1 /* Global common subexpression elimination/Partial redundancy elimination
2 and global constant/copy propagation for GNU compiler.
3 Copyright (C) 1997, 1998, 1999, 2000 Free Software Foundation, Inc.
5 This file is part of GNU CC.
7 GNU CC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 GNU CC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GNU CC; see the file COPYING. If not, write to
19 the Free Software Foundation, 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
23 - reordering of memory allocation and freeing to be more space efficient
24 - do rough calc of how many regs are needed in each block, and a rough
25 calc of how many regs are available in each class and use that to
26 throttle back the code in cases where RTX_COST is minimal.
27 - dead store elimination
28 - a store to the same address as a load does not kill the load if the
29 source of the store is also the destination of the load. Handling this
30 allows more load motion, particularly out of loops.
31 - ability to realloc sbitmap vectors would allow one initial computation
32 of reg_set_in_block with only subsequent additions, rather than
33 recomputing it for each pass
37 /* References searched while implementing this.
39 Compilers Principles, Techniques and Tools
43 Global Optimization by Suppression of Partial Redundancies
45 communications of the acm, Vol. 22, Num. 2, Feb. 1979
47 A Portable Machine-Independent Global Optimizer - Design and Measurements
49 Stanford Ph.D. thesis, Dec. 1983
51 A Fast Algorithm for Code Movement Optimization
53 SIGPLAN Notices, Vol. 23, Num. 10, Oct. 1988
55 A Solution to a Problem with Morel and Renvoise's
56 Global Optimization by Suppression of Partial Redundancies
57 K-H Drechsler, M.P. Stadel
58 ACM TOPLAS, Vol. 10, Num. 4, Oct. 1988
60 Practical Adaptation of the Global Optimization
61 Algorithm of Morel and Renvoise
63 ACM TOPLAS, Vol. 13, Num. 2. Apr. 1991
65 Efficiently Computing Static Single Assignment Form and the Control
67 R. Cytron, J. Ferrante, B.K. Rosen, M.N. Wegman, and F.K. Zadeck
68 ACM TOPLAS, Vol. 13, Num. 4, Oct. 1991
71 J. Knoop, O. Ruthing, B. Steffen
72 ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI
74 What's In a Region? Or Computing Control Dependence Regions in Near-Linear
75 Time for Reducible Flow Control
77 ACM Letters on Programming Languages and Systems,
78 Vol. 2, Num. 1-4, Mar-Dec 1993
80 An Efficient Representation for Sparse Sets
81 Preston Briggs, Linda Torczon
82 ACM Letters on Programming Languages and Systems,
83 Vol. 2, Num. 1-4, Mar-Dec 1993
85 A Variation of Knoop, Ruthing, and Steffen's Lazy Code Motion
86 K-H Drechsler, M.P. Stadel
87 ACM SIGPLAN Notices, Vol. 28, Num. 5, May 1993
89 Partial Dead Code Elimination
90 J. Knoop, O. Ruthing, B. Steffen
91 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
93 Effective Partial Redundancy Elimination
94 P. Briggs, K.D. Cooper
95 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
97 The Program Structure Tree: Computing Control Regions in Linear Time
98 R. Johnson, D. Pearson, K. Pingali
99 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
101 Optimal Code Motion: Theory and Practice
102 J. Knoop, O. Ruthing, B. Steffen
103 ACM TOPLAS, Vol. 16, Num. 4, Jul. 1994
105 The power of assignment motion
106 J. Knoop, O. Ruthing, B. Steffen
107 ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
109 Global code motion / global value numbering
111 ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
113 Value Driven Redundancy Elimination
115 Rice University Ph.D. thesis, Apr. 1996
119 Massively Scalar Compiler Project, Rice University, Sep. 1996
121 High Performance Compilers for Parallel Computing
125 Advanced Compiler Design and Implementation
127 Morgan Kaufmann, 1997
129 Building an Optimizing Compiler
133 People wishing to speed up the code here should read:
134 Elimination Algorithms for Data Flow Analysis
135 B.G. Ryder, M.C. Paull
136 ACM Computing Surveys, Vol. 18, Num. 3, Sep. 1986
138 How to Analyze Large Programs Efficiently and Informatively
139 D.M. Dhamdhere, B.K. Rosen, F.K. Zadeck
140 ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI
142 People wishing to do something different can find various possibilities
143 in the above papers and elsewhere.
153 #include "hard-reg-set.h"
156 #include "insn-config.h"
158 #include "basic-block.h"
160 #include "function.h"
164 #define obstack_chunk_alloc gmalloc
165 #define obstack_chunk_free free
167 /* Maximum number of passes to perform. */
170 /* Propagate flow information through back edges and thus enable PRE's
171 moving loop invariant calculations out of loops.
173 Originally this tended to create worse overall code, but several
174 improvements during the development of PRE seem to have made following
175 back edges generally a win.
177 Note much of the loop invariant code motion done here would normally
178 be done by loop.c, which has more heuristics for when to move invariants
179 out of loops. At some point we might need to move some of those
180 heuristics into gcse.c. */
181 #define FOLLOW_BACK_EDGES 1
183 /* We support GCSE via Partial Redundancy Elimination. PRE optimizations
184 are a superset of those done by GCSE.
186 We perform the following steps:
188 1) Compute basic block information.
190 2) Compute table of places where registers are set.
192 3) Perform copy/constant propagation.
194 4) Perform global cse.
196 5) Perform another pass of copy/constant propagation.
198 Two passes of copy/constant propagation are done because the first one
199 enables more GCSE and the second one helps to clean up the copies that
200 GCSE creates. This is needed more for PRE than for Classic because Classic
201 GCSE will try to use an existing register containing the common
202 subexpression rather than create a new one. This is harder to do for PRE
203 because of the code motion (which Classic GCSE doesn't do).
205 Expressions we are interested in GCSE-ing are of the form
206 (set (pseudo-reg) (expression)).
207 Function want_to_gcse_p says what these are.
209 PRE handles moving invariant expressions out of loops (by treating them as
210 partially redundant).
212 Eventually it would be nice to replace cse.c/gcse.c with SSA (static single
213 assignment) based GVN (global value numbering). L. T. Simpson's paper
214 (Rice University) on value numbering is a useful reference for this.
216 **********************
218 We used to support multiple passes but there are diminishing returns in
219 doing so. The first pass usually makes 90% of the changes that are doable.
220 A second pass can make a few more changes made possible by the first pass.
221 Experiments show any further passes don't make enough changes to justify
224 A study of spec92 using an unlimited number of passes:
225 [1 pass] = 1208 substitutions, [2] = 577, [3] = 202, [4] = 192, [5] = 83,
226 [6] = 34, [7] = 17, [8] = 9, [9] = 4, [10] = 4, [11] = 2,
227 [12] = 2, [13] = 1, [15] = 1, [16] = 2, [41] = 1
229 It was found doing copy propagation between each pass enables further
232 PRE is quite expensive in complicated functions because the DFA can take
233 awhile to converge. Hence we only perform one pass. Macro MAX_PASSES can
234 be modified if one wants to experiment.
236 **********************
238 The steps for PRE are:
240 1) Build the hash table of expressions we wish to GCSE (expr_hash_table).
242 2) Perform the data flow analysis for PRE.
244 3) Delete the redundant instructions
246 4) Insert the required copies [if any] that make the partially
247 redundant instructions fully redundant.
249 5) For other reaching expressions, insert an instruction to copy the value
250 to a newly created pseudo that will reach the redundant instruction.
252 The deletion is done first so that when we do insertions we
253 know which pseudo reg to use.
255 Various papers have argued that PRE DFA is expensive (O(n^2)) and others
256 argue it is not. The number of iterations for the algorithm to converge
257 is typically 2-4 so I don't view it as that expensive (relatively speaking).
259 PRE GCSE depends heavily on the second CSE pass to clean up the copies
260 we create. To make an expression reach the place where it's redundant,
261 the result of the expression is copied to a new register, and the redundant
262 expression is deleted by replacing it with this new register. Classic GCSE
263 doesn't have this problem as much as it computes the reaching defs of
264 each register in each block and thus can try to use an existing register.
266 **********************
268 A fair bit of simplicity is created by creating small functions for simple
269 tasks, even when the function is only called in one place. This may
270 measurably slow things down [or may not] by creating more function call
271 overhead than is necessary. The source is laid out so that it's trivial
272 to make the affected functions inline so that one can measure what speed
273 up, if any, can be achieved, and maybe later when things settle things can
276 Help stamp out big monolithic functions! */
278 /* GCSE global vars. */
281 static FILE *gcse_file;
283 /* Note whether or not we should run jump optimization after gcse. We
284 want to do this for two cases.
286 * If we changed any jumps via cprop.
288 * If we added any labels via edge splitting. */
290 static int run_jump_opt_after_gcse;
292 /* Bitmaps are normally not included in debugging dumps.
293 However it's useful to be able to print them from GDB.
294 We could create special functions for this, but it's simpler to
295 just allow passing stderr to the dump_foo fns. Since stderr can
296 be a macro, we store a copy here. */
297 static FILE *debug_stderr;
299 /* An obstack for our working variables. */
300 static struct obstack gcse_obstack;
302 /* Non-zero for each mode that supports (set (reg) (reg)).
303 This is trivially true for integer and floating point values.
304 It may or may not be true for condition codes. */
305 static char can_copy_p[(int) NUM_MACHINE_MODES];
307 /* Non-zero if can_copy_p has been initialized. */
308 static int can_copy_init_p;
310 struct reg_use {rtx reg_rtx; };
312 /* Hash table of expressions. */
316 /* The expression (SET_SRC for expressions, PATTERN for assignments). */
318 /* Index in the available expression bitmaps. */
320 /* Next entry with the same hash. */
321 struct expr *next_same_hash;
322 /* List of anticipatable occurrences in basic blocks in the function.
323 An "anticipatable occurrence" is one that is the first occurrence in the
324 basic block, the operands are not modified in the basic block prior
325 to the occurrence and the output is not used between the start of
326 the block and the occurrence. */
327 struct occr *antic_occr;
328 /* List of available occurrence in basic blocks in the function.
329 An "available occurrence" is one that is the last occurrence in the
330 basic block and the operands are not modified by following statements in
331 the basic block [including this insn]. */
332 struct occr *avail_occr;
333 /* Non-null if the computation is PRE redundant.
334 The value is the newly created pseudo-reg to record a copy of the
335 expression in all the places that reach the redundant copy. */
339 /* Occurrence of an expression.
340 There is one per basic block. If a pattern appears more than once the
341 last appearance is used [or first for anticipatable expressions]. */
345 /* Next occurrence of this expression. */
347 /* The insn that computes the expression. */
349 /* Non-zero if this [anticipatable] occurrence has been deleted. */
351 /* Non-zero if this [available] occurrence has been copied to
353 /* ??? This is mutually exclusive with deleted_p, so they could share
358 /* Expression and copy propagation hash tables.
359 Each hash table is an array of buckets.
360 ??? It is known that if it were an array of entries, structure elements
361 `next_same_hash' and `bitmap_index' wouldn't be necessary. However, it is
362 not clear whether in the final analysis a sufficient amount of memory would
363 be saved as the size of the available expression bitmaps would be larger
364 [one could build a mapping table without holes afterwards though].
365 Someday I'll perform the computation and figure it out. */
367 /* Total size of the expression hash table, in elements. */
368 static int expr_hash_table_size;
370 This is an array of `expr_hash_table_size' elements. */
371 static struct expr **expr_hash_table;
373 /* Total size of the copy propagation hash table, in elements. */
374 static int set_hash_table_size;
377 This is an array of `set_hash_table_size' elements. */
378 static struct expr **set_hash_table;
380 /* Mapping of uids to cuids.
381 Only real insns get cuids. */
382 static int *uid_cuid;
384 /* Highest UID in UID_CUID. */
387 /* Get the cuid of an insn. */
388 #define INSN_CUID(INSN) (uid_cuid[INSN_UID (INSN)])
390 /* Number of cuids. */
393 /* Mapping of cuids to insns. */
394 static rtx *cuid_insn;
396 /* Get insn from cuid. */
397 #define CUID_INSN(CUID) (cuid_insn[CUID])
399 /* Maximum register number in function prior to doing gcse + 1.
400 Registers created during this pass have regno >= max_gcse_regno.
401 This is named with "gcse" to not collide with global of same name. */
402 static int max_gcse_regno;
404 /* Maximum number of cse-able expressions found. */
407 /* Maximum number of assignments for copy propagation found. */
410 /* 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 (num-bbs x
420 num-regs) [however perhaps it may be useful to keep the data as is]. One
421 advantage of recording things this way is that `reg_set_table' is fairly
422 sparse with respect to pseudo regs but for hard regs could be fairly dense
423 [relatively speaking]. And recording sets of pseudo-regs in lists speeds
424 up functions like compute_transp since in the case of pseudo-regs we only
425 need to iterate over the number of times a pseudo-reg is set, not over the
426 number of basic blocks [clearly there is a bit of a slow down in the cases
427 where a pseudo is set more than once in a block, however it is believed
428 that the net effect is to speed things up]. This isn't done for hard-regs
429 because recording call-clobbered hard-regs in `reg_set_table' at each
430 function call can consume a fair bit of memory, and iterating over
431 hard-regs stored this way in compute_transp will be more expensive. */
433 typedef struct reg_set
435 /* The next setting of this register. */
436 struct reg_set *next;
437 /* The insn where it was set. */
441 static reg_set **reg_set_table;
443 /* Size of `reg_set_table'.
444 The table starts out at max_gcse_regno + slop, and is enlarged as
446 static int reg_set_table_size;
448 /* Amount to grow `reg_set_table' by when it's full. */
449 #define REG_SET_TABLE_SLOP 100
451 /* Bitmap containing one bit for each register in the program.
452 Used when performing GCSE to track which registers have been set since
453 the start of the basic block. */
454 static sbitmap reg_set_bitmap;
456 /* For each block, a bitmap of registers set in the block.
457 This is used by expr_killed_p and compute_transp.
458 It is computed during hash table computation and not by compute_sets
459 as it includes registers added since the last pass (or between cprop and
460 gcse) and it's currently not easy to realloc sbitmap vectors. */
461 static sbitmap *reg_set_in_block;
463 /* For each block, non-zero if memory is set in that block.
464 This is computed during hash table computation and is used by
465 expr_killed_p and compute_transp.
466 ??? Handling of memory is very simple, we don't make any attempt
467 to optimize things (later).
468 ??? This can be computed by compute_sets since the information
470 static char *mem_set_in_block;
472 /* Various variables for statistics gathering. */
474 /* Memory used in a pass.
475 This isn't intended to be absolutely precise. Its intent is only
476 to keep an eye on memory usage. */
477 static int bytes_used;
479 /* GCSE substitutions made. */
480 static int gcse_subst_count;
481 /* Number of copy instructions created. */
482 static int gcse_create_count;
483 /* Number of constants propagated. */
484 static int const_prop_count;
485 /* Number of copys propagated. */
486 static int copy_prop_count;
488 /* These variables are used by classic GCSE.
489 Normally they'd be defined a bit later, but `rd_gen' needs to
490 be declared sooner. */
492 /* A bitmap of all ones for implementing the algorithm for available
493 expressions and reaching definitions. */
494 /* ??? Available expression bitmaps have a different size than reaching
495 definition bitmaps. This should be the larger of the two, however, it
496 is not currently used for reaching definitions. */
497 static sbitmap u_bitmap;
499 /* Each block has a bitmap of each type.
500 The length of each blocks bitmap is:
502 max_cuid - for reaching definitions
503 n_exprs - for available expressions
505 Thus we view the bitmaps as 2 dimensional arrays. i.e.
506 rd_kill[block_num][cuid_num]
507 ae_kill[block_num][expr_num] */
509 /* For reaching defs */
510 static sbitmap *rd_kill, *rd_gen, *reaching_defs, *rd_out;
512 /* for available exprs */
513 static sbitmap *ae_kill, *ae_gen, *ae_in, *ae_out;
515 /* Objects of this type are passed around by the null-pointer check
517 struct null_pointer_info
519 /* The basic block being processed. */
521 /* The first register to be handled in this pass. */
523 /* One greater than the last register to be handled in this pass. */
525 sbitmap *nonnull_local;
526 sbitmap *nonnull_killed;
529 static void compute_can_copy PARAMS ((void));
530 static char *gmalloc PARAMS ((unsigned int));
531 static char *grealloc PARAMS ((char *, unsigned int));
532 static char *gcse_alloc PARAMS ((unsigned long));
533 static void alloc_gcse_mem PARAMS ((rtx));
534 static void free_gcse_mem PARAMS ((void));
535 static void alloc_reg_set_mem PARAMS ((int));
536 static void free_reg_set_mem PARAMS ((void));
537 static int get_bitmap_width PARAMS ((int, int, int));
538 static void record_one_set PARAMS ((int, rtx));
539 static void record_set_info PARAMS ((rtx, rtx, void *));
540 static void compute_sets PARAMS ((rtx));
541 static void hash_scan_insn PARAMS ((rtx, int, int));
542 static void hash_scan_set PARAMS ((rtx, rtx, int));
543 static void hash_scan_clobber PARAMS ((rtx, rtx));
544 static void hash_scan_call PARAMS ((rtx, rtx));
545 static int want_to_gcse_p PARAMS ((rtx));
546 static int oprs_unchanged_p PARAMS ((rtx, rtx, int));
547 static int oprs_anticipatable_p PARAMS ((rtx, rtx));
548 static int oprs_available_p PARAMS ((rtx, rtx));
549 static void insert_expr_in_table PARAMS ((rtx, enum machine_mode, rtx,
551 static void insert_set_in_table PARAMS ((rtx, rtx));
552 static unsigned int hash_expr PARAMS ((rtx, enum machine_mode, int *, int));
553 static unsigned int hash_expr_1 PARAMS ((rtx, enum machine_mode, int *));
554 static unsigned int hash_set PARAMS ((int, int));
555 static int expr_equiv_p PARAMS ((rtx, rtx));
556 static void record_last_reg_set_info PARAMS ((rtx, int));
557 static void record_last_mem_set_info PARAMS ((rtx));
558 static void record_last_set_info PARAMS ((rtx, rtx, void *));
559 static void compute_hash_table PARAMS ((int));
560 static void alloc_set_hash_table PARAMS ((int));
561 static void free_set_hash_table PARAMS ((void));
562 static void compute_set_hash_table PARAMS ((void));
563 static void alloc_expr_hash_table PARAMS ((int));
564 static void free_expr_hash_table PARAMS ((void));
565 static void compute_expr_hash_table PARAMS ((void));
566 static void dump_hash_table PARAMS ((FILE *, const char *, struct expr **,
568 static struct expr *lookup_expr PARAMS ((rtx));
569 static struct expr *lookup_set PARAMS ((int, rtx));
570 static struct expr *next_set PARAMS ((int, struct expr *));
571 static void reset_opr_set_tables PARAMS ((void));
572 static int oprs_not_set_p PARAMS ((rtx, rtx));
573 static void mark_call PARAMS ((rtx));
574 static void mark_set PARAMS ((rtx, rtx));
575 static void mark_clobber PARAMS ((rtx, rtx));
576 static void mark_oprs_set PARAMS ((rtx));
577 static void alloc_cprop_mem PARAMS ((int, int));
578 static void free_cprop_mem PARAMS ((void));
579 static void compute_transp PARAMS ((rtx, int, sbitmap *, int));
580 static void compute_transpout PARAMS ((void));
581 static void compute_local_properties PARAMS ((sbitmap *, sbitmap *, sbitmap *,
583 static void compute_cprop_data PARAMS ((void));
584 static void find_used_regs PARAMS ((rtx));
585 static int try_replace_reg PARAMS ((rtx, rtx, rtx));
586 static struct expr *find_avail_set PARAMS ((int, rtx));
587 static int cprop_jump PARAMS ((rtx, rtx, struct reg_use *, rtx));
589 static int cprop_cc0_jump PARAMS ((rtx, struct reg_use *, rtx));
591 static int cprop_insn PARAMS ((rtx, int));
592 static int cprop PARAMS ((int));
593 static int one_cprop_pass PARAMS ((int, int));
594 static void alloc_pre_mem PARAMS ((int, int));
595 static void free_pre_mem PARAMS ((void));
596 static void compute_pre_data PARAMS ((void));
597 static int pre_expr_reaches_here_p PARAMS ((int, struct expr *, int));
598 static void insert_insn_end_bb PARAMS ((struct expr *, int, int));
599 static void pre_insert_copy_insn PARAMS ((struct expr *, rtx));
600 static void pre_insert_copies PARAMS ((void));
601 static int pre_delete PARAMS ((void));
602 static int pre_gcse PARAMS ((void));
603 static int one_pre_gcse_pass PARAMS ((int));
604 static void add_label_notes PARAMS ((rtx, rtx));
605 static void alloc_code_hoist_mem PARAMS ((int, int));
606 static void free_code_hoist_mem PARAMS ((void));
607 static void compute_code_hoist_vbeinout PARAMS ((void));
608 static void compute_code_hoist_data PARAMS ((void));
609 static int hoist_expr_reaches_here_p PARAMS ((int, int, int, char *));
610 static void hoist_code PARAMS ((void));
611 static int one_code_hoisting_pass PARAMS ((void));
612 static void alloc_rd_mem PARAMS ((int, int));
613 static void free_rd_mem PARAMS ((void));
614 static void handle_rd_kill_set PARAMS ((rtx, int, int));
615 static void compute_kill_rd PARAMS ((void));
616 static void compute_rd PARAMS ((void));
617 static void alloc_avail_expr_mem PARAMS ((int, int));
618 static void free_avail_expr_mem PARAMS ((void));
619 static void compute_ae_gen PARAMS ((void));
620 static int expr_killed_p PARAMS ((rtx, int));
621 static void compute_ae_kill PARAMS ((sbitmap *, sbitmap *));
622 static int expr_reaches_here_p PARAMS ((struct occr *, struct expr *,
624 static rtx computing_insn PARAMS ((struct expr *, rtx));
625 static int def_reaches_here_p PARAMS ((rtx, rtx));
626 static int can_disregard_other_sets PARAMS ((struct reg_set **, rtx, int));
627 static int handle_avail_expr PARAMS ((rtx, struct expr *));
628 static int classic_gcse PARAMS ((void));
629 static int one_classic_gcse_pass PARAMS ((int));
630 static void invalidate_nonnull_info PARAMS ((rtx, rtx, void *));
631 static void delete_null_pointer_checks_1 PARAMS ((int *, sbitmap *, sbitmap *,
632 struct null_pointer_info *));
633 static rtx process_insert_insn PARAMS ((struct expr *));
634 static int pre_edge_insert PARAMS ((struct edge_list *, struct expr **));
635 static int expr_reaches_here_p_work PARAMS ((struct occr *, struct expr *,
637 static int pre_expr_reaches_here_p_work PARAMS ((int, struct expr *,
640 /* Entry point for global common subexpression elimination.
641 F is the first instruction in the function. */
649 /* Bytes used at start of pass. */
650 int initial_bytes_used;
651 /* Maximum number of bytes used by a pass. */
653 /* Point to release obstack data from for each pass. */
654 char *gcse_obstack_bottom;
656 /* We do not construct an accurate cfg in functions which call
657 setjmp, so just punt to be safe. */
658 if (current_function_calls_setjmp)
661 /* Assume that we do not need to run jump optimizations after gcse. */
662 run_jump_opt_after_gcse = 0;
664 /* For calling dump_foo fns from gdb. */
665 debug_stderr = stderr;
668 /* Identify the basic block information for this function, including
669 successors and predecessors. */
670 max_gcse_regno = max_reg_num ();
671 find_basic_blocks (f, max_gcse_regno, file);
675 dump_flow_info (file);
677 /* Return if there's nothing to do. */
678 if (n_basic_blocks <= 1)
680 free_basic_block_vars (0);
684 /* Trying to perform global optimizations on flow graphs which have
685 a high connectivity will take a long time and is unlikely to be
688 In normal circumstances a cfg should have about twice has many edges
689 as blocks. But we do not want to punish small functions which have
690 a couple switch statements. So we require a relatively large number
691 of basic blocks and the ratio of edges to blocks to be high. */
692 if (n_basic_blocks > 1000 && n_edges / n_basic_blocks >= 20)
694 free_basic_block_vars (0);
698 /* See what modes support reg/reg copy operations. */
699 if (! can_copy_init_p)
705 gcc_obstack_init (&gcse_obstack);
708 /* Record where pseudo-registers are set. This data is kept accurate
709 during each pass. ??? We could also record hard-reg information here
710 [since it's unchanging], however it is currently done during hash table
713 It may be tempting to compute MEM set information here too, but MEM sets
714 will be subject to code motion one day and thus we need to compute
715 information about memory sets when we build the hash tables. */
717 alloc_reg_set_mem (max_gcse_regno);
721 initial_bytes_used = bytes_used;
723 gcse_obstack_bottom = gcse_alloc (1);
725 while (changed && pass < MAX_PASSES)
729 fprintf (file, "GCSE pass %d\n\n", pass + 1);
731 /* Initialize bytes_used to the space for the pred/succ lists,
732 and the reg_set_table data. */
733 bytes_used = initial_bytes_used;
735 /* Each pass may create new registers, so recalculate each time. */
736 max_gcse_regno = max_reg_num ();
740 /* Don't allow constant propagation to modify jumps
742 changed = one_cprop_pass (pass + 1, 0);
745 changed |= one_classic_gcse_pass (pass + 1);
748 changed |= one_pre_gcse_pass (pass + 1);
750 alloc_reg_set_mem (max_reg_num ());
752 run_jump_opt_after_gcse = 1;
755 if (max_pass_bytes < bytes_used)
756 max_pass_bytes = bytes_used;
758 /* Free up memory, then reallocate for code hoisting. We can
759 not re-use the existing allocated memory because the tables
760 will not have info for the insns or registers created by
761 partial redundancy elimination. */
764 /* It does not make sense to run code hoisting unless we optimizing
765 for code size -- it rarely makes programs faster, and can make
766 them bigger if we did partial redundancy elimination (when optimizing
767 for space, we use a classic gcse algorithm instead of partial
768 redundancy algorithms). */
771 max_gcse_regno = max_reg_num ();
773 changed |= one_code_hoisting_pass ();
776 if (max_pass_bytes < bytes_used)
777 max_pass_bytes = bytes_used;
782 fprintf (file, "\n");
786 obstack_free (&gcse_obstack, gcse_obstack_bottom);
790 /* Do one last pass of copy propagation, including cprop into
791 conditional jumps. */
793 max_gcse_regno = max_reg_num ();
795 /* This time, go ahead and allow cprop to alter jumps. */
796 one_cprop_pass (pass + 1, 1);
801 fprintf (file, "GCSE of %s: %d basic blocks, ",
802 current_function_name, n_basic_blocks);
803 fprintf (file, "%d pass%s, %d bytes\n\n",
804 pass, pass > 1 ? "es" : "", max_pass_bytes);
807 obstack_free (&gcse_obstack, NULL_PTR);
809 free_basic_block_vars (0);
810 return run_jump_opt_after_gcse;
813 /* Misc. utilities. */
815 /* Compute which modes support reg/reg copy operations. */
821 #ifndef AVOID_CCMODE_COPIES
824 char *free_point = (char *) oballoc (1);
826 bzero (can_copy_p, NUM_MACHINE_MODES);
829 for (i = 0; i < NUM_MACHINE_MODES; i++)
830 if (GET_MODE_CLASS (i) == MODE_CC)
832 #ifdef AVOID_CCMODE_COPIES
835 reg = gen_rtx_REG ((enum machine_mode) i, LAST_VIRTUAL_REGISTER + 1);
836 insn = emit_insn (gen_rtx_SET (VOIDmode, reg, reg));
837 if (recog (PATTERN (insn), insn, NULL_PTR) >= 0)
846 /* Free the objects we just allocated. */
850 /* Cover function to xmalloc to record bytes allocated. */
857 return xmalloc (size);
860 /* Cover function to xrealloc.
861 We don't record the additional size since we don't know it.
862 It won't affect memory usage stats much anyway. */
869 return xrealloc (ptr, size);
872 /* Cover function to obstack_alloc.
873 We don't need to record the bytes allocated here since
874 obstack_chunk_alloc is set to gmalloc. */
880 return (char *) obstack_alloc (&gcse_obstack, size);
883 /* Allocate memory for the cuid mapping array,
884 and reg/memory set tracking tables.
886 This is called at the start of each pass. */
895 /* Find the largest UID and create a mapping from UIDs to CUIDs.
896 CUIDs are like UIDs except they increase monotonically, have no gaps,
897 and only apply to real insns. */
899 max_uid = get_max_uid ();
900 n = (max_uid + 1) * sizeof (int);
901 uid_cuid = (int *) gmalloc (n);
902 bzero ((char *) uid_cuid, n);
903 for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
905 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
906 INSN_CUID (insn) = i++;
908 INSN_CUID (insn) = i;
911 /* Create a table mapping cuids to insns. */
914 n = (max_cuid + 1) * sizeof (rtx);
915 cuid_insn = (rtx *) gmalloc (n);
916 bzero ((char *) cuid_insn, n);
917 for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
918 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
919 CUID_INSN (i++) = insn;
921 /* Allocate vars to track sets of regs. */
922 reg_set_bitmap = (sbitmap) sbitmap_alloc (max_gcse_regno);
924 /* Allocate vars to track sets of regs, memory per block. */
925 reg_set_in_block = (sbitmap *) sbitmap_vector_alloc (n_basic_blocks,
927 mem_set_in_block = (char *) gmalloc (n_basic_blocks);
930 /* Free memory allocated by alloc_gcse_mem. */
938 free (reg_set_bitmap);
940 free (reg_set_in_block);
941 free (mem_set_in_block);
944 /* Many of the global optimization algorithms work by solving dataflow
945 equations for various expressions. Initially, some local value is
946 computed for each expression in each block. Then, the values across the
947 various blocks are combined (by following flow graph edges) to arrive at
948 global values. Conceptually, each set of equations is independent. We
949 may therefore solve all the equations in parallel, solve them one at a
950 time, or pick any intermediate approach.
952 When you're going to need N two-dimensional bitmaps, each X (say, the
953 number of blocks) by Y (say, the number of expressions), call this
954 function. It's not important what X and Y represent; only that Y
955 correspond to the things that can be done in parallel. This function will
956 return an appropriate chunking factor C; you should solve C sets of
957 equations in parallel. By going through this function, we can easily
958 trade space against time; by solving fewer equations in parallel we use
962 get_bitmap_width (n, x, y)
967 /* It's not really worth figuring out *exactly* how much memory will
968 be used by a particular choice. The important thing is to get
969 something approximately right. */
970 size_t max_bitmap_memory = 10 * 1024 * 1024;
972 /* The number of bytes we'd use for a single column of minimum
974 size_t column_size = n * x * sizeof (SBITMAP_ELT_TYPE);
976 /* Often, it's reasonable just to solve all the equations in
978 if (column_size * SBITMAP_SET_SIZE (y) <= max_bitmap_memory)
981 /* Otherwise, pick the largest width we can, without going over the
983 return SBITMAP_ELT_BITS * ((max_bitmap_memory + column_size - 1)
987 /* Compute the local properties of each recorded expression.
989 Local properties are those that are defined by the block, irrespective of
992 An expression is transparent in a block if its operands are not modified
995 An expression is computed (locally available) in a block if it is computed
996 at least once and expression would contain the same value if the
997 computation was moved to the end of the block.
999 An expression is locally anticipatable in a block if it is computed at
1000 least once and expression would contain the same value if the computation
1001 was moved to the beginning of the block.
1003 We call this routine for cprop, pre and code hoisting. They all compute
1004 basically the same information and thus can easily share this code.
1006 TRANSP, COMP, and ANTLOC are destination sbitmaps for recording local
1007 properties. If NULL, then it is not necessary to compute or record that
1008 particular property.
1010 SETP controls which hash table to look at. If zero, this routine looks at
1011 the expr hash table; if nonzero this routine looks at the set hash table.
1012 Additionally, TRANSP is computed as ~TRANSP, since this is really cprop's
1016 compute_local_properties (transp, comp, antloc, setp)
1022 int i, hash_table_size;
1023 struct expr **hash_table;
1025 /* Initialize any bitmaps that were passed in. */
1029 sbitmap_vector_zero (transp, n_basic_blocks);
1031 sbitmap_vector_ones (transp, n_basic_blocks);
1035 sbitmap_vector_zero (comp, n_basic_blocks);
1037 sbitmap_vector_zero (antloc, n_basic_blocks);
1039 /* We use the same code for cprop, pre and hoisting. For cprop
1040 we care about the set hash table, for pre and hoisting we
1041 care about the expr hash table. */
1042 hash_table_size = setp ? set_hash_table_size : expr_hash_table_size;
1043 hash_table = setp ? set_hash_table : expr_hash_table;
1045 for (i = 0; i < hash_table_size; i++)
1049 for (expr = hash_table[i]; expr != NULL; expr = expr->next_same_hash)
1051 int indx = expr->bitmap_index;
1054 /* The expression is transparent in this block if it is not killed.
1055 We start by assuming all are transparent [none are killed], and
1056 then reset the bits for those that are. */
1058 compute_transp (expr->expr, indx, transp, setp);
1060 /* The occurrences recorded in antic_occr are exactly those that
1061 we want to set to non-zero in ANTLOC. */
1063 for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
1065 SET_BIT (antloc[BLOCK_NUM (occr->insn)], indx);
1067 /* While we're scanning the table, this is a good place to
1069 occr->deleted_p = 0;
1072 /* The occurrences recorded in avail_occr are exactly those that
1073 we want to set to non-zero in COMP. */
1075 for (occr = expr->avail_occr; occr != NULL; occr = occr->next)
1077 SET_BIT (comp[BLOCK_NUM (occr->insn)], indx);
1079 /* While we're scanning the table, this is a good place to
1084 /* While we're scanning the table, this is a good place to
1086 expr->reaching_reg = 0;
1091 /* Register set information.
1093 `reg_set_table' records where each register is set or otherwise
1096 static struct obstack reg_set_obstack;
1099 alloc_reg_set_mem (n_regs)
1104 reg_set_table_size = n_regs + REG_SET_TABLE_SLOP;
1105 n = reg_set_table_size * sizeof (struct reg_set *);
1106 reg_set_table = (struct reg_set **) gmalloc (n);
1107 bzero ((char *) reg_set_table, n);
1109 gcc_obstack_init (®_set_obstack);
1115 free (reg_set_table);
1116 obstack_free (®_set_obstack, NULL_PTR);
1119 /* Record REGNO in the reg_set table. */
1122 record_one_set (regno, insn)
1126 /* allocate a new reg_set element and link it onto the list */
1127 struct reg_set *new_reg_info, *reg_info_ptr1, *reg_info_ptr2;
1129 /* If the table isn't big enough, enlarge it. */
1130 if (regno >= reg_set_table_size)
1132 int new_size = regno + REG_SET_TABLE_SLOP;
1135 = (struct reg_set **) grealloc ((char *) reg_set_table,
1136 new_size * sizeof (struct reg_set *));
1137 bzero ((char *) (reg_set_table + reg_set_table_size),
1138 (new_size - reg_set_table_size) * sizeof (struct reg_set *));
1139 reg_set_table_size = new_size;
1142 new_reg_info = (struct reg_set *) obstack_alloc (®_set_obstack,
1143 sizeof (struct reg_set));
1144 bytes_used += sizeof (struct reg_set);
1145 new_reg_info->insn = insn;
1146 new_reg_info->next = NULL;
1147 if (reg_set_table[regno] == NULL)
1148 reg_set_table[regno] = new_reg_info;
1151 reg_info_ptr1 = reg_info_ptr2 = reg_set_table[regno];
1152 /* ??? One could keep a "last" pointer to speed this up. */
1153 while (reg_info_ptr1 != NULL)
1155 reg_info_ptr2 = reg_info_ptr1;
1156 reg_info_ptr1 = reg_info_ptr1->next;
1159 reg_info_ptr2->next = new_reg_info;
1163 /* Called from compute_sets via note_stores to handle one SET or CLOBBER in
1164 an insn. The DATA is really the instruction in which the SET is
1168 record_set_info (dest, setter, data)
1169 rtx dest, setter ATTRIBUTE_UNUSED;
1172 rtx record_set_insn = (rtx) data;
1174 if (GET_CODE (dest) == REG && REGNO (dest) >= FIRST_PSEUDO_REGISTER)
1175 record_one_set (REGNO (dest), record_set_insn);
1178 /* Scan the function and record each set of each pseudo-register.
1180 This is called once, at the start of the gcse pass. See the comments for
1181 `reg_set_table' for further documenation. */
1189 for (insn = f; insn != 0; insn = NEXT_INSN (insn))
1190 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
1191 note_stores (PATTERN (insn), record_set_info, insn);
1194 /* Hash table support. */
1196 /* For each register, the cuid of the first/last insn in the block to set it,
1197 or -1 if not set. */
1198 #define NEVER_SET -1
1199 static int *reg_first_set;
1200 static int *reg_last_set;
1202 /* While computing "first/last set" info, this is the CUID of first/last insn
1203 to set memory or -1 if not set. `mem_last_set' is also used when
1204 performing GCSE to record whether memory has been set since the beginning
1207 Note that handling of memory is very simple, we don't make any attempt
1208 to optimize things (later). */
1209 static int mem_first_set;
1210 static int mem_last_set;
1212 /* Perform a quick check whether X, the source of a set, is something
1213 we want to consider for GCSE. */
1219 switch (GET_CODE (x))
1235 /* Return non-zero if the operands of expression X are unchanged from the
1236 start of INSN's basic block up to but not including INSN (if AVAIL_P == 0),
1237 or from INSN to the end of INSN's basic block (if AVAIL_P != 0). */
1240 oprs_unchanged_p (x, insn, avail_p)
1251 code = GET_CODE (x);
1256 return (reg_last_set[REGNO (x)] == NEVER_SET
1257 || reg_last_set[REGNO (x)] < INSN_CUID (insn));
1259 return (reg_first_set[REGNO (x)] == NEVER_SET
1260 || reg_first_set[REGNO (x)] >= INSN_CUID (insn));
1263 if (avail_p && mem_last_set != NEVER_SET
1264 && mem_last_set >= INSN_CUID (insn))
1266 else if (! avail_p && mem_first_set != NEVER_SET
1267 && mem_first_set < INSN_CUID (insn))
1270 return oprs_unchanged_p (XEXP (x, 0), insn, avail_p);
1293 for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
1297 /* If we are about to do the last recursive call needed at this
1298 level, change it into iteration. This function is called enough
1301 return oprs_unchanged_p (XEXP (x, i), insn, avail_p);
1303 else if (! oprs_unchanged_p (XEXP (x, i), insn, avail_p))
1306 else if (fmt[i] == 'E')
1307 for (j = 0; j < XVECLEN (x, i); j++)
1308 if (! oprs_unchanged_p (XVECEXP (x, i, j), insn, avail_p))
1315 /* Return non-zero if the operands of expression X are unchanged from
1316 the start of INSN's basic block up to but not including INSN. */
1319 oprs_anticipatable_p (x, insn)
1322 return oprs_unchanged_p (x, insn, 0);
1325 /* Return non-zero if the operands of expression X are unchanged from
1326 INSN to the end of INSN's basic block. */
1329 oprs_available_p (x, insn)
1332 return oprs_unchanged_p (x, insn, 1);
1335 /* Hash expression X.
1337 MODE is only used if X is a CONST_INT. DO_NOT_RECORD_P is a boolean
1338 indicating if a volatile operand is found or if the expression contains
1339 something we don't want to insert in the table.
1341 ??? One might want to merge this with canon_hash. Later. */
1344 hash_expr (x, mode, do_not_record_p, hash_table_size)
1346 enum machine_mode mode;
1347 int *do_not_record_p;
1348 int hash_table_size;
1352 *do_not_record_p = 0;
1354 hash = hash_expr_1 (x, mode, do_not_record_p);
1355 return hash % hash_table_size;
1358 /* Subroutine of hash_expr to do the actual work. */
1361 hash_expr_1 (x, mode, do_not_record_p)
1363 enum machine_mode mode;
1364 int *do_not_record_p;
1371 /* Used to turn recursion into iteration. We can't rely on GCC's
1372 tail-recursion eliminatio since we need to keep accumulating values
1379 code = GET_CODE (x);
1383 hash += ((unsigned int) REG << 7) + REGNO (x);
1387 hash += (((unsigned int) CONST_INT << 7) + (unsigned int) mode
1388 + (unsigned int) INTVAL (x));
1392 /* This is like the general case, except that it only counts
1393 the integers representing the constant. */
1394 hash += (unsigned int) code + (unsigned int) GET_MODE (x);
1395 if (GET_MODE (x) != VOIDmode)
1396 for (i = 2; i < GET_RTX_LENGTH (CONST_DOUBLE); i++)
1397 hash += (unsigned int) XWINT (x, i);
1399 hash += ((unsigned int) CONST_DOUBLE_LOW (x)
1400 + (unsigned int) CONST_DOUBLE_HIGH (x));
1403 /* Assume there is only one rtx object for any given label. */
1405 /* We don't hash on the address of the CODE_LABEL to avoid bootstrap
1406 differences and differences between each stage's debugging dumps. */
1407 hash += (((unsigned int) LABEL_REF << 7)
1408 + CODE_LABEL_NUMBER (XEXP (x, 0)));
1413 /* Don't hash on the symbol's address to avoid bootstrap differences.
1414 Different hash values may cause expressions to be recorded in
1415 different orders and thus different registers to be used in the
1416 final assembler. This also avoids differences in the dump files
1417 between various stages. */
1419 unsigned char *p = (unsigned char *) XSTR (x, 0);
1422 h += (h << 7) + *p++; /* ??? revisit */
1424 hash += ((unsigned int) SYMBOL_REF << 7) + h;
1429 if (MEM_VOLATILE_P (x))
1431 *do_not_record_p = 1;
1435 hash += (unsigned int) MEM;
1436 hash += MEM_ALIAS_SET (x);
1447 case UNSPEC_VOLATILE:
1448 *do_not_record_p = 1;
1452 if (MEM_VOLATILE_P (x))
1454 *do_not_record_p = 1;
1462 hash += (unsigned) code + (unsigned) GET_MODE (x);
1463 for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
1467 /* If we are about to do the last recursive call
1468 needed at this level, change it into iteration.
1469 This function is called enough to be worth it. */
1476 hash += hash_expr_1 (XEXP (x, i), 0, do_not_record_p);
1477 if (*do_not_record_p)
1481 else if (fmt[i] == 'E')
1482 for (j = 0; j < XVECLEN (x, i); j++)
1484 hash += hash_expr_1 (XVECEXP (x, i, j), 0, do_not_record_p);
1485 if (*do_not_record_p)
1489 else if (fmt[i] == 's')
1491 register unsigned char *p = (unsigned char *) XSTR (x, i);
1497 else if (fmt[i] == 'i')
1498 hash += (unsigned int) XINT (x, i);
1506 /* Hash a set of register REGNO.
1508 Sets are hashed on the register that is set. This simplifies the PRE copy
1511 ??? May need to make things more elaborate. Later, as necessary. */
1514 hash_set (regno, hash_table_size)
1516 int hash_table_size;
1521 return hash % hash_table_size;
1524 /* Return non-zero if exp1 is equivalent to exp2.
1525 ??? Borrowed from cse.c. Might want to remerge with cse.c. Later. */
1532 register enum rtx_code code;
1533 register const char *fmt;
1538 if (x == 0 || y == 0)
1541 code = GET_CODE (x);
1542 if (code != GET_CODE (y))
1545 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. */
1546 if (GET_MODE (x) != GET_MODE (y))
1556 return INTVAL (x) == INTVAL (y);
1559 return XEXP (x, 0) == XEXP (y, 0);
1562 return XSTR (x, 0) == XSTR (y, 0);
1565 return REGNO (x) == REGNO (y);
1568 /* Can't merge two expressions in different alias sets, since we can
1569 decide that the expression is transparent in a block when it isn't,
1570 due to it being set with the different alias set. */
1571 if (MEM_ALIAS_SET (x) != MEM_ALIAS_SET (y))
1575 /* For commutative operations, check both orders. */
1583 return ((expr_equiv_p (XEXP (x, 0), XEXP (y, 0))
1584 && expr_equiv_p (XEXP (x, 1), XEXP (y, 1)))
1585 || (expr_equiv_p (XEXP (x, 0), XEXP (y, 1))
1586 && expr_equiv_p (XEXP (x, 1), XEXP (y, 0))));
1592 /* Compare the elements. If any pair of corresponding elements
1593 fail to match, return 0 for the whole thing. */
1595 fmt = GET_RTX_FORMAT (code);
1596 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1601 if (! expr_equiv_p (XEXP (x, i), XEXP (y, i)))
1606 if (XVECLEN (x, i) != XVECLEN (y, i))
1608 for (j = 0; j < XVECLEN (x, i); j++)
1609 if (! expr_equiv_p (XVECEXP (x, i, j), XVECEXP (y, i, j)))
1614 if (strcmp (XSTR (x, i), XSTR (y, i)))
1619 if (XINT (x, i) != XINT (y, i))
1624 if (XWINT (x, i) != XWINT (y, i))
1639 /* Insert expression X in INSN in the hash table.
1640 If it is already present, record it as the last occurrence in INSN's
1643 MODE is the mode of the value X is being stored into.
1644 It is only used if X is a CONST_INT.
1646 ANTIC_P is non-zero if X is an anticipatable expression.
1647 AVAIL_P is non-zero if X is an available expression. */
1650 insert_expr_in_table (x, mode, insn, antic_p, avail_p)
1652 enum machine_mode mode;
1654 int antic_p, avail_p;
1656 int found, do_not_record_p;
1658 struct expr *cur_expr, *last_expr = NULL;
1659 struct occr *antic_occr, *avail_occr;
1660 struct occr *last_occr = NULL;
1662 hash = hash_expr (x, mode, &do_not_record_p, expr_hash_table_size);
1664 /* Do not insert expression in table if it contains volatile operands,
1665 or if hash_expr determines the expression is something we don't want
1666 to or can't handle. */
1667 if (do_not_record_p)
1670 cur_expr = expr_hash_table[hash];
1673 while (cur_expr && 0 == (found = expr_equiv_p (cur_expr->expr, x)))
1675 /* If the expression isn't found, save a pointer to the end of
1677 last_expr = cur_expr;
1678 cur_expr = cur_expr->next_same_hash;
1683 cur_expr = (struct expr *) gcse_alloc (sizeof (struct expr));
1684 bytes_used += sizeof (struct expr);
1685 if (expr_hash_table[hash] == NULL)
1686 /* This is the first pattern that hashed to this index. */
1687 expr_hash_table[hash] = cur_expr;
1689 /* Add EXPR to end of this hash chain. */
1690 last_expr->next_same_hash = cur_expr;
1692 /* Set the fields of the expr element. */
1694 cur_expr->bitmap_index = n_exprs++;
1695 cur_expr->next_same_hash = NULL;
1696 cur_expr->antic_occr = NULL;
1697 cur_expr->avail_occr = NULL;
1700 /* Now record the occurrence(s). */
1703 antic_occr = cur_expr->antic_occr;
1705 /* Search for another occurrence in the same basic block. */
1706 while (antic_occr && BLOCK_NUM (antic_occr->insn) != BLOCK_NUM (insn))
1708 /* If an occurrence isn't found, save a pointer to the end of
1710 last_occr = antic_occr;
1711 antic_occr = antic_occr->next;
1715 /* Found another instance of the expression in the same basic block.
1716 Prefer the currently recorded one. We want the first one in the
1717 block and the block is scanned from start to end. */
1718 ; /* nothing to do */
1721 /* First occurrence of this expression in this basic block. */
1722 antic_occr = (struct occr *) gcse_alloc (sizeof (struct occr));
1723 bytes_used += sizeof (struct occr);
1724 /* First occurrence of this expression in any block? */
1725 if (cur_expr->antic_occr == NULL)
1726 cur_expr->antic_occr = antic_occr;
1728 last_occr->next = antic_occr;
1730 antic_occr->insn = insn;
1731 antic_occr->next = NULL;
1737 avail_occr = cur_expr->avail_occr;
1739 /* Search for another occurrence in the same basic block. */
1740 while (avail_occr && BLOCK_NUM (avail_occr->insn) != BLOCK_NUM (insn))
1742 /* If an occurrence isn't found, save a pointer to the end of
1744 last_occr = avail_occr;
1745 avail_occr = avail_occr->next;
1749 /* Found another instance of the expression in the same basic block.
1750 Prefer this occurrence to the currently recorded one. We want
1751 the last one in the block and the block is scanned from start
1753 avail_occr->insn = insn;
1756 /* First occurrence of this expression in this basic block. */
1757 avail_occr = (struct occr *) gcse_alloc (sizeof (struct occr));
1758 bytes_used += sizeof (struct occr);
1760 /* First occurrence of this expression in any block? */
1761 if (cur_expr->avail_occr == NULL)
1762 cur_expr->avail_occr = avail_occr;
1764 last_occr->next = avail_occr;
1766 avail_occr->insn = insn;
1767 avail_occr->next = NULL;
1772 /* Insert pattern X in INSN in the hash table.
1773 X is a SET of a reg to either another reg or a constant.
1774 If it is already present, record it as the last occurrence in INSN's
1778 insert_set_in_table (x, insn)
1784 struct expr *cur_expr, *last_expr = NULL;
1785 struct occr *cur_occr, *last_occr = NULL;
1787 if (GET_CODE (x) != SET
1788 || GET_CODE (SET_DEST (x)) != REG)
1791 hash = hash_set (REGNO (SET_DEST (x)), set_hash_table_size);
1793 cur_expr = set_hash_table[hash];
1796 while (cur_expr && 0 == (found = expr_equiv_p (cur_expr->expr, x)))
1798 /* If the expression isn't found, save a pointer to the end of
1800 last_expr = cur_expr;
1801 cur_expr = cur_expr->next_same_hash;
1806 cur_expr = (struct expr *) gcse_alloc (sizeof (struct expr));
1807 bytes_used += sizeof (struct expr);
1808 if (set_hash_table[hash] == NULL)
1809 /* This is the first pattern that hashed to this index. */
1810 set_hash_table[hash] = cur_expr;
1812 /* Add EXPR to end of this hash chain. */
1813 last_expr->next_same_hash = cur_expr;
1815 /* Set the fields of the expr element.
1816 We must copy X because it can be modified when copy propagation is
1817 performed on its operands. */
1818 /* ??? Should this go in a different obstack? */
1819 cur_expr->expr = copy_rtx (x);
1820 cur_expr->bitmap_index = n_sets++;
1821 cur_expr->next_same_hash = NULL;
1822 cur_expr->antic_occr = NULL;
1823 cur_expr->avail_occr = NULL;
1826 /* Now record the occurrence. */
1827 cur_occr = cur_expr->avail_occr;
1829 /* Search for another occurrence in the same basic block. */
1830 while (cur_occr && BLOCK_NUM (cur_occr->insn) != BLOCK_NUM (insn))
1832 /* If an occurrence isn't found, save a pointer to the end of
1834 last_occr = cur_occr;
1835 cur_occr = cur_occr->next;
1839 /* Found another instance of the expression in the same basic block.
1840 Prefer this occurrence to the currently recorded one. We want the
1841 last one in the block and the block is scanned from start to end. */
1842 cur_occr->insn = insn;
1845 /* First occurrence of this expression in this basic block. */
1846 cur_occr = (struct occr *) gcse_alloc (sizeof (struct occr));
1847 bytes_used += sizeof (struct occr);
1849 /* First occurrence of this expression in any block? */
1850 if (cur_expr->avail_occr == NULL)
1851 cur_expr->avail_occr = cur_occr;
1853 last_occr->next = cur_occr;
1855 cur_occr->insn = insn;
1856 cur_occr->next = NULL;
1860 /* Scan pattern PAT of INSN and add an entry to the hash table. If SET_P is
1861 non-zero, this is for the assignment hash table, otherwise it is for the
1862 expression hash table. */
1865 hash_scan_set (pat, insn, set_p)
1869 rtx src = SET_SRC (pat);
1870 rtx dest = SET_DEST (pat);
1872 if (GET_CODE (src) == CALL)
1873 hash_scan_call (src, insn);
1875 if (GET_CODE (dest) == REG)
1877 int regno = REGNO (dest);
1880 /* Only record sets of pseudo-regs in the hash table. */
1882 && regno >= FIRST_PSEUDO_REGISTER
1883 /* Don't GCSE something if we can't do a reg/reg copy. */
1884 && can_copy_p [GET_MODE (dest)]
1885 /* Is SET_SRC something we want to gcse? */
1886 && want_to_gcse_p (src))
1888 /* An expression is not anticipatable if its operands are
1889 modified before this insn. */
1890 int antic_p = oprs_anticipatable_p (src, insn);
1891 /* An expression is not available if its operands are
1892 subsequently modified, including this insn. */
1893 int avail_p = oprs_available_p (src, insn);
1895 insert_expr_in_table (src, GET_MODE (dest), insn, antic_p, avail_p);
1898 /* Record sets for constant/copy propagation. */
1900 && regno >= FIRST_PSEUDO_REGISTER
1901 && ((GET_CODE (src) == REG
1902 && REGNO (src) >= FIRST_PSEUDO_REGISTER
1903 && can_copy_p [GET_MODE (dest)])
1904 || GET_CODE (src) == CONST_INT
1905 || GET_CODE (src) == SYMBOL_REF
1906 || GET_CODE (src) == CONST_DOUBLE)
1907 /* A copy is not available if its src or dest is subsequently
1908 modified. Here we want to search from INSN+1 on, but
1909 oprs_available_p searches from INSN on. */
1910 && (insn == BLOCK_END (BLOCK_NUM (insn))
1911 || ((tmp = next_nonnote_insn (insn)) != NULL_RTX
1912 && oprs_available_p (pat, tmp))))
1913 insert_set_in_table (pat, insn);
1918 hash_scan_clobber (x, insn)
1919 rtx x ATTRIBUTE_UNUSED, insn ATTRIBUTE_UNUSED;
1921 /* Currently nothing to do. */
1925 hash_scan_call (x, insn)
1926 rtx x ATTRIBUTE_UNUSED, insn ATTRIBUTE_UNUSED;
1928 /* Currently nothing to do. */
1931 /* Process INSN and add hash table entries as appropriate.
1933 Only available expressions that set a single pseudo-reg are recorded.
1935 Single sets in a PARALLEL could be handled, but it's an extra complication
1936 that isn't dealt with right now. The trick is handling the CLOBBERs that
1937 are also in the PARALLEL. Later.
1939 If SET_P is non-zero, this is for the assignment hash table,
1940 otherwise it is for the expression hash table.
1941 If IN_LIBCALL_BLOCK nonzero, we are in a libcall block, and should
1942 not record any expressions. */
1945 hash_scan_insn (insn, set_p, in_libcall_block)
1948 int in_libcall_block;
1950 rtx pat = PATTERN (insn);
1953 /* Pick out the sets of INSN and for other forms of instructions record
1954 what's been modified. */
1956 if (GET_CODE (pat) == SET && ! in_libcall_block)
1958 /* Ignore obvious no-ops. */
1959 if (SET_SRC (pat) != SET_DEST (pat))
1960 hash_scan_set (pat, insn, set_p);
1962 else if (GET_CODE (pat) == PARALLEL)
1963 for (i = 0; i < XVECLEN (pat, 0); i++)
1965 rtx x = XVECEXP (pat, 0, i);
1967 if (GET_CODE (x) == SET)
1969 if (GET_CODE (SET_SRC (x)) == CALL)
1970 hash_scan_call (SET_SRC (x), insn);
1972 else if (GET_CODE (x) == CLOBBER)
1973 hash_scan_clobber (x, insn);
1974 else if (GET_CODE (x) == CALL)
1975 hash_scan_call (x, insn);
1978 else if (GET_CODE (pat) == CLOBBER)
1979 hash_scan_clobber (pat, insn);
1980 else if (GET_CODE (pat) == CALL)
1981 hash_scan_call (pat, insn);
1985 dump_hash_table (file, name, table, table_size, total_size)
1988 struct expr **table;
1989 int table_size, total_size;
1992 /* Flattened out table, so it's printed in proper order. */
1993 struct expr **flat_table;
1994 unsigned int *hash_val;
1998 = (struct expr **) xcalloc (total_size, sizeof (struct expr *));
1999 hash_val = (unsigned int *) xmalloc (total_size * sizeof (unsigned int));
2001 for (i = 0; i < table_size; i++)
2002 for (expr = table[i]; expr != NULL; expr = expr->next_same_hash)
2004 flat_table[expr->bitmap_index] = expr;
2005 hash_val[expr->bitmap_index] = i;
2008 fprintf (file, "%s hash table (%d buckets, %d entries)\n",
2009 name, table_size, total_size);
2011 for (i = 0; i < total_size; i++)
2012 if (flat_table[i] != 0)
2014 expr = flat_table[i];
2015 fprintf (file, "Index %d (hash value %d)\n ",
2016 expr->bitmap_index, hash_val[i]);
2017 print_rtl (file, expr->expr);
2018 fprintf (file, "\n");
2021 fprintf (file, "\n");
2027 /* Record register first/last/block set information for REGNO in INSN.
2029 reg_first_set records the first place in the block where the register
2030 is set and is used to compute "anticipatability".
2032 reg_last_set records the last place in the block where the register
2033 is set and is used to compute "availability".
2035 reg_set_in_block records whether the register is set in the block
2036 and is used to compute "transparency". */
2039 record_last_reg_set_info (insn, regno)
2043 if (reg_first_set[regno] == NEVER_SET)
2044 reg_first_set[regno] = INSN_CUID (insn);
2046 reg_last_set[regno] = INSN_CUID (insn);
2047 SET_BIT (reg_set_in_block[BLOCK_NUM (insn)], regno);
2050 /* Record memory first/last/block set information for INSN. */
2053 record_last_mem_set_info (insn)
2056 if (mem_first_set == NEVER_SET)
2057 mem_first_set = INSN_CUID (insn);
2059 mem_last_set = INSN_CUID (insn);
2060 mem_set_in_block[BLOCK_NUM (insn)] = 1;
2063 /* Called from compute_hash_table via note_stores to handle one
2064 SET or CLOBBER in an insn. DATA is really the instruction in which
2065 the SET is taking place. */
2068 record_last_set_info (dest, setter, data)
2069 rtx dest, setter ATTRIBUTE_UNUSED;
2072 rtx last_set_insn = (rtx) data;
2074 if (GET_CODE (dest) == SUBREG)
2075 dest = SUBREG_REG (dest);
2077 if (GET_CODE (dest) == REG)
2078 record_last_reg_set_info (last_set_insn, REGNO (dest));
2079 else if (GET_CODE (dest) == MEM
2080 /* Ignore pushes, they clobber nothing. */
2081 && ! push_operand (dest, GET_MODE (dest)))
2082 record_last_mem_set_info (last_set_insn);
2085 /* Top level function to create an expression or assignment hash table.
2087 Expression entries are placed in the hash table if
2088 - they are of the form (set (pseudo-reg) src),
2089 - src is something we want to perform GCSE on,
2090 - none of the operands are subsequently modified in the block
2092 Assignment entries are placed in the hash table if
2093 - they are of the form (set (pseudo-reg) src),
2094 - src is something we want to perform const/copy propagation on,
2095 - none of the operands or target are subsequently modified in the block
2097 Currently src must be a pseudo-reg or a const_int.
2099 F is the first insn.
2100 SET_P is non-zero for computing the assignment hash table. */
2103 compute_hash_table (set_p)
2108 /* While we compute the hash table we also compute a bit array of which
2109 registers are set in which blocks.
2110 We also compute which blocks set memory, in the absence of aliasing
2111 support [which is TODO].
2112 ??? This isn't needed during const/copy propagation, but it's cheap to
2114 sbitmap_vector_zero (reg_set_in_block, n_basic_blocks);
2115 bzero ((char *) mem_set_in_block, n_basic_blocks);
2117 /* Some working arrays used to track first and last set in each block. */
2118 /* ??? One could use alloca here, but at some size a threshold is crossed
2119 beyond which one should use malloc. Are we at that threshold here? */
2120 reg_first_set = (int *) gmalloc (max_gcse_regno * sizeof (int));
2121 reg_last_set = (int *) gmalloc (max_gcse_regno * sizeof (int));
2123 for (bb = 0; bb < n_basic_blocks; bb++)
2127 int in_libcall_block;
2130 /* First pass over the instructions records information used to
2131 determine when registers and memory are first and last set.
2132 ??? The mem_set_in_block and hard-reg reg_set_in_block computation
2133 could be moved to compute_sets since they currently don't change. */
2135 for (i = 0; i < max_gcse_regno; i++)
2136 reg_first_set[i] = reg_last_set[i] = NEVER_SET;
2137 mem_first_set = NEVER_SET;
2138 mem_last_set = NEVER_SET;
2140 for (insn = BLOCK_HEAD (bb);
2141 insn && insn != NEXT_INSN (BLOCK_END (bb));
2142 insn = NEXT_INSN (insn))
2144 #ifdef NON_SAVING_SETJMP
2145 if (NON_SAVING_SETJMP && GET_CODE (insn) == NOTE
2146 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_SETJMP)
2148 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
2149 record_last_reg_set_info (insn, regno);
2154 if (GET_RTX_CLASS (GET_CODE (insn)) != 'i')
2157 if (GET_CODE (insn) == CALL_INSN)
2159 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
2160 if ((call_used_regs[regno]
2161 && regno != STACK_POINTER_REGNUM
2162 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2163 && regno != HARD_FRAME_POINTER_REGNUM
2165 #if ARG_POINTER_REGNUM != FRAME_POINTER_REGNUM
2166 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2168 #if defined (PIC_OFFSET_TABLE_REGNUM) && !defined (PIC_OFFSET_TABLE_REG_CALL_CLOBBERED)
2169 && ! (regno == PIC_OFFSET_TABLE_REGNUM && flag_pic)
2172 && regno != FRAME_POINTER_REGNUM)
2173 || global_regs[regno])
2174 record_last_reg_set_info (insn, regno);
2176 if (! CONST_CALL_P (insn))
2177 record_last_mem_set_info (insn);
2180 note_stores (PATTERN (insn), record_last_set_info, insn);
2183 /* The next pass builds the hash table. */
2185 for (insn = BLOCK_HEAD (bb), in_libcall_block = 0;
2186 insn && insn != NEXT_INSN (BLOCK_END (bb));
2187 insn = NEXT_INSN (insn))
2188 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
2190 if (find_reg_note (insn, REG_LIBCALL, NULL_RTX))
2191 in_libcall_block = 1;
2192 else if (find_reg_note (insn, REG_RETVAL, NULL_RTX))
2193 in_libcall_block = 0;
2194 hash_scan_insn (insn, set_p, in_libcall_block);
2198 free (reg_first_set);
2199 free (reg_last_set);
2201 /* Catch bugs early. */
2202 reg_first_set = reg_last_set = 0;
2205 /* Allocate space for the set hash table.
2206 N_INSNS is the number of instructions in the function.
2207 It is used to determine the number of buckets to use. */
2210 alloc_set_hash_table (n_insns)
2215 set_hash_table_size = n_insns / 4;
2216 if (set_hash_table_size < 11)
2217 set_hash_table_size = 11;
2219 /* Attempt to maintain efficient use of hash table.
2220 Making it an odd number is simplest for now.
2221 ??? Later take some measurements. */
2222 set_hash_table_size |= 1;
2223 n = set_hash_table_size * sizeof (struct expr *);
2224 set_hash_table = (struct expr **) gmalloc (n);
2227 /* Free things allocated by alloc_set_hash_table. */
2230 free_set_hash_table ()
2232 free (set_hash_table);
2235 /* Compute the hash table for doing copy/const propagation. */
2238 compute_set_hash_table ()
2240 /* Initialize count of number of entries in hash table. */
2242 bzero ((char *) set_hash_table,
2243 set_hash_table_size * sizeof (struct expr *));
2245 compute_hash_table (1);
2248 /* Allocate space for the expression hash table.
2249 N_INSNS is the number of instructions in the function.
2250 It is used to determine the number of buckets to use. */
2253 alloc_expr_hash_table (n_insns)
2258 expr_hash_table_size = n_insns / 2;
2259 /* Make sure the amount is usable. */
2260 if (expr_hash_table_size < 11)
2261 expr_hash_table_size = 11;
2263 /* Attempt to maintain efficient use of hash table.
2264 Making it an odd number is simplest for now.
2265 ??? Later take some measurements. */
2266 expr_hash_table_size |= 1;
2267 n = expr_hash_table_size * sizeof (struct expr *);
2268 expr_hash_table = (struct expr **) gmalloc (n);
2271 /* Free things allocated by alloc_expr_hash_table. */
2274 free_expr_hash_table ()
2276 free (expr_hash_table);
2279 /* Compute the hash table for doing GCSE. */
2282 compute_expr_hash_table ()
2284 /* Initialize count of number of entries in hash table. */
2286 bzero ((char *) expr_hash_table,
2287 expr_hash_table_size * sizeof (struct expr *));
2289 compute_hash_table (0);
2292 /* Expression tracking support. */
2294 /* Lookup pattern PAT in the expression table.
2295 The result is a pointer to the table entry, or NULL if not found. */
2297 static struct expr *
2301 int do_not_record_p;
2302 unsigned int hash = hash_expr (pat, GET_MODE (pat), &do_not_record_p,
2303 expr_hash_table_size);
2306 if (do_not_record_p)
2309 expr = expr_hash_table[hash];
2311 while (expr && ! expr_equiv_p (expr->expr, pat))
2312 expr = expr->next_same_hash;
2317 /* Lookup REGNO in the set table. If PAT is non-NULL look for the entry that
2318 matches it, otherwise return the first entry for REGNO. The result is a
2319 pointer to the table entry, or NULL if not found. */
2321 static struct expr *
2322 lookup_set (regno, pat)
2326 unsigned int hash = hash_set (regno, set_hash_table_size);
2329 expr = set_hash_table[hash];
2333 while (expr && ! expr_equiv_p (expr->expr, pat))
2334 expr = expr->next_same_hash;
2338 while (expr && REGNO (SET_DEST (expr->expr)) != regno)
2339 expr = expr->next_same_hash;
2345 /* Return the next entry for REGNO in list EXPR. */
2347 static struct expr *
2348 next_set (regno, expr)
2353 expr = expr->next_same_hash;
2354 while (expr && REGNO (SET_DEST (expr->expr)) != regno);
2359 /* Reset tables used to keep track of what's still available [since the
2360 start of the block]. */
2363 reset_opr_set_tables ()
2365 /* Maintain a bitmap of which regs have been set since beginning of
2367 sbitmap_zero (reg_set_bitmap);
2369 /* Also keep a record of the last instruction to modify memory.
2370 For now this is very trivial, we only record whether any memory
2371 location has been modified. */
2375 /* Return non-zero if the operands of X are not set before INSN in
2376 INSN's basic block. */
2379 oprs_not_set_p (x, insn)
2389 code = GET_CODE (x);
2404 if (mem_last_set != 0)
2407 return oprs_not_set_p (XEXP (x, 0), insn);
2410 return ! TEST_BIT (reg_set_bitmap, REGNO (x));
2416 for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
2420 /* If we are about to do the last recursive call
2421 needed at this level, change it into iteration.
2422 This function is called enough to be worth it. */
2424 return oprs_not_set_p (XEXP (x, i), insn);
2426 if (! oprs_not_set_p (XEXP (x, i), insn))
2429 else if (fmt[i] == 'E')
2430 for (j = 0; j < XVECLEN (x, i); j++)
2431 if (! oprs_not_set_p (XVECEXP (x, i, j), insn))
2438 /* Mark things set by a CALL. */
2444 mem_last_set = INSN_CUID (insn);
2447 /* Mark things set by a SET. */
2450 mark_set (pat, insn)
2453 rtx dest = SET_DEST (pat);
2455 while (GET_CODE (dest) == SUBREG
2456 || GET_CODE (dest) == ZERO_EXTRACT
2457 || GET_CODE (dest) == SIGN_EXTRACT
2458 || GET_CODE (dest) == STRICT_LOW_PART)
2459 dest = XEXP (dest, 0);
2461 if (GET_CODE (dest) == REG)
2462 SET_BIT (reg_set_bitmap, REGNO (dest));
2463 else if (GET_CODE (dest) == MEM)
2464 mem_last_set = INSN_CUID (insn);
2466 if (GET_CODE (SET_SRC (pat)) == CALL)
2470 /* Record things set by a CLOBBER. */
2473 mark_clobber (pat, insn)
2476 rtx clob = XEXP (pat, 0);
2478 while (GET_CODE (clob) == SUBREG || GET_CODE (clob) == STRICT_LOW_PART)
2479 clob = XEXP (clob, 0);
2481 if (GET_CODE (clob) == REG)
2482 SET_BIT (reg_set_bitmap, REGNO (clob));
2484 mem_last_set = INSN_CUID (insn);
2487 /* Record things set by INSN.
2488 This data is used by oprs_not_set_p. */
2491 mark_oprs_set (insn)
2494 rtx pat = PATTERN (insn);
2497 if (GET_CODE (pat) == SET)
2498 mark_set (pat, insn);
2499 else if (GET_CODE (pat) == PARALLEL)
2500 for (i = 0; i < XVECLEN (pat, 0); i++)
2502 rtx x = XVECEXP (pat, 0, i);
2504 if (GET_CODE (x) == SET)
2506 else if (GET_CODE (x) == CLOBBER)
2507 mark_clobber (x, insn);
2508 else if (GET_CODE (x) == CALL)
2512 else if (GET_CODE (pat) == CLOBBER)
2513 mark_clobber (pat, insn);
2514 else if (GET_CODE (pat) == CALL)
2519 /* Classic GCSE reaching definition support. */
2521 /* Allocate reaching def variables. */
2524 alloc_rd_mem (n_blocks, n_insns)
2525 int n_blocks, n_insns;
2527 rd_kill = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
2528 sbitmap_vector_zero (rd_kill, n_basic_blocks);
2530 rd_gen = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
2531 sbitmap_vector_zero (rd_gen, n_basic_blocks);
2533 reaching_defs = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
2534 sbitmap_vector_zero (reaching_defs, n_basic_blocks);
2536 rd_out = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
2537 sbitmap_vector_zero (rd_out, n_basic_blocks);
2540 /* Free reaching def variables. */
2547 free (reaching_defs);
2551 /* Add INSN to the kills of BB. REGNO, set in BB, is killed by INSN. */
2554 handle_rd_kill_set (insn, regno, bb)
2558 struct reg_set *this_reg;
2560 for (this_reg = reg_set_table[regno]; this_reg; this_reg = this_reg ->next)
2561 if (BLOCK_NUM (this_reg->insn) != BLOCK_NUM (insn))
2562 SET_BIT (rd_kill[bb], INSN_CUID (this_reg->insn));
2565 /* Compute the set of kill's for reaching definitions. */
2574 For each set bit in `gen' of the block (i.e each insn which
2575 generates a definition in the block)
2576 Call the reg set by the insn corresponding to that bit regx
2577 Look at the linked list starting at reg_set_table[regx]
2578 For each setting of regx in the linked list, which is not in
2580 Set the bit in `kill' corresponding to that insn. */
2581 for (bb = 0; bb < n_basic_blocks; bb++)
2582 for (cuid = 0; cuid < max_cuid; cuid++)
2583 if (TEST_BIT (rd_gen[bb], cuid))
2585 rtx insn = CUID_INSN (cuid);
2586 rtx pat = PATTERN (insn);
2588 if (GET_CODE (insn) == CALL_INSN)
2590 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
2592 if ((call_used_regs[regno]
2593 && regno != STACK_POINTER_REGNUM
2594 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2595 && regno != HARD_FRAME_POINTER_REGNUM
2597 #if ARG_POINTER_REGNUM != FRAME_POINTER_REGNUM
2598 && ! (regno == ARG_POINTER_REGNUM
2599 && fixed_regs[regno])
2601 #if defined (PIC_OFFSET_TABLE_REGNUM) && !defined (PIC_OFFSET_TABLE_REG_CALL_CLOBBERED)
2602 && ! (regno == PIC_OFFSET_TABLE_REGNUM && flag_pic)
2604 && regno != FRAME_POINTER_REGNUM)
2605 || global_regs[regno])
2606 handle_rd_kill_set (insn, regno, bb);
2610 if (GET_CODE (pat) == PARALLEL)
2612 for (i = XVECLEN (pat, 0) - 1; i >= 0; i--)
2614 enum rtx_code code = GET_CODE (XVECEXP (pat, 0, i));
2616 if ((code == SET || code == CLOBBER)
2617 && GET_CODE (XEXP (XVECEXP (pat, 0, i), 0)) == REG)
2618 handle_rd_kill_set (insn,
2619 REGNO (XEXP (XVECEXP (pat, 0, i), 0)),
2623 else if (GET_CODE (pat) == SET && GET_CODE (SET_DEST (pat)) == REG)
2624 /* Each setting of this register outside of this block
2625 must be marked in the set of kills in this block. */
2626 handle_rd_kill_set (insn, REGNO (SET_DEST (pat)), bb);
2630 /* Compute the reaching definitions as in
2631 Compilers Principles, Techniques, and Tools. Aho, Sethi, Ullman,
2632 Chapter 10. It is the same algorithm as used for computing available
2633 expressions but applied to the gens and kills of reaching definitions. */
2638 int bb, changed, passes;
2640 for (bb = 0; bb < n_basic_blocks; bb++)
2641 sbitmap_copy (rd_out[bb] /*dst*/, rd_gen[bb] /*src*/);
2648 for (bb = 0; bb < n_basic_blocks; bb++)
2650 sbitmap_union_of_preds (reaching_defs[bb], rd_out, bb);
2651 changed |= sbitmap_union_of_diff (rd_out[bb], rd_gen[bb],
2652 reaching_defs[bb], rd_kill[bb]);
2658 fprintf (gcse_file, "reaching def computation: %d passes\n", passes);
2661 /* Classic GCSE available expression support. */
2663 /* Allocate memory for available expression computation. */
2666 alloc_avail_expr_mem (n_blocks, n_exprs)
2667 int n_blocks, n_exprs;
2669 ae_kill = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
2670 sbitmap_vector_zero (ae_kill, n_basic_blocks);
2672 ae_gen = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
2673 sbitmap_vector_zero (ae_gen, n_basic_blocks);
2675 ae_in = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
2676 sbitmap_vector_zero (ae_in, n_basic_blocks);
2678 ae_out = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
2679 sbitmap_vector_zero (ae_out, n_basic_blocks);
2681 u_bitmap = (sbitmap) sbitmap_alloc (n_exprs);
2682 sbitmap_ones (u_bitmap);
2686 free_avail_expr_mem ()
2695 /* Compute the set of available expressions generated in each basic block. */
2704 /* For each recorded occurrence of each expression, set ae_gen[bb][expr].
2705 This is all we have to do because an expression is not recorded if it
2706 is not available, and the only expressions we want to work with are the
2707 ones that are recorded. */
2708 for (i = 0; i < expr_hash_table_size; i++)
2709 for (expr = expr_hash_table[i]; expr != 0; expr = expr->next_same_hash)
2710 for (occr = expr->avail_occr; occr != 0; occr = occr->next)
2711 SET_BIT (ae_gen[BLOCK_NUM (occr->insn)], expr->bitmap_index);
2714 /* Return non-zero if expression X is killed in BB. */
2717 expr_killed_p (x, bb)
2728 code = GET_CODE (x);
2732 return TEST_BIT (reg_set_in_block[bb], REGNO (x));
2735 if (mem_set_in_block[bb])
2738 return expr_killed_p (XEXP (x, 0), bb);
2755 for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
2759 /* If we are about to do the last recursive call
2760 needed at this level, change it into iteration.
2761 This function is called enough to be worth it. */
2763 return expr_killed_p (XEXP (x, i), bb);
2764 else if (expr_killed_p (XEXP (x, i), bb))
2767 else if (fmt[i] == 'E')
2768 for (j = 0; j < XVECLEN (x, i); j++)
2769 if (expr_killed_p (XVECEXP (x, i, j), bb))
2776 /* Compute the set of available expressions killed in each basic block. */
2779 compute_ae_kill (ae_gen, ae_kill)
2780 sbitmap *ae_gen, *ae_kill;
2785 for (bb = 0; bb < n_basic_blocks; bb++)
2786 for (i = 0; i < expr_hash_table_size; i++)
2787 for (expr = expr_hash_table[i]; expr; expr = expr->next_same_hash)
2789 /* Skip EXPR if generated in this block. */
2790 if (TEST_BIT (ae_gen[bb], expr->bitmap_index))
2793 if (expr_killed_p (expr->expr, bb))
2794 SET_BIT (ae_kill[bb], expr->bitmap_index);
2798 /* Actually perform the Classic GCSE optimizations. */
2800 /* Return non-zero if occurrence OCCR of expression EXPR reaches block BB.
2802 CHECK_SELF_LOOP is non-zero if we should consider a block reaching itself
2803 as a positive reach. We want to do this when there are two computations
2804 of the expression in the block.
2806 VISITED is a pointer to a working buffer for tracking which BB's have
2807 been visited. It is NULL for the top-level call.
2809 We treat reaching expressions that go through blocks containing the same
2810 reaching expression as "not reaching". E.g. if EXPR is generated in blocks
2811 2 and 3, INSN is in block 4, and 2->3->4, we treat the expression in block
2812 2 as not reaching. The intent is to improve the probability of finding
2813 only one reaching expression and to reduce register lifetimes by picking
2814 the closest such expression. */
2817 expr_reaches_here_p_work (occr, expr, bb, check_self_loop, visited)
2821 int check_self_loop;
2826 for (pred = BASIC_BLOCK(bb)->pred; pred != NULL; pred = pred->pred_next)
2828 int pred_bb = pred->src->index;
2830 if (visited[pred_bb])
2831 /* This predecessor has already been visited. Nothing to do. */
2833 else if (pred_bb == bb)
2835 /* BB loops on itself. */
2837 && TEST_BIT (ae_gen[pred_bb], expr->bitmap_index)
2838 && BLOCK_NUM (occr->insn) == pred_bb)
2841 visited[pred_bb] = 1;
2844 /* Ignore this predecessor if it kills the expression. */
2845 else if (TEST_BIT (ae_kill[pred_bb], expr->bitmap_index))
2846 visited[pred_bb] = 1;
2848 /* Does this predecessor generate this expression? */
2849 else if (TEST_BIT (ae_gen[pred_bb], expr->bitmap_index))
2851 /* Is this the occurrence we're looking for?
2852 Note that there's only one generating occurrence per block
2853 so we just need to check the block number. */
2854 if (BLOCK_NUM (occr->insn) == pred_bb)
2857 visited[pred_bb] = 1;
2860 /* Neither gen nor kill. */
2863 visited[pred_bb] = 1;
2864 if (expr_reaches_here_p_work (occr, expr, pred_bb, check_self_loop,
2871 /* All paths have been checked. */
2875 /* This wrapper for expr_reaches_here_p_work() is to ensure that any
2876 memory allocated for that function is returned. */
2879 expr_reaches_here_p (occr, expr, bb, check_self_loop)
2883 int check_self_loop;
2886 char *visited = (char *) xcalloc (n_basic_blocks, 1);
2888 rval = expr_reaches_here_p_work (occr, expr, bb, check_self_loop, visited);
2894 /* Return the instruction that computes EXPR that reaches INSN's basic block.
2895 If there is more than one such instruction, return NULL.
2897 Called only by handle_avail_expr. */
2900 computing_insn (expr, insn)
2904 int bb = BLOCK_NUM (insn);
2906 if (expr->avail_occr->next == NULL)
2908 if (BLOCK_NUM (expr->avail_occr->insn) == bb)
2909 /* The available expression is actually itself
2910 (i.e. a loop in the flow graph) so do nothing. */
2913 /* (FIXME) Case that we found a pattern that was created by
2914 a substitution that took place. */
2915 return expr->avail_occr->insn;
2919 /* Pattern is computed more than once.
2920 Search backwards from this insn to see how many of these
2921 computations actually reach this insn. */
2923 rtx insn_computes_expr = NULL;
2926 for (occr = expr->avail_occr; occr != NULL; occr = occr->next)
2928 if (BLOCK_NUM (occr->insn) == bb)
2930 /* The expression is generated in this block.
2931 The only time we care about this is when the expression
2932 is generated later in the block [and thus there's a loop].
2933 We let the normal cse pass handle the other cases. */
2934 if (INSN_CUID (insn) < INSN_CUID (occr->insn)
2935 && expr_reaches_here_p (occr, expr, bb, 1))
2941 insn_computes_expr = occr->insn;
2944 else if (expr_reaches_here_p (occr, expr, bb, 0))
2950 insn_computes_expr = occr->insn;
2954 if (insn_computes_expr == NULL)
2957 return insn_computes_expr;
2961 /* Return non-zero if the definition in DEF_INSN can reach INSN.
2962 Only called by can_disregard_other_sets. */
2965 def_reaches_here_p (insn, def_insn)
2970 if (TEST_BIT (reaching_defs[BLOCK_NUM (insn)], INSN_CUID (def_insn)))
2973 if (BLOCK_NUM (insn) == BLOCK_NUM (def_insn))
2975 if (INSN_CUID (def_insn) < INSN_CUID (insn))
2977 if (GET_CODE (PATTERN (def_insn)) == PARALLEL)
2979 else if (GET_CODE (PATTERN (def_insn)) == CLOBBER)
2980 reg = XEXP (PATTERN (def_insn), 0);
2981 else if (GET_CODE (PATTERN (def_insn)) == SET)
2982 reg = SET_DEST (PATTERN (def_insn));
2986 return ! reg_set_between_p (reg, NEXT_INSN (def_insn), insn);
2995 /* Return non-zero if *ADDR_THIS_REG can only have one value at INSN. The
2996 value returned is the number of definitions that reach INSN. Returning a
2997 value of zero means that [maybe] more than one definition reaches INSN and
2998 the caller can't perform whatever optimization it is trying. i.e. it is
2999 always safe to return zero. */
3002 can_disregard_other_sets (addr_this_reg, insn, for_combine)
3003 struct reg_set **addr_this_reg;
3007 int number_of_reaching_defs = 0;
3008 struct reg_set *this_reg;
3010 for (this_reg = *addr_this_reg; this_reg != 0; this_reg = this_reg->next)
3011 if (def_reaches_here_p (insn, this_reg->insn))
3013 number_of_reaching_defs++;
3014 /* Ignore parallels for now. */
3015 if (GET_CODE (PATTERN (this_reg->insn)) == PARALLEL)
3019 && (GET_CODE (PATTERN (this_reg->insn)) == CLOBBER
3020 || ! rtx_equal_p (SET_SRC (PATTERN (this_reg->insn)),
3021 SET_SRC (PATTERN (insn)))))
3022 /* A setting of the reg to a different value reaches INSN. */
3025 if (number_of_reaching_defs > 1)
3027 /* If in this setting the value the register is being set to is
3028 equal to the previous value the register was set to and this
3029 setting reaches the insn we are trying to do the substitution
3030 on then we are ok. */
3031 if (GET_CODE (PATTERN (this_reg->insn)) == CLOBBER)
3033 else if (! rtx_equal_p (SET_SRC (PATTERN (this_reg->insn)),
3034 SET_SRC (PATTERN (insn))))
3038 *addr_this_reg = this_reg;
3041 return number_of_reaching_defs;
3044 /* Expression computed by insn is available and the substitution is legal,
3045 so try to perform the substitution.
3047 The result is non-zero if any changes were made. */
3050 handle_avail_expr (insn, expr)
3054 rtx pat, insn_computes_expr;
3056 struct reg_set *this_reg;
3057 int found_setting, use_src;
3060 /* We only handle the case where one computation of the expression
3061 reaches this instruction. */
3062 insn_computes_expr = computing_insn (expr, insn);
3063 if (insn_computes_expr == NULL)
3069 /* At this point we know only one computation of EXPR outside of this
3070 block reaches this insn. Now try to find a register that the
3071 expression is computed into. */
3072 if (GET_CODE (SET_SRC (PATTERN (insn_computes_expr))) == REG)
3074 /* This is the case when the available expression that reaches
3075 here has already been handled as an available expression. */
3076 int regnum_for_replacing
3077 = REGNO (SET_SRC (PATTERN (insn_computes_expr)));
3079 /* If the register was created by GCSE we can't use `reg_set_table',
3080 however we know it's set only once. */
3081 if (regnum_for_replacing >= max_gcse_regno
3082 /* If the register the expression is computed into is set only once,
3083 or only one set reaches this insn, we can use it. */
3084 || (((this_reg = reg_set_table[regnum_for_replacing]),
3085 this_reg->next == NULL)
3086 || can_disregard_other_sets (&this_reg, insn, 0)))
3095 int regnum_for_replacing
3096 = REGNO (SET_DEST (PATTERN (insn_computes_expr)));
3098 /* This shouldn't happen. */
3099 if (regnum_for_replacing >= max_gcse_regno)
3102 this_reg = reg_set_table[regnum_for_replacing];
3104 /* If the register the expression is computed into is set only once,
3105 or only one set reaches this insn, use it. */
3106 if (this_reg->next == NULL
3107 || can_disregard_other_sets (&this_reg, insn, 0))
3113 pat = PATTERN (insn);
3115 to = SET_SRC (PATTERN (insn_computes_expr));
3117 to = SET_DEST (PATTERN (insn_computes_expr));
3118 changed = validate_change (insn, &SET_SRC (pat), to, 0);
3120 /* We should be able to ignore the return code from validate_change but
3121 to play it safe we check. */
3125 if (gcse_file != NULL)
3127 fprintf (gcse_file, "GCSE: Replacing the source in insn %d with",
3129 fprintf (gcse_file, " reg %d %s insn %d\n",
3130 REGNO (to), use_src ? "from" : "set in",
3131 INSN_UID (insn_computes_expr));
3136 /* The register that the expr is computed into is set more than once. */
3137 else if (1 /*expensive_op(this_pattrn->op) && do_expensive_gcse)*/)
3139 /* Insert an insn after insnx that copies the reg set in insnx
3140 into a new pseudo register call this new register REGN.
3141 From insnb until end of basic block or until REGB is set
3142 replace all uses of REGB with REGN. */
3145 to = gen_reg_rtx (GET_MODE (SET_DEST (PATTERN (insn_computes_expr))));
3147 /* Generate the new insn. */
3148 /* ??? If the change fails, we return 0, even though we created
3149 an insn. I think this is ok. */
3151 = emit_insn_after (gen_rtx_SET (VOIDmode, to,
3153 (insn_computes_expr))),
3154 insn_computes_expr);
3156 /* Keep block number table up to date. */
3157 set_block_num (new_insn, BLOCK_NUM (insn_computes_expr));
3159 /* Keep register set table up to date. */
3160 record_one_set (REGNO (to), new_insn);
3162 gcse_create_count++;
3163 if (gcse_file != NULL)
3165 fprintf (gcse_file, "GCSE: Creating insn %d to copy value of reg %d",
3166 INSN_UID (NEXT_INSN (insn_computes_expr)),
3167 REGNO (SET_SRC (PATTERN (NEXT_INSN (insn_computes_expr)))));
3168 fprintf (gcse_file, ", computed in insn %d,\n",
3169 INSN_UID (insn_computes_expr));
3170 fprintf (gcse_file, " into newly allocated reg %d\n",
3174 pat = PATTERN (insn);
3176 /* Do register replacement for INSN. */
3177 changed = validate_change (insn, &SET_SRC (pat),
3179 (NEXT_INSN (insn_computes_expr))),
3182 /* We should be able to ignore the return code from validate_change but
3183 to play it safe we check. */
3187 if (gcse_file != NULL)
3190 "GCSE: Replacing the source in insn %d with reg %d ",
3192 REGNO (SET_DEST (PATTERN (NEXT_INSN
3193 (insn_computes_expr)))));
3194 fprintf (gcse_file, "set in insn %d\n",
3195 INSN_UID (insn_computes_expr));
3203 /* Perform classic GCSE. This is called by one_classic_gcse_pass after all
3204 the dataflow analysis has been done.
3206 The result is non-zero if a change was made. */
3214 /* Note we start at block 1. */
3217 for (bb = 1; bb < n_basic_blocks; bb++)
3219 /* Reset tables used to keep track of what's still valid [since the
3220 start of the block]. */
3221 reset_opr_set_tables ();
3223 for (insn = BLOCK_HEAD (bb);
3224 insn != NULL && insn != NEXT_INSN (BLOCK_END (bb));
3225 insn = NEXT_INSN (insn))
3227 /* Is insn of form (set (pseudo-reg) ...)? */
3228 if (GET_CODE (insn) == INSN
3229 && GET_CODE (PATTERN (insn)) == SET
3230 && GET_CODE (SET_DEST (PATTERN (insn))) == REG
3231 && REGNO (SET_DEST (PATTERN (insn))) >= FIRST_PSEUDO_REGISTER)
3233 rtx pat = PATTERN (insn);
3234 rtx src = SET_SRC (pat);
3237 if (want_to_gcse_p (src)
3238 /* Is the expression recorded? */
3239 && ((expr = lookup_expr (src)) != NULL)
3240 /* Is the expression available [at the start of the
3242 && TEST_BIT (ae_in[bb], expr->bitmap_index)
3243 /* Are the operands unchanged since the start of the
3245 && oprs_not_set_p (src, insn))
3246 changed |= handle_avail_expr (insn, expr);
3249 /* Keep track of everything modified by this insn. */
3250 /* ??? Need to be careful w.r.t. mods done to INSN. */
3251 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
3252 mark_oprs_set (insn);
3259 /* Top level routine to perform one classic GCSE pass.
3261 Return non-zero if a change was made. */
3264 one_classic_gcse_pass (pass)
3269 gcse_subst_count = 0;
3270 gcse_create_count = 0;
3272 alloc_expr_hash_table (max_cuid);
3273 alloc_rd_mem (n_basic_blocks, max_cuid);
3274 compute_expr_hash_table ();
3276 dump_hash_table (gcse_file, "Expression", expr_hash_table,
3277 expr_hash_table_size, n_exprs);
3283 alloc_avail_expr_mem (n_basic_blocks, n_exprs);
3285 compute_ae_kill (ae_gen, ae_kill);
3286 compute_available (ae_gen, ae_kill, ae_out, ae_in);
3287 changed = classic_gcse ();
3288 free_avail_expr_mem ();
3292 free_expr_hash_table ();
3296 fprintf (gcse_file, "\n");
3297 fprintf (gcse_file, "GCSE of %s, pass %d: %d bytes needed, %d substs,",
3298 current_function_name, pass, bytes_used, gcse_subst_count);
3299 fprintf (gcse_file, "%d insns created\n", gcse_create_count);
3305 /* Compute copy/constant propagation working variables. */
3307 /* Local properties of assignments. */
3308 static sbitmap *cprop_pavloc;
3309 static sbitmap *cprop_absaltered;
3311 /* Global properties of assignments (computed from the local properties). */
3312 static sbitmap *cprop_avin;
3313 static sbitmap *cprop_avout;
3315 /* Allocate vars used for copy/const propagation. N_BLOCKS is the number of
3316 basic blocks. N_SETS is the number of sets. */
3319 alloc_cprop_mem (n_blocks, n_sets)
3320 int n_blocks, n_sets;
3322 cprop_pavloc = sbitmap_vector_alloc (n_blocks, n_sets);
3323 cprop_absaltered = sbitmap_vector_alloc (n_blocks, n_sets);
3325 cprop_avin = sbitmap_vector_alloc (n_blocks, n_sets);
3326 cprop_avout = sbitmap_vector_alloc (n_blocks, n_sets);
3329 /* Free vars used by copy/const propagation. */
3334 free (cprop_pavloc);
3335 free (cprop_absaltered);
3340 /* For each block, compute whether X is transparent. X is either an
3341 expression or an assignment [though we don't care which, for this context
3342 an assignment is treated as an expression]. For each block where an
3343 element of X is modified, set (SET_P == 1) or reset (SET_P == 0) the INDX
3347 compute_transp (x, indx, bmap, set_p)
3358 /* repeat is used to turn tail-recursion into iteration since GCC
3359 can't do it when there's no return value. */
3365 code = GET_CODE (x);
3371 if (REGNO (x) < FIRST_PSEUDO_REGISTER)
3373 for (bb = 0; bb < n_basic_blocks; bb++)
3374 if (TEST_BIT (reg_set_in_block[bb], REGNO (x)))
3375 SET_BIT (bmap[bb], indx);
3379 for (r = reg_set_table[REGNO (x)]; r != NULL; r = r->next)
3380 SET_BIT (bmap[BLOCK_NUM (r->insn)], indx);
3385 if (REGNO (x) < FIRST_PSEUDO_REGISTER)
3387 for (bb = 0; bb < n_basic_blocks; bb++)
3388 if (TEST_BIT (reg_set_in_block[bb], REGNO (x)))
3389 RESET_BIT (bmap[bb], indx);
3393 for (r = reg_set_table[REGNO (x)]; r != NULL; r = r->next)
3394 RESET_BIT (bmap[BLOCK_NUM (r->insn)], indx);
3403 for (bb = 0; bb < n_basic_blocks; bb++)
3404 if (mem_set_in_block[bb])
3405 SET_BIT (bmap[bb], indx);
3409 for (bb = 0; bb < n_basic_blocks; bb++)
3410 if (mem_set_in_block[bb])
3411 RESET_BIT (bmap[bb], indx);
3432 for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
3436 /* If we are about to do the last recursive call
3437 needed at this level, change it into iteration.
3438 This function is called enough to be worth it. */
3445 compute_transp (XEXP (x, i), indx, bmap, set_p);
3447 else if (fmt[i] == 'E')
3448 for (j = 0; j < XVECLEN (x, i); j++)
3449 compute_transp (XVECEXP (x, i, j), indx, bmap, set_p);
3453 /* Top level routine to do the dataflow analysis needed by copy/const
3457 compute_cprop_data ()
3459 compute_local_properties (cprop_absaltered, cprop_pavloc, NULL, 1);
3460 compute_available (cprop_pavloc, cprop_absaltered,
3461 cprop_avout, cprop_avin);
3464 /* Copy/constant propagation. */
3466 /* Maximum number of register uses in an insn that we handle. */
3469 /* Table of uses found in an insn.
3470 Allocated statically to avoid alloc/free complexity and overhead. */
3471 static struct reg_use reg_use_table[MAX_USES];
3473 /* Index into `reg_use_table' while building it. */
3474 static int reg_use_count;
3476 /* Set up a list of register numbers used in INSN. The found uses are stored
3477 in `reg_use_table'. `reg_use_count' is initialized to zero before entry,
3478 and contains the number of uses in the table upon exit.
3480 ??? If a register appears multiple times we will record it multiple times.
3481 This doesn't hurt anything but it will slow things down. */
3491 /* repeat is used to turn tail-recursion into iteration since GCC
3492 can't do it when there's no return value. */
3498 code = GET_CODE (x);
3502 if (reg_use_count == MAX_USES)
3505 reg_use_table[reg_use_count].reg_rtx = x;
3523 case ASM_INPUT: /*FIXME*/
3527 if (GET_CODE (SET_DEST (x)) == MEM)
3528 find_used_regs (SET_DEST (x));
3536 /* Recursively scan the operands of this expression. */
3538 for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
3542 /* If we are about to do the last recursive call
3543 needed at this level, change it into iteration.
3544 This function is called enough to be worth it. */
3551 find_used_regs (XEXP (x, i));
3553 else if (fmt[i] == 'E')
3554 for (j = 0; j < XVECLEN (x, i); j++)
3555 find_used_regs (XVECEXP (x, i, j));
3559 /* Try to replace all non-SET_DEST occurrences of FROM in INSN with TO.
3560 Returns non-zero is successful. */
3563 try_replace_reg (from, to, insn)
3571 note = find_reg_note (insn, REG_EQUAL, NULL_RTX);
3574 note = find_reg_note (insn, REG_EQUIV, NULL_RTX);
3576 /* If this fails we could try to simplify the result of the
3577 replacement and attempt to recognize the simplified insn.
3579 But we need a general simplify_rtx that doesn't have pass
3580 specific state variables. I'm not aware of one at the moment. */
3582 success = validate_replace_src (from, to, insn);
3583 set = single_set (insn);
3585 /* We've failed to do replacement. Try to add REG_EQUAL note to not loose
3587 if (!success && !note)
3592 note = REG_NOTES (insn) = gen_rtx_EXPR_LIST (REG_EQUAL,
3593 copy_rtx (SET_SRC (set)),
3597 /* Always do the replacement in REQ_EQUAL and REG_EQUIV notes. Also
3598 try to simplify them. */
3603 src = XEXP (note, 0);
3604 replace_rtx (src, from, to);
3606 /* Try to simplify resulting note. */
3607 simplified = simplify_rtx (src);
3611 XEXP (note, 0) = src;
3614 /* REG_EQUAL may get simplified into register.
3615 We don't allow that. Remove that note. This code ought
3616 not to hapen, because previous code ought to syntetize
3617 reg-reg move, but be on the safe side. */
3618 else if (REG_P (src))
3619 remove_note (insn, note);
3624 /* Find a set of REGNOs that are available on entry to INSN's block. Returns
3625 NULL no such set is found. */
3627 static struct expr *
3628 find_avail_set (regno, insn)
3632 /* SET1 contains the last set found that can be returned to the caller for
3633 use in a substitution. */
3634 struct expr *set1 = 0;
3636 /* Loops are not possible here. To get a loop we would need two sets
3637 available at the start of the block containing INSN. ie we would
3638 need two sets like this available at the start of the block:
3640 (set (reg X) (reg Y))
3641 (set (reg Y) (reg X))
3643 This can not happen since the set of (reg Y) would have killed the
3644 set of (reg X) making it unavailable at the start of this block. */
3648 struct expr *set = lookup_set (regno, NULL_RTX);
3650 /* Find a set that is available at the start of the block
3651 which contains INSN. */
3654 if (TEST_BIT (cprop_avin[BLOCK_NUM (insn)], set->bitmap_index))
3656 set = next_set (regno, set);
3659 /* If no available set was found we've reached the end of the
3660 (possibly empty) copy chain. */
3664 if (GET_CODE (set->expr) != SET)
3667 src = SET_SRC (set->expr);
3669 /* We know the set is available.
3670 Now check that SRC is ANTLOC (i.e. none of the source operands
3671 have changed since the start of the block).
3673 If the source operand changed, we may still use it for the next
3674 iteration of this loop, but we may not use it for substitutions. */
3676 if (CONSTANT_P (src) || oprs_not_set_p (src, insn))
3679 /* If the source of the set is anything except a register, then
3680 we have reached the end of the copy chain. */
3681 if (GET_CODE (src) != REG)
3684 /* Follow the copy chain, ie start another iteration of the loop
3685 and see if we have an available copy into SRC. */
3686 regno = REGNO (src);
3689 /* SET1 holds the last set that was available and anticipatable at
3694 /* Subroutine of cprop_insn that tries to propagate constants into
3695 JUMP_INSNS. INSN must be a conditional jump; COPY is a copy of it
3696 that we can use for substitutions.
3697 REG_USED is the use we will try to replace, SRC is the constant we
3698 will try to substitute for it.
3699 Returns nonzero if a change was made. */
3702 cprop_jump (insn, copy, reg_used, src)
3704 struct reg_use *reg_used;
3707 rtx set = PATTERN (copy);
3710 /* Replace the register with the appropriate constant. */
3711 replace_rtx (SET_SRC (set), reg_used->reg_rtx, src);
3713 temp = simplify_ternary_operation (GET_CODE (SET_SRC (set)),
3714 GET_MODE (SET_SRC (set)),
3715 GET_MODE (XEXP (SET_SRC (set), 0)),
3716 XEXP (SET_SRC (set), 0),
3717 XEXP (SET_SRC (set), 1),
3718 XEXP (SET_SRC (set), 2));
3720 /* If no simplification can be made, then try the next
3725 SET_SRC (set) = temp;
3727 /* That may have changed the structure of TEMP, so
3728 force it to be rerecognized if it has not turned
3729 into a nop or unconditional jump. */
3731 INSN_CODE (copy) = -1;
3732 if ((SET_DEST (set) == pc_rtx
3733 && (SET_SRC (set) == pc_rtx
3734 || GET_CODE (SET_SRC (set)) == LABEL_REF))
3735 || recog (PATTERN (copy), copy, NULL) >= 0)
3737 /* This has either become an unconditional jump
3738 or a nop-jump. We'd like to delete nop jumps
3739 here, but doing so confuses gcse. So we just
3740 make the replacement and let later passes
3742 PATTERN (insn) = set;
3743 INSN_CODE (insn) = -1;
3745 /* One less use of the label this insn used to jump to
3746 if we turned this into a NOP jump. */
3747 if (SET_SRC (set) == pc_rtx && JUMP_LABEL (insn) != 0)
3748 --LABEL_NUSES (JUMP_LABEL (insn));
3750 /* If this has turned into an unconditional jump,
3751 then put a barrier after it so that the unreachable
3752 code will be deleted. */
3753 if (GET_CODE (SET_SRC (set)) == LABEL_REF)
3754 emit_barrier_after (insn);
3756 run_jump_opt_after_gcse = 1;
3759 if (gcse_file != NULL)
3762 "CONST-PROP: Replacing reg %d in insn %d with constant ",
3763 REGNO (reg_used->reg_rtx), INSN_UID (insn));
3764 print_rtl (gcse_file, src);
3765 fprintf (gcse_file, "\n");
3775 /* Subroutine of cprop_insn that tries to propagate constants into JUMP_INSNS
3776 for machines that have CC0. INSN is a single set that stores into CC0;
3777 the insn following it is a conditional jump. REG_USED is the use we will
3778 try to replace, SRC is the constant we will try to substitute for it.
3779 Returns nonzero if a change was made. */
3782 cprop_cc0_jump (insn, reg_used, src)
3784 struct reg_use *reg_used;
3787 rtx jump = NEXT_INSN (insn);
3788 rtx copy = copy_rtx (jump);
3789 rtx set = PATTERN (copy);
3791 /* We need to copy the source of the cc0 setter, as cprop_jump is going to
3792 substitute into it. */
3793 replace_rtx (SET_SRC (set), cc0_rtx, copy_rtx (SET_SRC (PATTERN (insn))));
3794 if (! cprop_jump (jump, copy, reg_used, src))
3797 /* If we succeeded, delete the cc0 setter. */
3798 PUT_CODE (insn, NOTE);
3799 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
3800 NOTE_SOURCE_FILE (insn) = 0;
3805 /* Perform constant and copy propagation on INSN.
3806 The result is non-zero if a change was made. */
3809 cprop_insn (insn, alter_jumps)
3813 struct reg_use *reg_used;
3817 /* Only propagate into SETs. Note that a conditional jump is a
3818 SET with pc_rtx as the destination. */
3819 if ((GET_CODE (insn) != INSN
3820 && GET_CODE (insn) != JUMP_INSN)
3821 || GET_CODE (PATTERN (insn)) != SET)
3825 find_used_regs (PATTERN (insn));
3827 note = find_reg_note (insn, REG_EQUIV, NULL_RTX);
3829 note = find_reg_note (insn, REG_EQUAL, NULL_RTX);
3831 /* We may win even when propagating constants into notes. */
3833 find_used_regs (XEXP (note, 0));
3835 for (reg_used = ®_use_table[0]; reg_use_count > 0;
3836 reg_used++, reg_use_count--)
3838 int regno = REGNO (reg_used->reg_rtx);
3842 /* Ignore registers created by GCSE.
3843 We do this because ... */
3844 if (regno >= max_gcse_regno)
3847 /* If the register has already been set in this block, there's
3848 nothing we can do. */
3849 if (! oprs_not_set_p (reg_used->reg_rtx, insn))
3852 /* Find an assignment that sets reg_used and is available
3853 at the start of the block. */
3854 set = find_avail_set (regno, insn);
3859 /* ??? We might be able to handle PARALLELs. Later. */
3860 if (GET_CODE (pat) != SET)
3863 src = SET_SRC (pat);
3865 /* Constant propagation. */
3866 if (GET_CODE (src) == CONST_INT || GET_CODE (src) == CONST_DOUBLE
3867 || GET_CODE (src) == SYMBOL_REF)
3869 /* Handle normal insns first. */
3870 if (GET_CODE (insn) == INSN
3871 && try_replace_reg (reg_used->reg_rtx, src, insn))
3875 if (gcse_file != NULL)
3877 fprintf (gcse_file, "CONST-PROP: Replacing reg %d in ",
3879 fprintf (gcse_file, "insn %d with constant ",
3881 print_rtl (gcse_file, src);
3882 fprintf (gcse_file, "\n");
3885 /* The original insn setting reg_used may or may not now be
3886 deletable. We leave the deletion to flow. */
3889 /* Try to propagate a CONST_INT into a conditional jump.
3890 We're pretty specific about what we will handle in this
3891 code, we can extend this as necessary over time.
3893 Right now the insn in question must look like
3894 (set (pc) (if_then_else ...)) */
3895 else if (alter_jumps
3896 && GET_CODE (insn) == JUMP_INSN
3897 && condjump_p (insn)
3898 && ! simplejump_p (insn))
3899 changed |= cprop_jump (insn, copy_rtx (insn), reg_used, src);
3901 /* Similar code for machines that use a pair of CC0 setter and
3902 conditional jump insn. */
3903 else if (alter_jumps
3904 && GET_CODE (PATTERN (insn)) == SET
3905 && SET_DEST (PATTERN (insn)) == cc0_rtx
3906 && GET_CODE (NEXT_INSN (insn)) == JUMP_INSN
3907 && condjump_p (NEXT_INSN (insn))
3908 && ! simplejump_p (NEXT_INSN (insn)))
3909 changed |= cprop_cc0_jump (insn, reg_used, src);
3912 else if (GET_CODE (src) == REG
3913 && REGNO (src) >= FIRST_PSEUDO_REGISTER
3914 && REGNO (src) != regno)
3916 if (try_replace_reg (reg_used->reg_rtx, src, insn))
3920 if (gcse_file != NULL)
3922 fprintf (gcse_file, "COPY-PROP: Replacing reg %d in insn %d",
3923 regno, INSN_UID (insn));
3924 fprintf (gcse_file, " with reg %d\n", REGNO (src));
3927 /* The original insn setting reg_used may or may not now be
3928 deletable. We leave the deletion to flow. */
3929 /* FIXME: If it turns out that the insn isn't deletable,
3930 then we may have unnecessarily extended register lifetimes
3931 and made things worse. */
3939 /* Forward propagate copies. This includes copies and constants. Return
3940 non-zero if a change was made. */
3949 /* Note we start at block 1. */
3952 for (bb = 1; bb < n_basic_blocks; bb++)
3954 /* Reset tables used to keep track of what's still valid [since the
3955 start of the block]. */
3956 reset_opr_set_tables ();
3958 for (insn = BLOCK_HEAD (bb);
3959 insn != NULL && insn != NEXT_INSN (BLOCK_END (bb));
3960 insn = NEXT_INSN (insn))
3962 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
3964 changed |= cprop_insn (insn, alter_jumps);
3966 /* Keep track of everything modified by this insn. */
3967 /* ??? Need to be careful w.r.t. mods done to INSN. Don't
3968 call mark_oprs_set if we turned the insn into a NOTE. */
3969 if (GET_CODE (insn) != NOTE)
3970 mark_oprs_set (insn);
3975 if (gcse_file != NULL)
3976 fprintf (gcse_file, "\n");
3981 /* Perform one copy/constant propagation pass.
3982 F is the first insn in the function.
3983 PASS is the pass count. */
3986 one_cprop_pass (pass, alter_jumps)
3992 const_prop_count = 0;
3993 copy_prop_count = 0;
3995 alloc_set_hash_table (max_cuid);
3996 compute_set_hash_table ();
3998 dump_hash_table (gcse_file, "SET", set_hash_table, set_hash_table_size,
4002 alloc_cprop_mem (n_basic_blocks, n_sets);
4003 compute_cprop_data ();
4004 changed = cprop (alter_jumps);
4008 free_set_hash_table ();
4012 fprintf (gcse_file, "CPROP of %s, pass %d: %d bytes needed, ",
4013 current_function_name, pass, bytes_used);
4014 fprintf (gcse_file, "%d const props, %d copy props\n\n",
4015 const_prop_count, copy_prop_count);
4021 /* Compute PRE+LCM working variables. */
4023 /* Local properties of expressions. */
4024 /* Nonzero for expressions that are transparent in the block. */
4025 static sbitmap *transp;
4027 /* Nonzero for expressions that are transparent at the end of the block.
4028 This is only zero for expressions killed by abnormal critical edge
4029 created by a calls. */
4030 static sbitmap *transpout;
4032 /* Nonzero for expressions that are computed (available) in the block. */
4033 static sbitmap *comp;
4035 /* Nonzero for expressions that are locally anticipatable in the block. */
4036 static sbitmap *antloc;
4038 /* Nonzero for expressions where this block is an optimal computation
4040 static sbitmap *pre_optimal;
4042 /* Nonzero for expressions which are redundant in a particular block. */
4043 static sbitmap *pre_redundant;
4045 /* Nonzero for expressions which should be inserted on a specific edge. */
4046 static sbitmap *pre_insert_map;
4048 /* Nonzero for expressions which should be deleted in a specific block. */
4049 static sbitmap *pre_delete_map;
4051 /* Contains the edge_list returned by pre_edge_lcm. */
4052 static struct edge_list *edge_list;
4054 static sbitmap *temp_bitmap;
4056 /* Redundant insns. */
4057 static sbitmap pre_redundant_insns;
4059 /* Allocate vars used for PRE analysis. */
4062 alloc_pre_mem (n_blocks, n_exprs)
4063 int n_blocks, n_exprs;
4065 transp = sbitmap_vector_alloc (n_blocks, n_exprs);
4066 comp = sbitmap_vector_alloc (n_blocks, n_exprs);
4067 antloc = sbitmap_vector_alloc (n_blocks, n_exprs);
4068 temp_bitmap = sbitmap_vector_alloc (n_blocks, n_exprs);
4071 pre_redundant = NULL;
4072 pre_insert_map = NULL;
4073 pre_delete_map = NULL;
4077 transpout = sbitmap_vector_alloc (n_blocks, n_exprs);
4078 ae_kill = sbitmap_vector_alloc (n_blocks, n_exprs);
4080 /* pre_insert and pre_delete are allocated later. */
4083 /* Free vars used for PRE analysis. */
4096 free (pre_redundant);
4098 free (pre_insert_map);
4100 free (pre_delete_map);
4113 transp = comp = antloc = NULL;
4114 pre_optimal = pre_redundant = pre_insert_map = pre_delete_map = NULL;
4115 transpout = ae_in = ae_out = ae_kill = NULL;
4120 /* Top level routine to do the dataflow analysis needed by PRE. */
4125 compute_local_properties (transp, comp, antloc, 0);
4126 compute_transpout ();
4127 sbitmap_vector_zero (ae_kill, n_basic_blocks);
4128 compute_ae_kill (comp, ae_kill);
4129 edge_list = pre_edge_lcm (gcse_file, n_exprs, transp, comp, antloc,
4130 ae_kill, &pre_insert_map, &pre_delete_map);
4135 /* Return non-zero if an occurrence of expression EXPR in OCCR_BB would reach
4138 VISITED is a pointer to a working buffer for tracking which BB's have
4139 been visited. It is NULL for the top-level call.
4141 We treat reaching expressions that go through blocks containing the same
4142 reaching expression as "not reaching". E.g. if EXPR is generated in blocks
4143 2 and 3, INSN is in block 4, and 2->3->4, we treat the expression in block
4144 2 as not reaching. The intent is to improve the probability of finding
4145 only one reaching expression and to reduce register lifetimes by picking
4146 the closest such expression. */
4149 pre_expr_reaches_here_p_work (occr_bb, expr, bb, visited)
4157 for (pred = BASIC_BLOCK (bb)->pred; pred != NULL; pred = pred->pred_next)
4159 int pred_bb = pred->src->index;
4161 if (pred->src == ENTRY_BLOCK_PTR
4162 /* Has predecessor has already been visited? */
4163 || visited[pred_bb])
4164 ;/* Nothing to do. */
4166 /* Does this predecessor generate this expression? */
4167 else if (TEST_BIT (comp[pred_bb], expr->bitmap_index))
4169 /* Is this the occurrence we're looking for?
4170 Note that there's only one generating occurrence per block
4171 so we just need to check the block number. */
4172 if (occr_bb == pred_bb)
4175 visited[pred_bb] = 1;
4177 /* Ignore this predecessor if it kills the expression. */
4178 else if (! TEST_BIT (transp[pred_bb], expr->bitmap_index))
4179 visited[pred_bb] = 1;
4181 /* Neither gen nor kill. */
4184 visited[pred_bb] = 1;
4185 if (pre_expr_reaches_here_p_work (occr_bb, expr, pred_bb, visited))
4190 /* All paths have been checked. */
4194 /* The wrapper for pre_expr_reaches_here_work that ensures that any
4195 memory allocated for that function is returned. */
4198 pre_expr_reaches_here_p (occr_bb, expr, bb)
4204 char *visited = (char *) xcalloc (n_basic_blocks, 1);
4206 rval = pre_expr_reaches_here_p_work(occr_bb, expr, bb, visited);
4213 /* Given an expr, generate RTL which we can insert at the end of a BB,
4214 or on an edge. Set the block number of any insns generated to
4218 process_insert_insn (expr)
4221 rtx reg = expr->reaching_reg;
4222 rtx pat, copied_expr;
4226 copied_expr = copy_rtx (expr->expr);
4227 emit_move_insn (reg, copied_expr);
4228 first_new_insn = get_insns ();
4229 pat = gen_sequence ();
4235 /* Add EXPR to the end of basic block BB.
4237 This is used by both the PRE and code hoisting.
4239 For PRE, we want to verify that the expr is either transparent
4240 or locally anticipatable in the target block. This check makes
4241 no sense for code hoisting. */
4244 insert_insn_end_bb (expr, bb, pre)
4249 rtx insn = BLOCK_END (bb);
4251 rtx reg = expr->reaching_reg;
4252 int regno = REGNO (reg);
4256 pat = process_insert_insn (expr);
4258 /* If the last insn is a jump, insert EXPR in front [taking care to
4259 handle cc0, etc. properly]. */
4261 if (GET_CODE (insn) == JUMP_INSN)
4267 /* If this is a jump table, then we can't insert stuff here. Since
4268 we know the previous real insn must be the tablejump, we insert
4269 the new instruction just before the tablejump. */
4270 if (GET_CODE (PATTERN (insn)) == ADDR_VEC
4271 || GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC)
4272 insn = prev_real_insn (insn);
4275 /* FIXME: 'twould be nice to call prev_cc0_setter here but it aborts
4276 if cc0 isn't set. */
4277 note = find_reg_note (insn, REG_CC_SETTER, NULL_RTX);
4279 insn = XEXP (note, 0);
4282 rtx maybe_cc0_setter = prev_nonnote_insn (insn);
4283 if (maybe_cc0_setter
4284 && GET_RTX_CLASS (GET_CODE (maybe_cc0_setter)) == 'i'
4285 && sets_cc0_p (PATTERN (maybe_cc0_setter)))
4286 insn = maybe_cc0_setter;
4289 /* FIXME: What if something in cc0/jump uses value set in new insn? */
4290 new_insn = emit_block_insn_before (pat, insn, BASIC_BLOCK (bb));
4293 /* Likewise if the last insn is a call, as will happen in the presence
4294 of exception handling. */
4295 else if (GET_CODE (insn) == CALL_INSN)
4297 HARD_REG_SET parm_regs;
4301 /* Keeping in mind SMALL_REGISTER_CLASSES and parameters in registers,
4302 we search backward and place the instructions before the first
4303 parameter is loaded. Do this for everyone for consistency and a
4304 presumtion that we'll get better code elsewhere as well.
4306 It should always be the case that we can put these instructions
4307 anywhere in the basic block with performing PRE optimizations.
4311 && !TEST_BIT (antloc[bb], expr->bitmap_index)
4312 && !TEST_BIT (transp[bb], expr->bitmap_index))
4315 /* Since different machines initialize their parameter registers
4316 in different orders, assume nothing. Collect the set of all
4317 parameter registers. */
4318 CLEAR_HARD_REG_SET (parm_regs);
4320 for (p = CALL_INSN_FUNCTION_USAGE (insn); p ; p = XEXP (p, 1))
4321 if (GET_CODE (XEXP (p, 0)) == USE
4322 && GET_CODE (XEXP (XEXP (p, 0), 0)) == REG)
4324 if (REGNO (XEXP (XEXP (p, 0), 0)) >= FIRST_PSEUDO_REGISTER)
4327 SET_HARD_REG_BIT (parm_regs, REGNO (XEXP (XEXP (p, 0), 0)));
4331 /* Search backward for the first set of a register in this set. */
4332 while (nparm_regs && BLOCK_HEAD (bb) != insn)
4334 insn = PREV_INSN (insn);
4335 p = single_set (insn);
4336 if (p && GET_CODE (SET_DEST (p)) == REG
4337 && REGNO (SET_DEST (p)) < FIRST_PSEUDO_REGISTER
4338 && TEST_HARD_REG_BIT (parm_regs, REGNO (SET_DEST (p))))
4340 CLEAR_HARD_REG_BIT (parm_regs, REGNO (SET_DEST (p)));
4345 /* If we found all the parameter loads, then we want to insert
4346 before the first parameter load.
4348 If we did not find all the parameter loads, then we might have
4349 stopped on the head of the block, which could be a CODE_LABEL.
4350 If we inserted before the CODE_LABEL, then we would be putting
4351 the insn in the wrong basic block. In that case, put the insn
4352 after the CODE_LABEL. Also, respect NOTE_INSN_BASIC_BLOCK. */
4353 if (GET_CODE (insn) == CODE_LABEL)
4354 insn = NEXT_INSN (insn);
4355 else if (GET_CODE (insn) == NOTE
4356 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_BASIC_BLOCK)
4357 insn = NEXT_INSN (insn);
4359 new_insn = emit_block_insn_before (pat, insn, BASIC_BLOCK (bb));
4363 new_insn = emit_insn_after (pat, insn);
4364 BLOCK_END (bb) = new_insn;
4367 /* Keep block number table up to date.
4368 Note, PAT could be a multiple insn sequence, we have to make
4369 sure that each insn in the sequence is handled. */
4370 if (GET_CODE (pat) == SEQUENCE)
4372 for (i = 0; i < XVECLEN (pat, 0); i++)
4374 rtx insn = XVECEXP (pat, 0, i);
4376 set_block_num (insn, bb);
4377 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
4378 add_label_notes (PATTERN (insn), new_insn);
4380 note_stores (PATTERN (insn), record_set_info, insn);
4385 add_label_notes (SET_SRC (pat), new_insn);
4386 set_block_num (new_insn, bb);
4388 /* Keep register set table up to date. */
4389 record_one_set (regno, new_insn);
4392 gcse_create_count++;
4396 fprintf (gcse_file, "PRE/HOIST: end of bb %d, insn %d, ",
4397 bb, INSN_UID (new_insn));
4398 fprintf (gcse_file, "copying expression %d to reg %d\n",
4399 expr->bitmap_index, regno);
4403 /* Insert partially redundant expressions on edges in the CFG to make
4404 the expressions fully redundant. */
4407 pre_edge_insert (edge_list, index_map)
4408 struct edge_list *edge_list;
4409 struct expr **index_map;
4411 int e, i, j, num_edges, set_size, did_insert = 0;
4414 /* Where PRE_INSERT_MAP is nonzero, we add the expression on that edge
4415 if it reaches any of the deleted expressions. */
4417 set_size = pre_insert_map[0]->size;
4418 num_edges = NUM_EDGES (edge_list);
4419 inserted = sbitmap_vector_alloc (num_edges, n_exprs);
4420 sbitmap_vector_zero (inserted, num_edges);
4422 for (e = 0; e < num_edges; e++)
4425 basic_block pred = INDEX_EDGE_PRED_BB (edge_list, e);
4426 int bb = pred->index;
4428 for (i = indx = 0; i < set_size; i++, indx += SBITMAP_ELT_BITS)
4430 SBITMAP_ELT_TYPE insert = pre_insert_map[e]->elms[i];
4432 for (j = indx; insert && j < n_exprs; j++, insert >>= 1)
4433 if ((insert & 1) != 0 && index_map[j]->reaching_reg != NULL_RTX)
4435 struct expr *expr = index_map[j];
4438 /* Now look at each deleted occurence of this expression. */
4439 for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
4441 if (! occr->deleted_p)
4444 /* Insert this expression on this edge if if it would
4445 reach the deleted occurence in BB. */
4446 if (!TEST_BIT (inserted[e], j))
4449 edge eg = INDEX_EDGE (edge_list, e);
4451 /* We can't insert anything on an abnormal and
4452 critical edge, so we insert the insn at the end of
4453 the previous block. There are several alternatives
4454 detailed in Morgans book P277 (sec 10.5) for
4455 handling this situation. This one is easiest for
4458 if ((eg->flags & EDGE_ABNORMAL) == EDGE_ABNORMAL)
4459 insert_insn_end_bb (index_map[j], bb, 0);
4462 insn = process_insert_insn (index_map[j]);
4463 insert_insn_on_edge (insn, eg);
4468 fprintf (gcse_file, "PRE/HOIST: edge (%d,%d), ",
4470 INDEX_EDGE_SUCC_BB (edge_list, e)->index);
4471 fprintf (gcse_file, "copy expression %d\n",
4472 expr->bitmap_index);
4475 SET_BIT (inserted[e], j);
4477 gcse_create_count++;
4488 /* Copy the result of INSN to REG. INDX is the expression number. */
4491 pre_insert_copy_insn (expr, insn)
4495 rtx reg = expr->reaching_reg;
4496 int regno = REGNO (reg);
4497 int indx = expr->bitmap_index;
4498 rtx set = single_set (insn);
4500 int bb = BLOCK_NUM (insn);
4505 new_insn = emit_insn_after (gen_rtx_SET (VOIDmode, reg, SET_DEST (set)),
4508 /* Keep block number table up to date. */
4509 set_block_num (new_insn, bb);
4511 /* Keep register set table up to date. */
4512 record_one_set (regno, new_insn);
4513 if (insn == BLOCK_END (bb))
4514 BLOCK_END (bb) = new_insn;
4516 gcse_create_count++;
4520 "PRE: bb %d, insn %d, copy expression %d in insn %d to reg %d\n",
4521 BLOCK_NUM (insn), INSN_UID (new_insn), indx,
4522 INSN_UID (insn), regno);
4525 /* Copy available expressions that reach the redundant expression
4526 to `reaching_reg'. */
4529 pre_insert_copies ()
4536 /* For each available expression in the table, copy the result to
4537 `reaching_reg' if the expression reaches a deleted one.
4539 ??? The current algorithm is rather brute force.
4540 Need to do some profiling. */
4542 for (i = 0; i < expr_hash_table_size; i++)
4543 for (expr = expr_hash_table[i]; expr != NULL; expr = expr->next_same_hash)
4545 /* If the basic block isn't reachable, PPOUT will be TRUE. However,
4546 we don't want to insert a copy here because the expression may not
4547 really be redundant. So only insert an insn if the expression was
4548 deleted. This test also avoids further processing if the
4549 expression wasn't deleted anywhere. */
4550 if (expr->reaching_reg == NULL)
4553 for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
4555 if (! occr->deleted_p)
4558 for (avail = expr->avail_occr; avail != NULL; avail = avail->next)
4560 rtx insn = avail->insn;
4562 /* No need to handle this one if handled already. */
4563 if (avail->copied_p)
4566 /* Don't handle this one if it's a redundant one. */
4567 if (TEST_BIT (pre_redundant_insns, INSN_CUID (insn)))
4570 /* Or if the expression doesn't reach the deleted one. */
4571 if (! pre_expr_reaches_here_p (BLOCK_NUM (avail->insn), expr,
4572 BLOCK_NUM (occr->insn)))
4575 /* Copy the result of avail to reaching_reg. */
4576 pre_insert_copy_insn (expr, insn);
4577 avail->copied_p = 1;
4583 /* Delete redundant computations.
4584 Deletion is done by changing the insn to copy the `reaching_reg' of
4585 the expression into the result of the SET. It is left to later passes
4586 (cprop, cse2, flow, combine, regmove) to propagate the copy or eliminate it.
4588 Returns non-zero if a change is made. */
4597 /* Compute the expressions which are redundant and need to be replaced by
4598 copies from the reaching reg to the target reg. */
4599 for (bb = 0; bb < n_basic_blocks; bb++)
4600 sbitmap_copy (temp_bitmap[bb], pre_delete_map[bb]);
4603 for (i = 0; i < expr_hash_table_size; i++)
4604 for (expr = expr_hash_table[i]; expr != NULL; expr = expr->next_same_hash)
4606 int indx = expr->bitmap_index;
4608 /* We only need to search antic_occr since we require
4611 for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
4613 rtx insn = occr->insn;
4615 int bb = BLOCK_NUM (insn);
4617 if (TEST_BIT (temp_bitmap[bb], indx))
4619 set = single_set (insn);
4623 /* Create a pseudo-reg to store the result of reaching
4624 expressions into. Get the mode for the new pseudo from
4625 the mode of the original destination pseudo. */
4626 if (expr->reaching_reg == NULL)
4628 = gen_reg_rtx (GET_MODE (SET_DEST (set)));
4630 /* In theory this should never fail since we're creating
4633 However, on the x86 some of the movXX patterns actually
4634 contain clobbers of scratch regs. This may cause the
4635 insn created by validate_change to not match any pattern
4636 and thus cause validate_change to fail. */
4637 if (validate_change (insn, &SET_SRC (set),
4638 expr->reaching_reg, 0))
4640 occr->deleted_p = 1;
4641 SET_BIT (pre_redundant_insns, INSN_CUID (insn));
4649 "PRE: redundant insn %d (expression %d) in ",
4650 INSN_UID (insn), indx);
4651 fprintf (gcse_file, "bb %d, reaching reg is %d\n",
4652 bb, REGNO (expr->reaching_reg));
4661 /* Perform GCSE optimizations using PRE.
4662 This is called by one_pre_gcse_pass after all the dataflow analysis
4665 This is based on the original Morel-Renvoise paper Fred Chow's thesis, and
4666 lazy code motion from Knoop, Ruthing and Steffen as described in Advanced
4667 Compiler Design and Implementation.
4669 ??? A new pseudo reg is created to hold the reaching expression. The nice
4670 thing about the classical approach is that it would try to use an existing
4671 reg. If the register can't be adequately optimized [i.e. we introduce
4672 reload problems], one could add a pass here to propagate the new register
4675 ??? We don't handle single sets in PARALLELs because we're [currently] not
4676 able to copy the rest of the parallel when we insert copies to create full
4677 redundancies from partial redundancies. However, there's no reason why we
4678 can't handle PARALLELs in the cases where there are no partial
4686 struct expr **index_map;
4689 /* Compute a mapping from expression number (`bitmap_index') to
4690 hash table entry. */
4692 index_map = (struct expr **) xcalloc (n_exprs, sizeof (struct expr *));
4693 for (i = 0; i < expr_hash_table_size; i++)
4694 for (expr = expr_hash_table[i]; expr != NULL; expr = expr->next_same_hash)
4695 index_map[expr->bitmap_index] = expr;
4697 /* Reset bitmap used to track which insns are redundant. */
4698 pre_redundant_insns = sbitmap_alloc (max_cuid);
4699 sbitmap_zero (pre_redundant_insns);
4701 /* Delete the redundant insns first so that
4702 - we know what register to use for the new insns and for the other
4703 ones with reaching expressions
4704 - we know which insns are redundant when we go to create copies */
4706 changed = pre_delete ();
4708 did_insert = pre_edge_insert (edge_list, index_map);
4710 /* In other places with reaching expressions, copy the expression to the
4711 specially allocated pseudo-reg that reaches the redundant expr. */
4712 pre_insert_copies ();
4715 commit_edge_insertions ();
4720 free (pre_redundant_insns);
4724 /* Top level routine to perform one PRE GCSE pass.
4726 Return non-zero if a change was made. */
4729 one_pre_gcse_pass (pass)
4734 gcse_subst_count = 0;
4735 gcse_create_count = 0;
4737 alloc_expr_hash_table (max_cuid);
4738 add_noreturn_fake_exit_edges ();
4739 compute_expr_hash_table ();
4741 dump_hash_table (gcse_file, "Expression", expr_hash_table,
4742 expr_hash_table_size, n_exprs);
4746 alloc_pre_mem (n_basic_blocks, n_exprs);
4747 compute_pre_data ();
4748 changed |= pre_gcse ();
4749 free_edge_list (edge_list);
4753 remove_fake_edges ();
4754 free_expr_hash_table ();
4758 fprintf (gcse_file, "\nPRE GCSE of %s, pass %d: %d bytes needed, ",
4759 current_function_name, pass, bytes_used);
4760 fprintf (gcse_file, "%d substs, %d insns created\n",
4761 gcse_subst_count, gcse_create_count);
4767 /* If X contains any LABEL_REF's, add REG_LABEL notes for them to INSN.
4768 We have to add REG_LABEL notes, because the following loop optimization
4769 pass requires them. */
4771 /* ??? This is very similar to the loop.c add_label_notes function. We
4772 could probably share code here. */
4774 /* ??? If there was a jump optimization pass after gcse and before loop,
4775 then we would not need to do this here, because jump would add the
4776 necessary REG_LABEL notes. */
4779 add_label_notes (x, insn)
4783 enum rtx_code code = GET_CODE (x);
4787 if (code == LABEL_REF && !LABEL_REF_NONLOCAL_P (x))
4789 /* This code used to ignore labels that referred to dispatch tables to
4790 avoid flow generating (slighly) worse code.
4792 We no longer ignore such label references (see LABEL_REF handling in
4793 mark_jump_label for additional information). */
4795 REG_NOTES (insn) = gen_rtx_EXPR_LIST (REG_LABEL, XEXP (x, 0),
4800 for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
4803 add_label_notes (XEXP (x, i), insn);
4804 else if (fmt[i] == 'E')
4805 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
4806 add_label_notes (XVECEXP (x, i, j), insn);
4810 /* Compute transparent outgoing information for each block.
4812 An expression is transparent to an edge unless it is killed by
4813 the edge itself. This can only happen with abnormal control flow,
4814 when the edge is traversed through a call. This happens with
4815 non-local labels and exceptions.
4817 This would not be necessary if we split the edge. While this is
4818 normally impossible for abnormal critical edges, with some effort
4819 it should be possible with exception handling, since we still have
4820 control over which handler should be invoked. But due to increased
4821 EH table sizes, this may not be worthwhile. */
4824 compute_transpout ()
4830 sbitmap_vector_ones (transpout, n_basic_blocks);
4832 for (bb = 0; bb < n_basic_blocks; ++bb)
4834 /* Note that flow inserted a nop a the end of basic blocks that
4835 end in call instructions for reasons other than abnormal
4837 if (GET_CODE (BLOCK_END (bb)) != CALL_INSN)
4840 for (i = 0; i < expr_hash_table_size; i++)
4841 for (expr = expr_hash_table[i]; expr ; expr = expr->next_same_hash)
4842 if (GET_CODE (expr->expr) == MEM)
4844 if (GET_CODE (XEXP (expr->expr, 0)) == SYMBOL_REF
4845 && CONSTANT_POOL_ADDRESS_P (XEXP (expr->expr, 0)))
4848 /* ??? Optimally, we would use interprocedural alias
4849 analysis to determine if this mem is actually killed
4851 RESET_BIT (transpout[bb], expr->bitmap_index);
4856 /* Removal of useless null pointer checks */
4858 /* Called via note_stores. X is set by SETTER. If X is a register we must
4859 invalidate nonnull_local and set nonnull_killed. DATA is really a
4860 `null_pointer_info *'.
4862 We ignore hard registers. */
4865 invalidate_nonnull_info (x, setter, data)
4867 rtx setter ATTRIBUTE_UNUSED;
4871 struct null_pointer_info* npi = (struct null_pointer_info *) data;
4875 while (GET_CODE (x) == SUBREG)
4878 /* Ignore anything that is not a register or is a hard register. */
4879 if (GET_CODE (x) != REG
4880 || REGNO (x) < npi->min_reg
4881 || REGNO (x) >= npi->max_reg)
4884 regno = REGNO (x) - npi->min_reg;
4886 RESET_BIT (npi->nonnull_local[npi->current_block], regno);
4887 SET_BIT (npi->nonnull_killed[npi->current_block], regno);
4890 /* Do null-pointer check elimination for the registers indicated in
4891 NPI. NONNULL_AVIN and NONNULL_AVOUT are pre-allocated sbitmaps;
4892 they are not our responsibility to free. */
4895 delete_null_pointer_checks_1 (block_reg, nonnull_avin, nonnull_avout, npi)
4897 sbitmap *nonnull_avin;
4898 sbitmap *nonnull_avout;
4899 struct null_pointer_info *npi;
4903 sbitmap *nonnull_local = npi->nonnull_local;
4904 sbitmap *nonnull_killed = npi->nonnull_killed;
4906 /* Compute local properties, nonnull and killed. A register will have
4907 the nonnull property if at the end of the current block its value is
4908 known to be nonnull. The killed property indicates that somewhere in
4909 the block any information we had about the register is killed.
4911 Note that a register can have both properties in a single block. That
4912 indicates that it's killed, then later in the block a new value is
4914 sbitmap_vector_zero (nonnull_local, n_basic_blocks);
4915 sbitmap_vector_zero (nonnull_killed, n_basic_blocks);
4917 for (current_block = 0; current_block < n_basic_blocks; current_block++)
4919 rtx insn, stop_insn;
4921 /* Set the current block for invalidate_nonnull_info. */
4922 npi->current_block = current_block;
4924 /* Scan each insn in the basic block looking for memory references and
4926 stop_insn = NEXT_INSN (BLOCK_END (current_block));
4927 for (insn = BLOCK_HEAD (current_block);
4929 insn = NEXT_INSN (insn))
4934 /* Ignore anything that is not a normal insn. */
4935 if (GET_RTX_CLASS (GET_CODE (insn)) != 'i')
4938 /* Basically ignore anything that is not a simple SET. We do have
4939 to make sure to invalidate nonnull_local and set nonnull_killed
4940 for such insns though. */
4941 set = single_set (insn);
4944 note_stores (PATTERN (insn), invalidate_nonnull_info, npi);
4948 /* See if we've got a useable memory load. We handle it first
4949 in case it uses its address register as a dest (which kills
4950 the nonnull property). */
4951 if (GET_CODE (SET_SRC (set)) == MEM
4952 && GET_CODE ((reg = XEXP (SET_SRC (set), 0))) == REG
4953 && REGNO (reg) >= npi->min_reg
4954 && REGNO (reg) < npi->max_reg)
4955 SET_BIT (nonnull_local[current_block],
4956 REGNO (reg) - npi->min_reg);
4958 /* Now invalidate stuff clobbered by this insn. */
4959 note_stores (PATTERN (insn), invalidate_nonnull_info, npi);
4961 /* And handle stores, we do these last since any sets in INSN can
4962 not kill the nonnull property if it is derived from a MEM
4963 appearing in a SET_DEST. */
4964 if (GET_CODE (SET_DEST (set)) == MEM
4965 && GET_CODE ((reg = XEXP (SET_DEST (set), 0))) == REG
4966 && REGNO (reg) >= npi->min_reg
4967 && REGNO (reg) < npi->max_reg)
4968 SET_BIT (nonnull_local[current_block],
4969 REGNO (reg) - npi->min_reg);
4973 /* Now compute global properties based on the local properties. This
4974 is a classic global availablity algorithm. */
4975 compute_available (nonnull_local, nonnull_killed,
4976 nonnull_avout, nonnull_avin);
4978 /* Now look at each bb and see if it ends with a compare of a value
4980 for (bb = 0; bb < n_basic_blocks; bb++)
4982 rtx last_insn = BLOCK_END (bb);
4983 rtx condition, earliest;
4984 int compare_and_branch;
4986 /* Since MIN_REG is always at least FIRST_PSEUDO_REGISTER, and
4987 since BLOCK_REG[BB] is zero if this block did not end with a
4988 comparison against zero, this condition works. */
4989 if (block_reg[bb] < npi->min_reg
4990 || block_reg[bb] >= npi->max_reg)
4993 /* LAST_INSN is a conditional jump. Get its condition. */
4994 condition = get_condition (last_insn, &earliest);
4996 /* If we can't determine the condition then skip. */
5000 /* Is the register known to have a nonzero value? */
5001 if (!TEST_BIT (nonnull_avout[bb], block_reg[bb] - npi->min_reg))
5004 /* Try to compute whether the compare/branch at the loop end is one or
5005 two instructions. */
5006 if (earliest == last_insn)
5007 compare_and_branch = 1;
5008 else if (earliest == prev_nonnote_insn (last_insn))
5009 compare_and_branch = 2;
5013 /* We know the register in this comparison is nonnull at exit from
5014 this block. We can optimize this comparison. */
5015 if (GET_CODE (condition) == NE)
5019 new_jump = emit_jump_insn_before (gen_jump (JUMP_LABEL (last_insn)),
5021 JUMP_LABEL (new_jump) = JUMP_LABEL (last_insn);
5022 LABEL_NUSES (JUMP_LABEL (new_jump))++;
5023 emit_barrier_after (new_jump);
5025 delete_insn (last_insn);
5026 if (compare_and_branch == 2)
5027 delete_insn (earliest);
5029 /* Don't check this block again. (Note that BLOCK_END is
5030 invalid here; we deleted the last instruction in the
5036 /* Find EQ/NE comparisons against zero which can be (indirectly) evaluated
5039 This is conceptually similar to global constant/copy propagation and
5040 classic global CSE (it even uses the same dataflow equations as cprop).
5042 If a register is used as memory address with the form (mem (reg)), then we
5043 know that REG can not be zero at that point in the program. Any instruction
5044 which sets REG "kills" this property.
5046 So, if every path leading to a conditional branch has an available memory
5047 reference of that form, then we know the register can not have the value
5048 zero at the conditional branch.
5050 So we merely need to compute the local properies and propagate that data
5051 around the cfg, then optimize where possible.
5053 We run this pass two times. Once before CSE, then again after CSE. This
5054 has proven to be the most profitable approach. It is rare for new
5055 optimization opportunities of this nature to appear after the first CSE
5058 This could probably be integrated with global cprop with a little work. */
5061 delete_null_pointer_checks (f)
5064 sbitmap *nonnull_avin, *nonnull_avout;
5070 struct null_pointer_info npi;
5072 /* First break the program into basic blocks. */
5073 find_basic_blocks (f, max_reg_num (), NULL);
5076 /* If we have only a single block, then there's nothing to do. */
5077 if (n_basic_blocks <= 1)
5079 /* Free storage allocated by find_basic_blocks. */
5080 free_basic_block_vars (0);
5084 /* Trying to perform global optimizations on flow graphs which have
5085 a high connectivity will take a long time and is unlikely to be
5086 particularly useful.
5088 In normal circumstances a cfg should have about twice has many edges
5089 as blocks. But we do not want to punish small functions which have
5090 a couple switch statements. So we require a relatively large number
5091 of basic blocks and the ratio of edges to blocks to be high. */
5092 if (n_basic_blocks > 1000 && n_edges / n_basic_blocks >= 20)
5094 /* Free storage allocated by find_basic_blocks. */
5095 free_basic_block_vars (0);
5099 /* We need four bitmaps, each with a bit for each register in each
5101 max_reg = max_reg_num ();
5102 regs_per_pass = get_bitmap_width (4, n_basic_blocks, max_reg);
5104 /* Allocate bitmaps to hold local and global properties. */
5105 npi.nonnull_local = sbitmap_vector_alloc (n_basic_blocks, regs_per_pass);
5106 npi.nonnull_killed = sbitmap_vector_alloc (n_basic_blocks, regs_per_pass);
5107 nonnull_avin = sbitmap_vector_alloc (n_basic_blocks, regs_per_pass);
5108 nonnull_avout = sbitmap_vector_alloc (n_basic_blocks, regs_per_pass);
5110 /* Go through the basic blocks, seeing whether or not each block
5111 ends with a conditional branch whose condition is a comparison
5112 against zero. Record the register compared in BLOCK_REG. */
5113 block_reg = (int *) xcalloc (n_basic_blocks, sizeof (int));
5114 for (bb = 0; bb < n_basic_blocks; bb++)
5116 rtx last_insn = BLOCK_END (bb);
5117 rtx condition, earliest, reg;
5119 /* We only want conditional branches. */
5120 if (GET_CODE (last_insn) != JUMP_INSN
5121 || !condjump_p (last_insn)
5122 || simplejump_p (last_insn))
5125 /* LAST_INSN is a conditional jump. Get its condition. */
5126 condition = get_condition (last_insn, &earliest);
5128 /* If we were unable to get the condition, or it is not a equality
5129 comparison against zero then there's nothing we can do. */
5131 || (GET_CODE (condition) != NE && GET_CODE (condition) != EQ)
5132 || GET_CODE (XEXP (condition, 1)) != CONST_INT
5133 || (XEXP (condition, 1)
5134 != CONST0_RTX (GET_MODE (XEXP (condition, 0)))))
5137 /* We must be checking a register against zero. */
5138 reg = XEXP (condition, 0);
5139 if (GET_CODE (reg) != REG)
5142 block_reg[bb] = REGNO (reg);
5145 /* Go through the algorithm for each block of registers. */
5146 for (reg = FIRST_PSEUDO_REGISTER; reg < max_reg; reg += regs_per_pass)
5149 npi.max_reg = MIN (reg + regs_per_pass, max_reg);
5150 delete_null_pointer_checks_1 (block_reg, nonnull_avin,
5151 nonnull_avout, &npi);
5154 /* Free storage allocated by find_basic_blocks. */
5155 free_basic_block_vars (0);
5157 /* Free the table of registers compared at the end of every block. */
5161 free (npi.nonnull_local);
5162 free (npi.nonnull_killed);
5163 free (nonnull_avin);
5164 free (nonnull_avout);
5167 /* Code Hoisting variables and subroutines. */
5169 /* Very busy expressions. */
5170 static sbitmap *hoist_vbein;
5171 static sbitmap *hoist_vbeout;
5173 /* Hoistable expressions. */
5174 static sbitmap *hoist_exprs;
5176 /* Dominator bitmaps. */
5177 static sbitmap *dominators;
5179 /* ??? We could compute post dominators and run this algorithm in
5180 reverse to to perform tail merging, doing so would probably be
5181 more effective than the tail merging code in jump.c.
5183 It's unclear if tail merging could be run in parallel with
5184 code hoisting. It would be nice. */
5186 /* Allocate vars used for code hoisting analysis. */
5189 alloc_code_hoist_mem (n_blocks, n_exprs)
5190 int n_blocks, n_exprs;
5192 antloc = sbitmap_vector_alloc (n_blocks, n_exprs);
5193 transp = sbitmap_vector_alloc (n_blocks, n_exprs);
5194 comp = sbitmap_vector_alloc (n_blocks, n_exprs);
5196 hoist_vbein = sbitmap_vector_alloc (n_blocks, n_exprs);
5197 hoist_vbeout = sbitmap_vector_alloc (n_blocks, n_exprs);
5198 hoist_exprs = sbitmap_vector_alloc (n_blocks, n_exprs);
5199 transpout = sbitmap_vector_alloc (n_blocks, n_exprs);
5201 dominators = sbitmap_vector_alloc (n_blocks, n_blocks);
5204 /* Free vars used for code hoisting analysis. */
5207 free_code_hoist_mem ()
5214 free (hoist_vbeout);
5221 /* Compute the very busy expressions at entry/exit from each block.
5223 An expression is very busy if all paths from a given point
5224 compute the expression. */
5227 compute_code_hoist_vbeinout ()
5229 int bb, changed, passes;
5231 sbitmap_vector_zero (hoist_vbeout, n_basic_blocks);
5232 sbitmap_vector_zero (hoist_vbein, n_basic_blocks);
5241 /* We scan the blocks in the reverse order to speed up
5243 for (bb = n_basic_blocks - 1; bb >= 0; bb--)
5245 changed |= sbitmap_a_or_b_and_c (hoist_vbein[bb], antloc[bb],
5246 hoist_vbeout[bb], transp[bb]);
5247 if (bb != n_basic_blocks - 1)
5248 sbitmap_intersection_of_succs (hoist_vbeout[bb], hoist_vbein, bb);
5255 fprintf (gcse_file, "hoisting vbeinout computation: %d passes\n", passes);
5258 /* Top level routine to do the dataflow analysis needed by code hoisting. */
5261 compute_code_hoist_data ()
5263 compute_local_properties (transp, comp, antloc, 0);
5264 compute_transpout ();
5265 compute_code_hoist_vbeinout ();
5266 compute_flow_dominators (dominators, NULL);
5268 fprintf (gcse_file, "\n");
5271 /* Determine if the expression identified by EXPR_INDEX would
5272 reach BB unimpared if it was placed at the end of EXPR_BB.
5274 It's unclear exactly what Muchnick meant by "unimpared". It seems
5275 to me that the expression must either be computed or transparent in
5276 *every* block in the path(s) from EXPR_BB to BB. Any other definition
5277 would allow the expression to be hoisted out of loops, even if
5278 the expression wasn't a loop invariant.
5280 Contrast this to reachability for PRE where an expression is
5281 considered reachable if *any* path reaches instead of *all*
5285 hoist_expr_reaches_here_p (expr_bb, expr_index, bb, visited)
5292 int visited_allocated_locally = 0;
5295 if (visited == NULL)
5297 visited_allocated_locally = 1;
5298 visited = xcalloc (n_basic_blocks, 1);
5301 visited[expr_bb] = 1;
5302 for (pred = BASIC_BLOCK (bb)->pred; pred != NULL; pred = pred->pred_next)
5304 int pred_bb = pred->src->index;
5306 if (pred->src == ENTRY_BLOCK_PTR)
5308 else if (visited[pred_bb])
5311 /* Does this predecessor generate this expression? */
5312 else if (TEST_BIT (comp[pred_bb], expr_index))
5314 else if (! TEST_BIT (transp[pred_bb], expr_index))
5320 visited[pred_bb] = 1;
5321 if (! hoist_expr_reaches_here_p (expr_bb, expr_index,
5326 if (visited_allocated_locally)
5329 return (pred == NULL);
5332 /* Actually perform code hoisting. */
5337 int bb, dominated, i;
5338 struct expr **index_map;
5341 sbitmap_vector_zero (hoist_exprs, n_basic_blocks);
5343 /* Compute a mapping from expression number (`bitmap_index') to
5344 hash table entry. */
5346 index_map = (struct expr **) xcalloc (n_exprs, sizeof (struct expr *));
5347 for (i = 0; i < expr_hash_table_size; i++)
5348 for (expr = expr_hash_table[i]; expr != NULL; expr = expr->next_same_hash)
5349 index_map[expr->bitmap_index] = expr;
5351 /* Walk over each basic block looking for potentially hoistable
5352 expressions, nothing gets hoisted from the entry block. */
5353 for (bb = 0; bb < n_basic_blocks; bb++)
5356 int insn_inserted_p;
5358 /* Examine each expression that is very busy at the exit of this
5359 block. These are the potentially hoistable expressions. */
5360 for (i = 0; i < hoist_vbeout[bb]->n_bits; i++)
5364 if (TEST_BIT (hoist_vbeout[bb], i) && TEST_BIT (transpout[bb], i))
5366 /* We've found a potentially hoistable expression, now
5367 we look at every block BB dominates to see if it
5368 computes the expression. */
5369 for (dominated = 0; dominated < n_basic_blocks; dominated++)
5371 /* Ignore self dominance. */
5373 || ! TEST_BIT (dominators[dominated], bb))
5376 /* We've found a dominated block, now see if it computes
5377 the busy expression and whether or not moving that
5378 expression to the "beginning" of that block is safe. */
5379 if (!TEST_BIT (antloc[dominated], i))
5382 /* Note if the expression would reach the dominated block
5383 unimpared if it was placed at the end of BB.
5385 Keep track of how many times this expression is hoistable
5386 from a dominated block into BB. */
5387 if (hoist_expr_reaches_here_p (bb, i, dominated, NULL))
5391 /* If we found more than one hoistable occurence of this
5392 expression, then note it in the bitmap of expressions to
5393 hoist. It makes no sense to hoist things which are computed
5394 in only one BB, and doing so tends to pessimize register
5395 allocation. One could increase this value to try harder
5396 to avoid any possible code expansion due to register
5397 allocation issues; however experiments have shown that
5398 the vast majority of hoistable expressions are only movable
5399 from two successors, so raising this threshhold is likely
5400 to nullify any benefit we get from code hoisting. */
5403 SET_BIT (hoist_exprs[bb], i);
5409 /* If we found nothing to hoist, then quit now. */
5413 /* Loop over all the hoistable expressions. */
5414 for (i = 0; i < hoist_exprs[bb]->n_bits; i++)
5416 /* We want to insert the expression into BB only once, so
5417 note when we've inserted it. */
5418 insn_inserted_p = 0;
5420 /* These tests should be the same as the tests above. */
5421 if (TEST_BIT (hoist_vbeout[bb], i))
5423 /* We've found a potentially hoistable expression, now
5424 we look at every block BB dominates to see if it
5425 computes the expression. */
5426 for (dominated = 0; dominated < n_basic_blocks; dominated++)
5428 /* Ignore self dominance. */
5430 || ! TEST_BIT (dominators[dominated], bb))
5433 /* We've found a dominated block, now see if it computes
5434 the busy expression and whether or not moving that
5435 expression to the "beginning" of that block is safe. */
5436 if (!TEST_BIT (antloc[dominated], i))
5439 /* The expression is computed in the dominated block and
5440 it would be safe to compute it at the start of the
5441 dominated block. Now we have to determine if the
5442 expresion would reach the dominated block if it was
5443 placed at the end of BB. */
5444 if (hoist_expr_reaches_here_p (bb, i, dominated, NULL))
5446 struct expr *expr = index_map[i];
5447 struct occr *occr = expr->antic_occr;
5451 /* Find the right occurence of this expression. */
5452 while (BLOCK_NUM (occr->insn) != dominated && occr)
5455 /* Should never happen. */
5461 set = single_set (insn);
5465 /* Create a pseudo-reg to store the result of reaching
5466 expressions into. Get the mode for the new pseudo
5467 from the mode of the original destination pseudo. */
5468 if (expr->reaching_reg == NULL)
5470 = gen_reg_rtx (GET_MODE (SET_DEST (set)));
5472 /* In theory this should never fail since we're creating
5475 However, on the x86 some of the movXX patterns
5476 actually contain clobbers of scratch regs. This may
5477 cause the insn created by validate_change to not
5478 match any pattern and thus cause validate_change to
5480 if (validate_change (insn, &SET_SRC (set),
5481 expr->reaching_reg, 0))
5483 occr->deleted_p = 1;
5484 if (!insn_inserted_p)
5486 insert_insn_end_bb (index_map[i], bb, 0);
5487 insn_inserted_p = 1;
5499 /* Top level routine to perform one code hoisting (aka unification) pass
5501 Return non-zero if a change was made. */
5504 one_code_hoisting_pass ()
5508 alloc_expr_hash_table (max_cuid);
5509 compute_expr_hash_table ();
5511 dump_hash_table (gcse_file, "Code Hosting Expressions", expr_hash_table,
5512 expr_hash_table_size, n_exprs);
5516 alloc_code_hoist_mem (n_basic_blocks, n_exprs);
5517 compute_code_hoist_data ();
5519 free_code_hoist_mem ();
5522 free_expr_hash_table ();