1 /* Global common subexpression elimination/Partial redundancy elimination
2 and global constant/copy propagation for GNU compiler.
3 Copyright (C) 1997, 1998, 1999 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 PROTO ((void));
528 static char *gmalloc PROTO ((unsigned int));
529 static char *grealloc PROTO ((char *, unsigned int));
530 static char *gcse_alloc PROTO ((unsigned long));
531 static void alloc_gcse_mem PROTO ((rtx));
532 static void free_gcse_mem PROTO ((void));
533 static void alloc_reg_set_mem PROTO ((int));
534 static void free_reg_set_mem PROTO ((void));
535 static int get_bitmap_width PROTO ((int, int, int));
536 static void record_one_set PROTO ((int, rtx));
537 static void record_set_info PROTO ((rtx, rtx, void *));
538 static void compute_sets PROTO ((rtx));
540 static void hash_scan_insn PROTO ((rtx, int, int));
541 static void hash_scan_set PROTO ((rtx, rtx, int));
542 static void hash_scan_clobber PROTO ((rtx, rtx));
543 static void hash_scan_call PROTO ((rtx, rtx));
544 static int want_to_gcse_p PROTO ((rtx));
545 static int oprs_unchanged_p PROTO ((rtx, rtx, int));
546 static int oprs_anticipatable_p PROTO ((rtx, rtx));
547 static int oprs_available_p PROTO ((rtx, rtx));
548 static void insert_expr_in_table PROTO ((rtx, enum machine_mode,
550 static void insert_set_in_table PROTO ((rtx, rtx));
551 static unsigned int hash_expr PROTO ((rtx, enum machine_mode,
553 static unsigned int hash_expr_1 PROTO ((rtx, enum machine_mode, int *));
554 static unsigned int hash_set PROTO ((int, int));
555 static int expr_equiv_p PROTO ((rtx, rtx));
556 static void record_last_reg_set_info PROTO ((rtx, int));
557 static void record_last_mem_set_info PROTO ((rtx));
558 static void record_last_set_info PROTO ((rtx, rtx, void *));
559 static void compute_hash_table PROTO ((int));
560 static void alloc_set_hash_table PROTO ((int));
561 static void free_set_hash_table PROTO ((void));
562 static void compute_set_hash_table PROTO ((void));
563 static void alloc_expr_hash_table PROTO ((int));
564 static void free_expr_hash_table PROTO ((void));
565 static void compute_expr_hash_table PROTO ((void));
566 static void dump_hash_table PROTO ((FILE *, const char *, struct expr **,
568 static struct expr *lookup_expr PROTO ((rtx));
569 static struct expr *lookup_set PROTO ((int, rtx));
570 static struct expr *next_set PROTO ((int, struct expr *));
571 static void reset_opr_set_tables PROTO ((void));
572 static int oprs_not_set_p PROTO ((rtx, rtx));
573 static void mark_call PROTO ((rtx));
574 static void mark_set PROTO ((rtx, rtx));
575 static void mark_clobber PROTO ((rtx, rtx));
576 static void mark_oprs_set PROTO ((rtx));
578 static void alloc_cprop_mem PROTO ((int, int));
579 static void free_cprop_mem PROTO ((void));
580 static void compute_transp PROTO ((rtx, int, sbitmap *, int));
581 static void compute_transpout PROTO ((void));
582 static void compute_local_properties PROTO ((sbitmap *, sbitmap *,
584 static void compute_cprop_data PROTO ((void));
585 static void find_used_regs PROTO ((rtx));
586 static int try_replace_reg PROTO ((rtx, rtx, rtx));
587 static struct expr *find_avail_set PROTO ((int, rtx));
588 static int cprop_jump PROTO((rtx, rtx, struct reg_use *, rtx));
590 static int cprop_cc0_jump PROTO((rtx, struct reg_use *, rtx));
592 static int cprop_insn PROTO ((rtx, int));
593 static int cprop PROTO ((int));
594 static int one_cprop_pass PROTO ((int, int));
596 static void alloc_pre_mem PROTO ((int, int));
597 static void free_pre_mem PROTO ((void));
598 static void compute_pre_data PROTO ((void));
599 static int pre_expr_reaches_here_p PROTO ((int, struct expr *,
601 static void insert_insn_end_bb PROTO ((struct expr *, int, int));
602 static void pre_insert_copy_insn PROTO ((struct expr *, rtx));
603 static void pre_insert_copies PROTO ((void));
604 static int pre_delete PROTO ((void));
605 static int pre_gcse PROTO ((void));
606 static int one_pre_gcse_pass PROTO ((int));
608 static void add_label_notes PROTO ((rtx, rtx));
610 static void alloc_code_hoist_mem PROTO ((int, int));
611 static void free_code_hoist_mem PROTO ((void));
612 static void compute_code_hoist_vbeinout PROTO ((void));
613 static void compute_code_hoist_data PROTO ((void));
614 static int hoist_expr_reaches_here_p PROTO ((int, int, int, char *));
615 static void hoist_code PROTO ((void));
616 static int one_code_hoisting_pass PROTO ((void));
618 static void alloc_rd_mem PROTO ((int, int));
619 static void free_rd_mem PROTO ((void));
620 static void handle_rd_kill_set PROTO ((rtx, int, int));
621 static void compute_kill_rd PROTO ((void));
622 static void compute_rd PROTO ((void));
623 static void alloc_avail_expr_mem PROTO ((int, int));
624 static void free_avail_expr_mem PROTO ((void));
625 static void compute_ae_gen PROTO ((void));
626 static int expr_killed_p PROTO ((rtx, int));
627 static void compute_ae_kill PROTO ((sbitmap *, sbitmap *));
628 static int expr_reaches_here_p PROTO ((struct occr *, struct expr *,
630 static rtx computing_insn PROTO ((struct expr *, rtx));
631 static int def_reaches_here_p PROTO ((rtx, rtx));
632 static int can_disregard_other_sets PROTO ((struct reg_set **, rtx, int));
633 static int handle_avail_expr PROTO ((rtx, struct expr *));
634 static int classic_gcse PROTO ((void));
635 static int one_classic_gcse_pass PROTO ((int));
636 static void invalidate_nonnull_info PROTO ((rtx, rtx, void *));
637 static void delete_null_pointer_checks_1 PROTO ((int_list_ptr *, int *,
638 sbitmap *, sbitmap *,
639 struct null_pointer_info *));
640 static rtx process_insert_insn PROTO ((struct expr *));
641 static int pre_edge_insert PROTO ((struct edge_list *, struct expr **));
642 static int expr_reaches_here_p_work PROTO ((struct occr *, struct expr *, int, int, char *));
643 static int pre_expr_reaches_here_p_work PROTO ((int, struct expr *, int, int, char *));
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 used to record predecessor/successor data. */
819 /* Free storage allocated by find_basic_blocks. */
820 free_basic_block_vars (0);
821 return run_jump_opt_after_gcse;
824 /* Misc. utilities. */
826 /* Compute which modes support reg/reg copy operations. */
832 #ifndef AVOID_CCMODE_COPIES
835 char *free_point = (char *) oballoc (1);
837 bzero (can_copy_p, NUM_MACHINE_MODES);
840 for (i = 0; i < NUM_MACHINE_MODES; i++)
842 switch (GET_MODE_CLASS (i))
845 #ifdef AVOID_CCMODE_COPIES
848 reg = gen_rtx_REG ((enum machine_mode) i, LAST_VIRTUAL_REGISTER + 1);
849 insn = emit_insn (gen_rtx_SET (VOIDmode, reg, reg));
850 if (recog (PATTERN (insn), insn, NULL_PTR) >= 0)
861 /* Free the objects we just allocated. */
865 /* Cover function to xmalloc to record bytes allocated. */
872 return xmalloc (size);
875 /* Cover function to xrealloc.
876 We don't record the additional size since we don't know it.
877 It won't affect memory usage stats much anyway. */
884 return xrealloc (ptr, size);
887 /* Cover function to obstack_alloc.
888 We don't need to record the bytes allocated here since
889 obstack_chunk_alloc is set to gmalloc. */
895 return (char *) obstack_alloc (&gcse_obstack, size);
898 /* Allocate memory for the cuid mapping array,
899 and reg/memory set tracking tables.
901 This is called at the start of each pass. */
910 /* Find the largest UID and create a mapping from UIDs to CUIDs.
911 CUIDs are like UIDs except they increase monotonically, have no gaps,
912 and only apply to real insns. */
914 max_uid = get_max_uid ();
915 n = (max_uid + 1) * sizeof (int);
916 uid_cuid = (int *) gmalloc (n);
917 bzero ((char *) uid_cuid, n);
918 for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
920 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
921 INSN_CUID (insn) = i++;
923 INSN_CUID (insn) = i;
926 /* Create a table mapping cuids to insns. */
929 n = (max_cuid + 1) * sizeof (rtx);
930 cuid_insn = (rtx *) gmalloc (n);
931 bzero ((char *) cuid_insn, n);
932 for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
934 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
936 CUID_INSN (i) = insn;
941 /* Allocate vars to track sets of regs. */
943 reg_set_bitmap = (sbitmap) sbitmap_alloc (max_gcse_regno);
945 /* Allocate vars to track sets of regs, memory per block. */
947 reg_set_in_block = (sbitmap *) sbitmap_vector_alloc (n_basic_blocks,
949 mem_set_in_block = (char *) gmalloc (n_basic_blocks);
952 /* Free memory allocated by alloc_gcse_mem. */
960 free (reg_set_bitmap);
962 free (reg_set_in_block);
963 free (mem_set_in_block);
966 /* Many of the global optimization algorithms work by solving dataflow
967 equations for various expressions. Initially, some local value is
968 computed for each expression in each block. Then, the values
969 across the various blocks are combined (by following flow graph
970 edges) to arrive at global values. Conceptually, each set of
971 equations is independent. We may therefore solve all the equations
972 in parallel, solve them one at a time, or pick any intermediate
975 When you're going to need N two-dimensional bitmaps, each X (say,
976 the number of blocks) by Y (say, the number of expressions), call
977 this function. It's not important what X and Y represent; only
978 that Y correspond to the things that can be done in parallel. This
979 function will return an appropriate chunking factor C; you should
980 solve C sets of equations in parallel. By going through this
981 function, we can easily trade space against time; by solving fewer
982 equations in parallel we use less space. */
985 get_bitmap_width (n, x, y)
990 /* It's not really worth figuring out *exactly* how much memory will
991 be used by a particular choice. The important thing is to get
992 something approximately right. */
993 size_t max_bitmap_memory = 10 * 1024 * 1024;
995 /* The number of bytes we'd use for a single column of minimum
997 size_t column_size = n * x * sizeof (SBITMAP_ELT_TYPE);
999 /* Often, it's reasonable just to solve all the equations in
1001 if (column_size * SBITMAP_SET_SIZE (y) <= max_bitmap_memory)
1004 /* Otherwise, pick the largest width we can, without going over the
1006 return SBITMAP_ELT_BITS * ((max_bitmap_memory + column_size - 1)
1011 /* Compute the local properties of each recorded expression.
1012 Local properties are those that are defined by the block, irrespective
1015 An expression is transparent in a block if its operands are not modified
1018 An expression is computed (locally available) in a block if it is computed
1019 at least once and expression would contain the same value if the
1020 computation was moved to the end of the block.
1022 An expression is locally anticipatable in a block if it is computed at
1023 least once and expression would contain the same value if the computation
1024 was moved to the beginning of the block.
1026 We call this routine for cprop, pre and code hoisting. They all
1027 compute basically the same information and thus can easily share
1030 TRANSP, COMP, and ANTLOC are destination sbitmaps for recording
1031 local properties. If NULL, then it is not necessary to compute
1032 or record that particular property.
1034 SETP controls which hash table to look at. If zero, this routine
1035 looks at the expr hash table; if nonzero this routine looks at
1036 the set hash table. Additionally, TRANSP is computed as ~TRANSP,
1037 since this is really cprop's ABSALTERED. */
1040 compute_local_properties (transp, comp, antloc, setp)
1046 int i, hash_table_size;
1047 struct expr **hash_table;
1049 /* Initialize any bitmaps that were passed in. */
1053 sbitmap_vector_zero (transp, n_basic_blocks);
1055 sbitmap_vector_ones (transp, n_basic_blocks);
1058 sbitmap_vector_zero (comp, n_basic_blocks);
1060 sbitmap_vector_zero (antloc, n_basic_blocks);
1062 /* We use the same code for cprop, pre and hoisting. For cprop
1063 we care about the set hash table, for pre and hoisting we
1064 care about the expr hash table. */
1065 hash_table_size = setp ? set_hash_table_size : expr_hash_table_size;
1066 hash_table = setp ? set_hash_table : expr_hash_table;
1068 for (i = 0; i < hash_table_size; i++)
1072 for (expr = hash_table[i]; expr != NULL; expr = expr->next_same_hash)
1075 int indx = expr->bitmap_index;
1077 /* The expression is transparent in this block if it is not killed.
1078 We start by assuming all are transparent [none are killed], and
1079 then reset the bits for those that are. */
1082 compute_transp (expr->expr, indx, transp, setp);
1084 /* The occurrences recorded in antic_occr are exactly those that
1085 we want to set to non-zero in ANTLOC. */
1089 for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
1091 int bb = BLOCK_NUM (occr->insn);
1092 SET_BIT (antloc[bb], indx);
1094 /* While we're scanning the table, this is a good place to
1096 occr->deleted_p = 0;
1100 /* The occurrences recorded in avail_occr are exactly those that
1101 we want to set to non-zero in COMP. */
1105 for (occr = expr->avail_occr; occr != NULL; occr = occr->next)
1107 int bb = BLOCK_NUM (occr->insn);
1108 SET_BIT (comp[bb], indx);
1110 /* While we're scanning the table, this is a good place to
1116 /* While we're scanning the table, this is a good place to
1118 expr->reaching_reg = 0;
1124 /* Register set information.
1126 `reg_set_table' records where each register is set or otherwise
1129 static struct obstack reg_set_obstack;
1132 alloc_reg_set_mem (n_regs)
1137 reg_set_table_size = n_regs + REG_SET_TABLE_SLOP;
1138 n = reg_set_table_size * sizeof (struct reg_set *);
1139 reg_set_table = (struct reg_set **) gmalloc (n);
1140 bzero ((char *) reg_set_table, n);
1142 gcc_obstack_init (®_set_obstack);
1148 free (reg_set_table);
1149 obstack_free (®_set_obstack, NULL_PTR);
1152 /* Record REGNO in the reg_set table. */
1155 record_one_set (regno, insn)
1159 /* allocate a new reg_set element and link it onto the list */
1160 struct reg_set *new_reg_info, *reg_info_ptr1, *reg_info_ptr2;
1162 /* If the table isn't big enough, enlarge it. */
1163 if (regno >= reg_set_table_size)
1165 int new_size = regno + REG_SET_TABLE_SLOP;
1166 reg_set_table = (struct reg_set **)
1167 grealloc ((char *) reg_set_table,
1168 new_size * sizeof (struct reg_set *));
1169 bzero ((char *) (reg_set_table + reg_set_table_size),
1170 (new_size - reg_set_table_size) * sizeof (struct reg_set *));
1171 reg_set_table_size = new_size;
1174 new_reg_info = (struct reg_set *) obstack_alloc (®_set_obstack,
1175 sizeof (struct reg_set));
1176 bytes_used += sizeof (struct reg_set);
1177 new_reg_info->insn = insn;
1178 new_reg_info->next = NULL;
1179 if (reg_set_table[regno] == NULL)
1180 reg_set_table[regno] = new_reg_info;
1183 reg_info_ptr1 = reg_info_ptr2 = reg_set_table[regno];
1184 /* ??? One could keep a "last" pointer to speed this up. */
1185 while (reg_info_ptr1 != NULL)
1187 reg_info_ptr2 = reg_info_ptr1;
1188 reg_info_ptr1 = reg_info_ptr1->next;
1190 reg_info_ptr2->next = new_reg_info;
1194 /* Called from compute_sets via note_stores to handle one
1195 SET or CLOBBER in an insn. The DATA is really the instruction
1196 in which the SET is occurring. */
1199 record_set_info (dest, setter, data)
1200 rtx dest, setter ATTRIBUTE_UNUSED;
1203 rtx record_set_insn = (rtx) data;
1205 if (GET_CODE (dest) == SUBREG)
1206 dest = SUBREG_REG (dest);
1208 if (GET_CODE (dest) == REG)
1210 if (REGNO (dest) >= FIRST_PSEUDO_REGISTER)
1211 record_one_set (REGNO (dest), record_set_insn);
1215 /* Scan the function and record each set of each pseudo-register.
1217 This is called once, at the start of the gcse pass.
1218 See the comments for `reg_set_table' for further docs. */
1228 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
1229 note_stores (PATTERN (insn), record_set_info, insn);
1230 insn = NEXT_INSN (insn);
1234 /* Hash table support. */
1236 #define NEVER_SET -1
1238 /* For each register, the cuid of the first/last insn in the block to set it,
1239 or -1 if not set. */
1240 static int *reg_first_set;
1241 static int *reg_last_set;
1243 /* While computing "first/last set" info, this is the CUID of first/last insn
1244 to set memory or -1 if not set. `mem_last_set' is also used when
1245 performing GCSE to record whether memory has been set since the beginning
1247 Note that handling of memory is very simple, we don't make any attempt
1248 to optimize things (later). */
1249 static int mem_first_set;
1250 static int mem_last_set;
1252 /* Perform a quick check whether X, the source of a set, is something
1253 we want to consider for GCSE. */
1259 enum rtx_code code = GET_CODE (x);
1277 /* Return non-zero if the operands of expression X are unchanged from the
1278 start of INSN's basic block up to but not including INSN (if AVAIL_P == 0),
1279 or from INSN to the end of INSN's basic block (if AVAIL_P != 0). */
1282 oprs_unchanged_p (x, insn, avail_p)
1290 /* repeat is used to turn tail-recursion into iteration. */
1296 code = GET_CODE (x);
1301 return (reg_last_set[REGNO (x)] == NEVER_SET
1302 || reg_last_set[REGNO (x)] < INSN_CUID (insn));
1304 return (reg_first_set[REGNO (x)] == NEVER_SET
1305 || reg_first_set[REGNO (x)] >= INSN_CUID (insn));
1310 if (mem_last_set != NEVER_SET
1311 && mem_last_set >= INSN_CUID (insn))
1316 if (mem_first_set != NEVER_SET
1317 && mem_first_set < INSN_CUID (insn))
1344 i = GET_RTX_LENGTH (code) - 1;
1345 fmt = GET_RTX_FORMAT (code);
1350 rtx tem = XEXP (x, i);
1352 /* If we are about to do the last recursive call
1353 needed at this level, change it into iteration.
1354 This function is called enough to be worth it. */
1360 if (! oprs_unchanged_p (tem, insn, avail_p))
1363 else if (fmt[i] == 'E')
1366 for (j = 0; j < XVECLEN (x, i); j++)
1368 if (! oprs_unchanged_p (XVECEXP (x, i, j), insn, avail_p))
1377 /* Return non-zero if the operands of expression X are unchanged from
1378 the start of INSN's basic block up to but not including INSN. */
1381 oprs_anticipatable_p (x, insn)
1384 return oprs_unchanged_p (x, insn, 0);
1387 /* Return non-zero if the operands of expression X are unchanged from
1388 INSN to the end of INSN's basic block. */
1391 oprs_available_p (x, insn)
1394 return oprs_unchanged_p (x, insn, 1);
1397 /* Hash expression X.
1398 MODE is only used if X is a CONST_INT.
1399 A boolean indicating if a volatile operand is found or if the expression
1400 contains something we don't want to insert in the table is stored in
1403 ??? One might want to merge this with canon_hash. Later. */
1406 hash_expr (x, mode, do_not_record_p, hash_table_size)
1408 enum machine_mode mode;
1409 int *do_not_record_p;
1410 int hash_table_size;
1414 *do_not_record_p = 0;
1416 hash = hash_expr_1 (x, mode, do_not_record_p);
1417 return hash % hash_table_size;
1420 /* Subroutine of hash_expr to do the actual work. */
1423 hash_expr_1 (x, mode, do_not_record_p)
1425 enum machine_mode mode;
1426 int *do_not_record_p;
1433 /* repeat is used to turn tail-recursion into iteration. */
1439 code = GET_CODE (x);
1444 register int regno = REGNO (x);
1445 hash += ((unsigned) REG << 7) + regno;
1451 unsigned HOST_WIDE_INT tem = INTVAL (x);
1452 hash += ((unsigned) CONST_INT << 7) + (unsigned) mode + tem;
1457 /* This is like the general case, except that it only counts
1458 the integers representing the constant. */
1459 hash += (unsigned) code + (unsigned) GET_MODE (x);
1460 if (GET_MODE (x) != VOIDmode)
1461 for (i = 2; i < GET_RTX_LENGTH (CONST_DOUBLE); i++)
1463 unsigned tem = XWINT (x, i);
1467 hash += ((unsigned) CONST_DOUBLE_LOW (x)
1468 + (unsigned) CONST_DOUBLE_HIGH (x));
1471 /* Assume there is only one rtx object for any given label. */
1473 /* We don't hash on the address of the CODE_LABEL to avoid bootstrap
1474 differences and differences between each stage's debugging dumps. */
1475 hash += ((unsigned) LABEL_REF << 7) + CODE_LABEL_NUMBER (XEXP (x, 0));
1480 /* Don't hash on the symbol's address to avoid bootstrap differences.
1481 Different hash values may cause expressions to be recorded in
1482 different orders and thus different registers to be used in the
1483 final assembler. This also avoids differences in the dump files
1484 between various stages. */
1486 unsigned char *p = (unsigned char *) XSTR (x, 0);
1488 h += (h << 7) + *p++; /* ??? revisit */
1489 hash += ((unsigned) SYMBOL_REF << 7) + h;
1494 if (MEM_VOLATILE_P (x))
1496 *do_not_record_p = 1;
1499 hash += (unsigned) MEM;
1500 hash += MEM_ALIAS_SET (x);
1511 case UNSPEC_VOLATILE:
1512 *do_not_record_p = 1;
1516 if (MEM_VOLATILE_P (x))
1518 *do_not_record_p = 1;
1526 i = GET_RTX_LENGTH (code) - 1;
1527 hash += (unsigned) code + (unsigned) GET_MODE (x);
1528 fmt = GET_RTX_FORMAT (code);
1533 rtx tem = XEXP (x, i);
1535 /* If we are about to do the last recursive call
1536 needed at this level, change it into iteration.
1537 This function is called enough to be worth it. */
1543 hash += hash_expr_1 (tem, 0, do_not_record_p);
1544 if (*do_not_record_p)
1547 else if (fmt[i] == 'E')
1548 for (j = 0; j < XVECLEN (x, i); j++)
1550 hash += hash_expr_1 (XVECEXP (x, i, j), 0, do_not_record_p);
1551 if (*do_not_record_p)
1554 else if (fmt[i] == 's')
1556 register unsigned char *p = (unsigned char *) XSTR (x, i);
1561 else if (fmt[i] == 'i')
1563 register unsigned tem = XINT (x, i);
1573 /* Hash a set of register REGNO.
1575 Sets are hashed on the register that is set.
1576 This simplifies the PRE copy propagation code.
1578 ??? May need to make things more elaborate. Later, as necessary. */
1581 hash_set (regno, hash_table_size)
1583 int hash_table_size;
1588 return hash % hash_table_size;
1591 /* Return non-zero if exp1 is equivalent to exp2.
1592 ??? Borrowed from cse.c. Might want to remerge with cse.c. Later. */
1599 register enum rtx_code code;
1600 register const char *fmt;
1604 if (x == 0 || y == 0)
1607 code = GET_CODE (x);
1608 if (code != GET_CODE (y))
1611 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. */
1612 if (GET_MODE (x) != GET_MODE (y))
1622 return INTVAL (x) == INTVAL (y);
1625 return XEXP (x, 0) == XEXP (y, 0);
1628 return XSTR (x, 0) == XSTR (y, 0);
1631 return REGNO (x) == REGNO (y);
1634 /* Can't merge two expressions in different alias sets, since we can
1635 decide that the expression is transparent in a block when it isn't,
1636 due to it being set with the different alias set. */
1637 if (MEM_ALIAS_SET (x) != MEM_ALIAS_SET (y))
1641 /* For commutative operations, check both orders. */
1649 return ((expr_equiv_p (XEXP (x, 0), XEXP (y, 0))
1650 && expr_equiv_p (XEXP (x, 1), XEXP (y, 1)))
1651 || (expr_equiv_p (XEXP (x, 0), XEXP (y, 1))
1652 && expr_equiv_p (XEXP (x, 1), XEXP (y, 0))));
1658 /* Compare the elements. If any pair of corresponding elements
1659 fail to match, return 0 for the whole thing. */
1661 fmt = GET_RTX_FORMAT (code);
1662 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1667 if (! expr_equiv_p (XEXP (x, i), XEXP (y, i)))
1672 if (XVECLEN (x, i) != XVECLEN (y, i))
1674 for (j = 0; j < XVECLEN (x, i); j++)
1675 if (! expr_equiv_p (XVECEXP (x, i, j), XVECEXP (y, i, j)))
1680 if (strcmp (XSTR (x, i), XSTR (y, i)))
1685 if (XINT (x, i) != XINT (y, i))
1690 if (XWINT (x, i) != XWINT (y, i))
1705 /* Insert expression X in INSN in the hash table.
1706 If it is already present, record it as the last occurrence in INSN's
1709 MODE is the mode of the value X is being stored into.
1710 It is only used if X is a CONST_INT.
1712 ANTIC_P is non-zero if X is an anticipatable expression.
1713 AVAIL_P is non-zero if X is an available expression. */
1716 insert_expr_in_table (x, mode, insn, antic_p, avail_p)
1718 enum machine_mode mode;
1720 int antic_p, avail_p;
1722 int found, do_not_record_p;
1724 struct expr *cur_expr, *last_expr = NULL;
1725 struct occr *antic_occr, *avail_occr;
1726 struct occr *last_occr = NULL;
1728 hash = hash_expr (x, mode, &do_not_record_p, expr_hash_table_size);
1730 /* Do not insert expression in table if it contains volatile operands,
1731 or if hash_expr determines the expression is something we don't want
1732 to or can't handle. */
1733 if (do_not_record_p)
1736 cur_expr = expr_hash_table[hash];
1739 while (cur_expr && ! (found = expr_equiv_p (cur_expr->expr, x)))
1741 /* If the expression isn't found, save a pointer to the end of
1743 last_expr = cur_expr;
1744 cur_expr = cur_expr->next_same_hash;
1749 cur_expr = (struct expr *) gcse_alloc (sizeof (struct expr));
1750 bytes_used += sizeof (struct expr);
1751 if (expr_hash_table[hash] == NULL)
1753 /* This is the first pattern that hashed to this index. */
1754 expr_hash_table[hash] = cur_expr;
1758 /* Add EXPR to end of this hash chain. */
1759 last_expr->next_same_hash = cur_expr;
1761 /* Set the fields of the expr element. */
1763 cur_expr->bitmap_index = n_exprs++;
1764 cur_expr->next_same_hash = NULL;
1765 cur_expr->antic_occr = NULL;
1766 cur_expr->avail_occr = NULL;
1769 /* Now record the occurrence(s). */
1773 antic_occr = cur_expr->antic_occr;
1775 /* Search for another occurrence in the same basic block. */
1776 while (antic_occr && BLOCK_NUM (antic_occr->insn) != BLOCK_NUM (insn))
1778 /* If an occurrence isn't found, save a pointer to the end of
1780 last_occr = antic_occr;
1781 antic_occr = antic_occr->next;
1786 /* Found another instance of the expression in the same basic block.
1787 Prefer the currently recorded one. We want the first one in the
1788 block and the block is scanned from start to end. */
1789 ; /* nothing to do */
1793 /* First occurrence of this expression in this basic block. */
1794 antic_occr = (struct occr *) gcse_alloc (sizeof (struct occr));
1795 bytes_used += sizeof (struct occr);
1796 /* First occurrence of this expression in any block? */
1797 if (cur_expr->antic_occr == NULL)
1798 cur_expr->antic_occr = antic_occr;
1800 last_occr->next = antic_occr;
1801 antic_occr->insn = insn;
1802 antic_occr->next = NULL;
1808 avail_occr = cur_expr->avail_occr;
1810 /* Search for another occurrence in the same basic block. */
1811 while (avail_occr && BLOCK_NUM (avail_occr->insn) != BLOCK_NUM (insn))
1813 /* If an occurrence isn't found, save a pointer to the end of
1815 last_occr = avail_occr;
1816 avail_occr = avail_occr->next;
1821 /* Found another instance of the expression in the same basic block.
1822 Prefer this occurrence to the currently recorded one. We want
1823 the last one in the block and the block is scanned from start
1825 avail_occr->insn = insn;
1829 /* First occurrence of this expression in this basic block. */
1830 avail_occr = (struct occr *) gcse_alloc (sizeof (struct occr));
1831 bytes_used += sizeof (struct occr);
1832 /* First occurrence of this expression in any block? */
1833 if (cur_expr->avail_occr == NULL)
1834 cur_expr->avail_occr = avail_occr;
1836 last_occr->next = avail_occr;
1837 avail_occr->insn = insn;
1838 avail_occr->next = NULL;
1843 /* Insert pattern X in INSN in the hash table.
1844 X is a SET of a reg to either another reg or a constant.
1845 If it is already present, record it as the last occurrence in INSN's
1849 insert_set_in_table (x, insn)
1855 struct expr *cur_expr, *last_expr = NULL;
1856 struct occr *cur_occr, *last_occr = NULL;
1858 if (GET_CODE (x) != SET
1859 || GET_CODE (SET_DEST (x)) != REG)
1862 hash = hash_set (REGNO (SET_DEST (x)), set_hash_table_size);
1864 cur_expr = set_hash_table[hash];
1867 while (cur_expr && ! (found = expr_equiv_p (cur_expr->expr, x)))
1869 /* If the expression isn't found, save a pointer to the end of
1871 last_expr = cur_expr;
1872 cur_expr = cur_expr->next_same_hash;
1877 cur_expr = (struct expr *) gcse_alloc (sizeof (struct expr));
1878 bytes_used += sizeof (struct expr);
1879 if (set_hash_table[hash] == NULL)
1881 /* This is the first pattern that hashed to this index. */
1882 set_hash_table[hash] = cur_expr;
1886 /* Add EXPR to end of this hash chain. */
1887 last_expr->next_same_hash = cur_expr;
1889 /* Set the fields of the expr element.
1890 We must copy X because it can be modified when copy propagation is
1891 performed on its operands. */
1892 /* ??? Should this go in a different obstack? */
1893 cur_expr->expr = copy_rtx (x);
1894 cur_expr->bitmap_index = n_sets++;
1895 cur_expr->next_same_hash = NULL;
1896 cur_expr->antic_occr = NULL;
1897 cur_expr->avail_occr = NULL;
1900 /* Now record the occurrence. */
1902 cur_occr = cur_expr->avail_occr;
1904 /* Search for another occurrence in the same basic block. */
1905 while (cur_occr && BLOCK_NUM (cur_occr->insn) != BLOCK_NUM (insn))
1907 /* If an occurrence isn't found, save a pointer to the end of
1909 last_occr = cur_occr;
1910 cur_occr = cur_occr->next;
1915 /* Found another instance of the expression in the same basic block.
1916 Prefer this occurrence to the currently recorded one. We want
1917 the last one in the block and the block is scanned from start
1919 cur_occr->insn = insn;
1923 /* First occurrence of this expression in this basic block. */
1924 cur_occr = (struct occr *) gcse_alloc (sizeof (struct occr));
1925 bytes_used += sizeof (struct occr);
1926 /* First occurrence of this expression in any block? */
1927 if (cur_expr->avail_occr == NULL)
1928 cur_expr->avail_occr = cur_occr;
1930 last_occr->next = cur_occr;
1931 cur_occr->insn = insn;
1932 cur_occr->next = NULL;
1936 /* Scan pattern PAT of INSN and add an entry to the hash table.
1937 If SET_P is non-zero, this is for the assignment hash table,
1938 otherwise it is for the expression hash table. */
1941 hash_scan_set (pat, insn, set_p)
1945 rtx src = SET_SRC (pat);
1946 rtx dest = SET_DEST (pat);
1948 if (GET_CODE (src) == CALL)
1949 hash_scan_call (src, insn);
1951 if (GET_CODE (dest) == REG)
1953 int regno = REGNO (dest);
1956 /* Only record sets of pseudo-regs in the hash table. */
1958 && regno >= FIRST_PSEUDO_REGISTER
1959 /* Don't GCSE something if we can't do a reg/reg copy. */
1960 && can_copy_p [GET_MODE (dest)]
1961 /* Is SET_SRC something we want to gcse? */
1962 && want_to_gcse_p (src))
1964 /* An expression is not anticipatable if its operands are
1965 modified before this insn. */
1966 int antic_p = oprs_anticipatable_p (src, insn);
1967 /* An expression is not available if its operands are
1968 subsequently modified, including this insn. */
1969 int avail_p = oprs_available_p (src, insn);
1970 insert_expr_in_table (src, GET_MODE (dest), insn, antic_p, avail_p);
1972 /* Record sets for constant/copy propagation. */
1974 && regno >= FIRST_PSEUDO_REGISTER
1975 && ((GET_CODE (src) == REG
1976 && REGNO (src) >= FIRST_PSEUDO_REGISTER
1977 && can_copy_p [GET_MODE (dest)])
1978 || GET_CODE (src) == CONST_INT
1979 || GET_CODE (src) == SYMBOL_REF
1980 || GET_CODE (src) == CONST_DOUBLE)
1981 /* A copy is not available if its src or dest is subsequently
1982 modified. Here we want to search from INSN+1 on, but
1983 oprs_available_p searches from INSN on. */
1984 && (insn == BLOCK_END (BLOCK_NUM (insn))
1985 || ((tmp = next_nonnote_insn (insn)) != NULL_RTX
1986 && oprs_available_p (pat, tmp))))
1987 insert_set_in_table (pat, insn);
1992 hash_scan_clobber (x, insn)
1993 rtx x ATTRIBUTE_UNUSED, insn ATTRIBUTE_UNUSED;
1995 /* Currently nothing to do. */
1999 hash_scan_call (x, insn)
2000 rtx x ATTRIBUTE_UNUSED, insn ATTRIBUTE_UNUSED;
2002 /* Currently nothing to do. */
2005 /* Process INSN and add hash table entries as appropriate.
2007 Only available expressions that set a single pseudo-reg are recorded.
2009 Single sets in a PARALLEL could be handled, but it's an extra complication
2010 that isn't dealt with right now. The trick is handling the CLOBBERs that
2011 are also in the PARALLEL. Later.
2013 If SET_P is non-zero, this is for the assignment hash table,
2014 otherwise it is for the expression hash table.
2015 If IN_LIBCALL_BLOCK nonzero, we are in a libcall block, and should
2016 not record any expressions. */
2019 hash_scan_insn (insn, set_p, in_libcall_block)
2022 int in_libcall_block;
2024 rtx pat = PATTERN (insn);
2026 /* Pick out the sets of INSN and for other forms of instructions record
2027 what's been modified. */
2029 if (GET_CODE (pat) == SET && ! in_libcall_block)
2031 /* Ignore obvious no-ops. */
2032 if (SET_SRC (pat) != SET_DEST (pat))
2033 hash_scan_set (pat, insn, set_p);
2035 else if (GET_CODE (pat) == PARALLEL)
2039 for (i = 0; i < XVECLEN (pat, 0); i++)
2041 rtx x = XVECEXP (pat, 0, i);
2043 if (GET_CODE (x) == SET)
2045 if (GET_CODE (SET_SRC (x)) == CALL)
2046 hash_scan_call (SET_SRC (x), insn);
2048 else if (GET_CODE (x) == CLOBBER)
2049 hash_scan_clobber (x, insn);
2050 else if (GET_CODE (x) == CALL)
2051 hash_scan_call (x, insn);
2054 else if (GET_CODE (pat) == CLOBBER)
2055 hash_scan_clobber (pat, insn);
2056 else if (GET_CODE (pat) == CALL)
2057 hash_scan_call (pat, insn);
2061 dump_hash_table (file, name, table, table_size, total_size)
2064 struct expr **table;
2065 int table_size, total_size;
2068 /* Flattened out table, so it's printed in proper order. */
2069 struct expr **flat_table;
2070 unsigned int *hash_val;
2073 = (struct expr **) xcalloc (total_size, sizeof (struct expr *));
2074 hash_val = (unsigned int *) xmalloc (total_size * sizeof (unsigned int));
2076 for (i = 0; i < table_size; i++)
2080 for (expr = table[i]; expr != NULL; expr = expr->next_same_hash)
2082 flat_table[expr->bitmap_index] = expr;
2083 hash_val[expr->bitmap_index] = i;
2087 fprintf (file, "%s hash table (%d buckets, %d entries)\n",
2088 name, table_size, total_size);
2090 for (i = 0; i < total_size; i++)
2092 struct expr *expr = flat_table[i];
2094 fprintf (file, "Index %d (hash value %d)\n ",
2095 expr->bitmap_index, hash_val[i]);
2096 print_rtl (file, expr->expr);
2097 fprintf (file, "\n");
2100 fprintf (file, "\n");
2107 /* Record register first/last/block set information for REGNO in INSN.
2108 reg_first_set records the first place in the block where the register
2109 is set and is used to compute "anticipatability".
2110 reg_last_set records the last place in the block where the register
2111 is set and is used to compute "availability".
2112 reg_set_in_block records whether the register is set in the block
2113 and is used to compute "transparency". */
2116 record_last_reg_set_info (insn, regno)
2120 if (reg_first_set[regno] == NEVER_SET)
2121 reg_first_set[regno] = INSN_CUID (insn);
2122 reg_last_set[regno] = INSN_CUID (insn);
2123 SET_BIT (reg_set_in_block[BLOCK_NUM (insn)], regno);
2126 /* Record memory first/last/block set information for INSN. */
2129 record_last_mem_set_info (insn)
2132 if (mem_first_set == NEVER_SET)
2133 mem_first_set = INSN_CUID (insn);
2134 mem_last_set = INSN_CUID (insn);
2135 mem_set_in_block[BLOCK_NUM (insn)] = 1;
2138 /* Called from compute_hash_table via note_stores to handle one
2139 SET or CLOBBER in an insn. DATA is really the instruction in which
2140 the SET is taking place. */
2143 record_last_set_info (dest, setter, data)
2144 rtx dest, setter ATTRIBUTE_UNUSED;
2147 rtx last_set_insn = (rtx) data;
2149 if (GET_CODE (dest) == SUBREG)
2150 dest = SUBREG_REG (dest);
2152 if (GET_CODE (dest) == REG)
2153 record_last_reg_set_info (last_set_insn, REGNO (dest));
2154 else if (GET_CODE (dest) == MEM
2155 /* Ignore pushes, they clobber nothing. */
2156 && ! push_operand (dest, GET_MODE (dest)))
2157 record_last_mem_set_info (last_set_insn);
2160 /* Top level function to create an expression or assignment hash table.
2162 Expression entries are placed in the hash table if
2163 - they are of the form (set (pseudo-reg) src),
2164 - src is something we want to perform GCSE on,
2165 - none of the operands are subsequently modified in the block
2167 Assignment entries are placed in the hash table if
2168 - they are of the form (set (pseudo-reg) src),
2169 - src is something we want to perform const/copy propagation on,
2170 - none of the operands or target are subsequently modified in the block
2171 Currently src must be a pseudo-reg or a const_int.
2173 F is the first insn.
2174 SET_P is non-zero for computing the assignment hash table. */
2177 compute_hash_table (set_p)
2182 /* While we compute the hash table we also compute a bit array of which
2183 registers are set in which blocks.
2184 We also compute which blocks set memory, in the absence of aliasing
2185 support [which is TODO].
2186 ??? This isn't needed during const/copy propagation, but it's cheap to
2188 sbitmap_vector_zero (reg_set_in_block, n_basic_blocks);
2189 bzero ((char *) mem_set_in_block, n_basic_blocks);
2191 /* Some working arrays used to track first and last set in each block. */
2192 /* ??? One could use alloca here, but at some size a threshold is crossed
2193 beyond which one should use malloc. Are we at that threshold here? */
2194 reg_first_set = (int *) gmalloc (max_gcse_regno * sizeof (int));
2195 reg_last_set = (int *) gmalloc (max_gcse_regno * sizeof (int));
2197 for (bb = 0; bb < n_basic_blocks; bb++)
2201 int in_libcall_block;
2204 /* First pass over the instructions records information used to
2205 determine when registers and memory are first and last set.
2206 ??? The mem_set_in_block and hard-reg reg_set_in_block computation
2207 could be moved to compute_sets since they currently don't change. */
2209 for (i = 0; i < max_gcse_regno; i++)
2210 reg_first_set[i] = reg_last_set[i] = NEVER_SET;
2211 mem_first_set = NEVER_SET;
2212 mem_last_set = NEVER_SET;
2214 for (insn = BLOCK_HEAD (bb);
2215 insn && insn != NEXT_INSN (BLOCK_END (bb));
2216 insn = NEXT_INSN (insn))
2218 #ifdef NON_SAVING_SETJMP
2219 if (NON_SAVING_SETJMP && GET_CODE (insn) == NOTE
2220 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_SETJMP)
2222 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
2223 record_last_reg_set_info (insn, regno);
2228 if (GET_RTX_CLASS (GET_CODE (insn)) != 'i')
2231 if (GET_CODE (insn) == CALL_INSN)
2233 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
2234 if ((call_used_regs[regno]
2235 && regno != STACK_POINTER_REGNUM
2236 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2237 && regno != HARD_FRAME_POINTER_REGNUM
2239 #if ARG_POINTER_REGNUM != FRAME_POINTER_REGNUM
2240 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2242 #if defined (PIC_OFFSET_TABLE_REGNUM) && !defined (PIC_OFFSET_TABLE_REG_CALL_CLOBBERED)
2243 && ! (regno == PIC_OFFSET_TABLE_REGNUM && flag_pic)
2246 && regno != FRAME_POINTER_REGNUM)
2247 || global_regs[regno])
2248 record_last_reg_set_info (insn, regno);
2249 if (! CONST_CALL_P (insn))
2250 record_last_mem_set_info (insn);
2253 note_stores (PATTERN (insn), record_last_set_info, insn);
2256 /* The next pass builds the hash table. */
2258 for (insn = BLOCK_HEAD (bb), in_libcall_block = 0;
2259 insn && insn != NEXT_INSN (BLOCK_END (bb));
2260 insn = NEXT_INSN (insn))
2262 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
2264 if (find_reg_note (insn, REG_LIBCALL, NULL_RTX))
2265 in_libcall_block = 1;
2266 else if (find_reg_note (insn, REG_RETVAL, NULL_RTX))
2267 in_libcall_block = 0;
2268 hash_scan_insn (insn, set_p, in_libcall_block);
2273 free (reg_first_set);
2274 free (reg_last_set);
2275 /* Catch bugs early. */
2276 reg_first_set = reg_last_set = 0;
2279 /* Allocate space for the set hash table.
2280 N_INSNS is the number of instructions in the function.
2281 It is used to determine the number of buckets to use. */
2284 alloc_set_hash_table (n_insns)
2289 set_hash_table_size = n_insns / 4;
2290 if (set_hash_table_size < 11)
2291 set_hash_table_size = 11;
2292 /* Attempt to maintain efficient use of hash table.
2293 Making it an odd number is simplest for now.
2294 ??? Later take some measurements. */
2295 set_hash_table_size |= 1;
2296 n = set_hash_table_size * sizeof (struct expr *);
2297 set_hash_table = (struct expr **) gmalloc (n);
2300 /* Free things allocated by alloc_set_hash_table. */
2303 free_set_hash_table ()
2305 free (set_hash_table);
2308 /* Compute the hash table for doing copy/const propagation. */
2311 compute_set_hash_table ()
2313 /* Initialize count of number of entries in hash table. */
2315 bzero ((char *) set_hash_table, set_hash_table_size * sizeof (struct expr *));
2317 compute_hash_table (1);
2320 /* Allocate space for the expression hash table.
2321 N_INSNS is the number of instructions in the function.
2322 It is used to determine the number of buckets to use. */
2325 alloc_expr_hash_table (n_insns)
2330 expr_hash_table_size = n_insns / 2;
2331 /* Make sure the amount is usable. */
2332 if (expr_hash_table_size < 11)
2333 expr_hash_table_size = 11;
2334 /* Attempt to maintain efficient use of hash table.
2335 Making it an odd number is simplest for now.
2336 ??? Later take some measurements. */
2337 expr_hash_table_size |= 1;
2338 n = expr_hash_table_size * sizeof (struct expr *);
2339 expr_hash_table = (struct expr **) gmalloc (n);
2342 /* Free things allocated by alloc_expr_hash_table. */
2345 free_expr_hash_table ()
2347 free (expr_hash_table);
2350 /* Compute the hash table for doing GCSE. */
2353 compute_expr_hash_table ()
2355 /* Initialize count of number of entries in hash table. */
2357 bzero ((char *) expr_hash_table, expr_hash_table_size * sizeof (struct expr *));
2359 compute_hash_table (0);
2362 /* Expression tracking support. */
2364 /* Lookup pattern PAT in the expression table.
2365 The result is a pointer to the table entry, or NULL if not found. */
2367 static struct expr *
2371 int do_not_record_p;
2372 unsigned int hash = hash_expr (pat, GET_MODE (pat), &do_not_record_p,
2373 expr_hash_table_size);
2376 if (do_not_record_p)
2379 expr = expr_hash_table[hash];
2381 while (expr && ! expr_equiv_p (expr->expr, pat))
2382 expr = expr->next_same_hash;
2387 /* Lookup REGNO in the set table.
2388 If PAT is non-NULL look for the entry that matches it, otherwise return
2389 the first entry for REGNO.
2390 The result is a pointer to the table entry, or NULL if not found. */
2392 static struct expr *
2393 lookup_set (regno, pat)
2397 unsigned int hash = hash_set (regno, set_hash_table_size);
2400 expr = set_hash_table[hash];
2404 while (expr && ! expr_equiv_p (expr->expr, pat))
2405 expr = expr->next_same_hash;
2409 while (expr && REGNO (SET_DEST (expr->expr)) != regno)
2410 expr = expr->next_same_hash;
2416 /* Return the next entry for REGNO in list EXPR. */
2418 static struct expr *
2419 next_set (regno, expr)
2424 expr = expr->next_same_hash;
2425 while (expr && REGNO (SET_DEST (expr->expr)) != regno);
2429 /* Reset tables used to keep track of what's still available [since the
2430 start of the block]. */
2433 reset_opr_set_tables ()
2435 /* Maintain a bitmap of which regs have been set since beginning of
2437 sbitmap_zero (reg_set_bitmap);
2438 /* Also keep a record of the last instruction to modify memory.
2439 For now this is very trivial, we only record whether any memory
2440 location has been modified. */
2444 /* Return non-zero if the operands of X are not set before INSN in
2445 INSN's basic block. */
2448 oprs_not_set_p (x, insn)
2455 /* repeat is used to turn tail-recursion into iteration. */
2461 code = GET_CODE (x);
2476 if (mem_last_set != 0)
2482 return ! TEST_BIT (reg_set_bitmap, REGNO (x));
2488 fmt = GET_RTX_FORMAT (code);
2489 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2494 /* If we are about to do the last recursive call
2495 needed at this level, change it into iteration.
2496 This function is called enough to be worth it. */
2502 not_set_p = oprs_not_set_p (XEXP (x, i), insn);
2506 else if (fmt[i] == 'E')
2509 for (j = 0; j < XVECLEN (x, i); j++)
2511 int not_set_p = oprs_not_set_p (XVECEXP (x, i, j), insn);
2521 /* Mark things set by a CALL. */
2527 mem_last_set = INSN_CUID (insn);
2530 /* Mark things set by a SET. */
2533 mark_set (pat, insn)
2536 rtx dest = SET_DEST (pat);
2538 while (GET_CODE (dest) == SUBREG
2539 || GET_CODE (dest) == ZERO_EXTRACT
2540 || GET_CODE (dest) == SIGN_EXTRACT
2541 || GET_CODE (dest) == STRICT_LOW_PART)
2542 dest = XEXP (dest, 0);
2544 if (GET_CODE (dest) == REG)
2545 SET_BIT (reg_set_bitmap, REGNO (dest));
2546 else if (GET_CODE (dest) == MEM)
2547 mem_last_set = INSN_CUID (insn);
2549 if (GET_CODE (SET_SRC (pat)) == CALL)
2553 /* Record things set by a CLOBBER. */
2556 mark_clobber (pat, insn)
2559 rtx clob = XEXP (pat, 0);
2561 while (GET_CODE (clob) == SUBREG || GET_CODE (clob) == STRICT_LOW_PART)
2562 clob = XEXP (clob, 0);
2564 if (GET_CODE (clob) == REG)
2565 SET_BIT (reg_set_bitmap, REGNO (clob));
2567 mem_last_set = INSN_CUID (insn);
2570 /* Record things set by INSN.
2571 This data is used by oprs_not_set_p. */
2574 mark_oprs_set (insn)
2577 rtx pat = PATTERN (insn);
2579 if (GET_CODE (pat) == SET)
2580 mark_set (pat, insn);
2581 else if (GET_CODE (pat) == PARALLEL)
2585 for (i = 0; i < XVECLEN (pat, 0); i++)
2587 rtx x = XVECEXP (pat, 0, i);
2589 if (GET_CODE (x) == SET)
2591 else if (GET_CODE (x) == CLOBBER)
2592 mark_clobber (x, insn);
2593 else if (GET_CODE (x) == CALL)
2597 else if (GET_CODE (pat) == CLOBBER)
2598 mark_clobber (pat, insn);
2599 else if (GET_CODE (pat) == CALL)
2604 /* Classic GCSE reaching definition support. */
2606 /* Allocate reaching def variables. */
2609 alloc_rd_mem (n_blocks, n_insns)
2610 int n_blocks, n_insns;
2612 rd_kill = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
2613 sbitmap_vector_zero (rd_kill, n_basic_blocks);
2615 rd_gen = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
2616 sbitmap_vector_zero (rd_gen, n_basic_blocks);
2618 reaching_defs = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
2619 sbitmap_vector_zero (reaching_defs, n_basic_blocks);
2621 rd_out = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
2622 sbitmap_vector_zero (rd_out, n_basic_blocks);
2625 /* Free reaching def variables. */
2632 free (reaching_defs);
2636 /* Add INSN to the kills of BB.
2637 REGNO, set in BB, is killed by INSN. */
2640 handle_rd_kill_set (insn, regno, bb)
2644 struct reg_set *this_reg = reg_set_table[regno];
2648 if (BLOCK_NUM (this_reg->insn) != BLOCK_NUM (insn))
2649 SET_BIT (rd_kill[bb], INSN_CUID (this_reg->insn));
2650 this_reg = this_reg->next;
2654 /* Compute the set of kill's for reaching definitions. */
2662 For each set bit in `gen' of the block (i.e each insn which
2663 generates a definition in the block)
2664 Call the reg set by the insn corresponding to that bit regx
2665 Look at the linked list starting at reg_set_table[regx]
2666 For each setting of regx in the linked list, which is not in
2668 Set the bit in `kill' corresponding to that insn
2671 for (bb = 0; bb < n_basic_blocks; bb++)
2673 for (cuid = 0; cuid < max_cuid; cuid++)
2675 if (TEST_BIT (rd_gen[bb], cuid))
2677 rtx insn = CUID_INSN (cuid);
2678 rtx pat = PATTERN (insn);
2680 if (GET_CODE (insn) == CALL_INSN)
2684 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
2686 if ((call_used_regs[regno]
2687 && regno != STACK_POINTER_REGNUM
2688 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2689 && regno != HARD_FRAME_POINTER_REGNUM
2691 #if ARG_POINTER_REGNUM != FRAME_POINTER_REGNUM
2692 && ! (regno == ARG_POINTER_REGNUM
2693 && fixed_regs[regno])
2695 #if defined (PIC_OFFSET_TABLE_REGNUM) && !defined (PIC_OFFSET_TABLE_REG_CALL_CLOBBERED)
2696 && ! (regno == PIC_OFFSET_TABLE_REGNUM && flag_pic)
2698 && regno != FRAME_POINTER_REGNUM)
2699 || global_regs[regno])
2700 handle_rd_kill_set (insn, regno, bb);
2704 if (GET_CODE (pat) == PARALLEL)
2708 /* We work backwards because ... */
2709 for (i = XVECLEN (pat, 0) - 1; i >= 0; i--)
2711 enum rtx_code code = GET_CODE (XVECEXP (pat, 0, i));
2712 if ((code == SET || code == CLOBBER)
2713 && GET_CODE (XEXP (XVECEXP (pat, 0, i), 0)) == REG)
2714 handle_rd_kill_set (insn,
2715 REGNO (XEXP (XVECEXP (pat, 0, i), 0)),
2719 else if (GET_CODE (pat) == SET)
2721 if (GET_CODE (SET_DEST (pat)) == REG)
2723 /* Each setting of this register outside of this block
2724 must be marked in the set of kills in this block. */
2725 handle_rd_kill_set (insn, REGNO (SET_DEST (pat)), bb);
2728 /* FIXME: CLOBBER? */
2734 /* Compute the reaching definitions as in
2735 Compilers Principles, Techniques, and Tools. Aho, Sethi, Ullman,
2736 Chapter 10. It is the same algorithm as used for computing available
2737 expressions but applied to the gens and kills of reaching definitions. */
2742 int bb, changed, passes;
2744 for (bb = 0; bb < n_basic_blocks; bb++)
2745 sbitmap_copy (rd_out[bb] /*dst*/, rd_gen[bb] /*src*/);
2752 for (bb = 0; bb < n_basic_blocks; bb++)
2754 sbitmap_union_of_preds (reaching_defs[bb], rd_out, bb);
2755 changed |= sbitmap_union_of_diff (rd_out[bb], rd_gen[bb],
2756 reaching_defs[bb], rd_kill[bb]);
2762 fprintf (gcse_file, "reaching def computation: %d passes\n", passes);
2765 /* Classic GCSE available expression support. */
2767 /* Allocate memory for available expression computation. */
2770 alloc_avail_expr_mem (n_blocks, n_exprs)
2771 int n_blocks, n_exprs;
2773 ae_kill = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
2774 sbitmap_vector_zero (ae_kill, n_basic_blocks);
2776 ae_gen = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
2777 sbitmap_vector_zero (ae_gen, n_basic_blocks);
2779 ae_in = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
2780 sbitmap_vector_zero (ae_in, n_basic_blocks);
2782 ae_out = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
2783 sbitmap_vector_zero (ae_out, n_basic_blocks);
2785 u_bitmap = (sbitmap) sbitmap_alloc (n_exprs);
2786 sbitmap_ones (u_bitmap);
2790 free_avail_expr_mem ()
2799 /* Compute the set of available expressions generated in each basic block. */
2806 /* For each recorded occurrence of each expression, set ae_gen[bb][expr].
2807 This is all we have to do because an expression is not recorded if it
2808 is not available, and the only expressions we want to work with are the
2809 ones that are recorded. */
2811 for (i = 0; i < expr_hash_table_size; i++)
2813 struct expr *expr = expr_hash_table[i];
2814 while (expr != NULL)
2816 struct occr *occr = expr->avail_occr;
2817 while (occr != NULL)
2819 SET_BIT (ae_gen[BLOCK_NUM (occr->insn)], expr->bitmap_index);
2822 expr = expr->next_same_hash;
2827 /* Return non-zero if expression X is killed in BB. */
2830 expr_killed_p (x, bb)
2838 /* repeat is used to turn tail-recursion into iteration. */
2844 code = GET_CODE (x);
2848 return TEST_BIT (reg_set_in_block[bb], REGNO (x));
2851 if (mem_set_in_block[bb])
2871 i = GET_RTX_LENGTH (code) - 1;
2872 fmt = GET_RTX_FORMAT (code);
2877 rtx tem = XEXP (x, i);
2879 /* If we are about to do the last recursive call
2880 needed at this level, change it into iteration.
2881 This function is called enough to be worth it. */
2887 if (expr_killed_p (tem, bb))
2890 else if (fmt[i] == 'E')
2893 for (j = 0; j < XVECLEN (x, i); j++)
2895 if (expr_killed_p (XVECEXP (x, i, j), bb))
2904 /* Compute the set of available expressions killed in each basic block. */
2907 compute_ae_kill (ae_gen, ae_kill)
2908 sbitmap *ae_gen, *ae_kill;
2912 for (bb = 0; bb < n_basic_blocks; bb++)
2914 for (i = 0; i < expr_hash_table_size; i++)
2916 struct expr *expr = expr_hash_table[i];
2918 for ( ; expr != NULL; expr = expr->next_same_hash)
2920 /* Skip EXPR if generated in this block. */
2921 if (TEST_BIT (ae_gen[bb], expr->bitmap_index))
2924 if (expr_killed_p (expr->expr, bb))
2925 SET_BIT (ae_kill[bb], expr->bitmap_index);
2931 /* Actually perform the Classic GCSE optimizations. */
2933 /* Return non-zero if occurrence OCCR of expression EXPR reaches block BB.
2935 CHECK_SELF_LOOP is non-zero if we should consider a block reaching itself
2936 as a positive reach. We want to do this when there are two computations
2937 of the expression in the block.
2939 VISITED is a pointer to a working buffer for tracking which BB's have
2940 been visited. It is NULL for the top-level call.
2942 We treat reaching expressions that go through blocks containing the same
2943 reaching expression as "not reaching". E.g. if EXPR is generated in blocks
2944 2 and 3, INSN is in block 4, and 2->3->4, we treat the expression in block
2945 2 as not reaching. The intent is to improve the probability of finding
2946 only one reaching expression and to reduce register lifetimes by picking
2947 the closest such expression. */
2950 expr_reaches_here_p_work (occr, expr, bb, check_self_loop, visited)
2954 int check_self_loop;
2959 for (pred = BASIC_BLOCK(bb)->pred; pred != NULL; pred = pred->pred_next)
2961 int pred_bb = pred->src->index;
2963 if (visited[pred_bb])
2965 /* This predecessor has already been visited.
2969 else if (pred_bb == bb)
2971 /* BB loops on itself. */
2973 && TEST_BIT (ae_gen[pred_bb], expr->bitmap_index)
2974 && BLOCK_NUM (occr->insn) == pred_bb)
2976 visited[pred_bb] = 1;
2978 /* Ignore this predecessor if it kills the expression. */
2979 else if (TEST_BIT (ae_kill[pred_bb], expr->bitmap_index))
2980 visited[pred_bb] = 1;
2981 /* Does this predecessor generate this expression? */
2982 else if (TEST_BIT (ae_gen[pred_bb], expr->bitmap_index))
2984 /* Is this the occurrence we're looking for?
2985 Note that there's only one generating occurrence per block
2986 so we just need to check the block number. */
2987 if (BLOCK_NUM (occr->insn) == pred_bb)
2989 visited[pred_bb] = 1;
2991 /* Neither gen nor kill. */
2994 visited[pred_bb] = 1;
2995 if (expr_reaches_here_p_work (occr, expr, pred_bb, check_self_loop,
3001 /* All paths have been checked. */
3005 /* This wrapper for expr_reaches_here_p_work() is to ensure that any
3006 memory allocated for that function is returned. */
3009 expr_reaches_here_p (occr, expr, bb, check_self_loop)
3013 int check_self_loop;
3016 char * visited = (char *) xcalloc (n_basic_blocks, 1);
3018 rval = expr_reaches_here_p_work(occr, expr, bb, check_self_loop, visited);
3025 /* Return the instruction that computes EXPR that reaches INSN's basic block.
3026 If there is more than one such instruction, return NULL.
3028 Called only by handle_avail_expr. */
3031 computing_insn (expr, insn)
3035 int bb = BLOCK_NUM (insn);
3037 if (expr->avail_occr->next == NULL)
3039 if (BLOCK_NUM (expr->avail_occr->insn) == bb)
3041 /* The available expression is actually itself
3042 (i.e. a loop in the flow graph) so do nothing. */
3045 /* (FIXME) Case that we found a pattern that was created by
3046 a substitution that took place. */
3047 return expr->avail_occr->insn;
3051 /* Pattern is computed more than once.
3052 Search backwards from this insn to see how many of these
3053 computations actually reach this insn. */
3055 rtx insn_computes_expr = NULL;
3058 for (occr = expr->avail_occr; occr != NULL; occr = occr->next)
3060 if (BLOCK_NUM (occr->insn) == bb)
3062 /* The expression is generated in this block.
3063 The only time we care about this is when the expression
3064 is generated later in the block [and thus there's a loop].
3065 We let the normal cse pass handle the other cases. */
3066 if (INSN_CUID (insn) < INSN_CUID (occr->insn))
3068 if (expr_reaches_here_p (occr, expr, bb, 1))
3073 insn_computes_expr = occr->insn;
3077 else /* Computation of the pattern outside this block. */
3079 if (expr_reaches_here_p (occr, expr, bb, 0))
3084 insn_computes_expr = occr->insn;
3089 if (insn_computes_expr == NULL)
3091 return insn_computes_expr;
3095 /* Return non-zero if the definition in DEF_INSN can reach INSN.
3096 Only called by can_disregard_other_sets. */
3099 def_reaches_here_p (insn, def_insn)
3104 if (TEST_BIT (reaching_defs[BLOCK_NUM (insn)], INSN_CUID (def_insn)))
3107 if (BLOCK_NUM (insn) == BLOCK_NUM (def_insn))
3109 if (INSN_CUID (def_insn) < INSN_CUID (insn))
3111 if (GET_CODE (PATTERN (def_insn)) == PARALLEL)
3113 if (GET_CODE (PATTERN (def_insn)) == CLOBBER)
3114 reg = XEXP (PATTERN (def_insn), 0);
3115 else if (GET_CODE (PATTERN (def_insn)) == SET)
3116 reg = SET_DEST (PATTERN (def_insn));
3119 return ! reg_set_between_p (reg, NEXT_INSN (def_insn), insn);
3128 /* Return non-zero if *ADDR_THIS_REG can only have one value at INSN.
3129 The value returned is the number of definitions that reach INSN.
3130 Returning a value of zero means that [maybe] more than one definition
3131 reaches INSN and the caller can't perform whatever optimization it is
3132 trying. i.e. it is always safe to return zero. */
3135 can_disregard_other_sets (addr_this_reg, insn, for_combine)
3136 struct reg_set **addr_this_reg;
3140 int number_of_reaching_defs = 0;
3141 struct reg_set *this_reg = *addr_this_reg;
3145 if (def_reaches_here_p (insn, this_reg->insn))
3147 number_of_reaching_defs++;
3148 /* Ignore parallels for now. */
3149 if (GET_CODE (PATTERN (this_reg->insn)) == PARALLEL)
3152 && (GET_CODE (PATTERN (this_reg->insn)) == CLOBBER
3153 || ! rtx_equal_p (SET_SRC (PATTERN (this_reg->insn)),
3154 SET_SRC (PATTERN (insn)))))
3156 /* A setting of the reg to a different value reaches INSN. */
3159 if (number_of_reaching_defs > 1)
3161 /* If in this setting the value the register is being
3162 set to is equal to the previous value the register
3163 was set to and this setting reaches the insn we are
3164 trying to do the substitution on then we are ok. */
3166 if (GET_CODE (PATTERN (this_reg->insn)) == CLOBBER)
3168 if (! rtx_equal_p (SET_SRC (PATTERN (this_reg->insn)),
3169 SET_SRC (PATTERN (insn))))
3172 *addr_this_reg = this_reg;
3175 /* prev_this_reg = this_reg; */
3176 this_reg = this_reg->next;
3179 return number_of_reaching_defs;
3182 /* Expression computed by insn is available and the substitution is legal,
3183 so try to perform the substitution.
3185 The result is non-zero if any changes were made. */
3188 handle_avail_expr (insn, expr)
3192 rtx pat, insn_computes_expr;
3194 struct reg_set *this_reg;
3195 int found_setting, use_src;
3198 /* We only handle the case where one computation of the expression
3199 reaches this instruction. */
3200 insn_computes_expr = computing_insn (expr, insn);
3201 if (insn_computes_expr == NULL)
3207 /* At this point we know only one computation of EXPR outside of this
3208 block reaches this insn. Now try to find a register that the
3209 expression is computed into. */
3211 if (GET_CODE (SET_SRC (PATTERN (insn_computes_expr))) == REG)
3213 /* This is the case when the available expression that reaches
3214 here has already been handled as an available expression. */
3215 int regnum_for_replacing = REGNO (SET_SRC (PATTERN (insn_computes_expr)));
3216 /* If the register was created by GCSE we can't use `reg_set_table',
3217 however we know it's set only once. */
3218 if (regnum_for_replacing >= max_gcse_regno
3219 /* If the register the expression is computed into is set only once,
3220 or only one set reaches this insn, we can use it. */
3221 || (((this_reg = reg_set_table[regnum_for_replacing]),
3222 this_reg->next == NULL)
3223 || can_disregard_other_sets (&this_reg, insn, 0)))
3232 int regnum_for_replacing = REGNO (SET_DEST (PATTERN (insn_computes_expr)));
3233 /* This shouldn't happen. */
3234 if (regnum_for_replacing >= max_gcse_regno)
3236 this_reg = reg_set_table[regnum_for_replacing];
3237 /* If the register the expression is computed into is set only once,
3238 or only one set reaches this insn, use it. */
3239 if (this_reg->next == NULL
3240 || can_disregard_other_sets (&this_reg, insn, 0))
3246 pat = PATTERN (insn);
3248 to = SET_SRC (PATTERN (insn_computes_expr));
3250 to = SET_DEST (PATTERN (insn_computes_expr));
3251 changed = validate_change (insn, &SET_SRC (pat), to, 0);
3253 /* We should be able to ignore the return code from validate_change but
3254 to play it safe we check. */
3258 if (gcse_file != NULL)
3260 fprintf (gcse_file, "GCSE: Replacing the source in insn %d with reg %d %s insn %d\n",
3261 INSN_UID (insn), REGNO (to),
3262 use_src ? "from" : "set in",
3263 INSN_UID (insn_computes_expr));
3268 /* The register that the expr is computed into is set more than once. */
3269 else if (1 /*expensive_op(this_pattrn->op) && do_expensive_gcse)*/)
3271 /* Insert an insn after insnx that copies the reg set in insnx
3272 into a new pseudo register call this new register REGN.
3273 From insnb until end of basic block or until REGB is set
3274 replace all uses of REGB with REGN. */
3277 to = gen_reg_rtx (GET_MODE (SET_DEST (PATTERN (insn_computes_expr))));
3279 /* Generate the new insn. */
3280 /* ??? If the change fails, we return 0, even though we created
3281 an insn. I think this is ok. */
3283 = emit_insn_after (gen_rtx_SET (VOIDmode, to,
3284 SET_DEST (PATTERN (insn_computes_expr))),
3285 insn_computes_expr);
3286 /* Keep block number table up to date. */
3287 set_block_num (new_insn, BLOCK_NUM (insn_computes_expr));
3288 /* Keep register set table up to date. */
3289 record_one_set (REGNO (to), new_insn);
3291 gcse_create_count++;
3292 if (gcse_file != NULL)
3294 fprintf (gcse_file, "GCSE: Creating insn %d to copy value of reg %d, computed in insn %d,\n",
3295 INSN_UID (NEXT_INSN (insn_computes_expr)),
3296 REGNO (SET_SRC (PATTERN (NEXT_INSN (insn_computes_expr)))),
3297 INSN_UID (insn_computes_expr));
3298 fprintf (gcse_file, " into newly allocated reg %d\n", REGNO (to));
3301 pat = PATTERN (insn);
3303 /* Do register replacement for INSN. */
3304 changed = validate_change (insn, &SET_SRC (pat),
3305 SET_DEST (PATTERN (NEXT_INSN (insn_computes_expr))),
3308 /* We should be able to ignore the return code from validate_change but
3309 to play it safe we check. */
3313 if (gcse_file != NULL)
3315 fprintf (gcse_file, "GCSE: Replacing the source in insn %d with reg %d set in insn %d\n",
3317 REGNO (SET_DEST (PATTERN (NEXT_INSN (insn_computes_expr)))),
3318 INSN_UID (insn_computes_expr));
3327 /* Perform classic GCSE.
3328 This is called by one_classic_gcse_pass after all the dataflow analysis
3331 The result is non-zero if a change was made. */
3339 /* Note we start at block 1. */
3342 for (bb = 1; bb < n_basic_blocks; bb++)
3344 /* Reset tables used to keep track of what's still valid [since the
3345 start of the block]. */
3346 reset_opr_set_tables ();
3348 for (insn = BLOCK_HEAD (bb);
3349 insn != NULL && insn != NEXT_INSN (BLOCK_END (bb));
3350 insn = NEXT_INSN (insn))
3352 /* Is insn of form (set (pseudo-reg) ...)? */
3354 if (GET_CODE (insn) == INSN
3355 && GET_CODE (PATTERN (insn)) == SET
3356 && GET_CODE (SET_DEST (PATTERN (insn))) == REG
3357 && REGNO (SET_DEST (PATTERN (insn))) >= FIRST_PSEUDO_REGISTER)
3359 rtx pat = PATTERN (insn);
3360 rtx src = SET_SRC (pat);
3363 if (want_to_gcse_p (src)
3364 /* Is the expression recorded? */
3365 && ((expr = lookup_expr (src)) != NULL)
3366 /* Is the expression available [at the start of the
3368 && TEST_BIT (ae_in[bb], expr->bitmap_index)
3369 /* Are the operands unchanged since the start of the
3371 && oprs_not_set_p (src, insn))
3372 changed |= handle_avail_expr (insn, expr);
3375 /* Keep track of everything modified by this insn. */
3376 /* ??? Need to be careful w.r.t. mods done to INSN. */
3377 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
3378 mark_oprs_set (insn);
3385 /* Top level routine to perform one classic GCSE pass.
3387 Return non-zero if a change was made. */
3390 one_classic_gcse_pass (pass)
3395 gcse_subst_count = 0;
3396 gcse_create_count = 0;
3398 alloc_expr_hash_table (max_cuid);
3399 alloc_rd_mem (n_basic_blocks, max_cuid);
3400 compute_expr_hash_table ();
3402 dump_hash_table (gcse_file, "Expression", expr_hash_table,
3403 expr_hash_table_size, n_exprs);
3408 alloc_avail_expr_mem (n_basic_blocks, n_exprs);
3410 compute_ae_kill (ae_gen, ae_kill);
3411 compute_available (ae_gen, ae_kill, ae_out, ae_in);
3412 changed = classic_gcse ();
3413 free_avail_expr_mem ();
3416 free_expr_hash_table ();
3420 fprintf (gcse_file, "\n");
3421 fprintf (gcse_file, "GCSE of %s, pass %d: %d bytes needed, %d substs, %d insns created\n",
3422 current_function_name, pass,
3423 bytes_used, gcse_subst_count, gcse_create_count);
3429 /* Compute copy/constant propagation working variables. */
3431 /* Local properties of assignments. */
3433 static sbitmap *cprop_pavloc;
3434 static sbitmap *cprop_absaltered;
3436 /* Global properties of assignments (computed from the local properties). */
3438 static sbitmap *cprop_avin;
3439 static sbitmap *cprop_avout;
3441 /* Allocate vars used for copy/const propagation.
3442 N_BLOCKS is the number of basic blocks.
3443 N_SETS is the number of sets. */
3446 alloc_cprop_mem (n_blocks, n_sets)
3447 int n_blocks, n_sets;
3449 cprop_pavloc = sbitmap_vector_alloc (n_blocks, n_sets);
3450 cprop_absaltered = sbitmap_vector_alloc (n_blocks, n_sets);
3452 cprop_avin = sbitmap_vector_alloc (n_blocks, n_sets);
3453 cprop_avout = sbitmap_vector_alloc (n_blocks, n_sets);
3456 /* Free vars used by copy/const propagation. */
3461 free (cprop_pavloc);
3462 free (cprop_absaltered);
3467 /* For each block, compute whether X is transparent.
3468 X is either an expression or an assignment [though we don't care which,
3469 for this context an assignment is treated as an expression].
3470 For each block where an element of X is modified, set (SET_P == 1) or reset
3471 (SET_P == 0) the INDX bit in BMAP. */
3474 compute_transp (x, indx, bmap, set_p)
3484 /* repeat is used to turn tail-recursion into iteration. */
3490 code = GET_CODE (x);
3496 int regno = REGNO (x);
3500 if (regno < FIRST_PSEUDO_REGISTER)
3502 for (bb = 0; bb < n_basic_blocks; bb++)
3503 if (TEST_BIT (reg_set_in_block[bb], regno))
3504 SET_BIT (bmap[bb], indx);
3508 for (r = reg_set_table[regno]; r != NULL; r = r->next)
3510 bb = BLOCK_NUM (r->insn);
3511 SET_BIT (bmap[bb], indx);
3517 if (regno < FIRST_PSEUDO_REGISTER)
3519 for (bb = 0; bb < n_basic_blocks; bb++)
3520 if (TEST_BIT (reg_set_in_block[bb], regno))
3521 RESET_BIT (bmap[bb], indx);
3525 for (r = reg_set_table[regno]; r != NULL; r = r->next)
3527 bb = BLOCK_NUM (r->insn);
3528 RESET_BIT (bmap[bb], indx);
3538 for (bb = 0; bb < n_basic_blocks; bb++)
3539 if (mem_set_in_block[bb])
3540 SET_BIT (bmap[bb], indx);
3544 for (bb = 0; bb < n_basic_blocks; bb++)
3545 if (mem_set_in_block[bb])
3546 RESET_BIT (bmap[bb], indx);
3566 i = GET_RTX_LENGTH (code) - 1;
3567 fmt = GET_RTX_FORMAT (code);
3572 rtx tem = XEXP (x, i);
3574 /* If we are about to do the last recursive call
3575 needed at this level, change it into iteration.
3576 This function is called enough to be worth it. */
3582 compute_transp (tem, indx, bmap, set_p);
3584 else if (fmt[i] == 'E')
3587 for (j = 0; j < XVECLEN (x, i); j++)
3588 compute_transp (XVECEXP (x, i, j), indx, bmap, set_p);
3593 /* Top level routine to do the dataflow analysis needed by copy/const
3597 compute_cprop_data ()
3599 compute_local_properties (cprop_absaltered, cprop_pavloc, NULL, 1);
3600 compute_available (cprop_pavloc, cprop_absaltered,
3601 cprop_avout, cprop_avin);
3604 /* Copy/constant propagation. */
3606 /* Maximum number of register uses in an insn that we handle. */
3609 /* Table of uses found in an insn.
3610 Allocated statically to avoid alloc/free complexity and overhead. */
3611 static struct reg_use reg_use_table[MAX_USES];
3613 /* Index into `reg_use_table' while building it. */
3614 static int reg_use_count;
3616 /* Set up a list of register numbers used in INSN.
3617 The found uses are stored in `reg_use_table'.
3618 `reg_use_count' is initialized to zero before entry, and
3619 contains the number of uses in the table upon exit.
3621 ??? If a register appears multiple times we will record it multiple
3622 times. This doesn't hurt anything but it will slow things down. */
3632 /* repeat is used to turn tail-recursion into iteration. */
3638 code = GET_CODE (x);
3642 if (reg_use_count == MAX_USES)
3644 reg_use_table[reg_use_count].reg_rtx = x;
3662 case ASM_INPUT: /*FIXME*/
3666 if (GET_CODE (SET_DEST (x)) == MEM)
3667 find_used_regs (SET_DEST (x));
3675 /* Recursively scan the operands of this expression. */
3677 fmt = GET_RTX_FORMAT (code);
3678 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
3682 /* If we are about to do the last recursive call
3683 needed at this level, change it into iteration.
3684 This function is called enough to be worth it. */
3690 find_used_regs (XEXP (x, i));
3692 else if (fmt[i] == 'E')
3695 for (j = 0; j < XVECLEN (x, i); j++)
3696 find_used_regs (XVECEXP (x, i, j));
3701 /* Try to replace all non-SET_DEST occurrences of FROM in INSN with TO.
3702 Returns non-zero is successful. */
3705 try_replace_reg (from, to, insn)
3708 /* If this fails we could try to simplify the result of the
3709 replacement and attempt to recognize the simplified insn.
3711 But we need a general simplify_rtx that doesn't have pass
3712 specific state variables. I'm not aware of one at the moment. */
3713 return validate_replace_src (from, to, insn);
3716 /* Find a set of REGNO that is available on entry to INSN's block.
3717 Returns NULL if not found. */
3719 static struct expr *
3720 find_avail_set (regno, insn)
3724 /* SET1 contains the last set found that can be returned to the caller for
3725 use in a substitution. */
3726 struct expr *set1 = 0;
3728 /* Loops are not possible here. To get a loop we would need two sets
3729 available at the start of the block containing INSN. ie we would
3730 need two sets like this available at the start of the block:
3732 (set (reg X) (reg Y))
3733 (set (reg Y) (reg X))
3735 This can not happen since the set of (reg Y) would have killed the
3736 set of (reg X) making it unavailable at the start of this block. */
3740 struct expr *set = lookup_set (regno, NULL_RTX);
3742 /* Find a set that is available at the start of the block
3743 which contains INSN. */
3746 if (TEST_BIT (cprop_avin[BLOCK_NUM (insn)], set->bitmap_index))
3748 set = next_set (regno, set);
3751 /* If no available set was found we've reached the end of the
3752 (possibly empty) copy chain. */
3756 if (GET_CODE (set->expr) != SET)
3759 src = SET_SRC (set->expr);
3761 /* We know the set is available.
3762 Now check that SRC is ANTLOC (i.e. none of the source operands
3763 have changed since the start of the block).
3765 If the source operand changed, we may still use it for the next
3766 iteration of this loop, but we may not use it for substitutions. */
3767 if (CONSTANT_P (src) || oprs_not_set_p (src, insn))
3770 /* If the source of the set is anything except a register, then
3771 we have reached the end of the copy chain. */
3772 if (GET_CODE (src) != REG)
3775 /* Follow the copy chain, ie start another iteration of the loop
3776 and see if we have an available copy into SRC. */
3777 regno = REGNO (src);
3780 /* SET1 holds the last set that was available and anticipatable at
3785 /* Subroutine of cprop_insn that tries to propagate constants into
3786 JUMP_INSNS. INSN must be a conditional jump; COPY is a copy of it
3787 that we can use for substitutions.
3788 REG_USED is the use we will try to replace, SRC is the constant we
3789 will try to substitute for it.
3790 Returns nonzero if a change was made. */
3792 cprop_jump (insn, copy, reg_used, src)
3794 struct reg_use *reg_used;
3797 rtx set = PATTERN (copy);
3800 /* Replace the register with the appropriate constant. */
3801 replace_rtx (SET_SRC (set), reg_used->reg_rtx, src);
3803 temp = simplify_ternary_operation (GET_CODE (SET_SRC (set)),
3804 GET_MODE (SET_SRC (set)),
3805 GET_MODE (XEXP (SET_SRC (set), 0)),
3806 XEXP (SET_SRC (set), 0),
3807 XEXP (SET_SRC (set), 1),
3808 XEXP (SET_SRC (set), 2));
3810 /* If no simplification can be made, then try the next
3815 SET_SRC (set) = temp;
3817 /* That may have changed the structure of TEMP, so
3818 force it to be rerecognized if it has not turned
3819 into a nop or unconditional jump. */
3821 INSN_CODE (copy) = -1;
3822 if ((SET_DEST (set) == pc_rtx
3823 && (SET_SRC (set) == pc_rtx
3824 || GET_CODE (SET_SRC (set)) == LABEL_REF))
3825 || recog (PATTERN (copy), copy, NULL) >= 0)
3827 /* This has either become an unconditional jump
3828 or a nop-jump. We'd like to delete nop jumps
3829 here, but doing so confuses gcse. So we just
3830 make the replacement and let later passes
3832 PATTERN (insn) = set;
3833 INSN_CODE (insn) = -1;
3835 /* One less use of the label this insn used to jump to
3836 if we turned this into a NOP jump. */
3837 if (SET_SRC (set) == pc_rtx && JUMP_LABEL (insn) != 0)
3838 --LABEL_NUSES (JUMP_LABEL (insn));
3840 /* If this has turned into an unconditional jump,
3841 then put a barrier after it so that the unreachable
3842 code will be deleted. */
3843 if (GET_CODE (SET_SRC (set)) == LABEL_REF)
3844 emit_barrier_after (insn);
3846 run_jump_opt_after_gcse = 1;
3849 if (gcse_file != NULL)
3851 int regno = REGNO (reg_used->reg_rtx);
3852 fprintf (gcse_file, "CONST-PROP: Replacing reg %d in insn %d with constant ",
3853 regno, INSN_UID (insn));
3854 print_rtl (gcse_file, src);
3855 fprintf (gcse_file, "\n");
3863 /* Subroutine of cprop_insn that tries to propagate constants into
3864 JUMP_INSNS for machines that have CC0. INSN is a single set that
3865 stores into CC0; the insn following it is a conditional jump.
3866 REG_USED is the use we will try to replace, SRC is the constant we
3867 will try to substitute for it.
3868 Returns nonzero if a change was made. */
3870 cprop_cc0_jump (insn, reg_used, src)
3872 struct reg_use *reg_used;
3875 rtx jump = NEXT_INSN (insn);
3876 rtx copy = copy_rtx (jump);
3877 rtx set = PATTERN (copy);
3879 /* We need to copy the source of the cc0 setter, as cprop_jump is going to
3880 substitute into it. */
3881 replace_rtx (SET_SRC (set), cc0_rtx, copy_rtx (SET_SRC (PATTERN (insn))));
3882 if (! cprop_jump (jump, copy, reg_used, src))
3885 /* If we succeeded, delete the cc0 setter. */
3886 PUT_CODE (insn, NOTE);
3887 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
3888 NOTE_SOURCE_FILE (insn) = 0;
3893 /* Perform constant and copy propagation on INSN.
3894 The result is non-zero if a change was made. */
3897 cprop_insn (insn, alter_jumps)
3901 struct reg_use *reg_used;
3904 /* Only propagate into SETs. Note that a conditional jump is a
3905 SET with pc_rtx as the destination. */
3906 if ((GET_CODE (insn) != INSN
3907 && GET_CODE (insn) != JUMP_INSN)
3908 || GET_CODE (PATTERN (insn)) != SET)
3912 find_used_regs (PATTERN (insn));
3914 reg_used = ®_use_table[0];
3915 for ( ; reg_use_count > 0; reg_used++, reg_use_count--)
3919 int regno = REGNO (reg_used->reg_rtx);
3921 /* Ignore registers created by GCSE.
3922 We do this because ... */
3923 if (regno >= max_gcse_regno)
3926 /* If the register has already been set in this block, there's
3927 nothing we can do. */
3928 if (! oprs_not_set_p (reg_used->reg_rtx, insn))
3931 /* Find an assignment that sets reg_used and is available
3932 at the start of the block. */
3933 set = find_avail_set (regno, insn);
3938 /* ??? We might be able to handle PARALLELs. Later. */
3939 if (GET_CODE (pat) != SET)
3941 src = SET_SRC (pat);
3943 /* Constant propagation. */
3944 if (GET_CODE (src) == CONST_INT || GET_CODE (src) == CONST_DOUBLE
3945 || GET_CODE (src) == SYMBOL_REF)
3947 /* Handle normal insns first. */
3948 if (GET_CODE (insn) == INSN
3949 && try_replace_reg (reg_used->reg_rtx, src, insn))
3953 if (gcse_file != NULL)
3955 fprintf (gcse_file, "CONST-PROP: Replacing reg %d in insn %d with constant ",
3956 regno, INSN_UID (insn));
3957 print_rtl (gcse_file, src);
3958 fprintf (gcse_file, "\n");
3961 /* The original insn setting reg_used may or may not now be
3962 deletable. We leave the deletion to flow. */
3965 /* Try to propagate a CONST_INT into a conditional jump.
3966 We're pretty specific about what we will handle in this
3967 code, we can extend this as necessary over time.
3969 Right now the insn in question must look like
3970 (set (pc) (if_then_else ...)) */
3971 else if (alter_jumps
3972 && GET_CODE (insn) == JUMP_INSN
3973 && condjump_p (insn)
3974 && ! simplejump_p (insn))
3975 changed |= cprop_jump (insn, copy_rtx (insn), reg_used, src);
3977 /* Similar code for machines that use a pair of CC0 setter and
3978 conditional jump insn. */
3979 else if (alter_jumps
3980 && GET_CODE (PATTERN (insn)) == SET
3981 && SET_DEST (PATTERN (insn)) == cc0_rtx
3982 && GET_CODE (NEXT_INSN (insn)) == JUMP_INSN
3983 && condjump_p (NEXT_INSN (insn))
3984 && ! simplejump_p (NEXT_INSN (insn)))
3985 changed |= cprop_cc0_jump (insn, reg_used, src);
3988 else if (GET_CODE (src) == REG
3989 && REGNO (src) >= FIRST_PSEUDO_REGISTER
3990 && REGNO (src) != regno)
3992 if (try_replace_reg (reg_used->reg_rtx, src, insn))
3996 if (gcse_file != NULL)
3998 fprintf (gcse_file, "COPY-PROP: Replacing reg %d in insn %d with reg %d\n",
3999 regno, INSN_UID (insn), REGNO (src));
4002 /* The original insn setting reg_used may or may not now be
4003 deletable. We leave the deletion to flow. */
4004 /* FIXME: If it turns out that the insn isn't deletable,
4005 then we may have unnecessarily extended register lifetimes
4006 and made things worse. */
4014 /* Forward propagate copies.
4015 This includes copies and constants.
4016 Return non-zero if a change was made. */
4025 /* Note we start at block 1. */
4028 for (bb = 1; bb < n_basic_blocks; bb++)
4030 /* Reset tables used to keep track of what's still valid [since the
4031 start of the block]. */
4032 reset_opr_set_tables ();
4034 for (insn = BLOCK_HEAD (bb);
4035 insn != NULL && insn != NEXT_INSN (BLOCK_END (bb));
4036 insn = NEXT_INSN (insn))
4038 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
4040 changed |= cprop_insn (insn, alter_jumps);
4042 /* Keep track of everything modified by this insn. */
4043 /* ??? Need to be careful w.r.t. mods done to INSN. Don't
4044 call mark_oprs_set if we turned the insn into a NOTE. */
4045 if (GET_CODE (insn) != NOTE)
4046 mark_oprs_set (insn);
4051 if (gcse_file != NULL)
4052 fprintf (gcse_file, "\n");
4057 /* Perform one copy/constant propagation pass.
4058 F is the first insn in the function.
4059 PASS is the pass count. */
4062 one_cprop_pass (pass, alter_jumps)
4068 const_prop_count = 0;
4069 copy_prop_count = 0;
4071 alloc_set_hash_table (max_cuid);
4072 compute_set_hash_table ();
4074 dump_hash_table (gcse_file, "SET", set_hash_table, set_hash_table_size,
4078 alloc_cprop_mem (n_basic_blocks, n_sets);
4079 compute_cprop_data ();
4080 changed = cprop (alter_jumps);
4083 free_set_hash_table ();
4087 fprintf (gcse_file, "CPROP of %s, pass %d: %d bytes needed, %d const props, %d copy props\n",
4088 current_function_name, pass,
4089 bytes_used, const_prop_count, copy_prop_count);
4090 fprintf (gcse_file, "\n");
4096 /* Compute PRE+LCM working variables. */
4098 /* Local properties of expressions. */
4099 /* Nonzero for expressions that are transparent in the block. */
4100 static sbitmap *transp;
4102 /* Nonzero for expressions that are transparent at the end of the block.
4103 This is only zero for expressions killed by abnormal critical edge
4104 created by a calls. */
4105 static sbitmap *transpout;
4107 /* Nonzero for expressions that are computed (available) in the block. */
4108 static sbitmap *comp;
4110 /* Nonzero for expressions that are locally anticipatable in the block. */
4111 static sbitmap *antloc;
4113 /* Nonzero for expressions where this block is an optimal computation
4115 static sbitmap *pre_optimal;
4117 /* Nonzero for expressions which are redundant in a particular block. */
4118 static sbitmap *pre_redundant;
4120 /* Nonzero for expressions which should be inserted on a specific edge. */
4121 static sbitmap *pre_insert_map;
4123 /* Nonzero for expressions which should be deleted in a specific block. */
4124 static sbitmap *pre_delete_map;
4126 /* Contains the edge_list returned by pre_edge_lcm. */
4127 static struct edge_list *edge_list;
4129 static sbitmap *temp_bitmap;
4131 /* Redundant insns. */
4132 static sbitmap pre_redundant_insns;
4134 /* Allocate vars used for PRE analysis. */
4137 alloc_pre_mem (n_blocks, n_exprs)
4138 int n_blocks, n_exprs;
4140 transp = sbitmap_vector_alloc (n_blocks, n_exprs);
4141 comp = sbitmap_vector_alloc (n_blocks, n_exprs);
4142 antloc = sbitmap_vector_alloc (n_blocks, n_exprs);
4143 temp_bitmap = sbitmap_vector_alloc (n_blocks, n_exprs);
4146 pre_redundant = NULL;
4147 pre_insert_map = NULL;
4148 pre_delete_map = NULL;
4152 transpout = sbitmap_vector_alloc (n_blocks, n_exprs);
4153 ae_kill = sbitmap_vector_alloc (n_blocks, n_exprs);
4154 /* pre_insert and pre_delete are allocated later. */
4157 /* Free vars used for PRE analysis. */
4170 free (pre_redundant);
4172 free (pre_insert_map);
4174 free (pre_delete_map);
4187 transp = comp = antloc = NULL;
4188 pre_optimal = pre_redundant = pre_insert_map = pre_delete_map = NULL;
4189 transpout = ae_in = ae_out = ae_kill = NULL;
4194 /* Top level routine to do the dataflow analysis needed by PRE. */
4199 compute_local_properties (transp, comp, antloc, 0);
4200 compute_transpout ();
4201 sbitmap_vector_zero (ae_kill, n_basic_blocks);
4202 compute_ae_kill (comp, ae_kill);
4203 edge_list = pre_edge_lcm (gcse_file, n_exprs, transp, comp, antloc,
4204 ae_kill, &pre_insert_map, &pre_delete_map);
4210 /* Return non-zero if an occurrence of expression EXPR in OCCR_BB would reach
4213 VISITED is a pointer to a working buffer for tracking which BB's have
4214 been visited. It is NULL for the top-level call.
4216 CHECK_PRE_COMP controls whether or not we check for a computation of
4219 We treat reaching expressions that go through blocks containing the same
4220 reaching expression as "not reaching". E.g. if EXPR is generated in blocks
4221 2 and 3, INSN is in block 4, and 2->3->4, we treat the expression in block
4222 2 as not reaching. The intent is to improve the probability of finding
4223 only one reaching expression and to reduce register lifetimes by picking
4224 the closest such expression. */
4227 pre_expr_reaches_here_p_work (occr_bb, expr, bb, check_pre_comp, visited)
4236 for (pred = BASIC_BLOCK (bb)->pred; pred != NULL; pred = pred->pred_next)
4238 int pred_bb = pred->src->index;
4240 if (pred->src == ENTRY_BLOCK_PTR
4241 /* Has predecessor has already been visited? */
4242 || visited[pred_bb])
4244 /* Nothing to do. */
4246 /* Does this predecessor generate this expression? */
4247 else if ((!check_pre_comp && occr_bb == pred_bb)
4248 || TEST_BIT (comp[pred_bb], expr->bitmap_index))
4250 /* Is this the occurrence we're looking for?
4251 Note that there's only one generating occurrence per block
4252 so we just need to check the block number. */
4253 if (occr_bb == pred_bb)
4255 visited[pred_bb] = 1;
4257 /* Ignore this predecessor if it kills the expression. */
4258 else if (! TEST_BIT (transp[pred_bb], expr->bitmap_index))
4259 visited[pred_bb] = 1;
4260 /* Neither gen nor kill. */
4263 visited[pred_bb] = 1;
4264 if (pre_expr_reaches_here_p_work (occr_bb, expr, pred_bb,
4265 check_pre_comp, visited))
4270 /* All paths have been checked. */
4274 /* The wrapper for pre_expr_reaches_here_work that ensures that any
4275 memory allocated for that function is returned. */
4278 pre_expr_reaches_here_p (occr_bb, expr, bb, check_pre_comp)
4285 char * visited = (char *) xcalloc (n_basic_blocks, 1);
4287 rval = pre_expr_reaches_here_p_work(occr_bb, expr, bb, check_pre_comp,
4296 /* Given an expr, generate RTL which we can insert at the end of a BB,
4297 or on an edge. Set the block number of any insns generated to
4301 process_insert_insn (expr)
4304 rtx reg = expr->reaching_reg;
4305 rtx pat, copied_expr;
4309 copied_expr = copy_rtx (expr->expr);
4310 emit_move_insn (reg, copied_expr);
4311 first_new_insn = get_insns ();
4312 pat = gen_sequence ();
4318 /* Add EXPR to the end of basic block BB.
4320 This is used by both the PRE and code hoisting.
4322 For PRE, we want to verify that the expr is either transparent
4323 or locally anticipatable in the target block. This check makes
4324 no sense for code hoisting. */
4327 insert_insn_end_bb (expr, bb, pre)
4332 rtx insn = BLOCK_END (bb);
4334 rtx reg = expr->reaching_reg;
4335 int regno = REGNO (reg);
4338 pat = process_insert_insn (expr);
4340 /* If the last insn is a jump, insert EXPR in front [taking care to
4341 handle cc0, etc. properly]. */
4343 if (GET_CODE (insn) == JUMP_INSN)
4349 /* If this is a jump table, then we can't insert stuff here. Since
4350 we know the previous real insn must be the tablejump, we insert
4351 the new instruction just before the tablejump. */
4352 if (GET_CODE (PATTERN (insn)) == ADDR_VEC
4353 || GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC)
4354 insn = prev_real_insn (insn);
4357 /* FIXME: 'twould be nice to call prev_cc0_setter here but it aborts
4358 if cc0 isn't set. */
4359 note = find_reg_note (insn, REG_CC_SETTER, NULL_RTX);
4361 insn = XEXP (note, 0);
4364 rtx maybe_cc0_setter = prev_nonnote_insn (insn);
4365 if (maybe_cc0_setter
4366 && GET_RTX_CLASS (GET_CODE (maybe_cc0_setter)) == 'i'
4367 && sets_cc0_p (PATTERN (maybe_cc0_setter)))
4368 insn = maybe_cc0_setter;
4371 /* FIXME: What if something in cc0/jump uses value set in new insn? */
4372 new_insn = emit_insn_before (pat, insn);
4373 if (BLOCK_HEAD (bb) == insn)
4374 BLOCK_HEAD (bb) = new_insn;
4376 /* Likewise if the last insn is a call, as will happen in the presence
4377 of exception handling. */
4378 else if (GET_CODE (insn) == CALL_INSN)
4380 HARD_REG_SET parm_regs;
4384 /* Keeping in mind SMALL_REGISTER_CLASSES and parameters in registers,
4385 we search backward and place the instructions before the first
4386 parameter is loaded. Do this for everyone for consistency and a
4387 presumtion that we'll get better code elsewhere as well. */
4389 /* It should always be the case that we can put these instructions
4390 anywhere in the basic block with performing PRE optimizations.
4393 && !TEST_BIT (antloc[bb], expr->bitmap_index)
4394 && !TEST_BIT (transp[bb], expr->bitmap_index))
4397 /* Since different machines initialize their parameter registers
4398 in different orders, assume nothing. Collect the set of all
4399 parameter registers. */
4400 CLEAR_HARD_REG_SET (parm_regs);
4402 for (p = CALL_INSN_FUNCTION_USAGE (insn); p ; p = XEXP (p, 1))
4403 if (GET_CODE (XEXP (p, 0)) == USE
4404 && GET_CODE (XEXP (XEXP (p, 0), 0)) == REG)
4406 int regno = REGNO (XEXP (XEXP (p, 0), 0));
4407 if (regno >= FIRST_PSEUDO_REGISTER)
4409 SET_HARD_REG_BIT (parm_regs, regno);
4413 /* Search backward for the first set of a register in this set. */
4414 while (nparm_regs && BLOCK_HEAD (bb) != insn)
4416 insn = PREV_INSN (insn);
4417 p = single_set (insn);
4418 if (p && GET_CODE (SET_DEST (p)) == REG
4419 && REGNO (SET_DEST (p)) < FIRST_PSEUDO_REGISTER
4420 && TEST_HARD_REG_BIT (parm_regs, REGNO (SET_DEST (p))))
4422 CLEAR_HARD_REG_BIT (parm_regs, REGNO (SET_DEST (p)));
4427 /* If we found all the parameter loads, then we want to insert
4428 before the first parameter load.
4430 If we did not find all the parameter loads, then we might have
4431 stopped on the head of the block, which could be a CODE_LABEL.
4432 If we inserted before the CODE_LABEL, then we would be putting
4433 the insn in the wrong basic block. In that case, put the insn
4434 after the CODE_LABEL.
4436 ?!? Do we need to account for NOTE_INSN_BASIC_BLOCK here? */
4437 if (GET_CODE (insn) != CODE_LABEL)
4439 new_insn = emit_insn_before (pat, insn);
4440 if (BLOCK_HEAD (bb) == insn)
4441 BLOCK_HEAD (bb) = new_insn;
4445 new_insn = emit_insn_after (pat, insn);
4450 new_insn = emit_insn_after (pat, insn);
4451 BLOCK_END (bb) = new_insn;
4454 /* Keep block number table up to date.
4455 Note, PAT could be a multiple insn sequence, we have to make
4456 sure that each insn in the sequence is handled. */
4457 if (GET_CODE (pat) == SEQUENCE)
4461 for (i = 0; i < XVECLEN (pat, 0); i++)
4463 rtx insn = XVECEXP (pat, 0, i);
4464 set_block_num (insn, bb);
4465 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
4466 add_label_notes (PATTERN (insn), new_insn);
4467 note_stores (PATTERN (insn), record_set_info, insn);
4472 add_label_notes (SET_SRC (pat), new_insn);
4473 set_block_num (new_insn, bb);
4474 /* Keep register set table up to date. */
4475 record_one_set (regno, new_insn);
4478 gcse_create_count++;
4482 fprintf (gcse_file, "PRE/HOIST: end of bb %d, insn %d, copying expression %d to reg %d\n",
4483 bb, INSN_UID (new_insn), expr->bitmap_index, regno);
4487 /* Insert partially redundant expressions on edges in the CFG to make
4488 the expressions fully redundant. */
4491 pre_edge_insert (edge_list, index_map)
4492 struct edge_list *edge_list;
4493 struct expr **index_map;
4495 int e, i, num_edges, set_size, did_insert = 0;
4498 /* Where PRE_INSERT_MAP is nonzero, we add the expression on that edge
4499 if it reaches any of the deleted expressions. */
4501 set_size = pre_insert_map[0]->size;
4502 num_edges = NUM_EDGES (edge_list);
4503 inserted = sbitmap_vector_alloc (num_edges, n_exprs);
4504 sbitmap_vector_zero (inserted, num_edges);
4506 for (e = 0; e < num_edges; e++)
4509 basic_block pred = INDEX_EDGE_PRED_BB (edge_list, e);
4510 int bb = pred->index;
4512 for (i = indx = 0; i < set_size; i++, indx += SBITMAP_ELT_BITS)
4514 SBITMAP_ELT_TYPE insert = pre_insert_map[e]->elms[i];
4517 for (j = indx; insert && j < n_exprs; j++, insert >>= 1)
4519 if ((insert & 1) != 0 && index_map[j]->reaching_reg != NULL_RTX)
4521 struct expr *expr = index_map[j];
4524 /* Now look at each deleted occurence of this expression. */
4525 for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
4527 if (! occr->deleted_p)
4530 /* Insert this expression on this edge if if it would
4531 reach the deleted occurence in BB. */
4532 if (!TEST_BIT (inserted[e], j)
4533 && (bb == ENTRY_BLOCK
4534 || pre_expr_reaches_here_p (bb, expr,
4535 BLOCK_NUM (occr->insn), 0)))
4538 edge eg = INDEX_EDGE (edge_list, e);
4539 /* We can't insert anything on an abnormal
4540 and critical edge, so we insert the
4541 insn at the end of the previous block. There
4542 are several alternatives detailed in
4543 Morgans book P277 (sec 10.5) for handling
4544 this situation. This one is easiest for now. */
4546 if ((eg->flags & EDGE_ABNORMAL) == EDGE_ABNORMAL)
4548 insert_insn_end_bb (index_map[j], bb, 0);
4552 insn = process_insert_insn (index_map[j]);
4553 insert_insn_on_edge (insn, eg);
4558 "PRE/HOIST: edge (%d,%d), copy expression %d\n",
4560 INDEX_EDGE_SUCC_BB (edge_list, e)->index, expr->bitmap_index);
4562 SET_BIT (inserted[e], j);
4564 gcse_create_count++;
4578 /* Copy the result of INSN to REG.
4579 INDX is the expression number. */
4582 pre_insert_copy_insn (expr, insn)
4586 rtx reg = expr->reaching_reg;
4587 int regno = REGNO (reg);
4588 int indx = expr->bitmap_index;
4589 rtx set = single_set (insn);
4591 int bb = BLOCK_NUM (insn);
4595 new_insn = emit_insn_after (gen_rtx_SET (VOIDmode, reg, SET_DEST (set)),
4597 /* Keep block number table up to date. */
4598 set_block_num (new_insn, bb);
4599 /* Keep register set table up to date. */
4600 record_one_set (regno, new_insn);
4601 if (insn == BLOCK_END (bb))
4602 BLOCK_END (bb) = new_insn;
4604 gcse_create_count++;
4608 "PRE: bb %d, insn %d, copy expression %d in insn %d to reg %d\n",
4609 BLOCK_NUM (insn), INSN_UID (new_insn), indx,
4610 INSN_UID (insn), regno);
4613 /* Copy available expressions that reach the redundant expression
4614 to `reaching_reg'. */
4617 pre_insert_copies ()
4621 /* For each available expression in the table, copy the result to
4622 `reaching_reg' if the expression reaches a deleted one.
4624 ??? The current algorithm is rather brute force.
4625 Need to do some profiling. */
4627 for (i = 0; i < expr_hash_table_size; i++)
4631 for (expr = expr_hash_table[i]; expr != NULL; expr = expr->next_same_hash)
4635 /* If the basic block isn't reachable, PPOUT will be TRUE.
4636 However, we don't want to insert a copy here because the
4637 expression may not really be redundant. So only insert
4638 an insn if the expression was deleted.
4639 This test also avoids further processing if the expression
4640 wasn't deleted anywhere. */
4641 if (expr->reaching_reg == NULL)
4644 for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
4648 if (! occr->deleted_p)
4651 for (avail = expr->avail_occr; avail != NULL; avail = avail->next)
4653 rtx insn = avail->insn;
4655 /* No need to handle this one if handled already. */
4656 if (avail->copied_p)
4658 /* Don't handle this one if it's a redundant one. */
4659 if (TEST_BIT (pre_redundant_insns, INSN_CUID (insn)))
4661 /* Or if the expression doesn't reach the deleted one. */
4662 if (! pre_expr_reaches_here_p (BLOCK_NUM (avail->insn), expr,
4663 BLOCK_NUM (occr->insn),1))
4666 /* Copy the result of avail to reaching_reg. */
4667 pre_insert_copy_insn (expr, insn);
4668 avail->copied_p = 1;
4675 /* Delete redundant computations.
4676 Deletion is done by changing the insn to copy the `reaching_reg' of
4677 the expression into the result of the SET. It is left to later passes
4678 (cprop, cse2, flow, combine, regmove) to propagate the copy or eliminate it.
4680 Returns non-zero if a change is made. */
4687 /* Compute the expressions which are redundant and need to be replaced by
4688 copies from the reaching reg to the target reg. */
4689 for (bb = 0; bb < n_basic_blocks; bb++)
4690 sbitmap_copy (temp_bitmap[bb], pre_delete_map[bb]);
4693 for (i = 0; i < expr_hash_table_size; i++)
4697 for (expr = expr_hash_table[i]; expr != NULL; expr = expr->next_same_hash)
4700 int indx = expr->bitmap_index;
4702 /* We only need to search antic_occr since we require
4705 for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
4707 rtx insn = occr->insn;
4709 int bb = BLOCK_NUM (insn);
4711 if (TEST_BIT (temp_bitmap[bb], indx))
4713 set = single_set (insn);
4717 /* Create a pseudo-reg to store the result of reaching
4718 expressions into. Get the mode for the new pseudo
4719 from the mode of the original destination pseudo. */
4720 if (expr->reaching_reg == NULL)
4722 = gen_reg_rtx (GET_MODE (SET_DEST (set)));
4724 /* In theory this should never fail since we're creating
4727 However, on the x86 some of the movXX patterns actually
4728 contain clobbers of scratch regs. This may cause the
4729 insn created by validate_change to not match any pattern
4730 and thus cause validate_change to fail. */
4731 if (validate_change (insn, &SET_SRC (set),
4732 expr->reaching_reg, 0))
4734 occr->deleted_p = 1;
4735 SET_BIT (pre_redundant_insns, INSN_CUID (insn));
4743 "PRE: redundant insn %d (expression %d) in bb %d, reaching reg is %d\n",
4744 INSN_UID (insn), indx, bb, REGNO (expr->reaching_reg));
4754 /* Perform GCSE optimizations using PRE.
4755 This is called by one_pre_gcse_pass after all the dataflow analysis
4758 This is based on the original Morel-Renvoise paper Fred Chow's thesis,
4759 and lazy code motion from Knoop, Ruthing and Steffen as described in
4760 Advanced Compiler Design and Implementation.
4762 ??? A new pseudo reg is created to hold the reaching expression.
4763 The nice thing about the classical approach is that it would try to
4764 use an existing reg. If the register can't be adequately optimized
4765 [i.e. we introduce reload problems], one could add a pass here to
4766 propagate the new register through the block.
4768 ??? We don't handle single sets in PARALLELs because we're [currently]
4769 not able to copy the rest of the parallel when we insert copies to create
4770 full redundancies from partial redundancies. However, there's no reason
4771 why we can't handle PARALLELs in the cases where there are no partial
4779 struct expr **index_map;
4781 /* Compute a mapping from expression number (`bitmap_index') to
4782 hash table entry. */
4784 index_map = xcalloc (n_exprs, sizeof (struct expr *));
4785 for (i = 0; i < expr_hash_table_size; i++)
4789 for (expr = expr_hash_table[i]; expr != NULL; expr = expr->next_same_hash)
4790 index_map[expr->bitmap_index] = expr;
4793 /* Reset bitmap used to track which insns are redundant. */
4794 pre_redundant_insns = sbitmap_alloc (max_cuid);
4795 sbitmap_zero (pre_redundant_insns);
4797 /* Delete the redundant insns first so that
4798 - we know what register to use for the new insns and for the other
4799 ones with reaching expressions
4800 - we know which insns are redundant when we go to create copies */
4801 changed = pre_delete ();
4803 did_insert = pre_edge_insert (edge_list, index_map);
4804 /* In other places with reaching expressions, copy the expression to the
4805 specially allocated pseudo-reg that reaches the redundant expr. */
4806 pre_insert_copies ();
4809 commit_edge_insertions ();
4814 free (pre_redundant_insns);
4819 /* Top level routine to perform one PRE GCSE pass.
4821 Return non-zero if a change was made. */
4824 one_pre_gcse_pass (pass)
4829 gcse_subst_count = 0;
4830 gcse_create_count = 0;
4832 alloc_expr_hash_table (max_cuid);
4833 add_noreturn_fake_exit_edges ();
4834 compute_expr_hash_table ();
4836 dump_hash_table (gcse_file, "Expression", expr_hash_table,
4837 expr_hash_table_size, n_exprs);
4840 alloc_pre_mem (n_basic_blocks, n_exprs);
4841 compute_pre_data ();
4842 changed |= pre_gcse ();
4843 free_edge_list (edge_list);
4846 remove_fake_edges ();
4847 free_expr_hash_table ();
4851 fprintf (gcse_file, "\n");
4852 fprintf (gcse_file, "PRE GCSE of %s, pass %d: %d bytes needed, %d substs, %d insns created\n",
4853 current_function_name, pass,
4854 bytes_used, gcse_subst_count, gcse_create_count);
4860 /* If X contains any LABEL_REF's, add REG_LABEL notes for them to INSN.
4861 We have to add REG_LABEL notes, because the following loop optimization
4862 pass requires them. */
4864 /* ??? This is very similar to the loop.c add_label_notes function. We
4865 could probably share code here. */
4867 /* ??? If there was a jump optimization pass after gcse and before loop,
4868 then we would not need to do this here, because jump would add the
4869 necessary REG_LABEL notes. */
4872 add_label_notes (x, insn)
4876 enum rtx_code code = GET_CODE (x);
4880 if (code == LABEL_REF && !LABEL_REF_NONLOCAL_P (x))
4882 /* This code used to ignore labels that referred to dispatch tables to
4883 avoid flow generating (slighly) worse code.
4885 We no longer ignore such label references (see LABEL_REF handling in
4886 mark_jump_label for additional information). */
4887 REG_NOTES (insn) = gen_rtx_EXPR_LIST (REG_LABEL, XEXP (x, 0),
4892 fmt = GET_RTX_FORMAT (code);
4893 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
4896 add_label_notes (XEXP (x, i), insn);
4897 else if (fmt[i] == 'E')
4898 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
4899 add_label_notes (XVECEXP (x, i, j), insn);
4903 /* Compute transparent outgoing information for each block.
4905 An expression is transparent to an edge unless it is killed by
4906 the edge itself. This can only happen with abnormal control flow,
4907 when the edge is traversed through a call. This happens with
4908 non-local labels and exceptions.
4910 This would not be necessary if we split the edge. While this is
4911 normally impossible for abnormal critical edges, with some effort
4912 it should be possible with exception handling, since we still have
4913 control over which handler should be invoked. But due to increased
4914 EH table sizes, this may not be worthwhile. */
4917 compute_transpout ()
4921 sbitmap_vector_ones (transpout, n_basic_blocks);
4923 for (bb = 0; bb < n_basic_blocks; ++bb)
4927 /* Note that flow inserted a nop a the end of basic blocks that
4928 end in call instructions for reasons other than abnormal
4930 if (GET_CODE (BLOCK_END (bb)) != CALL_INSN)
4933 for (i = 0; i < expr_hash_table_size; i++)
4936 for (expr = expr_hash_table[i]; expr ; expr = expr->next_same_hash)
4937 if (GET_CODE (expr->expr) == MEM)
4939 rtx addr = XEXP (expr->expr, 0);
4941 if (GET_CODE (addr) == SYMBOL_REF
4942 && CONSTANT_POOL_ADDRESS_P (addr))
4945 /* ??? Optimally, we would use interprocedural alias
4946 analysis to determine if this mem is actually killed
4948 RESET_BIT (transpout[bb], expr->bitmap_index);
4954 /* Removal of useless null pointer checks */
4956 /* Called via note_stores. X is set by SETTER. If X is a register we must
4957 invalidate nonnull_local and set nonnull_killed. DATA is really a
4958 `null_pointer_info *'.
4960 We ignore hard registers. */
4962 invalidate_nonnull_info (x, setter, data)
4964 rtx setter ATTRIBUTE_UNUSED;
4968 struct null_pointer_info* npi = (struct null_pointer_info *) data;
4971 while (GET_CODE (x) == SUBREG)
4974 /* Ignore anything that is not a register or is a hard register. */
4975 if (GET_CODE (x) != REG
4976 || REGNO (x) < npi->min_reg
4977 || REGNO (x) >= npi->max_reg)
4980 regno = REGNO (x) - npi->min_reg;
4982 RESET_BIT (npi->nonnull_local[npi->current_block], regno);
4983 SET_BIT (npi->nonnull_killed[npi->current_block], regno);
4986 /* Do null-pointer check elimination for the registers indicated in
4987 NPI. NONNULL_AVIN and NONNULL_AVOUT are pre-allocated sbitmaps;
4988 they are not our responsibility to free. */
4991 delete_null_pointer_checks_1 (s_preds, block_reg, nonnull_avin,
4993 int_list_ptr *s_preds;
4995 sbitmap *nonnull_avin;
4996 sbitmap *nonnull_avout;
4997 struct null_pointer_info *npi;
5001 sbitmap *nonnull_local = npi->nonnull_local;
5002 sbitmap *nonnull_killed = npi->nonnull_killed;
5004 /* Compute local properties, nonnull and killed. A register will have
5005 the nonnull property if at the end of the current block its value is
5006 known to be nonnull. The killed property indicates that somewhere in
5007 the block any information we had about the register is killed.
5009 Note that a register can have both properties in a single block. That
5010 indicates that it's killed, then later in the block a new value is
5012 sbitmap_vector_zero (nonnull_local, n_basic_blocks);
5013 sbitmap_vector_zero (nonnull_killed, n_basic_blocks);
5014 for (current_block = 0; current_block < n_basic_blocks; current_block++)
5016 rtx insn, stop_insn;
5018 /* Set the current block for invalidate_nonnull_info. */
5019 npi->current_block = current_block;
5021 /* Scan each insn in the basic block looking for memory references and
5023 stop_insn = NEXT_INSN (BLOCK_END (current_block));
5024 for (insn = BLOCK_HEAD (current_block);
5026 insn = NEXT_INSN (insn))
5031 /* Ignore anything that is not a normal insn. */
5032 if (GET_RTX_CLASS (GET_CODE (insn)) != 'i')
5035 /* Basically ignore anything that is not a simple SET. We do have
5036 to make sure to invalidate nonnull_local and set nonnull_killed
5037 for such insns though. */
5038 set = single_set (insn);
5041 note_stores (PATTERN (insn), invalidate_nonnull_info, npi);
5045 /* See if we've got a useable memory load. We handle it first
5046 in case it uses its address register as a dest (which kills
5047 the nonnull property). */
5048 if (GET_CODE (SET_SRC (set)) == MEM
5049 && GET_CODE ((reg = XEXP (SET_SRC (set), 0))) == REG
5050 && REGNO (reg) >= npi->min_reg
5051 && REGNO (reg) < npi->max_reg)
5052 SET_BIT (nonnull_local[current_block],
5053 REGNO (reg) - npi->min_reg);
5055 /* Now invalidate stuff clobbered by this insn. */
5056 note_stores (PATTERN (insn), invalidate_nonnull_info, npi);
5058 /* And handle stores, we do these last since any sets in INSN can
5059 not kill the nonnull property if it is derived from a MEM
5060 appearing in a SET_DEST. */
5061 if (GET_CODE (SET_DEST (set)) == MEM
5062 && GET_CODE ((reg = XEXP (SET_DEST (set), 0))) == REG
5063 && REGNO (reg) >= npi->min_reg
5064 && REGNO (reg) < npi->max_reg)
5065 SET_BIT (nonnull_local[current_block],
5066 REGNO (reg) - npi->min_reg);
5070 /* Now compute global properties based on the local properties. This
5071 is a classic global availablity algorithm. */
5072 compute_available (nonnull_local, nonnull_killed,
5073 nonnull_avout, nonnull_avin);
5075 /* Now look at each bb and see if it ends with a compare of a value
5077 for (bb = 0; bb < n_basic_blocks; bb++)
5079 rtx last_insn = BLOCK_END (bb);
5080 rtx condition, earliest;
5081 int compare_and_branch;
5083 /* Since MIN_REG is always at least FIRST_PSEUDO_REGISTER, and
5084 since BLOCK_REG[BB] is zero if this block did not end with a
5085 comparison against zero, this condition works. */
5086 if (block_reg[bb] < npi->min_reg
5087 || block_reg[bb] >= npi->max_reg)
5090 /* LAST_INSN is a conditional jump. Get its condition. */
5091 condition = get_condition (last_insn, &earliest);
5093 /* Is the register known to have a nonzero value? */
5094 if (!TEST_BIT (nonnull_avout[bb], block_reg[bb] - npi->min_reg))
5097 /* Try to compute whether the compare/branch at the loop end is one or
5098 two instructions. */
5099 if (earliest == last_insn)
5100 compare_and_branch = 1;
5101 else if (earliest == prev_nonnote_insn (last_insn))
5102 compare_and_branch = 2;
5106 /* We know the register in this comparison is nonnull at exit from
5107 this block. We can optimize this comparison. */
5108 if (GET_CODE (condition) == NE)
5112 new_jump = emit_jump_insn_before (gen_jump (JUMP_LABEL (last_insn)),
5114 JUMP_LABEL (new_jump) = JUMP_LABEL (last_insn);
5115 LABEL_NUSES (JUMP_LABEL (new_jump))++;
5116 emit_barrier_after (new_jump);
5118 delete_insn (last_insn);
5119 if (compare_and_branch == 2)
5120 delete_insn (earliest);
5122 /* Don't check this block again. (Note that BLOCK_END is
5123 invalid here; we deleted the last instruction in the
5129 /* Find EQ/NE comparisons against zero which can be (indirectly) evaluated
5132 This is conceptually similar to global constant/copy propagation and
5133 classic global CSE (it even uses the same dataflow equations as cprop).
5135 If a register is used as memory address with the form (mem (reg)), then we
5136 know that REG can not be zero at that point in the program. Any instruction
5137 which sets REG "kills" this property.
5139 So, if every path leading to a conditional branch has an available memory
5140 reference of that form, then we know the register can not have the value
5141 zero at the conditional branch.
5143 So we merely need to compute the local properies and propagate that data
5144 around the cfg, then optimize where possible.
5146 We run this pass two times. Once before CSE, then again after CSE. This
5147 has proven to be the most profitable approach. It is rare for new
5148 optimization opportunities of this nature to appear after the first CSE
5151 This could probably be integrated with global cprop with a little work. */
5154 delete_null_pointer_checks (f)
5157 int_list_ptr *s_preds, *s_succs;
5158 int *num_preds, *num_succs;
5159 sbitmap *nonnull_avin, *nonnull_avout;
5165 struct null_pointer_info npi;
5167 /* First break the program into basic blocks. */
5168 find_basic_blocks (f, max_reg_num (), NULL, 1);
5170 /* If we have only a single block, then there's nothing to do. */
5171 if (n_basic_blocks <= 1)
5173 /* Free storage allocated by find_basic_blocks. */
5174 free_basic_block_vars (0);
5178 /* Trying to perform global optimizations on flow graphs which have
5179 a high connectivity will take a long time and is unlikely to be
5180 particularly useful.
5182 In normal circumstances a cfg should have about twice has many edges
5183 as blocks. But we do not want to punish small functions which have
5184 a couple switch statements. So we require a relatively large number
5185 of basic blocks and the ratio of edges to blocks to be high. */
5186 if (n_basic_blocks > 1000 && n_edges / n_basic_blocks >= 20)
5188 /* Free storage allocated by find_basic_blocks. */
5189 free_basic_block_vars (0);
5193 /* We need predecessor/successor lists as well as pred/succ counts for
5194 each basic block. */
5195 s_preds = (int_list_ptr *) gmalloc (n_basic_blocks * sizeof (int_list_ptr));
5196 s_succs = (int_list_ptr *) gmalloc (n_basic_blocks * sizeof (int_list_ptr));
5197 num_preds = (int *) gmalloc (n_basic_blocks * sizeof (int));
5198 num_succs = (int *) gmalloc (n_basic_blocks * sizeof (int));
5199 compute_preds_succs (s_preds, s_succs, num_preds, num_succs);
5201 /* We need four bitmaps, each with a bit for each register in each
5203 max_reg = max_reg_num ();
5204 regs_per_pass = get_bitmap_width (4, n_basic_blocks, max_reg);
5206 /* Allocate bitmaps to hold local and global properties. */
5207 npi.nonnull_local = sbitmap_vector_alloc (n_basic_blocks, regs_per_pass);
5208 npi.nonnull_killed = sbitmap_vector_alloc (n_basic_blocks, regs_per_pass);
5209 nonnull_avin = sbitmap_vector_alloc (n_basic_blocks, regs_per_pass);
5210 nonnull_avout = sbitmap_vector_alloc (n_basic_blocks, regs_per_pass);
5212 /* Go through the basic blocks, seeing whether or not each block
5213 ends with a conditional branch whose condition is a comparison
5214 against zero. Record the register compared in BLOCK_REG. */
5215 block_reg = (int *) xcalloc (n_basic_blocks, sizeof (int));
5216 for (bb = 0; bb < n_basic_blocks; bb++)
5218 rtx last_insn = BLOCK_END (bb);
5219 rtx condition, earliest, reg;
5221 /* We only want conditional branches. */
5222 if (GET_CODE (last_insn) != JUMP_INSN
5223 || !condjump_p (last_insn)
5224 || simplejump_p (last_insn))
5227 /* LAST_INSN is a conditional jump. Get its condition. */
5228 condition = get_condition (last_insn, &earliest);
5230 /* If we were unable to get the condition, or it is not a equality
5231 comparison against zero then there's nothing we can do. */
5233 || (GET_CODE (condition) != NE && GET_CODE (condition) != EQ)
5234 || GET_CODE (XEXP (condition, 1)) != CONST_INT
5235 || (XEXP (condition, 1)
5236 != CONST0_RTX (GET_MODE (XEXP (condition, 0)))))
5239 /* We must be checking a register against zero. */
5240 reg = XEXP (condition, 0);
5241 if (GET_CODE (reg) != REG)
5244 block_reg[bb] = REGNO (reg);
5247 /* Go through the algorithm for each block of registers. */
5248 for (reg = FIRST_PSEUDO_REGISTER; reg < max_reg; reg += regs_per_pass)
5251 npi.max_reg = MIN (reg + regs_per_pass, max_reg);
5252 delete_null_pointer_checks_1 (s_preds, block_reg, nonnull_avin,
5253 nonnull_avout, &npi);
5256 /* Free storage allocated by find_basic_blocks. */
5257 free_basic_block_vars (0);
5259 /* Free our local predecessor/successor lists. */
5265 /* Free the table of registers compared at the end of every block. */
5269 free (npi.nonnull_local);
5270 free (npi.nonnull_killed);
5271 free (nonnull_avin);
5272 free (nonnull_avout);
5275 /* Code Hoisting variables and subroutines. */
5277 /* Very busy expressions. */
5278 static sbitmap *hoist_vbein;
5279 static sbitmap *hoist_vbeout;
5281 /* Hoistable expressions. */
5282 static sbitmap *hoist_exprs;
5284 /* Dominator bitmaps. */
5285 static sbitmap *dominators;
5287 /* ??? We could compute post dominators and run this algorithm in
5288 reverse to to perform tail merging, doing so would probably be
5289 more effective than the tail merging code in jump.c.
5291 It's unclear if tail merging could be run in parallel with
5292 code hoisting. It would be nice. */
5294 /* Allocate vars used for code hoisting analysis. */
5297 alloc_code_hoist_mem (n_blocks, n_exprs)
5298 int n_blocks, n_exprs;
5300 antloc = sbitmap_vector_alloc (n_blocks, n_exprs);
5301 transp = sbitmap_vector_alloc (n_blocks, n_exprs);
5302 comp = sbitmap_vector_alloc (n_blocks, n_exprs);
5304 hoist_vbein = sbitmap_vector_alloc (n_blocks, n_exprs);
5305 hoist_vbeout = sbitmap_vector_alloc (n_blocks, n_exprs);
5306 hoist_exprs = sbitmap_vector_alloc (n_blocks, n_exprs);
5307 transpout = sbitmap_vector_alloc (n_blocks, n_exprs);
5309 dominators = sbitmap_vector_alloc (n_blocks, n_blocks);
5312 /* Free vars used for code hoisting analysis. */
5315 free_code_hoist_mem ()
5322 free (hoist_vbeout);
5329 /* Compute the very busy expressions at entry/exit from each block.
5331 An expression is very busy if all paths from a given point
5332 compute the expression. */
5335 compute_code_hoist_vbeinout ()
5337 int bb, changed, passes;
5339 sbitmap_vector_zero (hoist_vbeout, n_basic_blocks);
5340 sbitmap_vector_zero (hoist_vbein, n_basic_blocks);
5347 /* We scan the blocks in the reverse order to speed up
5349 for (bb = n_basic_blocks - 1; bb >= 0; bb--)
5351 changed |= sbitmap_a_or_b_and_c (hoist_vbein[bb], antloc[bb],
5352 hoist_vbeout[bb], transp[bb]);
5353 if (bb != n_basic_blocks - 1)
5354 sbitmap_intersection_of_succs (hoist_vbeout[bb], hoist_vbein, bb);
5360 fprintf (gcse_file, "hoisting vbeinout computation: %d passes\n", passes);
5363 /* Top level routine to do the dataflow analysis needed by code hoisting. */
5366 compute_code_hoist_data ()
5368 compute_local_properties (transp, comp, antloc, 0);
5369 compute_transpout ();
5370 compute_code_hoist_vbeinout ();
5371 compute_flow_dominators (dominators, NULL);
5373 fprintf (gcse_file, "\n");
5376 /* Determine if the expression identified by EXPR_INDEX would
5377 reach BB unimpared if it was placed at the end of EXPR_BB.
5379 It's unclear exactly what Muchnick meant by "unimpared". It seems
5380 to me that the expression must either be computed or transparent in
5381 *every* block in the path(s) from EXPR_BB to BB. Any other definition
5382 would allow the expression to be hoisted out of loops, even if
5383 the expression wasn't a loop invariant.
5385 Contrast this to reachability for PRE where an expression is
5386 considered reachable if *any* path reaches instead of *all*
5390 hoist_expr_reaches_here_p (expr_bb, expr_index, bb, visited)
5397 int visited_allocated_locally = 0;
5400 if (visited == NULL)
5402 visited_allocated_locally = 1;
5403 visited = xcalloc (n_basic_blocks, 1);
5406 visited[expr_bb] = 1;
5407 for (pred = BASIC_BLOCK (bb)->pred; pred != NULL; pred = pred->pred_next)
5409 int pred_bb = pred->src->index;
5411 if (pred->src == ENTRY_BLOCK_PTR)
5413 else if (visited[pred_bb])
5415 /* Does this predecessor generate this expression? */
5416 else if (TEST_BIT (comp[pred_bb], expr_index))
5418 else if (! TEST_BIT (transp[pred_bb], expr_index))
5423 visited[pred_bb] = 1;
5424 if (! hoist_expr_reaches_here_p (expr_bb, expr_index,
5429 if (visited_allocated_locally)
5431 return (pred == NULL);
5434 /* Actually perform code hoisting. */
5438 int bb, dominated, i;
5439 struct expr **index_map;
5441 sbitmap_vector_zero (hoist_exprs, n_basic_blocks);
5443 /* Compute a mapping from expression number (`bitmap_index') to
5444 hash table entry. */
5446 index_map = xcalloc (n_exprs, sizeof (struct expr *));
5447 for (i = 0; i < expr_hash_table_size; i++)
5451 for (expr = expr_hash_table[i]; expr != NULL; expr = expr->next_same_hash)
5452 index_map[expr->bitmap_index] = expr;
5455 /* Walk over each basic block looking for potentially hoistable
5456 expressions, nothing gets hoisted from the entry block. */
5457 for (bb = 0; bb < n_basic_blocks; bb++)
5460 int insn_inserted_p;
5462 /* Examine each expression that is very busy at the exit of this
5463 block. These are the potentially hoistable expressions. */
5464 for (i = 0; i < hoist_vbeout[bb]->n_bits; i++)
5467 if (TEST_BIT (hoist_vbeout[bb], i)
5468 && TEST_BIT (transpout[bb], i))
5470 /* We've found a potentially hoistable expression, now
5471 we look at every block BB dominates to see if it
5472 computes the expression. */
5473 for (dominated = 0; dominated < n_basic_blocks; dominated++)
5475 /* Ignore self dominance. */
5477 || ! TEST_BIT (dominators[dominated], bb))
5480 /* We've found a dominated block, now see if it computes
5481 the busy expression and whether or not moving that
5482 expression to the "beginning" of that block is safe. */
5483 if (!TEST_BIT (antloc[dominated], i))
5486 /* Note if the expression would reach the dominated block
5487 unimpared if it was placed at the end of BB.
5489 Keep track of how many times this expression is hoistable
5490 from a dominated block into BB. */
5491 if (hoist_expr_reaches_here_p (bb, i, dominated, NULL))
5495 /* If we found more than one hoistable occurence of this
5496 expression, then note it in the bitmap of expressions to
5497 hoist. It makes no sense to hoist things which are computed
5498 in only one BB, and doing so tends to pessimize register
5499 allocation. One could increase this value to try harder
5500 to avoid any possible code expansion due to register
5501 allocation issues; however experiments have shown that
5502 the vast majority of hoistable expressions are only movable
5503 from two successors, so raising this threshhold is likely
5504 to nullify any benefit we get from code hoisting. */
5507 SET_BIT (hoist_exprs[bb], i);
5513 /* If we found nothing to hoist, then quit now. */
5517 /* Loop over all the hoistable expressions. */
5518 for (i = 0; i < hoist_exprs[bb]->n_bits; i++)
5520 /* We want to insert the expression into BB only once, so
5521 note when we've inserted it. */
5522 insn_inserted_p = 0;
5524 /* These tests should be the same as the tests above. */
5525 if (TEST_BIT (hoist_vbeout[bb], i))
5527 /* We've found a potentially hoistable expression, now
5528 we look at every block BB dominates to see if it
5529 computes the expression. */
5530 for (dominated = 0; dominated < n_basic_blocks; dominated++)
5532 /* Ignore self dominance. */
5534 || ! TEST_BIT (dominators[dominated], bb))
5537 /* We've found a dominated block, now see if it computes
5538 the busy expression and whether or not moving that
5539 expression to the "beginning" of that block is safe. */
5540 if (!TEST_BIT (antloc[dominated], i))
5543 /* The expression is computed in the dominated block and
5544 it would be safe to compute it at the start of the
5545 dominated block. Now we have to determine if the
5546 expresion would reach the dominated block if it was
5547 placed at the end of BB. */
5548 if (hoist_expr_reaches_here_p (bb, i, dominated, NULL))
5550 struct expr *expr = index_map[i];
5551 struct occr *occr = expr->antic_occr;
5556 /* Find the right occurence of this expression. */
5557 while (BLOCK_NUM (occr->insn) != dominated && occr)
5560 /* Should never happen. */
5566 set = single_set (insn);
5570 /* Create a pseudo-reg to store the result of reaching
5571 expressions into. Get the mode for the new pseudo
5572 from the mode of the original destination pseudo. */
5573 if (expr->reaching_reg == NULL)
5575 = gen_reg_rtx (GET_MODE (SET_DEST (set)));
5577 /* In theory this should never fail since we're creating
5580 However, on the x86 some of the movXX patterns actually
5581 contain clobbers of scratch regs. This may cause the
5582 insn created by validate_change to not match any
5583 pattern and thus cause validate_change to fail. */
5584 if (validate_change (insn, &SET_SRC (set),
5585 expr->reaching_reg, 0))
5587 occr->deleted_p = 1;
5588 if (!insn_inserted_p)
5590 insert_insn_end_bb (index_map[i], bb, 0);
5591 insn_inserted_p = 1;
5602 /* Top level routine to perform one code hoisting (aka unification) pass
5604 Return non-zero if a change was made. */
5607 one_code_hoisting_pass ()
5611 alloc_expr_hash_table (max_cuid);
5612 compute_expr_hash_table ();
5614 dump_hash_table (gcse_file, "Code Hosting Expressions", expr_hash_table,
5615 expr_hash_table_size, n_exprs);
5618 alloc_code_hoist_mem (n_basic_blocks, n_exprs);
5619 compute_code_hoist_data ();
5621 free_code_hoist_mem ();
5623 free_expr_hash_table ();