1 holds the last set that was available and anticipatable at
3831 /* Subroutine of cprop_insn that tries to propagate constants into
3832 JUMP_INSNS. INSN must be a conditional jump; COPY is a copy of it
3833 that we can use for substitutions.
3834 REG_USED is the use we will try to replace, SRC is the constant we
3835 will try to substitute for it.
3836 Returns nonzero if a change was made. */
3838 cprop_jump (insn, copy, reg_used, src)
3840 struct reg_use *reg_used;
3843 rtx set = PATTERN (copy);
3846 /* Replace the register with the appropriate constant. */
3847 replace_rtx (SET_SRC (set), reg_used->reg_rtx, src);
3849 temp = simplify_ternary_operation (GET_CODE (SET_SRC (set)),
3850 GET_MODE (SET_SRC (set)),
3851 GET_MODE (XEXP (SET_SRC (set), 0)),
3852 XEXP (SET_SRC (set), 0),
3853 XEXP (SET_SRC (set), 1),
3854 XEXP (SET_SRC (set), 2));
3856 /* If no simplification can be made, then try the next
3861 SET_SRC (set) = temp;
3863 /* That may have changed the structure of TEMP, so
3864 force it to be rerecognized if it has not turned
3865 into a nop or unconditional jump. */
3867 INSN_CODE (copy) = -1;
3868 if ((SET_DEST (set) == pc_rtx
3869 && (SET_SRC (set) == pc_rtx
3870 || GET_CODE (SET_SRC (set)) == LABEL_REF))
3871 || recog (PATTERN (copy), copy, NULL) >= 0)
3873 /* This has either become an unconditional jump
3874 or a nop-jump. We'd like to delete nop jumps
3875 here, but doing so confuses gcse. So we just
3876 make the replacement and let later passes
3878 PATTERN (insn) = set;
3879 INSN_CODE (insn) = -1;
3881 /* One less use of the label this insn used to jump to
3882 if we turned this into a NOP jump. */
3883 if (SET_SRC (set) == pc_rtx && JUMP_LABEL (insn) != 0)
3884 --LABEL_NUSES (JUMP_LABEL (insn));
3886 /* If this has turned into an unconditional jump,
3887 then put a barrier after it so that the unreachable
3888 code will be deleted. */
3889 if (GET_CODE (SET_SRC (set)) == LABEL_REF)
3890 emit_barrier_after (insn);
3892 run_jump_opt_after_gcse = 1;
3895 if (gcse_file != NULL)
3897 int regno = REGNO (reg_used->reg_rtx);
3898 fprintf (gcse_file, "CONST-PROP: Replacing reg %d in insn %d with constant ",
3899 regno, INSN_UID (insn));
3900 print_rtl (gcse_file, src);
3901 fprintf (gcse_file, "\n");
3909 /* Subroutine of cprop_insn that tries to propagate constants into
3910 JUMP_INSNS for machines that have CC0. INSN is a single set that
3911 stores into CC0; the insn following it is a conditional jump.
3912 REG_USED is the use we will try to replace, SRC is the constant we
3913 will try to substitute for it.
3914 Returns nonzero if a change was made. */
3916 cprop_cc0_jump (insn, reg_used, src)
3918 struct reg_use *reg_used;
3921 rtx jump = NEXT_INSN (insn);
3922 rtx copy = copy_rtx (jump);
3923 rtx set = PATTERN (copy);
3925 /* We need to copy the source of the cc0 setter, as cprop_jump is going to
3926 substitute into it. */
3927 replace_rtx (SET_SRC (set), cc0_rtx, copy_rtx (SET_SRC (PATTERN (insn))));
3928 if (! cprop_jump (jump, copy, reg_used, src))
3931 /* If we succeeded, delete the cc0 setter. */
3932 PUT_CODE (insn, NOTE);
3933 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
3934 NOTE_SOURCE_FILE (insn) = 0;
3939 /* Perform constant and copy propagation on INSN.
3940 The result is non-zero if a change was made. */
3943 cprop_insn (insn, alter_jumps)
3947 struct reg_use *reg_used;
3951 /* Only propagate into SETs. Note that a conditional jump is a
3952 SET with pc_rtx as the destination. */
3953 if ((GET_CODE (insn) != INSN
3954 && GET_CODE (insn) != JUMP_INSN)
3955 || GET_CODE (PATTERN (insn)) != SET)
3959 find_used_regs (PATTERN (insn));
3961 note = find_reg_note (insn, REG_EQUIV, NULL_RTX);
3963 note = find_reg_note (insn, REG_EQUAL, NULL_RTX);
3965 /* We may win even when propagating constants into notes. */
3967 find_used_regs (XEXP (note, 0));
3969 reg_used = ®_use_table[0];
3970 for ( ; reg_use_count > 0; reg_used++, reg_use_count--)
3974 int regno = REGNO (reg_used->reg_rtx);
3976 /* Ignore registers created by GCSE.
3977 We do this because ... */
3978 if (regno >= max_gcse_regno)
3981 /* If the register has already been set in this block, there's
3982 nothing we can do. */
3983 if (! oprs_not_set_p (reg_used->reg_rtx, insn))
3986 /* Find an assignment that sets reg_used and is available
3987 at the start of the block. */
3988 set = find_avail_set (regno, insn);
3993 /* ??? We might be able to handle PARALLELs. Later. */
3994 if (GET_CODE (pat) != SET)
3996 src = SET_SRC (pat);
3998 /* Constant propagation. */
3999 if (GET_CODE (src) == CONST_INT || GET_CODE (src) == CONST_DOUBLE
4000 || GET_CODE (src) == SYMBOL_REF)
4002 /* Handle normal insns first. */
4003 if (GET_CODE (insn) == INSN
4004 && try_replace_reg (reg_used->reg_rtx, src, insn))
4008 if (gcse_file != NULL)
4010 fprintf (gcse_file, "CONST-PROP: Replacing reg %d in insn %d with constant ",
4011 regno, INSN_UID (insn));
4012 print_rtl (gcse_file, src);
4013 fprintf (gcse_file, "\n");
4016 /* The original insn setting reg_used may or may not now be
4017 deletable. We leave the deletion to flow. */
4020 /* Try to propagate a CONST_INT into a conditional jump.
4021 We're pretty specific about what we will handle in this
4022 code, we can extend this as necessary over time.
4024 Right now the insn in question must look like
4025 (set (pc) (if_then_else ...)) */
4026 else if (alter_jumps
4027 && GET_CODE (insn) == JUMP_INSN
4028 && condjump_p (insn)
4029 && ! simplejump_p (insn))
4030 changed |= cprop_jump (insn, copy_rtx (insn), reg_used, src);
4032 /* Similar code for machines that use a pair of CC0 setter and
4033 conditional jump insn. */
4034 else if (alter_jumps
4035 && GET_CODE (PATTERN (insn)) == SET
4036 && SET_DEST (PATTERN (insn)) == cc0_rtx
4037 && GET_CODE (NEXT_INSN (insn)) == JUMP_INSN
4038 && condjump_p (NEXT_INSN (insn))
4039 && ! simplejump_p (NEXT_INSN (insn)))
4040 changed |= cprop_cc0_jump (insn, reg_used, src);
4043 else if (GET_CODE (src) == REG
4044 && REGNO (src) >= FIRST_PSEUDO_REGISTER
4045 && REGNO (src) != regno)
4047 if (try_replace_reg (reg_used->reg_rtx, src, insn))
4051 if (gcse_file != NULL)
4053 fprintf (gcse_file, "COPY-PROP: Replacing reg %d in insn %d with reg %d\n",
4054 regno, INSN_UID (insn), REGNO (src));
4057 /* The original insn setting reg_used may or may not now be
4058 deletable. We leave the deletion to flow. */
4059 /* FIXME: If it turns out that the insn isn't deletable,
4060 then we may have unnecessarily extended register lifetimes
4061 and made things worse. */
4069 /* Forward propagate copies.
4070 This includes copies and constants.
4071 Return non-zero if a change was made. */
4080 /* Note we start at block 1. */
4083 for (bb = 1; bb < n_basic_blocks; bb++)
4085 /* Reset tables used to keep track of what's still valid [since the
4086 start of the block]. */
4087 reset_opr_set_tables ();
4089 for (insn = BLOCK_HEAD (bb);
4090 insn != NULL && insn != NEXT_INSN (BLOCK_END (bb));
4091 insn = NEXT_INSN (insn))
4093 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
4095 changed |= cprop_insn (insn, alter_jumps);
4097 /* Keep track of everything modified by this insn. */
4098 /* ??? Need to be careful w.r.t. mods done to INSN. Don't
4099 call mark_oprs_set if we turned the insn into a NOTE. */
4100 if (GET_CODE (insn) != NOTE)
4101 mark_oprs_set (insn);
4106 if (gcse_file != NULL)
4107 fprintf (gcse_file, "\n");
4112 /* Perform one copy/constant propagation pass.
4113 F is the first insn in the function.
4114 PASS is the pass count. */
4117 one_cprop_pass (pass, alter_jumps)
4123 const_prop_count = 0;
4124 copy_prop_count = 0;
4126 alloc_set_hash_table (max_cuid);
4127 compute_set_hash_table ();
4129 dump_hash_table (gcse_file, "SET", set_hash_table, set_hash_table_size,
4133 alloc_cprop_mem (n_basic_blocks, n_sets);
4134 compute_cprop_data ();
4135 changed = cprop (alter_jumps);
4138 free_set_hash_table ();
4142 fprintf (gcse_file, "CPROP of %s, pass %d: %d bytes needed, %d const props, %d copy props\n",
4143 current_function_name, pass,
4144 bytes_used, const_prop_count, copy_prop_count);
4145 fprintf (gcse_file, "\n");
4151 /* Compute PRE+LCM working variables. */
4153 /* Local properties of expressions. */
4154 /* Nonzero for expressions that are transparent in the block. */
4155 static sbitmap *transp;
4157 /* Nonzero for expressions that are transparent at the end of the block.
4158 This is only zero for expressions killed by abnormal critical edge
4159 created by a calls. */
4160 static sbitmap *transpout;
4162 /* Nonzero for expressions that are computed (available) in the block. */
4163 static sbitmap *comp;
4165 /* Nonzero for expressions that are locally anticipatable in the block. */
4166 static sbitmap *antloc;
4168 /* Nonzero for expressions where this block is an optimal computation
4170 static sbitmap *pre_optimal;
4172 /* Nonzero for expressions which are redundant in a particular block. */
4173 static sbitmap *pre_redundant;
4175 /* Nonzero for expressions which should be inserted on a specific edge. */
4176 static sbitmap *pre_insert_map;
4178 /* Nonzero for expressions which should be deleted in a specific block. */
4179 static sbitmap *pre_delete_map;
4181 /* Contains the edge_list returned by pre_edge_lcm. */
4182 static struct edge_list *edge_list;
4184 static sbitmap *temp_bitmap;
4186 /* Redundant insns. */
4187 static sbitmap pre_redundant_insns;
4189 /* Allocate vars used for PRE analysis. */
4192 alloc_pre_mem (n_blocks, n_exprs)
4193 int n_blocks, n_exprs;
4195 transp = sbitmap_vector_alloc (n_blocks, n_exprs);
4196 comp = sbitmap_vector_alloc (n_blocks, n_exprs);
4197 antloc = sbitmap_vector_alloc (n_blocks, n_exprs);
4198 temp_bitmap = sbitmap_vector_alloc (n_blocks, n_exprs);
4201 pre_redundant = NULL;
4202 pre_insert_map = NULL;
4203 pre_delete_map = NULL;
4207 transpout = sbitmap_vector_alloc (n_blocks, n_exprs);
4208 ae_kill = sbitmap_vector_alloc (n_blocks, n_exprs);
4209 /* pre_insert and pre_delete are allocated later. */
4212 /* Free vars used for PRE analysis. */
4225 free (pre_redundant);
4227 free (pre_insert_map);
4229 free (pre_delete_map);
4242 transp = comp = antloc = NULL;
4243 pre_optimal = pre_redundant = pre_insert_map = pre_delete_map = NULL;
4244 transpout = ae_in = ae_out = ae_kill = NULL;
4249 /* Top level routine to do the dataflow analysis needed by PRE. */
4254 compute_local_properties (transp, comp, antloc, 0);
4255 compute_transpout ();
4256 sbitmap_vector_zero (ae_kill, n_basic_blocks);
4257 compute_ae_kill (comp, ae_kill);
4258 edge_list = pre_edge_lcm (gcse_file, n_exprs, transp, comp, antloc,
4259 ae_kill, &pre_insert_map, &pre_delete_map);
4265 /* Return non-zero if an occurrence of expression EXPR in OCCR_BB would reach
4268 VISITED is a pointer to a working buffer for tracking which BB's have
4269 been visited. It is NULL for the top-level call.
4271 We treat reaching expressions that go through blocks containing the same
4272 reaching expression as "not reaching". E.g. if EXPR is generated in blocks
4273 2 and 3, INSN is in block 4, and 2->3->4, we treat the expression in block
4274 2 as not reaching. The intent is to improve the probability of finding
4275 only one reaching expression and to reduce register lifetimes by picking
4276 the closest such expression. */
4279 pre_expr_reaches_here_p_work (occr_bb, expr, bb, visited)
4287 for (pred = BASIC_BLOCK (bb)->pred; pred != NULL; pred = pred->pred_next)
4289 int pred_bb = pred->src->index;
4291 if (pred->src == ENTRY_BLOCK_PTR
4292 /* Has predecessor has already been visited? */
4293 || visited[pred_bb])
4295 /* Nothing to do. */
4297 /* Does this predecessor generate this expression? */
4298 else if (TEST_BIT (comp[pred_bb], expr->bitmap_index))
4300 /* Is this the occurrence we're looking for?
4301 Note that there's only one generating occurrence per block
4302 so we just need to check the block number. */
4303 if (occr_bb == pred_bb)
4305 visited[pred_bb] = 1;
4307 /* Ignore this predecessor if it kills the expression. */
4308 else if (! TEST_BIT (transp[pred_bb], expr->bitmap_index))
4309 visited[pred_bb] = 1;
4310 /* Neither gen nor kill. */
4313 visited[pred_bb] = 1;
4314 if (pre_expr_reaches_here_p_work (occr_bb, expr, pred_bb, visited))
4319 /* All paths have been checked. */
4323 /* The wrapper for pre_expr_reaches_here_work that ensures that any
4324 memory allocated for that function is returned. */
4327 pre_expr_reaches_here_p (occr_bb, expr, bb)
4333 char * visited = (char *) xcalloc (n_basic_blocks, 1);
4335 rval = pre_expr_reaches_here_p_work(occr_bb, expr, bb, visited);
4343 /* Given an expr, generate RTL which we can insert at the end of a BB,
4344 or on an edge. Set the block number of any insns generated to
4348 process_insert_insn (expr)
4351 rtx reg = expr->reaching_reg;
4352 rtx pat, copied_expr;
4356 copied_expr = copy_rtx (expr->expr);
4357 emit_move_insn (reg, copied_expr);
4358 first_new_insn = get_insns ();
4359 pat = gen_sequence ();
4365 /* Add EXPR to the end of basic block BB.
4367 This is used by both the PRE and code hoisting.
4369 For PRE, we want to verify that the expr is either transparent
4370 or locally anticipatable in the target block. This check makes
4371 no sense for code hoisting. */
4374 insert_insn_end_bb (expr, bb, pre)
4379 rtx insn = BLOCK_END (bb);
4381 rtx reg = expr->reaching_reg;
4382 int regno = REGNO (reg);
4385 pat = process_insert_insn (expr);
4387 /* If the last insn is a jump, insert EXPR in front [taking care to
4388 handle cc0, etc. properly]. */
4390 if (GET_CODE (insn) == JUMP_INSN)
4396 /* If this is a jump table, then we can't insert stuff here. Since
4397 we know the previous real insn must be the tablejump, we insert
4398 the new instruction just before the tablejump. */
4399 if (GET_CODE (PATTERN (insn)) == ADDR_VEC
4400 || GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC)
4401 insn = prev_real_insn (insn);
4404 /* FIXME: 'twould be nice to call prev_cc0_setter here but it aborts
4405 if cc0 isn't set. */
4406 note = find_reg_note (insn, REG_CC_SETTER, NULL_RTX);
4408 insn = XEXP (note, 0);
4411 rtx maybe_cc0_setter = prev_nonnote_insn (insn);
4412 if (maybe_cc0_setter
4413 && GET_RTX_CLASS (GET_CODE (maybe_cc0_setter)) == 'i'
4414 && sets_cc0_p (PATTERN (maybe_cc0_setter)))
4415 insn = maybe_cc0_setter;
4418 /* FIXME: What if something in cc0/jump uses value set in new insn? */
4419 new_insn = emit_block_insn_before (pat, insn, BASIC_BLOCK (bb));
4421 /* Likewise if the last insn is a call, as will happen in the presence
4422 of exception handling. */
4423 else if (GET_CODE (insn) == CALL_INSN)
4425 HARD_REG_SET parm_regs;
4429 /* Keeping in mind SMALL_REGISTER_CLASSES and parameters in registers,
4430 we search backward and place the instructions before the first
4431 parameter is loaded. Do this for everyone for consistency and a
4432 presumtion that we'll get better code elsewhere as well. */
4434 /* It should always be the case that we can put these instructions
4435 anywhere in the basic block with performing PRE optimizations.
4438 && !TEST_BIT (antloc[bb], expr->bitmap_index)
4439 && !TEST_BIT (transp[bb], expr->bitmap_index))
4442 /* Since different machines initialize their parameter registers
4443 in different orders, assume nothing. Collect the set of all
4444 parameter registers. */
4445 CLEAR_HARD_REG_SET (parm_regs);
4447 for (p = CALL_INSN_FUNCTION_USAGE (insn); p ; p = XEXP (p, 1))
4448 if (GET_CODE (XEXP (p, 0)) == USE
4449 && GET_CODE (XEXP (XEXP (p, 0), 0)) == REG)
4451 int regno = REGNO (XEXP (XEXP (p, 0), 0));
4452 if (regno >= FIRST_PSEUDO_REGISTER)
4454 SET_HARD_REG_BIT (parm_regs, regno);
4458 /* Search backward for the first set of a register in this set. */
4459 while (nparm_regs && BLOCK_HEAD (bb) != insn)
4461 insn = PREV_INSN (insn);
4462 p = single_set (insn);
4463 if (p && GET_CODE (SET_DEST (p)) == REG
4464 && REGNO (SET_DEST (p)) < FIRST_PSEUDO_REGISTER
4465 && TEST_HARD_REG_BIT (parm_regs, REGNO (SET_DEST (p))))
4467 CLEAR_HARD_REG_BIT (parm_regs, REGNO (SET_DEST (p)));
4472 /* If we found all the parameter loads, then we want to insert
4473 before the first parameter load.
4475 If we did not find all the parameter loads, then we might have
4476 stopped on the head of the block, which could be a CODE_LABEL.
4477 If we inserted before the CODE_LABEL, then we would be putting
4478 the insn in the wrong basic block. In that case, put the insn
4479 after the CODE_LABEL. Also, respect NOTE_INSN_BASIC_BLOCK. */
4480 if (GET_CODE (insn) == CODE_LABEL)
4481 insn = NEXT_INSN (insn);
4482 if (GET_CODE (insn) == NOTE
4483 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_BASIC_BLOCK)
4484 insn = NEXT_INSN (insn);
4485 new_insn = emit_block_insn_before (pat, insn, BASIC_BLOCK (bb));
4489 new_insn = emit_insn_after (pat, insn);
4490 BLOCK_END (bb) = new_insn;
4493 /* Keep block number table up to date.
4494 Note, PAT could be a multiple insn sequence, we have to make
4495 sure that each insn in the sequence is handled. */
4496 if (GET_CODE (pat) == SEQUENCE)
4500 for (i = 0; i < XVECLEN (pat, 0); i++)
4502 rtx insn = XVECEXP (pat, 0, i);
4503 set_block_num (insn, bb);
4504 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
4505 add_label_notes (PATTERN (insn), new_insn);
4506 note_stores (PATTERN (insn), record_set_info, insn);
4511 add_label_notes (SET_SRC (pat), new_insn);
4512 set_block_num (new_insn, bb);
4513 /* Keep register set table up to date. */
4514 record_one_set (regno, new_insn);
4517 gcse_create_count++;
4521 fprintf (gcse_file, "PRE/HOIST: end of bb %d, insn %d, copying expression %d to reg %d\n",
4522 bb, INSN_UID (new_insn), expr->bitmap_index, regno);
4526 /* Insert partially redundant expressions on edges in the CFG to make
4527 the expressions fully redundant. */
4530 pre_edge_insert (edge_list, index_map)
4531 struct edge_list *edge_list;
4532 struct expr **index_map;
4534 int e, i, num_edges, set_size, did_insert = 0;
4537 /* Where PRE_INSERT_MAP is nonzero, we add the expression on that edge
4538 if it reaches any of the deleted expressions. */
4540 set_size = pre_insert_map[0]->size;
4541 num_edges = NUM_EDGES (edge_list);
4542 inserted = sbitmap_vector_alloc (num_edges, n_exprs);
4543 sbitmap_vector_zero (inserted, num_edges);
4545 for (e = 0; e < num_edges; e++)
4548 basic_block pred = INDEX_EDGE_PRED_BB (edge_list, e);
4549 int bb = pred->index;
4551 for (i = indx = 0; i < set_size; i++, indx += SBITMAP_ELT_BITS)
4553 SBITMAP_ELT_TYPE insert = pre_insert_map[e]->elms[i];
4556 for (j = indx; insert && j < n_exprs; j++, insert >>= 1)
4558 if ((insert & 1) != 0 && index_map[j]->reaching_reg != NULL_RTX)
4560 struct expr *expr = index_map[j];
4563 /* Now look at each deleted occurence of this expression. */
4564 for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
4566 if (! occr->deleted_p)
4569 /* Insert this expression on this edge if if it would
4570 reach the deleted occurence in BB. */
4571 if (!TEST_BIT (inserted[e], j))
4574 edge eg = INDEX_EDGE (edge_list, e);
4575 /* We can't insert anything on an abnormal
4576 and critical edge, so we insert the
4577 insn at the end of the previous block. There
4578 are several alternatives detailed in
4579 Morgans book P277 (sec 10.5) for handling
4580 this situation. This one is easiest for now. */
4582 if ((eg->flags & EDGE_ABNORMAL) == EDGE_ABNORMAL)
4584 insert_insn_end_bb (index_map[j], bb, 0);
4588 insn = process_insert_insn (index_map[j]);
4589 insert_insn_on_edge (insn, eg);
4594 "PRE/HOIST: edge (%d,%d), copy expression %d\n",
4596 INDEX_EDGE_SUCC_BB (edge_list, e)->index, expr->bitmap_index);
4598 SET_BIT (inserted[e], j);
4600 gcse_create_count++;
4614 /* Copy the result of INSN to REG.
4615 INDX is the expression number. */
4618 pre_insert_copy_insn (expr, insn)
4622 rtx reg = expr->reaching_reg;
4623 int regno = REGNO (reg);
4624 int indx = expr->bitmap_index;
4625 rtx set = single_set (insn);
4627 int bb = BLOCK_NUM (insn);
4631 new_insn = emit_insn_after (gen_rtx_SET (VOIDmode, reg, SET_DEST (set)),
4633 /* Keep block number table up to date. */
4634 set_block_num (new_insn, bb);
4635 /* Keep register set table up to date. */
4636 record_one_set (regno, new_insn);
4637 if (insn == BLOCK_END (bb))
4638 BLOCK_END (bb) = new_insn;
4640 gcse_create_count++;
4644 "PRE: bb %d, insn %d, copy expression %d in insn %d to reg %d\n",
4645 BLOCK_NUM (insn), INSN_UID (new_insn), indx,
4646 INSN_UID (insn), regno);
4649 /* Copy available expressions that reach the redundant expression
4650 to `reaching_reg'. */
4653 pre_insert_copies ()
4657 /* For each available expression in the table, copy the result to
4658 `reaching_reg' if the expression reaches a deleted one.
4660 ??? The current algorithm is rather brute force.
4661 Need to do some profiling. */
4663 for (i = 0; i < expr_hash_table_size; i++)
4667 for (expr = expr_hash_table[i]; expr != NULL; expr = expr->next_same_hash)
4671 /* If the basic block isn't reachable, PPOUT will be TRUE.
4672 However, we don't want to insert a copy here because the
4673 expression may not really be redundant. So only insert
4674 an insn if the expression was deleted.
4675 This test also avoids further processing if the expression
4676 wasn't deleted anywhere. */
4677 if (expr->reaching_reg == NULL)
4680 for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
4684 if (! occr->deleted_p)
4687 for (avail = expr->avail_occr; avail != NULL; avail = avail->next)
4689 rtx insn = avail->insn;
4691 /* No need to handle this one if handled already. */
4692 if (avail->copied_p)
4694 /* Don't handle this one if it's a redundant one. */
4695 if (TEST_BIT (pre_redundant_insns, INSN_CUID (insn)))
4697 /* Or if the expression doesn't reach the deleted one. */
4698 if (! pre_expr_reaches_here_p (BLOCK_NUM (avail->insn), expr,
4699 BLOCK_NUM (occr->insn)))
4702 /* Copy the result of avail to reaching_reg. */
4703 pre_insert_copy_insn (expr, insn);
4704 avail->copied_p = 1;
4711 /* Delete redundant computations.
4712 Deletion is done by changing the insn to copy the `reaching_reg' of
4713 the expression into the result of the SET. It is left to later passes
4714 (cprop, cse2, flow, combine, regmove) to propagate the copy or eliminate it.
4716 Returns non-zero if a change is made. */
4723 /* Compute the expressions which are redundant and need to be replaced by
4724 copies from the reaching reg to the target reg. */
4725 for (bb = 0; bb < n_basic_blocks; bb++)
4726 sbitmap_copy (temp_bitmap[bb], pre_delete_map[bb]);
4729 for (i = 0; i < expr_hash_table_size; i++)
4733 for (expr = expr_hash_table[i]; expr != NULL; expr = expr->next_same_hash)
4736 int indx = expr->bitmap_index;
4738 /* We only need to search antic_occr since we require
4741 for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
4743 rtx insn = occr->insn;
4745 int bb = BLOCK_NUM (insn);
4747 if (TEST_BIT (temp_bitmap[bb], indx))
4749 set = single_set (insn);
4753 /* Create a pseudo-reg to store the result of reaching
4754 expressions into. Get the mode for the new pseudo
4755 from the mode of the original destination pseudo. */
4756 if (expr->reaching_reg == NULL)
4758 = gen_reg_rtx (GET_MODE (SET_DEST (set)));
4760 /* In theory this should never fail since we're creating
4763 However, on the x86 some of the movXX patterns actually
4764 contain clobbers of scratch regs. This may cause the
4765 insn created by validate_change to not match any pattern
4766 and thus cause validate_change to fail. */
4767 if (validate_change (insn, &SET_SRC (set),
4768 expr->reaching_reg, 0))
4770 occr->deleted_p = 1;
4771 SET_BIT (pre_redundant_insns, INSN_CUID (insn));
4779 "PRE: redundant insn %d (expression %d) in bb %d, reaching reg is %d\n",
4780 INSN_UID (insn), indx, bb, REGNO (expr->reaching_reg));
4790 /* Perform GCSE optimizations using PRE.
4791 This is called by one_pre_gcse_pass after all the dataflow analysis
4794 This is based on the original Morel-Renvoise paper Fred Chow's thesis,
4795 and lazy code motion from Knoop, Ruthing and Steffen as described in
4796 Advanced Compiler Design and Implementation.
4798 ??? A new pseudo reg is created to hold the reaching expression.
4799 The nice thing about the classical approach is that it would try to
4800 use an existing reg. If the register can't be adequately optimized
4801 [i.e. we introduce reload problems], one could add a pass here to
4802 propagate the new register through the block.
4804 ??? We don't handle single sets in PARALLELs because we're [currently]
4805 not able to copy the rest of the parallel when we insert copies to create
4806 full redundancies from partial redundancies. However, there's no reason
4807 why we can't handle PARALLELs in the cases where there are no partial
4815 struct expr **index_map;
4817 /* Compute a mapping from expression number (`bitmap_index') to
4818 hash table entry. */
4820 index_map = (struct expr **) xcalloc (n_exprs, sizeof (struct expr *));
4821 for (i = 0; i < expr_hash_table_size; i++)
4825 for (expr = expr_hash_table[i]; expr != NULL; expr = expr->next_same_hash)
4826 index_map[expr->bitmap_index] = expr;
4829 /* Reset bitmap used to track which insns are redundant. */
4830 pre_redundant_insns = sbitmap_alloc (max_cuid);
4831 sbitmap_zero (pre_redundant_insns);
4833 /* Delete the redundant insns first so that
4834 - we know what register to use for the new insns and for the other
4835 ones with reaching expressions
4836 - we know which insns are redundant when we go to create copies */
4837 changed = pre_delete ();
4839 did_insert = pre_edge_insert (edge_list, index_map);
4840 /* In other places with reaching expressions, copy the expression to the
4841 specially allocated pseudo-reg that reaches the redundant expr. */
4842 pre_insert_copies ();
4845 commit_edge_insertions ();
4850 free (pre_redundant_insns);
4855 /* Top level routine to perform one PRE GCSE pass.
4857 Return non-zero if a change was made. */
4860 one_pre_gcse_pass (pass)
4865 gcse_subst_count = 0;
4866 gcse_create_count = 0;
4868 alloc_expr_hash_table (max_cuid);
4869 add_noreturn_fake_exit_edges ();
4870 compute_expr_hash_table ();
4872 dump_hash_table (gcse_file, "Expression", expr_hash_table,
4873 expr_hash_table_size, n_exprs);
4876 alloc_pre_mem (n_basic_blocks, n_exprs);
4877 compute_pre_data ();
4878 changed |= pre_gcse ();
4879 free_edge_list (edge_list);
4882 remove_fake_edges ();
4883 free_expr_hash_table ();
4887 fprintf (gcse_file, "\n");
4888 fprintf (gcse_file, "PRE GCSE of %s, pass %d: %d bytes needed, %d substs, %d insns created\n",
4889 current_function_name, pass,
4890 bytes_used, gcse_subst_count, gcse_create_count);
4896 /* If X contains any LABEL_REF's, add REG_LABEL notes for them to INSN.
4897 We have to add REG_LABEL notes, because the following loop optimization
4898 pass requires them. */
4900 /* ??? This is very similar to the loop.c add_label_notes function. We
4901 could probably share code here. */
4903 /* ??? If there was a jump optimization pass after gcse and before loop,
4904 then we would not need to do this here, because jump would add the
4905 necessary REG_LABEL notes. */
4908 add_label_notes (x, insn)
4912 enum rtx_code code = GET_CODE (x);
4916 if (code == LABEL_REF && !LABEL_REF_NONLOCAL_P (x))
4918 /* This code used to ignore labels that referred to dispatch tables to
4919 avoid flow generating (slighly) worse code.
4921 We no longer ignore such label references (see LABEL_REF handling in
4922 mark_jump_label for additional information). */
4923 REG_NOTES (insn) = gen_rtx_EXPR_LIST (REG_LABEL, XEXP (x, 0),
4928 fmt = GET_RTX_FORMAT (code);
4929 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
4932 add_label_notes (XEXP (x, i), insn);
4933 else if (fmt[i] == 'E')
4934 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
4935 add_label_notes (XVECEXP (x, i, j), insn);
4939 /* Compute transparent outgoing information for each block.
4941 An expression is transparent to an edge unless it is killed by
4942 the edge itself. This can only happen with abnormal control flow,
4943 when the edge is traversed through a call. This happens with
4944 non-local labels and exceptions.
4946 This would not be necessary if we split the edge. While this is
4947 normally impossible for abnormal critical edges, with some effort
4948 it should be possible with exception handling, since we still have
4949 control over which handler should be invoked. But due to increased
4950 EH table sizes, this may not be worthwhile. */
4953 compute_transpout ()
4957 sbitmap_vector_ones (transpout, n_basic_blocks);
4959 for (bb = 0; bb < n_basic_blocks; ++bb)
4963 /* Note that flow inserted a nop a the end of basic blocks that
4964 end in call instructions for reasons other than abnormal
4966 if (GET_CODE (BLOCK_END (bb)) != CALL_INSN)
4969 for (i = 0; i < expr_hash_table_size; i++)
4972 for (expr = expr_hash_table[i]; expr ; expr = expr->next_same_hash)
4973 if (GET_CODE (expr->expr) == MEM)
4975 rtx addr = XEXP (expr->expr, 0);
4977 if (GET_CODE (addr) == SYMBOL_REF
4978 && CONSTANT_POOL_ADDRESS_P (addr))
4981 /* ??? Optimally, we would use interprocedural alias
4982 analysis to determine if this mem is actually killed
4984 RESET_BIT (transpout[bb], expr->bitmap_index);
4990 /* Removal of useless null pointer checks */
4992 /* Called via note_stores. X is set by SETTER. If X is a register we must
4993 invalidate nonnull_local and set nonnull_killed. DATA is really a
4994 `null_pointer_info *'.
4996 We ignore hard registers. */
4998 invalidate_nonnull_info (x, setter, data)
5000 rtx setter ATTRIBUTE_UNUSED;
5004 struct null_pointer_info* npi = (struct null_pointer_info *) data;
5007 while (GET_CODE (x) == SUBREG)
5010 /* Ignore anything that is not a register or is a hard register. */
5011 if (GET_CODE (x) != REG
5012 || REGNO (x) < npi->min_reg
5013 || REGNO (x) >= npi->max_reg)
5016 regno = REGNO (x) - npi->min_reg;
5018 RESET_BIT (npi->nonnull_local[npi->current_block], regno);
5019 SET_BIT (npi->nonnull_killed[npi->current_block], regno);
5022 /* Do null-pointer check elimination for the registers indicated in
5023 NPI. NONNULL_AVIN and NONNULL_AVOUT are pre-allocated sbitmaps;
5024 they are not our responsibility to free. */
5027 delete_null_pointer_checks_1 (block_reg, nonnull_avin, nonnull_avout, npi)
5029 sbitmap *nonnull_avin;
5030 sbitmap *nonnull_avout;
5031 struct null_pointer_info *npi;
5035 sbitmap *nonnull_local = npi->nonnull_local;
5036 sbitmap *nonnull_killed = npi->nonnull_killed;
5038 /* Compute local properties, nonnull and killed. A register will have
5039 the nonnull property if at the end of the current block its value is
5040 known to be nonnull. The killed property indicates that somewhere in
5041 the block any information we had about the register is killed.
5043 Note that a register can have both properties in a single block. That
5044 indicates that it's killed, then later in the block a new value is
5046 sbitmap_vector_zero (nonnull_local, n_basic_blocks);
5047 sbitmap_vector_zero (nonnull_killed, n_basic_blocks);
5048 for (current_block = 0; current_block < n_basic_blocks; current_block++)
5050 rtx insn, stop_insn;
5052 /* Set the current block for invalidate_nonnull_info. */
5053 npi->current_block = current_block;
5055 /* Scan each insn in the basic block looking for memory references and
5057 stop_insn = NEXT_INSN (BLOCK_END (current_block));
5058 for (insn = BLOCK_HEAD (current_block);
5060 insn = NEXT_INSN (insn))
5065 /* Ignore anything that is not a normal insn. */
5066 if (GET_RTX_CLASS (GET_CODE (insn)) != 'i')
5069 /* Basically ignore anything that is not a simple SET. We do have
5070 to make sure to invalidate nonnull_local and set nonnull_killed
5071 for such insns though. */
5072 set = single_set (insn);
5075 note_stores (PATTERN (insn), invalidate_nonnull_info, npi);
5079 /* See if we've got a useable memory load. We handle it first
5080 in case it uses its address register as a dest (which kills
5081 the nonnull property). */
5082 if (GET_CODE (SET_SRC (set)) == MEM
5083 && GET_CODE ((reg = XEXP (SET_SRC (set), 0))) == REG
5084 && REGNO (reg) >= npi->min_reg
5085 && REGNO (reg) < npi->max_reg)
5086 SET_BIT (nonnull_local[current_block],
5087 REGNO (reg) - npi->min_reg);
5089 /* Now invalidate stuff clobbered by this insn. */
5090 note_stores (PATTERN (insn), invalidate_nonnull_info, npi);
5092 /* And handle stores, we do these last since any sets in INSN can
5093 not kill the nonnull property if it is derived from a MEM
5094 appearing in a SET_DEST. */
5095 if (GET_CODE (SET_DEST (set)) == MEM
5096 && GET_CODE ((reg = XEXP (SET_DEST (set), 0))) == REG
5097 && REGNO (reg) >= npi->min_reg
5098 && REGNO (reg) < npi->max_reg)
5099 SET_BIT (nonnull_local[current_block],
5100 REGNO (reg) - npi->min_reg);
5104 /* Now compute global properties based on the local properties. This
5105 is a classic global availablity algorithm. */
5106 compute_available (nonnull_local, nonnull_killed,
5107 nonnull_avout, nonnull_avin);
5109 /* Now look at each bb and see if it ends with a compare of a value
5111 for (bb = 0; bb < n_basic_blocks; bb++)
5113 rtx last_insn = BLOCK_END (bb);
5114 rtx condition, earliest;
5115 int compare_and_branch;
5117 /* Since MIN_REG is always at least FIRST_PSEUDO_REGISTER, and
5118 since BLOCK_REG[BB] is zero if this block did not end with a
5119 comparison against zero, this condition works. */
5120 if (block_reg[bb] < npi->min_reg
5121 || block_reg[bb] >= npi->max_reg)
5124 /* LAST_INSN is a conditional jump. Get its condition. */
5125 condition = get_condition (last_insn, &earliest);
5127 /* If we can't determine the condition then skip. */
5131 /* Is the register known to have a nonzero value? */
5132 if (!TEST_BIT (nonnull_avout[bb], block_reg[bb] - npi->min_reg))
5135 /* Try to compute whether the compare/branch at the loop end is one or
5136 two instructions. */
5137 if (earliest == last_insn)
5138 compare_and_branch = 1;
5139 else if (earliest == prev_nonnote_insn (last_insn))
5140 compare_and_branch = 2;
5144 /* We know the register in this comparison is nonnull at exit from
5145 this block. We can optimize this comparison. */
5146 if (GET_CODE (condition) == NE)
5150 new_jump = emit_jump_insn_before (gen_jump (JUMP_LABEL (last_insn)),
5152 JUMP_LABEL (new_jump) = JUMP_LABEL (last_insn);
5153 LABEL_NUSES (JUMP_LABEL (new_jump))++;
5154 emit_barrier_after (new_jump);
5156 delete_insn (last_insn);
5157 if (compare_and_branch == 2)
5158 delete_insn (earliest);
5160 /* Don't check this block again. (Note that BLOCK_END is
5161 invalid here; we deleted the last instruction in the
5167 /* Find EQ/NE comparisons against zero which can be (indirectly) evaluated
5170 This is conceptually similar to global constant/copy propagation and
5171 classic global CSE (it even uses the same dataflow equations as cprop).
5173 If a register is used as memory address with the form (mem (reg)), then we
5174 know that REG can not be zero at that point in the program. Any instruction
5175 which sets REG "kills" this property.
5177 So, if every path leading to a conditional branch has an available memory
5178 reference of that form, then we know the register can not have the value
5179 zero at the conditional branch.
5181 So we merely need to compute the local properies and propagate that data
5182 around the cfg, then optimize where possible.
5184 We run this pass two times. Once before CSE, then again after CSE. This
5185 has proven to be the most profitable approach. It is rare for new
5186 optimization opportunities of this nature to appear after the first CSE
5189 This could probably be integrated with global cprop with a little work. */
5192 delete_null_pointer_checks (f)
5195 sbitmap *nonnull_avin, *nonnull_avout;
5201 struct null_pointer_info npi;
5203 /* First break the program into basic blocks. */
5204 find_basic_blocks (f, max_reg_num (), NULL, 1);
5206 /* If we have only a single block, then there's nothing to do. */
5207 if (n_basic_blocks <= 1)
5209 /* Free storage allocated by find_basic_blocks. */
5210 free_basic_block_vars (0);
5214 /* Trying to perform global optimizations on flow graphs which have
5215 a high connectivity will take a long time and is unlikely to be
5216 particularly useful.
5218 In normal circumstances a cfg should have about twice has many edges
5219 as blocks. But we do not want to punish small functions which have
5220 a couple switch statements. So we require a relatively large number
5221 of basic blocks and the ratio of edges to blocks to be high. */
5222 if (n_basic_blocks > 1000 && n_edges / n_basic_blocks >= 20)
5224 /* Free storage allocated by find_basic_blocks. */
5225 free_basic_block_vars (0);
5229 /* We need four bitmaps, each with a bit for each register in each
5231 max_reg = max_reg_num ();
5232 regs_per_pass = get_bitmap_width (4, n_basic_blocks, max_reg);
5234 /* Allocate bitmaps to hold local and global properties. */
5235 npi.nonnull_local = sbitmap_vector_alloc (n_basic_blocks, regs_per_pass);
5236 npi.nonnull_killed = sbitmap_vector_alloc (n_basic_blocks, regs_per_pass);
5237 nonnull_avin = sbitmap_vector_alloc (n_basic_blocks, regs_per_pass);
5238 nonnull_avout = sbitmap_vector_alloc (n_basic_blocks, regs_per_pass);
5240 /* Go through the basic blocks, seeing whether or not each block
5241 ends with a conditional branch whose condition is a comparison
5242 against zero. Record the register compared in BLOCK_REG. */
5243 block_reg = (int *) xcalloc (n_basic_blocks, sizeof (int));
5244 for (bb = 0; bb < n_basic_blocks; bb++)
5246 rtx last_insn = BLOCK_END (bb);
5247 rtx condition, earliest, reg;
5249 /* We only want conditional branches. */
5250 if (GET_CODE (last_insn) != JUMP_INSN
5251 || !condjump_p (last_insn)
5252 || simplejump_p (last_insn))
5255 /* LAST_INSN is a conditional jump. Get its condition. */
5256 condition = get_condition (last_insn, &earliest);
5258 /* If we were unable to get the condition, or it is not a equality
5259 comparison against zero then there's nothing we can do. */
5261 || (GET_CODE (condition) != NE && GET_CODE (condition) != EQ)
5262 || GET_CODE (XEXP (condition, 1)) != CONST_INT
5263 || (XEXP (condition, 1)
5264 != CONST0_RTX (GET_MODE (XEXP (condition, 0)))))
5267 /* We must be checking a register against zero. */
5268 reg = XEXP (condition, 0);
5269 if (GET_CODE (reg) != REG)
5272 block_reg[bb] = REGNO (reg);
5275 /* Go through the algorithm for each block of registers. */
5276 for (reg = FIRST_PSEUDO_REGISTER; reg < max_reg; reg += regs_per_pass)
5279 npi.max_reg = MIN (reg + regs_per_pass, max_reg);
5280 delete_null_pointer_checks_1 (block_reg, nonnull_avin,
5281 nonnull_avout, &npi);
5284 /* Free storage allocated by find_basic_blocks. */
5285 free_basic_block_vars (0);
5287 /* Free the table of registers compared at the end of every block. */
5291 free (npi.nonnull_local);
5292 free (npi.nonnull_killed);
5293 free (nonnull_avin);
5294 free (nonnull_avout);
5297 /* Code Hoisting variables and subroutines. */
5299 /* Very busy expressions. */
5300 static sbitmap *hoist_vbein;
5301 static sbitmap *hoist_vbeout;
5303 /* Hoistable expressions. */
5304 static sbitmap *hoist_exprs;
5306 /* Dominator bitmaps. */
5307 static sbitmap *dominators;
5309 /* ??? We could compute post dominators and run this algorithm in
5310 reverse to to perform tail merging, doing so would probably be
5311 more effective than the tail merging code in jump.c.
5313 It's unclear if tail merging could be run in parallel with
5314 code hoisting. It would be nice. */
5316 /* Allocate vars used for code hoisting analysis. */
5319 alloc_code_hoist_mem (n_blocks, n_exprs)
5320 int n_blocks, n_exprs;
5322 antloc = sbitmap_vector_alloc (n_blocks, n_exprs);
5323 transp = sbitmap_vector_alloc (n_blocks, n_exprs);
5324 comp = sbitmap_vector_alloc (n_blocks, n_exprs);
5326 hoist_vbein = sbitmap_vector_alloc (n_blocks, n_exprs);
5327 hoist_vbeout = sbitmap_vector_alloc (n_blocks, n_exprs);
5328 hoist_exprs = sbitmap_vector_alloc (n_blocks, n_exprs);
5329 transpout = sbitmap_vector_alloc (n_blocks, n_exprs);
5331 dominators = sbitmap_vector_alloc (n_blocks, n_blocks);
5334 /* Free vars used for code hoisting analysis. */
5337 free_code_hoist_mem ()
5344 free (hoist_vbeout);
5351 /* Compute the very busy expressions at entry/exit from each block.
5353 An expression is very busy if all paths from a given point
5354 compute the expression. */
5357 compute_code_hoist_vbeinout ()
5359 int bb, changed, passes;
5361 sbitmap_vector_zero (hoist_vbeout, n_basic_blocks);
5362 sbitmap_vector_zero (hoist_vbein, n_basic_blocks);
5369 /* We scan the blocks in the reverse order to speed up
5371 for (bb = n_basic_blocks - 1; bb >= 0; bb--)
5373 changed |= sbitmap_a_or_b_and_c (hoist_vbein[bb], antloc[bb],
5374 hoist_vbeout[bb], transp[bb]);
5375 if (bb != n_basic_blocks - 1)
5376 sbitmap_intersection_of_succs (hoist_vbeout[bb], hoist_vbein, bb);
5382 fprintf (gcse_file, "hoisting vbeinout computation: %d passes\n", passes);
5385 /* Top level routine to do the dataflow analysis needed by code hoisting. */
5388 compute_code_hoist_data ()
5390 compute_local_properties (transp, comp, antloc, 0);
5391 compute_transpout ();
5392 compute_code_hoist_vbeinout ();
5393 compute_flow_dominators (dominators, NULL);
5395 fprintf (gcse_file, "\n");
5398 /* Determine if the expression identified by EXPR_INDEX would
5399 reach BB unimpared if it was placed at the end of EXPR_BB.
5401 It's unclear exactly what Muchnick meant by "unimpared". It seems
5402 to me that the expression must either be computed or transparent in
5403 *every* block in the path(s) from EXPR_BB to BB. Any other definition
5404 would allow the expression to be hoisted out of loops, even if
5405 the expression wasn't a loop invariant.
5407 Contrast this to reachability for PRE where an expression is
5408 considered reachable if *any* path reaches instead of *all*
5412 hoist_expr_reaches_here_p (expr_bb, expr_index, bb, visited)
5419 int visited_allocated_locally = 0;
5422 if (visited == NULL)
5424 visited_allocated_locally = 1;
5425 visited = xcalloc (n_basic_blocks, 1);
5428 visited[expr_bb] = 1;
5429 for (pred = BASIC_BLOCK (bb)->pred; pred != NULL; pred = pred->pred_next)
5431 int pred_bb = pred->src->index;
5433 if (pred->src == ENTRY_BLOCK_PTR)
5435 else if (visited[pred_bb])
5437 /* Does this predecessor generate this expression? */
5438 else if (TEST_BIT (comp[pred_bb], expr_index))
5440 else if (! TEST_BIT (transp[pred_bb], expr_index))
5445 visited[pred_bb] = 1;
5446 if (! hoist_expr_reaches_here_p (expr_bb, expr_index,
5451 if (visited_allocated_locally)
5453 return (pred == NULL);
5456 /* Actually perform code hoisting. */
5460 int bb, dominated, i;
5461 struct expr **index_map;
5463 sbitmap_vector_zero (hoist_exprs, n_basic_blocks);
5465 /* Compute a mapping from expression number (`bitmap_index') to
5466 hash table entry. */
5468 index_map = (struct expr **) xcalloc (n_exprs, sizeof (struct expr *));
5469 for (i = 0; i < expr_hash_table_size; i++)
5473 for (expr = expr_hash_table[i]; expr != NULL; expr = expr->next_same_hash)
5474 index_map[expr->bitmap_index] = expr;
5477 /* Walk over each basic block looking for potentially hoistable
5478 expressions, nothing gets hoisted from the entry block. */
5479 for (bb = 0; bb < n_basic_blocks; bb++)
5482 int insn_inserted_p;
5484 /* Examine each expression that is very busy at the exit of this
5485 block. These are the potentially hoistable expressions. */
5486 for (i = 0; i < hoist_vbeout[bb]->n_bits; i++)
5489 if (TEST_BIT (hoist_vbeout[bb], i)
5490 && TEST_BIT (transpout[bb], i))
5492 /* We've found a potentially hoistable expression, now
5493 we look at every block BB dominates to see if it
5494 computes the expression. */
5495 for (dominated = 0; dominated < n_basic_blocks; dominated++)
5497 /* Ignore self dominance. */
5499 || ! TEST_BIT (dominators[dominated], bb))
5502 /* We've found a dominated block, now see if it computes
5503 the busy expression and whether or not moving that
5504 expression to the "beginning" of that block is safe. */
5505 if (!TEST_BIT (antloc[dominated], i))
5508 /* Note if the expression would reach the dominated block
5509 unimpared if it was placed at the end of BB.
5511 Keep track of how many times this expression is hoistable
5512 from a dominated block into BB. */
5513 if (hoist_expr_reaches_here_p (bb, i, dominated, NULL))
5517 /* If we found more than one hoistable occurence of this
5518 expression, then note it in the bitmap of expressions to
5519 hoist. It makes no sense to hoist things which are computed
5520 in only one BB, and doing so tends to pessimize register
5521 allocation. One could increase this value to try harder
5522 to avoid any possible code expansion due to register
5523 allocation issues; however experiments have shown that
5524 the vast majority of hoistable expressions are only movable
5525 from two successors, so raising this threshhold is likely
5526 to nullify any benefit we get from code hoisting. */
5529 SET_BIT (hoist_exprs[bb], i);
5535 /* If we found nothing to hoist, then quit now. */
5539 /* Loop over all the hoistable expressions. */
5540 for (i = 0; i < hoist_exprs[bb]->n_bits; i++)
5542 /* We want to insert the expression into BB only once, so
5543 note when we've inserted it. */
5544 insn_inserted_p = 0;
5546 /* These tests should be the same as the tests above. */
5547 if (TEST_BIT (hoist_vbeout[bb], i))
5549 /* We've found a potentially hoistable expression, now
5550 we look at every block BB dominates to see if it
5551 computes the expression. */
5552 for (dominated = 0; dominated < n_basic_blocks; dominated++)
5554 /* Ignore self dominance. */
5556 || ! TEST_BIT (dominators[dominated], bb))
5559 /* We've found a dominated block, now see if it computes
5560 the busy expression and whether or not moving that
5561 expression to the "beginning" of that block is safe. */
5562 if (!TEST_BIT (antloc[dominated], i))
5565 /* The expression is computed in the dominated block and
5566 it would be safe to compute it at the start of the
5567 dominated block. Now we have to determine if the
5568 expresion would reach the dominated block if it was
5569 placed at the end of BB. */
5570 if (hoist_expr_reaches_here_p (bb, i, dominated, NULL))
5572 struct expr *expr = index_map[i];
5573 struct occr *occr = expr->antic_occr;
5578 /* Find the right occurence of this expression. */
5579 while (BLOCK_NUM (occr->insn) != dominated && occr)
5582 /* Should never happen. */
5588 set = single_set (insn);
5592 /* Create a pseudo-reg to store the result of reaching
5593 expressions into. Get the mode for the new pseudo
5594 from the mode of the original destination pseudo. */
5595 if (expr->reaching_reg == NULL)
5597 = gen_reg_rtx (GET_MODE (SET_DEST (set)));
5599 /* In theory this should never fail since we're creating
5602 However, on the x86 some of the movXX patterns actually
5603 contain clobbers of scratch regs. This may cause the
5604 insn created by validate_change to not match any
5605 pattern and thus cause validate_change to fail. */
5606 if (validate_change (insn, &SET_SRC (set),
5607 expr->reaching_reg, 0))
5609 occr->deleted_p = 1;
5610 if (!insn_inserted_p)
5612 insert_insn_end_bb (index_map[i], bb, 0);
5613 insn_inserted_p = 1;
5624 /* Top level routine to perform one code hoisting (aka unification) pass
5626 Return non-zero if a change was made. */
5629 one_code_hoisting_pass ()
5633 alloc_expr_hash_table (max_cuid);
5634 compute_expr_hash_table ();
5636 dump_hash_table (gcse_file, "Code Hosting Expressions", expr_hash_table,
5637 expr_hash_table_size, n_exprs);
5640 alloc_code_hoist_mem (n_basic_blocks, n_exprs);
5641 compute_code_hoist_data ();
5643 free_code_hoist_mem ();
5645 free_expr_hash_table ();