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 unsigned int expr_hash_table_size;
371 This is an array of `expr_hash_table_size' elements. */
372 static struct expr **expr_hash_table;
374 /* Total size of the copy propagation hash table, in elements. */
375 static int set_hash_table_size;
378 This is an array of `set_hash_table_size' elements. */
379 static struct expr **set_hash_table;
381 /* Mapping of uids to cuids.
382 Only real insns get cuids. */
383 static int *uid_cuid;
385 /* Highest UID in UID_CUID. */
388 /* Get the cuid of an insn. */
389 #ifdef ENABLE_CHECKING
390 #define INSN_CUID(INSN) (INSN_UID (INSN) > max_uid ? (abort (), 0) : uid_cuid[INSN_UID (INSN)])
392 #define INSN_CUID(INSN) (uid_cuid[INSN_UID (INSN)])
395 /* Number of cuids. */
398 /* Mapping of cuids to insns. */
399 static rtx *cuid_insn;
401 /* Get insn from cuid. */
402 #define CUID_INSN(CUID) (cuid_insn[CUID])
404 /* Maximum register number in function prior to doing gcse + 1.
405 Registers created during this pass have regno >= max_gcse_regno.
406 This is named with "gcse" to not collide with global of same name. */
407 static unsigned int max_gcse_regno;
409 /* Maximum number of cse-able expressions found. */
412 /* Maximum number of assignments for copy propagation found. */
415 /* Table of registers that are modified.
417 For each register, each element is a list of places where the pseudo-reg
420 For simplicity, GCSE is done on sets of pseudo-regs only. PRE GCSE only
421 requires knowledge of which blocks kill which regs [and thus could use
422 a bitmap instead of the lists `reg_set_table' uses].
424 `reg_set_table' and could be turned into an array of bitmaps (num-bbs x
425 num-regs) [however perhaps it may be useful to keep the data as is]. One
426 advantage of recording things this way is that `reg_set_table' is fairly
427 sparse with respect to pseudo regs but for hard regs could be fairly dense
428 [relatively speaking]. And recording sets of pseudo-regs in lists speeds
429 up functions like compute_transp since in the case of pseudo-regs we only
430 need to iterate over the number of times a pseudo-reg is set, not over the
431 number of basic blocks [clearly there is a bit of a slow down in the cases
432 where a pseudo is set more than once in a block, however it is believed
433 that the net effect is to speed things up]. This isn't done for hard-regs
434 because recording call-clobbered hard-regs in `reg_set_table' at each
435 function call can consume a fair bit of memory, and iterating over
436 hard-regs stored this way in compute_transp will be more expensive. */
438 typedef struct reg_set
440 /* The next setting of this register. */
441 struct reg_set *next;
442 /* The insn where it was set. */
446 static reg_set **reg_set_table;
448 /* Size of `reg_set_table'.
449 The table starts out at max_gcse_regno + slop, and is enlarged as
451 static int reg_set_table_size;
453 /* Amount to grow `reg_set_table' by when it's full. */
454 #define REG_SET_TABLE_SLOP 100
456 /* Bitmap containing one bit for each register in the program.
457 Used when performing GCSE to track which registers have been set since
458 the start of the basic block. */
459 static sbitmap reg_set_bitmap;
461 /* For each block, a bitmap of registers set in the block.
462 This is used by expr_killed_p and compute_transp.
463 It is computed during hash table computation and not by compute_sets
464 as it includes registers added since the last pass (or between cprop and
465 gcse) and it's currently not easy to realloc sbitmap vectors. */
466 static sbitmap *reg_set_in_block;
468 /* For each block, non-zero if memory is set in that block.
469 This is computed during hash table computation and is used by
470 expr_killed_p and compute_transp.
471 ??? Handling of memory is very simple, we don't make any attempt
472 to optimize things (later).
473 ??? This can be computed by compute_sets since the information
475 static char *mem_set_in_block;
477 /* Various variables for statistics gathering. */
479 /* Memory used in a pass.
480 This isn't intended to be absolutely precise. Its intent is only
481 to keep an eye on memory usage. */
482 static int bytes_used;
484 /* GCSE substitutions made. */
485 static int gcse_subst_count;
486 /* Number of copy instructions created. */
487 static int gcse_create_count;
488 /* Number of constants propagated. */
489 static int const_prop_count;
490 /* Number of copys propagated. */
491 static int copy_prop_count;
493 /* These variables are used by classic GCSE.
494 Normally they'd be defined a bit later, but `rd_gen' needs to
495 be declared sooner. */
497 /* Each block has a bitmap of each type.
498 The length of each blocks bitmap is:
500 max_cuid - for reaching definitions
501 n_exprs - for available expressions
503 Thus we view the bitmaps as 2 dimensional arrays. i.e.
504 rd_kill[block_num][cuid_num]
505 ae_kill[block_num][expr_num] */
507 /* For reaching defs */
508 static sbitmap *rd_kill, *rd_gen, *reaching_defs, *rd_out;
510 /* for available exprs */
511 static sbitmap *ae_kill, *ae_gen, *ae_in, *ae_out;
513 /* Objects of this type are passed around by the null-pointer check
515 struct null_pointer_info
517 /* The basic block being processed. */
519 /* The first register to be handled in this pass. */
520 unsigned int min_reg;
521 /* One greater than the last register to be handled in this pass. */
522 unsigned int max_reg;
523 sbitmap *nonnull_local;
524 sbitmap *nonnull_killed;
527 static void compute_can_copy PARAMS ((void));
528 static char *gmalloc PARAMS ((unsigned int));
529 static char *grealloc PARAMS ((char *, unsigned int));
530 static char *gcse_alloc PARAMS ((unsigned long));
531 static void alloc_gcse_mem PARAMS ((rtx));
532 static void free_gcse_mem PARAMS ((void));
533 static void alloc_reg_set_mem PARAMS ((int));
534 static void free_reg_set_mem PARAMS ((void));
535 static int get_bitmap_width PARAMS ((int, int, int));
536 static void record_one_set PARAMS ((int, rtx));
537 static void record_set_info PARAMS ((rtx, rtx, void *));
538 static void compute_sets PARAMS ((rtx));
539 static void hash_scan_insn PARAMS ((rtx, int, int));
540 static void hash_scan_set PARAMS ((rtx, rtx, int));
541 static void hash_scan_clobber PARAMS ((rtx, rtx));
542 static void hash_scan_call PARAMS ((rtx, rtx));
543 static int want_to_gcse_p PARAMS ((rtx));
544 static int oprs_unchanged_p PARAMS ((rtx, rtx, int));
545 static int oprs_anticipatable_p PARAMS ((rtx, rtx));
546 static int oprs_available_p PARAMS ((rtx, rtx));
547 static void insert_expr_in_table PARAMS ((rtx, enum machine_mode, rtx,
549 static void insert_set_in_table PARAMS ((rtx, rtx));
550 static unsigned int hash_expr PARAMS ((rtx, enum machine_mode, int *, int));
551 static unsigned int hash_expr_1 PARAMS ((rtx, enum machine_mode, int *));
552 static unsigned int hash_set PARAMS ((int, int));
553 static int expr_equiv_p PARAMS ((rtx, rtx));
554 static void record_last_reg_set_info PARAMS ((rtx, int));
555 static void record_last_mem_set_info PARAMS ((rtx));
556 static void record_last_set_info PARAMS ((rtx, rtx, void *));
557 static void compute_hash_table PARAMS ((int));
558 static void alloc_set_hash_table PARAMS ((int));
559 static void free_set_hash_table PARAMS ((void));
560 static void compute_set_hash_table PARAMS ((void));
561 static void alloc_expr_hash_table PARAMS ((unsigned int));
562 static void free_expr_hash_table PARAMS ((void));
563 static void compute_expr_hash_table PARAMS ((void));
564 static void dump_hash_table PARAMS ((FILE *, const char *, struct expr **,
566 static struct expr *lookup_expr PARAMS ((rtx));
567 static struct expr *lookup_set PARAMS ((unsigned int, rtx));
568 static struct expr *next_set PARAMS ((unsigned int, struct expr *));
569 static void reset_opr_set_tables PARAMS ((void));
570 static int oprs_not_set_p PARAMS ((rtx, rtx));
571 static void mark_call PARAMS ((rtx));
572 static void mark_set PARAMS ((rtx, rtx));
573 static void mark_clobber PARAMS ((rtx, rtx));
574 static void mark_oprs_set PARAMS ((rtx));
575 static void alloc_cprop_mem PARAMS ((int, int));
576 static void free_cprop_mem PARAMS ((void));
577 static void compute_transp PARAMS ((rtx, int, sbitmap *, int));
578 static void compute_transpout PARAMS ((void));
579 static void compute_local_properties PARAMS ((sbitmap *, sbitmap *, sbitmap *,
581 static void compute_cprop_data PARAMS ((void));
582 static void find_used_regs PARAMS ((rtx));
583 static int try_replace_reg PARAMS ((rtx, rtx, rtx));
584 static struct expr *find_avail_set PARAMS ((int, rtx));
585 static int cprop_jump PARAMS ((rtx, rtx, struct reg_use *, rtx));
587 static int cprop_cc0_jump PARAMS ((rtx, struct reg_use *, rtx));
589 static int cprop_insn PARAMS ((rtx, int));
590 static int cprop PARAMS ((int));
591 static int one_cprop_pass PARAMS ((int, int));
592 static void alloc_pre_mem PARAMS ((int, int));
593 static void free_pre_mem PARAMS ((void));
594 static void compute_pre_data PARAMS ((void));
595 static int pre_expr_reaches_here_p PARAMS ((int, struct expr *, int));
596 static void insert_insn_end_bb PARAMS ((struct expr *, int, int));
597 static void pre_insert_copy_insn PARAMS ((struct expr *, rtx));
598 static void pre_insert_copies PARAMS ((void));
599 static int pre_delete PARAMS ((void));
600 static int pre_gcse PARAMS ((void));
601 static int one_pre_gcse_pass PARAMS ((int));
602 static void add_label_notes PARAMS ((rtx, rtx));
603 static void alloc_code_hoist_mem PARAMS ((int, int));
604 static void free_code_hoist_mem PARAMS ((void));
605 static void compute_code_hoist_vbeinout PARAMS ((void));
606 static void compute_code_hoist_data PARAMS ((void));
607 static int hoist_expr_reaches_here_p PARAMS ((int, int, int, char *));
608 static void hoist_code PARAMS ((void));
609 static int one_code_hoisting_pass PARAMS ((void));
610 static void alloc_rd_mem PARAMS ((int, int));
611 static void free_rd_mem PARAMS ((void));
612 static void handle_rd_kill_set PARAMS ((rtx, int, int));
613 static void compute_kill_rd PARAMS ((void));
614 static void compute_rd PARAMS ((void));
615 static void alloc_avail_expr_mem PARAMS ((int, int));
616 static void free_avail_expr_mem PARAMS ((void));
617 static void compute_ae_gen PARAMS ((void));
618 static int expr_killed_p PARAMS ((rtx, int));
619 static void compute_ae_kill PARAMS ((sbitmap *, sbitmap *));
620 static int expr_reaches_here_p PARAMS ((struct occr *, struct expr *,
622 static rtx computing_insn PARAMS ((struct expr *, rtx));
623 static int def_reaches_here_p PARAMS ((rtx, rtx));
624 static int can_disregard_other_sets PARAMS ((struct reg_set **, rtx, int));
625 static int handle_avail_expr PARAMS ((rtx, struct expr *));
626 static int classic_gcse PARAMS ((void));
627 static int one_classic_gcse_pass PARAMS ((int));
628 static void invalidate_nonnull_info PARAMS ((rtx, rtx, void *));
629 static void delete_null_pointer_checks_1 PARAMS ((unsigned int *, sbitmap *,
631 struct null_pointer_info *));
632 static rtx process_insert_insn PARAMS ((struct expr *));
633 static int pre_edge_insert PARAMS ((struct edge_list *, struct expr **));
634 static int expr_reaches_here_p_work PARAMS ((struct occr *, struct expr *,
636 static int pre_expr_reaches_here_p_work PARAMS ((int, struct expr *,
639 /* Entry point for global common subexpression elimination.
640 F is the first instruction in the function. */
648 /* Bytes used at start of pass. */
649 int initial_bytes_used;
650 /* Maximum number of bytes used by a pass. */
652 /* Point to release obstack data from for each pass. */
653 char *gcse_obstack_bottom;
655 /* We do not construct an accurate cfg in functions which call
656 setjmp, so just punt to be safe. */
657 if (current_function_calls_setjmp)
660 /* Assume that we do not need to run jump optimizations after gcse. */
661 run_jump_opt_after_gcse = 0;
663 /* For calling dump_foo fns from gdb. */
664 debug_stderr = stderr;
667 /* Identify the basic block information for this function, including
668 successors and predecessors. */
669 max_gcse_regno = max_reg_num ();
672 dump_flow_info (file);
674 /* Return if there's nothing to do. */
675 if (n_basic_blocks <= 1)
678 /* Trying to perform global optimizations on flow graphs which have
679 a high connectivity will take a long time and is unlikely to be
682 In normal circumstances a cfg should have about twice has many edges
683 as blocks. But we do not want to punish small functions which have
684 a couple switch statements. So we require a relatively large number
685 of basic blocks and the ratio of edges to blocks to be high. */
686 if (n_basic_blocks > 1000 && n_edges / n_basic_blocks >= 20)
689 /* See what modes support reg/reg copy operations. */
690 if (! can_copy_init_p)
696 gcc_obstack_init (&gcse_obstack);
699 /* Record where pseudo-registers are set. This data is kept accurate
700 during each pass. ??? We could also record hard-reg information here
701 [since it's unchanging], however it is currently done during hash table
704 It may be tempting to compute MEM set information here too, but MEM sets
705 will be subject to code motion one day and thus we need to compute
706 information about memory sets when we build the hash tables. */
708 alloc_reg_set_mem (max_gcse_regno);
712 initial_bytes_used = bytes_used;
714 gcse_obstack_bottom = gcse_alloc (1);
716 while (changed && pass < MAX_PASSES)
720 fprintf (file, "GCSE pass %d\n\n", pass + 1);
722 /* Initialize bytes_used to the space for the pred/succ lists,
723 and the reg_set_table data. */
724 bytes_used = initial_bytes_used;
726 /* Each pass may create new registers, so recalculate each time. */
727 max_gcse_regno = max_reg_num ();
731 /* Don't allow constant propagation to modify jumps
733 changed = one_cprop_pass (pass + 1, 0);
736 changed |= one_classic_gcse_pass (pass + 1);
739 changed |= one_pre_gcse_pass (pass + 1);
741 alloc_reg_set_mem (max_reg_num ());
743 run_jump_opt_after_gcse = 1;
746 if (max_pass_bytes < bytes_used)
747 max_pass_bytes = bytes_used;
749 /* Free up memory, then reallocate for code hoisting. We can
750 not re-use the existing allocated memory because the tables
751 will not have info for the insns or registers created by
752 partial redundancy elimination. */
755 /* It does not make sense to run code hoisting unless we optimizing
756 for code size -- it rarely makes programs faster, and can make
757 them bigger if we did partial redundancy elimination (when optimizing
758 for space, we use a classic gcse algorithm instead of partial
759 redundancy algorithms). */
762 max_gcse_regno = max_reg_num ();
764 changed |= one_code_hoisting_pass ();
767 if (max_pass_bytes < bytes_used)
768 max_pass_bytes = bytes_used;
773 fprintf (file, "\n");
777 obstack_free (&gcse_obstack, gcse_obstack_bottom);
781 /* Do one last pass of copy propagation, including cprop into
782 conditional jumps. */
784 max_gcse_regno = max_reg_num ();
786 /* This time, go ahead and allow cprop to alter jumps. */
787 one_cprop_pass (pass + 1, 1);
792 fprintf (file, "GCSE of %s: %d basic blocks, ",
793 current_function_name, n_basic_blocks);
794 fprintf (file, "%d pass%s, %d bytes\n\n",
795 pass, pass > 1 ? "es" : "", max_pass_bytes);
798 obstack_free (&gcse_obstack, NULL_PTR);
800 return run_jump_opt_after_gcse;
803 /* Misc. utilities. */
805 /* Compute which modes support reg/reg copy operations. */
811 #ifndef AVOID_CCMODE_COPIES
814 char *free_point = (char *) oballoc (1);
816 bzero (can_copy_p, NUM_MACHINE_MODES);
819 for (i = 0; i < NUM_MACHINE_MODES; i++)
820 if (GET_MODE_CLASS (i) == MODE_CC)
822 #ifdef AVOID_CCMODE_COPIES
825 reg = gen_rtx_REG ((enum machine_mode) i, LAST_VIRTUAL_REGISTER + 1);
826 insn = emit_insn (gen_rtx_SET (VOIDmode, reg, reg));
827 if (recog (PATTERN (insn), insn, NULL_PTR) >= 0)
836 /* Free the objects we just allocated. */
840 /* Cover function to xmalloc to record bytes allocated. */
847 return xmalloc (size);
850 /* Cover function to xrealloc.
851 We don't record the additional size since we don't know it.
852 It won't affect memory usage stats much anyway. */
859 return xrealloc (ptr, size);
862 /* Cover function to obstack_alloc.
863 We don't need to record the bytes allocated here since
864 obstack_chunk_alloc is set to gmalloc. */
870 return (char *) obstack_alloc (&gcse_obstack, size);
873 /* Allocate memory for the cuid mapping array,
874 and reg/memory set tracking tables.
876 This is called at the start of each pass. */
885 /* Find the largest UID and create a mapping from UIDs to CUIDs.
886 CUIDs are like UIDs except they increase monotonically, have no gaps,
887 and only apply to real insns. */
889 max_uid = get_max_uid ();
890 n = (max_uid + 1) * sizeof (int);
891 uid_cuid = (int *) gmalloc (n);
892 bzero ((char *) uid_cuid, n);
893 for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
895 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
896 uid_cuid[INSN_UID (insn)] = i++;
898 uid_cuid[INSN_UID (insn)] = i;
901 /* Create a table mapping cuids to insns. */
904 n = (max_cuid + 1) * sizeof (rtx);
905 cuid_insn = (rtx *) gmalloc (n);
906 bzero ((char *) cuid_insn, n);
907 for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
908 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
909 CUID_INSN (i++) = insn;
911 /* Allocate vars to track sets of regs. */
912 reg_set_bitmap = (sbitmap) sbitmap_alloc (max_gcse_regno);
914 /* Allocate vars to track sets of regs, memory per block. */
915 reg_set_in_block = (sbitmap *) sbitmap_vector_alloc (n_basic_blocks,
917 mem_set_in_block = (char *) gmalloc (n_basic_blocks);
920 /* Free memory allocated by alloc_gcse_mem. */
928 free (reg_set_bitmap);
930 free (reg_set_in_block);
931 free (mem_set_in_block);
934 /* Many of the global optimization algorithms work by solving dataflow
935 equations for various expressions. Initially, some local value is
936 computed for each expression in each block. Then, the values across the
937 various blocks are combined (by following flow graph edges) to arrive at
938 global values. Conceptually, each set of equations is independent. We
939 may therefore solve all the equations in parallel, solve them one at a
940 time, or pick any intermediate approach.
942 When you're going to need N two-dimensional bitmaps, each X (say, the
943 number of blocks) by Y (say, the number of expressions), call this
944 function. It's not important what X and Y represent; only that Y
945 correspond to the things that can be done in parallel. This function will
946 return an appropriate chunking factor C; you should solve C sets of
947 equations in parallel. By going through this function, we can easily
948 trade space against time; by solving fewer equations in parallel we use
952 get_bitmap_width (n, x, y)
957 /* It's not really worth figuring out *exactly* how much memory will
958 be used by a particular choice. The important thing is to get
959 something approximately right. */
960 size_t max_bitmap_memory = 10 * 1024 * 1024;
962 /* The number of bytes we'd use for a single column of minimum
964 size_t column_size = n * x * sizeof (SBITMAP_ELT_TYPE);
966 /* Often, it's reasonable just to solve all the equations in
968 if (column_size * SBITMAP_SET_SIZE (y) <= max_bitmap_memory)
971 /* Otherwise, pick the largest width we can, without going over the
973 return SBITMAP_ELT_BITS * ((max_bitmap_memory + column_size - 1)
977 /* Compute the local properties of each recorded expression.
979 Local properties are those that are defined by the block, irrespective of
982 An expression is transparent in a block if its operands are not modified
985 An expression is computed (locally available) in a block if it is computed
986 at least once and expression would contain the same value if the
987 computation was moved to the end of the block.
989 An expression is locally anticipatable in a block if it is computed at
990 least once and expression would contain the same value if the computation
991 was moved to the beginning of the block.
993 We call this routine for cprop, pre and code hoisting. They all compute
994 basically the same information and thus can easily share this code.
996 TRANSP, COMP, and ANTLOC are destination sbitmaps for recording local
997 properties. If NULL, then it is not necessary to compute or record that
1000 SETP controls which hash table to look at. If zero, this routine looks at
1001 the expr hash table; if nonzero this routine looks at the set hash table.
1002 Additionally, TRANSP is computed as ~TRANSP, since this is really cprop's
1006 compute_local_properties (transp, comp, antloc, setp)
1012 unsigned int i, hash_table_size;
1013 struct expr **hash_table;
1015 /* Initialize any bitmaps that were passed in. */
1019 sbitmap_vector_zero (transp, n_basic_blocks);
1021 sbitmap_vector_ones (transp, n_basic_blocks);
1025 sbitmap_vector_zero (comp, n_basic_blocks);
1027 sbitmap_vector_zero (antloc, n_basic_blocks);
1029 /* We use the same code for cprop, pre and hoisting. For cprop
1030 we care about the set hash table, for pre and hoisting we
1031 care about the expr hash table. */
1032 hash_table_size = setp ? set_hash_table_size : expr_hash_table_size;
1033 hash_table = setp ? set_hash_table : expr_hash_table;
1035 for (i = 0; i < hash_table_size; i++)
1039 for (expr = hash_table[i]; expr != NULL; expr = expr->next_same_hash)
1041 int indx = expr->bitmap_index;
1044 /* The expression is transparent in this block if it is not killed.
1045 We start by assuming all are transparent [none are killed], and
1046 then reset the bits for those that are. */
1048 compute_transp (expr->expr, indx, transp, setp);
1050 /* The occurrences recorded in antic_occr are exactly those that
1051 we want to set to non-zero in ANTLOC. */
1053 for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
1055 SET_BIT (antloc[BLOCK_NUM (occr->insn)], indx);
1057 /* While we're scanning the table, this is a good place to
1059 occr->deleted_p = 0;
1062 /* The occurrences recorded in avail_occr are exactly those that
1063 we want to set to non-zero in COMP. */
1065 for (occr = expr->avail_occr; occr != NULL; occr = occr->next)
1067 SET_BIT (comp[BLOCK_NUM (occr->insn)], indx);
1069 /* While we're scanning the table, this is a good place to
1074 /* While we're scanning the table, this is a good place to
1076 expr->reaching_reg = 0;
1081 /* Register set information.
1083 `reg_set_table' records where each register is set or otherwise
1086 static struct obstack reg_set_obstack;
1089 alloc_reg_set_mem (n_regs)
1094 reg_set_table_size = n_regs + REG_SET_TABLE_SLOP;
1095 n = reg_set_table_size * sizeof (struct reg_set *);
1096 reg_set_table = (struct reg_set **) gmalloc (n);
1097 bzero ((char *) reg_set_table, n);
1099 gcc_obstack_init (®_set_obstack);
1105 free (reg_set_table);
1106 obstack_free (®_set_obstack, NULL_PTR);
1109 /* Record REGNO in the reg_set table. */
1112 record_one_set (regno, insn)
1116 /* allocate a new reg_set element and link it onto the list */
1117 struct reg_set *new_reg_info;
1119 /* If the table isn't big enough, enlarge it. */
1120 if (regno >= reg_set_table_size)
1122 int new_size = regno + REG_SET_TABLE_SLOP;
1125 = (struct reg_set **) grealloc ((char *) reg_set_table,
1126 new_size * sizeof (struct reg_set *));
1127 bzero ((char *) (reg_set_table + reg_set_table_size),
1128 (new_size - reg_set_table_size) * sizeof (struct reg_set *));
1129 reg_set_table_size = new_size;
1132 new_reg_info = (struct reg_set *) obstack_alloc (®_set_obstack,
1133 sizeof (struct reg_set));
1134 bytes_used += sizeof (struct reg_set);
1135 new_reg_info->insn = insn;
1136 new_reg_info->next = reg_set_table[regno];
1137 reg_set_table[regno] = new_reg_info;
1140 /* Called from compute_sets via note_stores to handle one SET or CLOBBER in
1141 an insn. The DATA is really the instruction in which the SET is
1145 record_set_info (dest, setter, data)
1146 rtx dest, setter ATTRIBUTE_UNUSED;
1149 rtx record_set_insn = (rtx) data;
1151 if (GET_CODE (dest) == REG && REGNO (dest) >= FIRST_PSEUDO_REGISTER)
1152 record_one_set (REGNO (dest), record_set_insn);
1155 /* Scan the function and record each set of each pseudo-register.
1157 This is called once, at the start of the gcse pass. See the comments for
1158 `reg_set_table' for further documenation. */
1166 for (insn = f; insn != 0; insn = NEXT_INSN (insn))
1167 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
1168 note_stores (PATTERN (insn), record_set_info, insn);
1171 /* Hash table support. */
1173 /* For each register, the cuid of the first/last insn in the block to set it,
1174 or -1 if not set. */
1175 #define NEVER_SET -1
1176 static int *reg_first_set;
1177 static int *reg_last_set;
1179 /* While computing "first/last set" info, this is the CUID of first/last insn
1180 to set memory or -1 if not set. `mem_last_set' is also used when
1181 performing GCSE to record whether memory has been set since the beginning
1184 Note that handling of memory is very simple, we don't make any attempt
1185 to optimize things (later). */
1186 static int mem_first_set;
1187 static int mem_last_set;
1189 /* Perform a quick check whether X, the source of a set, is something
1190 we want to consider for GCSE. */
1196 switch (GET_CODE (x))
1212 /* Return non-zero if the operands of expression X are unchanged from the
1213 start of INSN's basic block up to but not including INSN (if AVAIL_P == 0),
1214 or from INSN to the end of INSN's basic block (if AVAIL_P != 0). */
1217 oprs_unchanged_p (x, insn, avail_p)
1228 code = GET_CODE (x);
1233 return (reg_last_set[REGNO (x)] == NEVER_SET
1234 || reg_last_set[REGNO (x)] < INSN_CUID (insn));
1236 return (reg_first_set[REGNO (x)] == NEVER_SET
1237 || reg_first_set[REGNO (x)] >= INSN_CUID (insn));
1240 if (avail_p && mem_last_set != NEVER_SET
1241 && mem_last_set >= INSN_CUID (insn))
1243 else if (! avail_p && mem_first_set != NEVER_SET
1244 && mem_first_set < INSN_CUID (insn))
1247 return oprs_unchanged_p (XEXP (x, 0), insn, avail_p);
1270 for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
1274 /* If we are about to do the last recursive call needed at this
1275 level, change it into iteration. This function is called enough
1278 return oprs_unchanged_p (XEXP (x, i), insn, avail_p);
1280 else if (! oprs_unchanged_p (XEXP (x, i), insn, avail_p))
1283 else if (fmt[i] == 'E')
1284 for (j = 0; j < XVECLEN (x, i); j++)
1285 if (! oprs_unchanged_p (XVECEXP (x, i, j), insn, avail_p))
1292 /* Return non-zero if the operands of expression X are unchanged from
1293 the start of INSN's basic block up to but not including INSN. */
1296 oprs_anticipatable_p (x, insn)
1299 return oprs_unchanged_p (x, insn, 0);
1302 /* Return non-zero if the operands of expression X are unchanged from
1303 INSN to the end of INSN's basic block. */
1306 oprs_available_p (x, insn)
1309 return oprs_unchanged_p (x, insn, 1);
1312 /* Hash expression X.
1314 MODE is only used if X is a CONST_INT. DO_NOT_RECORD_P is a boolean
1315 indicating if a volatile operand is found or if the expression contains
1316 something we don't want to insert in the table.
1318 ??? One might want to merge this with canon_hash. Later. */
1321 hash_expr (x, mode, do_not_record_p, hash_table_size)
1323 enum machine_mode mode;
1324 int *do_not_record_p;
1325 int hash_table_size;
1329 *do_not_record_p = 0;
1331 hash = hash_expr_1 (x, mode, do_not_record_p);
1332 return hash % hash_table_size;
1335 /* Subroutine of hash_expr to do the actual work. */
1338 hash_expr_1 (x, mode, do_not_record_p)
1340 enum machine_mode mode;
1341 int *do_not_record_p;
1348 /* Used to turn recursion into iteration. We can't rely on GCC's
1349 tail-recursion eliminatio since we need to keep accumulating values
1356 code = GET_CODE (x);
1360 hash += ((unsigned int) REG << 7) + REGNO (x);
1364 hash += (((unsigned int) CONST_INT << 7) + (unsigned int) mode
1365 + (unsigned int) INTVAL (x));
1369 /* This is like the general case, except that it only counts
1370 the integers representing the constant. */
1371 hash += (unsigned int) code + (unsigned int) GET_MODE (x);
1372 if (GET_MODE (x) != VOIDmode)
1373 for (i = 2; i < GET_RTX_LENGTH (CONST_DOUBLE); i++)
1374 hash += (unsigned int) XWINT (x, i);
1376 hash += ((unsigned int) CONST_DOUBLE_LOW (x)
1377 + (unsigned int) CONST_DOUBLE_HIGH (x));
1380 /* Assume there is only one rtx object for any given label. */
1382 /* We don't hash on the address of the CODE_LABEL to avoid bootstrap
1383 differences and differences between each stage's debugging dumps. */
1384 hash += (((unsigned int) LABEL_REF << 7)
1385 + CODE_LABEL_NUMBER (XEXP (x, 0)));
1390 /* Don't hash on the symbol's address to avoid bootstrap differences.
1391 Different hash values may cause expressions to be recorded in
1392 different orders and thus different registers to be used in the
1393 final assembler. This also avoids differences in the dump files
1394 between various stages. */
1396 const unsigned char *p = (const unsigned char *) XSTR (x, 0);
1399 h += (h << 7) + *p++; /* ??? revisit */
1401 hash += ((unsigned int) SYMBOL_REF << 7) + h;
1406 if (MEM_VOLATILE_P (x))
1408 *do_not_record_p = 1;
1412 hash += (unsigned int) MEM;
1413 hash += MEM_ALIAS_SET (x);
1424 case UNSPEC_VOLATILE:
1425 *do_not_record_p = 1;
1429 if (MEM_VOLATILE_P (x))
1431 *do_not_record_p = 1;
1439 hash += (unsigned) code + (unsigned) GET_MODE (x);
1440 for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
1444 /* If we are about to do the last recursive call
1445 needed at this level, change it into iteration.
1446 This function is called enough to be worth it. */
1453 hash += hash_expr_1 (XEXP (x, i), 0, do_not_record_p);
1454 if (*do_not_record_p)
1458 else if (fmt[i] == 'E')
1459 for (j = 0; j < XVECLEN (x, i); j++)
1461 hash += hash_expr_1 (XVECEXP (x, i, j), 0, do_not_record_p);
1462 if (*do_not_record_p)
1466 else if (fmt[i] == 's')
1468 register const unsigned char *p =
1469 (const unsigned char *) XSTR (x, i);
1475 else if (fmt[i] == 'i')
1476 hash += (unsigned int) XINT (x, i);
1484 /* Hash a set of register REGNO.
1486 Sets are hashed on the register that is set. This simplifies the PRE copy
1489 ??? May need to make things more elaborate. Later, as necessary. */
1492 hash_set (regno, hash_table_size)
1494 int hash_table_size;
1499 return hash % hash_table_size;
1502 /* Return non-zero if exp1 is equivalent to exp2.
1503 ??? Borrowed from cse.c. Might want to remerge with cse.c. Later. */
1510 register enum rtx_code code;
1511 register const char *fmt;
1516 if (x == 0 || y == 0)
1519 code = GET_CODE (x);
1520 if (code != GET_CODE (y))
1523 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. */
1524 if (GET_MODE (x) != GET_MODE (y))
1534 return INTVAL (x) == INTVAL (y);
1537 return XEXP (x, 0) == XEXP (y, 0);
1540 return XSTR (x, 0) == XSTR (y, 0);
1543 return REGNO (x) == REGNO (y);
1546 /* Can't merge two expressions in different alias sets, since we can
1547 decide that the expression is transparent in a block when it isn't,
1548 due to it being set with the different alias set. */
1549 if (MEM_ALIAS_SET (x) != MEM_ALIAS_SET (y))
1553 /* For commutative operations, check both orders. */
1561 return ((expr_equiv_p (XEXP (x, 0), XEXP (y, 0))
1562 && expr_equiv_p (XEXP (x, 1), XEXP (y, 1)))
1563 || (expr_equiv_p (XEXP (x, 0), XEXP (y, 1))
1564 && expr_equiv_p (XEXP (x, 1), XEXP (y, 0))));
1570 /* Compare the elements. If any pair of corresponding elements
1571 fail to match, return 0 for the whole thing. */
1573 fmt = GET_RTX_FORMAT (code);
1574 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1579 if (! expr_equiv_p (XEXP (x, i), XEXP (y, i)))
1584 if (XVECLEN (x, i) != XVECLEN (y, i))
1586 for (j = 0; j < XVECLEN (x, i); j++)
1587 if (! expr_equiv_p (XVECEXP (x, i, j), XVECEXP (y, i, j)))
1592 if (strcmp (XSTR (x, i), XSTR (y, i)))
1597 if (XINT (x, i) != XINT (y, i))
1602 if (XWINT (x, i) != XWINT (y, i))
1617 /* Insert expression X in INSN in the hash table.
1618 If it is already present, record it as the last occurrence in INSN's
1621 MODE is the mode of the value X is being stored into.
1622 It is only used if X is a CONST_INT.
1624 ANTIC_P is non-zero if X is an anticipatable expression.
1625 AVAIL_P is non-zero if X is an available expression. */
1628 insert_expr_in_table (x, mode, insn, antic_p, avail_p)
1630 enum machine_mode mode;
1632 int antic_p, avail_p;
1634 int found, do_not_record_p;
1636 struct expr *cur_expr, *last_expr = NULL;
1637 struct occr *antic_occr, *avail_occr;
1638 struct occr *last_occr = NULL;
1640 hash = hash_expr (x, mode, &do_not_record_p, expr_hash_table_size);
1642 /* Do not insert expression in table if it contains volatile operands,
1643 or if hash_expr determines the expression is something we don't want
1644 to or can't handle. */
1645 if (do_not_record_p)
1648 cur_expr = expr_hash_table[hash];
1651 while (cur_expr && 0 == (found = expr_equiv_p (cur_expr->expr, x)))
1653 /* If the expression isn't found, save a pointer to the end of
1655 last_expr = cur_expr;
1656 cur_expr = cur_expr->next_same_hash;
1661 cur_expr = (struct expr *) gcse_alloc (sizeof (struct expr));
1662 bytes_used += sizeof (struct expr);
1663 if (expr_hash_table[hash] == NULL)
1664 /* This is the first pattern that hashed to this index. */
1665 expr_hash_table[hash] = cur_expr;
1667 /* Add EXPR to end of this hash chain. */
1668 last_expr->next_same_hash = cur_expr;
1670 /* Set the fields of the expr element. */
1672 cur_expr->bitmap_index = n_exprs++;
1673 cur_expr->next_same_hash = NULL;
1674 cur_expr->antic_occr = NULL;
1675 cur_expr->avail_occr = NULL;
1678 /* Now record the occurrence(s). */
1681 antic_occr = cur_expr->antic_occr;
1683 /* Search for another occurrence in the same basic block. */
1684 while (antic_occr && BLOCK_NUM (antic_occr->insn) != BLOCK_NUM (insn))
1686 /* If an occurrence isn't found, save a pointer to the end of
1688 last_occr = antic_occr;
1689 antic_occr = antic_occr->next;
1693 /* Found another instance of the expression in the same basic block.
1694 Prefer the currently recorded one. We want the first one in the
1695 block and the block is scanned from start to end. */
1696 ; /* nothing to do */
1699 /* First occurrence of this expression in this basic block. */
1700 antic_occr = (struct occr *) gcse_alloc (sizeof (struct occr));
1701 bytes_used += sizeof (struct occr);
1702 /* First occurrence of this expression in any block? */
1703 if (cur_expr->antic_occr == NULL)
1704 cur_expr->antic_occr = antic_occr;
1706 last_occr->next = antic_occr;
1708 antic_occr->insn = insn;
1709 antic_occr->next = NULL;
1715 avail_occr = cur_expr->avail_occr;
1717 /* Search for another occurrence in the same basic block. */
1718 while (avail_occr && BLOCK_NUM (avail_occr->insn) != BLOCK_NUM (insn))
1720 /* If an occurrence isn't found, save a pointer to the end of
1722 last_occr = avail_occr;
1723 avail_occr = avail_occr->next;
1727 /* Found another instance of the expression in the same basic block.
1728 Prefer this occurrence to the currently recorded one. We want
1729 the last one in the block and the block is scanned from start
1731 avail_occr->insn = insn;
1734 /* First occurrence of this expression in this basic block. */
1735 avail_occr = (struct occr *) gcse_alloc (sizeof (struct occr));
1736 bytes_used += sizeof (struct occr);
1738 /* First occurrence of this expression in any block? */
1739 if (cur_expr->avail_occr == NULL)
1740 cur_expr->avail_occr = avail_occr;
1742 last_occr->next = avail_occr;
1744 avail_occr->insn = insn;
1745 avail_occr->next = NULL;
1750 /* Insert pattern X in INSN in the hash table.
1751 X is a SET of a reg to either another reg or a constant.
1752 If it is already present, record it as the last occurrence in INSN's
1756 insert_set_in_table (x, insn)
1762 struct expr *cur_expr, *last_expr = NULL;
1763 struct occr *cur_occr, *last_occr = NULL;
1765 if (GET_CODE (x) != SET
1766 || GET_CODE (SET_DEST (x)) != REG)
1769 hash = hash_set (REGNO (SET_DEST (x)), set_hash_table_size);
1771 cur_expr = set_hash_table[hash];
1774 while (cur_expr && 0 == (found = expr_equiv_p (cur_expr->expr, x)))
1776 /* If the expression isn't found, save a pointer to the end of
1778 last_expr = cur_expr;
1779 cur_expr = cur_expr->next_same_hash;
1784 cur_expr = (struct expr *) gcse_alloc (sizeof (struct expr));
1785 bytes_used += sizeof (struct expr);
1786 if (set_hash_table[hash] == NULL)
1787 /* This is the first pattern that hashed to this index. */
1788 set_hash_table[hash] = cur_expr;
1790 /* Add EXPR to end of this hash chain. */
1791 last_expr->next_same_hash = cur_expr;
1793 /* Set the fields of the expr element.
1794 We must copy X because it can be modified when copy propagation is
1795 performed on its operands. */
1796 /* ??? Should this go in a different obstack? */
1797 cur_expr->expr = copy_rtx (x);
1798 cur_expr->bitmap_index = n_sets++;
1799 cur_expr->next_same_hash = NULL;
1800 cur_expr->antic_occr = NULL;
1801 cur_expr->avail_occr = NULL;
1804 /* Now record the occurrence. */
1805 cur_occr = cur_expr->avail_occr;
1807 /* Search for another occurrence in the same basic block. */
1808 while (cur_occr && BLOCK_NUM (cur_occr->insn) != BLOCK_NUM (insn))
1810 /* If an occurrence isn't found, save a pointer to the end of
1812 last_occr = cur_occr;
1813 cur_occr = cur_occr->next;
1817 /* Found another instance of the expression in the same basic block.
1818 Prefer this occurrence to the currently recorded one. We want the
1819 last one in the block and the block is scanned from start to end. */
1820 cur_occr->insn = insn;
1823 /* First occurrence of this expression in this basic block. */
1824 cur_occr = (struct occr *) gcse_alloc (sizeof (struct occr));
1825 bytes_used += sizeof (struct occr);
1827 /* First occurrence of this expression in any block? */
1828 if (cur_expr->avail_occr == NULL)
1829 cur_expr->avail_occr = cur_occr;
1831 last_occr->next = cur_occr;
1833 cur_occr->insn = insn;
1834 cur_occr->next = NULL;
1838 /* Scan pattern PAT of INSN and add an entry to the hash table. If SET_P is
1839 non-zero, this is for the assignment hash table, otherwise it is for the
1840 expression hash table. */
1843 hash_scan_set (pat, insn, set_p)
1847 rtx src = SET_SRC (pat);
1848 rtx dest = SET_DEST (pat);
1850 if (GET_CODE (src) == CALL)
1851 hash_scan_call (src, insn);
1853 if (GET_CODE (dest) == REG)
1855 int regno = REGNO (dest);
1858 /* Only record sets of pseudo-regs in the hash table. */
1860 && regno >= FIRST_PSEUDO_REGISTER
1861 /* Don't GCSE something if we can't do a reg/reg copy. */
1862 && can_copy_p [GET_MODE (dest)]
1863 /* Is SET_SRC something we want to gcse? */
1864 && want_to_gcse_p (src))
1866 /* An expression is not anticipatable if its operands are
1867 modified before this insn. */
1868 int antic_p = oprs_anticipatable_p (src, insn);
1869 /* An expression is not available if its operands are
1870 subsequently modified, including this insn. */
1871 int avail_p = oprs_available_p (src, insn);
1873 insert_expr_in_table (src, GET_MODE (dest), insn, antic_p, avail_p);
1876 /* Record sets for constant/copy propagation. */
1878 && regno >= FIRST_PSEUDO_REGISTER
1879 && ((GET_CODE (src) == REG
1880 && REGNO (src) >= FIRST_PSEUDO_REGISTER
1881 && can_copy_p [GET_MODE (dest)])
1882 || GET_CODE (src) == CONST_INT
1883 || GET_CODE (src) == SYMBOL_REF
1884 || GET_CODE (src) == CONST_DOUBLE)
1885 /* A copy is not available if its src or dest is subsequently
1886 modified. Here we want to search from INSN+1 on, but
1887 oprs_available_p searches from INSN on. */
1888 && (insn == BLOCK_END (BLOCK_NUM (insn))
1889 || ((tmp = next_nonnote_insn (insn)) != NULL_RTX
1890 && oprs_available_p (pat, tmp))))
1891 insert_set_in_table (pat, insn);
1896 hash_scan_clobber (x, insn)
1897 rtx x ATTRIBUTE_UNUSED, insn ATTRIBUTE_UNUSED;
1899 /* Currently nothing to do. */
1903 hash_scan_call (x, insn)
1904 rtx x ATTRIBUTE_UNUSED, insn ATTRIBUTE_UNUSED;
1906 /* Currently nothing to do. */
1909 /* Process INSN and add hash table entries as appropriate.
1911 Only available expressions that set a single pseudo-reg are recorded.
1913 Single sets in a PARALLEL could be handled, but it's an extra complication
1914 that isn't dealt with right now. The trick is handling the CLOBBERs that
1915 are also in the PARALLEL. Later.
1917 If SET_P is non-zero, this is for the assignment hash table,
1918 otherwise it is for the expression hash table.
1919 If IN_LIBCALL_BLOCK nonzero, we are in a libcall block, and should
1920 not record any expressions. */
1923 hash_scan_insn (insn, set_p, in_libcall_block)
1926 int in_libcall_block;
1928 rtx pat = PATTERN (insn);
1931 /* Pick out the sets of INSN and for other forms of instructions record
1932 what's been modified. */
1934 if (GET_CODE (pat) == SET && ! in_libcall_block)
1936 /* Ignore obvious no-ops. */
1937 if (SET_SRC (pat) != SET_DEST (pat))
1938 hash_scan_set (pat, insn, set_p);
1940 else if (GET_CODE (pat) == PARALLEL)
1941 for (i = 0; i < XVECLEN (pat, 0); i++)
1943 rtx x = XVECEXP (pat, 0, i);
1945 if (GET_CODE (x) == SET)
1947 if (GET_CODE (SET_SRC (x)) == CALL)
1948 hash_scan_call (SET_SRC (x), insn);
1950 else if (GET_CODE (x) == CLOBBER)
1951 hash_scan_clobber (x, insn);
1952 else if (GET_CODE (x) == CALL)
1953 hash_scan_call (x, insn);
1956 else if (GET_CODE (pat) == CLOBBER)
1957 hash_scan_clobber (pat, insn);
1958 else if (GET_CODE (pat) == CALL)
1959 hash_scan_call (pat, insn);
1963 dump_hash_table (file, name, table, table_size, total_size)
1966 struct expr **table;
1967 int table_size, total_size;
1970 /* Flattened out table, so it's printed in proper order. */
1971 struct expr **flat_table;
1972 unsigned int *hash_val;
1976 = (struct expr **) xcalloc (total_size, sizeof (struct expr *));
1977 hash_val = (unsigned int *) xmalloc (total_size * sizeof (unsigned int));
1979 for (i = 0; i < table_size; i++)
1980 for (expr = table[i]; expr != NULL; expr = expr->next_same_hash)
1982 flat_table[expr->bitmap_index] = expr;
1983 hash_val[expr->bitmap_index] = i;
1986 fprintf (file, "%s hash table (%d buckets, %d entries)\n",
1987 name, table_size, total_size);
1989 for (i = 0; i < total_size; i++)
1990 if (flat_table[i] != 0)
1992 expr = flat_table[i];
1993 fprintf (file, "Index %d (hash value %d)\n ",
1994 expr->bitmap_index, hash_val[i]);
1995 print_rtl (file, expr->expr);
1996 fprintf (file, "\n");
1999 fprintf (file, "\n");
2005 /* Record register first/last/block set information for REGNO in INSN.
2007 reg_first_set records the first place in the block where the register
2008 is set and is used to compute "anticipatability".
2010 reg_last_set records the last place in the block where the register
2011 is set and is used to compute "availability".
2013 reg_set_in_block records whether the register is set in the block
2014 and is used to compute "transparency". */
2017 record_last_reg_set_info (insn, regno)
2021 if (reg_first_set[regno] == NEVER_SET)
2022 reg_first_set[regno] = INSN_CUID (insn);
2024 reg_last_set[regno] = INSN_CUID (insn);
2025 SET_BIT (reg_set_in_block[BLOCK_NUM (insn)], regno);
2028 /* Record memory first/last/block set information for INSN. */
2031 record_last_mem_set_info (insn)
2034 if (mem_first_set == NEVER_SET)
2035 mem_first_set = INSN_CUID (insn);
2037 mem_last_set = INSN_CUID (insn);
2038 mem_set_in_block[BLOCK_NUM (insn)] = 1;
2041 /* Called from compute_hash_table via note_stores to handle one
2042 SET or CLOBBER in an insn. DATA is really the instruction in which
2043 the SET is taking place. */
2046 record_last_set_info (dest, setter, data)
2047 rtx dest, setter ATTRIBUTE_UNUSED;
2050 rtx last_set_insn = (rtx) data;
2052 if (GET_CODE (dest) == SUBREG)
2053 dest = SUBREG_REG (dest);
2055 if (GET_CODE (dest) == REG)
2056 record_last_reg_set_info (last_set_insn, REGNO (dest));
2057 else if (GET_CODE (dest) == MEM
2058 /* Ignore pushes, they clobber nothing. */
2059 && ! push_operand (dest, GET_MODE (dest)))
2060 record_last_mem_set_info (last_set_insn);
2063 /* Top level function to create an expression or assignment hash table.
2065 Expression entries are placed in the hash table if
2066 - they are of the form (set (pseudo-reg) src),
2067 - src is something we want to perform GCSE on,
2068 - none of the operands are subsequently modified in the block
2070 Assignment entries are placed in the hash table if
2071 - they are of the form (set (pseudo-reg) src),
2072 - src is something we want to perform const/copy propagation on,
2073 - none of the operands or target are subsequently modified in the block
2075 Currently src must be a pseudo-reg or a const_int.
2077 F is the first insn.
2078 SET_P is non-zero for computing the assignment hash table. */
2081 compute_hash_table (set_p)
2086 /* While we compute the hash table we also compute a bit array of which
2087 registers are set in which blocks.
2088 We also compute which blocks set memory, in the absence of aliasing
2089 support [which is TODO].
2090 ??? This isn't needed during const/copy propagation, but it's cheap to
2092 sbitmap_vector_zero (reg_set_in_block, n_basic_blocks);
2093 bzero ((char *) mem_set_in_block, n_basic_blocks);
2095 /* Some working arrays used to track first and last set in each block. */
2096 /* ??? One could use alloca here, but at some size a threshold is crossed
2097 beyond which one should use malloc. Are we at that threshold here? */
2098 reg_first_set = (int *) gmalloc (max_gcse_regno * sizeof (int));
2099 reg_last_set = (int *) gmalloc (max_gcse_regno * sizeof (int));
2101 for (bb = 0; bb < n_basic_blocks; bb++)
2105 int in_libcall_block;
2108 /* First pass over the instructions records information used to
2109 determine when registers and memory are first and last set.
2110 ??? The mem_set_in_block and hard-reg reg_set_in_block computation
2111 could be moved to compute_sets since they currently don't change. */
2113 for (i = 0; i < max_gcse_regno; i++)
2114 reg_first_set[i] = reg_last_set[i] = NEVER_SET;
2116 mem_first_set = NEVER_SET;
2117 mem_last_set = NEVER_SET;
2119 for (insn = BLOCK_HEAD (bb);
2120 insn && insn != NEXT_INSN (BLOCK_END (bb));
2121 insn = NEXT_INSN (insn))
2123 #ifdef NON_SAVING_SETJMP
2124 if (NON_SAVING_SETJMP && GET_CODE (insn) == NOTE
2125 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_SETJMP)
2127 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
2128 record_last_reg_set_info (insn, regno);
2133 if (GET_RTX_CLASS (GET_CODE (insn)) != 'i')
2136 if (GET_CODE (insn) == CALL_INSN)
2138 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
2139 if ((call_used_regs[regno]
2140 && regno != STACK_POINTER_REGNUM
2141 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2142 && regno != HARD_FRAME_POINTER_REGNUM
2144 #if ARG_POINTER_REGNUM != FRAME_POINTER_REGNUM
2145 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2147 #if defined (PIC_OFFSET_TABLE_REGNUM) && !defined (PIC_OFFSET_TABLE_REG_CALL_CLOBBERED)
2148 && ! (regno == PIC_OFFSET_TABLE_REGNUM && flag_pic)
2151 && regno != FRAME_POINTER_REGNUM)
2152 || global_regs[regno])
2153 record_last_reg_set_info (insn, regno);
2155 if (! CONST_CALL_P (insn))
2156 record_last_mem_set_info (insn);
2159 note_stores (PATTERN (insn), record_last_set_info, insn);
2162 /* The next pass builds the hash table. */
2164 for (insn = BLOCK_HEAD (bb), in_libcall_block = 0;
2165 insn && insn != NEXT_INSN (BLOCK_END (bb));
2166 insn = NEXT_INSN (insn))
2167 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
2169 if (find_reg_note (insn, REG_LIBCALL, NULL_RTX))
2170 in_libcall_block = 1;
2171 else if (find_reg_note (insn, REG_RETVAL, NULL_RTX))
2172 in_libcall_block = 0;
2173 hash_scan_insn (insn, set_p, in_libcall_block);
2177 free (reg_first_set);
2178 free (reg_last_set);
2180 /* Catch bugs early. */
2181 reg_first_set = reg_last_set = 0;
2184 /* Allocate space for the set hash table.
2185 N_INSNS is the number of instructions in the function.
2186 It is used to determine the number of buckets to use. */
2189 alloc_set_hash_table (n_insns)
2194 set_hash_table_size = n_insns / 4;
2195 if (set_hash_table_size < 11)
2196 set_hash_table_size = 11;
2198 /* Attempt to maintain efficient use of hash table.
2199 Making it an odd number is simplest for now.
2200 ??? Later take some measurements. */
2201 set_hash_table_size |= 1;
2202 n = set_hash_table_size * sizeof (struct expr *);
2203 set_hash_table = (struct expr **) gmalloc (n);
2206 /* Free things allocated by alloc_set_hash_table. */
2209 free_set_hash_table ()
2211 free (set_hash_table);
2214 /* Compute the hash table for doing copy/const propagation. */
2217 compute_set_hash_table ()
2219 /* Initialize count of number of entries in hash table. */
2221 bzero ((char *) set_hash_table,
2222 set_hash_table_size * sizeof (struct expr *));
2224 compute_hash_table (1);
2227 /* Allocate space for the expression hash table.
2228 N_INSNS is the number of instructions in the function.
2229 It is used to determine the number of buckets to use. */
2232 alloc_expr_hash_table (n_insns)
2233 unsigned int n_insns;
2237 expr_hash_table_size = n_insns / 2;
2238 /* Make sure the amount is usable. */
2239 if (expr_hash_table_size < 11)
2240 expr_hash_table_size = 11;
2242 /* Attempt to maintain efficient use of hash table.
2243 Making it an odd number is simplest for now.
2244 ??? Later take some measurements. */
2245 expr_hash_table_size |= 1;
2246 n = expr_hash_table_size * sizeof (struct expr *);
2247 expr_hash_table = (struct expr **) gmalloc (n);
2250 /* Free things allocated by alloc_expr_hash_table. */
2253 free_expr_hash_table ()
2255 free (expr_hash_table);
2258 /* Compute the hash table for doing GCSE. */
2261 compute_expr_hash_table ()
2263 /* Initialize count of number of entries in hash table. */
2265 bzero ((char *) expr_hash_table,
2266 expr_hash_table_size * sizeof (struct expr *));
2268 compute_hash_table (0);
2271 /* Expression tracking support. */
2273 /* Lookup pattern PAT in the expression table.
2274 The result is a pointer to the table entry, or NULL if not found. */
2276 static struct expr *
2280 int do_not_record_p;
2281 unsigned int hash = hash_expr (pat, GET_MODE (pat), &do_not_record_p,
2282 expr_hash_table_size);
2285 if (do_not_record_p)
2288 expr = expr_hash_table[hash];
2290 while (expr && ! expr_equiv_p (expr->expr, pat))
2291 expr = expr->next_same_hash;
2296 /* Lookup REGNO in the set table. If PAT is non-NULL look for the entry that
2297 matches it, otherwise return the first entry for REGNO. The result is a
2298 pointer to the table entry, or NULL if not found. */
2300 static struct expr *
2301 lookup_set (regno, pat)
2305 unsigned int hash = hash_set (regno, set_hash_table_size);
2308 expr = set_hash_table[hash];
2312 while (expr && ! expr_equiv_p (expr->expr, pat))
2313 expr = expr->next_same_hash;
2317 while (expr && REGNO (SET_DEST (expr->expr)) != regno)
2318 expr = expr->next_same_hash;
2324 /* Return the next entry for REGNO in list EXPR. */
2326 static struct expr *
2327 next_set (regno, expr)
2332 expr = expr->next_same_hash;
2333 while (expr && REGNO (SET_DEST (expr->expr)) != regno);
2338 /* Reset tables used to keep track of what's still available [since the
2339 start of the block]. */
2342 reset_opr_set_tables ()
2344 /* Maintain a bitmap of which regs have been set since beginning of
2346 sbitmap_zero (reg_set_bitmap);
2348 /* Also keep a record of the last instruction to modify memory.
2349 For now this is very trivial, we only record whether any memory
2350 location has been modified. */
2354 /* Return non-zero if the operands of X are not set before INSN in
2355 INSN's basic block. */
2358 oprs_not_set_p (x, insn)
2368 code = GET_CODE (x);
2383 if (mem_last_set != 0)
2386 return oprs_not_set_p (XEXP (x, 0), insn);
2389 return ! TEST_BIT (reg_set_bitmap, REGNO (x));
2395 for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
2399 /* If we are about to do the last recursive call
2400 needed at this level, change it into iteration.
2401 This function is called enough to be worth it. */
2403 return oprs_not_set_p (XEXP (x, i), insn);
2405 if (! oprs_not_set_p (XEXP (x, i), insn))
2408 else if (fmt[i] == 'E')
2409 for (j = 0; j < XVECLEN (x, i); j++)
2410 if (! oprs_not_set_p (XVECEXP (x, i, j), insn))
2417 /* Mark things set by a CALL. */
2423 mem_last_set = INSN_CUID (insn);
2426 /* Mark things set by a SET. */
2429 mark_set (pat, insn)
2432 rtx dest = SET_DEST (pat);
2434 while (GET_CODE (dest) == SUBREG
2435 || GET_CODE (dest) == ZERO_EXTRACT
2436 || GET_CODE (dest) == SIGN_EXTRACT
2437 || GET_CODE (dest) == STRICT_LOW_PART)
2438 dest = XEXP (dest, 0);
2440 if (GET_CODE (dest) == REG)
2441 SET_BIT (reg_set_bitmap, REGNO (dest));
2442 else if (GET_CODE (dest) == MEM)
2443 mem_last_set = INSN_CUID (insn);
2445 if (GET_CODE (SET_SRC (pat)) == CALL)
2449 /* Record things set by a CLOBBER. */
2452 mark_clobber (pat, insn)
2455 rtx clob = XEXP (pat, 0);
2457 while (GET_CODE (clob) == SUBREG || GET_CODE (clob) == STRICT_LOW_PART)
2458 clob = XEXP (clob, 0);
2460 if (GET_CODE (clob) == REG)
2461 SET_BIT (reg_set_bitmap, REGNO (clob));
2463 mem_last_set = INSN_CUID (insn);
2466 /* Record things set by INSN.
2467 This data is used by oprs_not_set_p. */
2470 mark_oprs_set (insn)
2473 rtx pat = PATTERN (insn);
2476 if (GET_CODE (pat) == SET)
2477 mark_set (pat, insn);
2478 else if (GET_CODE (pat) == PARALLEL)
2479 for (i = 0; i < XVECLEN (pat, 0); i++)
2481 rtx x = XVECEXP (pat, 0, i);
2483 if (GET_CODE (x) == SET)
2485 else if (GET_CODE (x) == CLOBBER)
2486 mark_clobber (x, insn);
2487 else if (GET_CODE (x) == CALL)
2491 else if (GET_CODE (pat) == CLOBBER)
2492 mark_clobber (pat, insn);
2493 else if (GET_CODE (pat) == CALL)
2498 /* Classic GCSE reaching definition support. */
2500 /* Allocate reaching def variables. */
2503 alloc_rd_mem (n_blocks, n_insns)
2504 int n_blocks, n_insns;
2506 rd_kill = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
2507 sbitmap_vector_zero (rd_kill, n_basic_blocks);
2509 rd_gen = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
2510 sbitmap_vector_zero (rd_gen, n_basic_blocks);
2512 reaching_defs = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
2513 sbitmap_vector_zero (reaching_defs, n_basic_blocks);
2515 rd_out = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
2516 sbitmap_vector_zero (rd_out, n_basic_blocks);
2519 /* Free reaching def variables. */
2526 free (reaching_defs);
2530 /* Add INSN to the kills of BB. REGNO, set in BB, is killed by INSN. */
2533 handle_rd_kill_set (insn, regno, bb)
2537 struct reg_set *this_reg;
2539 for (this_reg = reg_set_table[regno]; this_reg; this_reg = this_reg ->next)
2540 if (BLOCK_NUM (this_reg->insn) != BLOCK_NUM (insn))
2541 SET_BIT (rd_kill[bb], INSN_CUID (this_reg->insn));
2544 /* Compute the set of kill's for reaching definitions. */
2553 For each set bit in `gen' of the block (i.e each insn which
2554 generates a definition in the block)
2555 Call the reg set by the insn corresponding to that bit regx
2556 Look at the linked list starting at reg_set_table[regx]
2557 For each setting of regx in the linked list, which is not in
2559 Set the bit in `kill' corresponding to that insn. */
2560 for (bb = 0; bb < n_basic_blocks; bb++)
2561 for (cuid = 0; cuid < max_cuid; cuid++)
2562 if (TEST_BIT (rd_gen[bb], cuid))
2564 rtx insn = CUID_INSN (cuid);
2565 rtx pat = PATTERN (insn);
2567 if (GET_CODE (insn) == CALL_INSN)
2569 for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
2571 if ((call_used_regs[regno]
2572 && regno != STACK_POINTER_REGNUM
2573 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2574 && regno != HARD_FRAME_POINTER_REGNUM
2576 #if ARG_POINTER_REGNUM != FRAME_POINTER_REGNUM
2577 && ! (regno == ARG_POINTER_REGNUM
2578 && fixed_regs[regno])
2580 #if defined (PIC_OFFSET_TABLE_REGNUM) && !defined (PIC_OFFSET_TABLE_REG_CALL_CLOBBERED)
2581 && ! (regno == PIC_OFFSET_TABLE_REGNUM && flag_pic)
2583 && regno != FRAME_POINTER_REGNUM)
2584 || global_regs[regno])
2585 handle_rd_kill_set (insn, regno, bb);
2589 if (GET_CODE (pat) == PARALLEL)
2591 for (i = XVECLEN (pat, 0) - 1; i >= 0; i--)
2593 enum rtx_code code = GET_CODE (XVECEXP (pat, 0, i));
2595 if ((code == SET || code == CLOBBER)
2596 && GET_CODE (XEXP (XVECEXP (pat, 0, i), 0)) == REG)
2597 handle_rd_kill_set (insn,
2598 REGNO (XEXP (XVECEXP (pat, 0, i), 0)),
2602 else if (GET_CODE (pat) == SET && GET_CODE (SET_DEST (pat)) == REG)
2603 /* Each setting of this register outside of this block
2604 must be marked in the set of kills in this block. */
2605 handle_rd_kill_set (insn, REGNO (SET_DEST (pat)), bb);
2609 /* Compute the reaching definitions as in
2610 Compilers Principles, Techniques, and Tools. Aho, Sethi, Ullman,
2611 Chapter 10. It is the same algorithm as used for computing available
2612 expressions but applied to the gens and kills of reaching definitions. */
2617 int bb, changed, passes;
2619 for (bb = 0; bb < n_basic_blocks; bb++)
2620 sbitmap_copy (rd_out[bb] /*dst*/, rd_gen[bb] /*src*/);
2627 for (bb = 0; bb < n_basic_blocks; bb++)
2629 sbitmap_union_of_preds (reaching_defs[bb], rd_out, bb);
2630 changed |= sbitmap_union_of_diff (rd_out[bb], rd_gen[bb],
2631 reaching_defs[bb], rd_kill[bb]);
2637 fprintf (gcse_file, "reaching def computation: %d passes\n", passes);
2640 /* Classic GCSE available expression support. */
2642 /* Allocate memory for available expression computation. */
2645 alloc_avail_expr_mem (n_blocks, n_exprs)
2646 int n_blocks, n_exprs;
2648 ae_kill = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
2649 sbitmap_vector_zero (ae_kill, n_basic_blocks);
2651 ae_gen = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
2652 sbitmap_vector_zero (ae_gen, n_basic_blocks);
2654 ae_in = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
2655 sbitmap_vector_zero (ae_in, n_basic_blocks);
2657 ae_out = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
2658 sbitmap_vector_zero (ae_out, n_basic_blocks);
2662 free_avail_expr_mem ()
2670 /* Compute the set of available expressions generated in each basic block. */
2679 /* For each recorded occurrence of each expression, set ae_gen[bb][expr].
2680 This is all we have to do because an expression is not recorded if it
2681 is not available, and the only expressions we want to work with are the
2682 ones that are recorded. */
2683 for (i = 0; i < expr_hash_table_size; i++)
2684 for (expr = expr_hash_table[i]; expr != 0; expr = expr->next_same_hash)
2685 for (occr = expr->avail_occr; occr != 0; occr = occr->next)
2686 SET_BIT (ae_gen[BLOCK_NUM (occr->insn)], expr->bitmap_index);
2689 /* Return non-zero if expression X is killed in BB. */
2692 expr_killed_p (x, bb)
2703 code = GET_CODE (x);
2707 return TEST_BIT (reg_set_in_block[bb], REGNO (x));
2710 if (mem_set_in_block[bb])
2713 return expr_killed_p (XEXP (x, 0), bb);
2730 for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
2734 /* If we are about to do the last recursive call
2735 needed at this level, change it into iteration.
2736 This function is called enough to be worth it. */
2738 return expr_killed_p (XEXP (x, i), bb);
2739 else if (expr_killed_p (XEXP (x, i), bb))
2742 else if (fmt[i] == 'E')
2743 for (j = 0; j < XVECLEN (x, i); j++)
2744 if (expr_killed_p (XVECEXP (x, i, j), bb))
2751 /* Compute the set of available expressions killed in each basic block. */
2754 compute_ae_kill (ae_gen, ae_kill)
2755 sbitmap *ae_gen, *ae_kill;
2761 for (bb = 0; bb < n_basic_blocks; bb++)
2762 for (i = 0; i < expr_hash_table_size; i++)
2763 for (expr = expr_hash_table[i]; expr; expr = expr->next_same_hash)
2765 /* Skip EXPR if generated in this block. */
2766 if (TEST_BIT (ae_gen[bb], expr->bitmap_index))
2769 if (expr_killed_p (expr->expr, bb))
2770 SET_BIT (ae_kill[bb], expr->bitmap_index);
2774 /* Actually perform the Classic GCSE optimizations. */
2776 /* Return non-zero if occurrence OCCR of expression EXPR reaches block BB.
2778 CHECK_SELF_LOOP is non-zero if we should consider a block reaching itself
2779 as a positive reach. We want to do this when there are two computations
2780 of the expression in the block.
2782 VISITED is a pointer to a working buffer for tracking which BB's have
2783 been visited. It is NULL for the top-level call.
2785 We treat reaching expressions that go through blocks containing the same
2786 reaching expression as "not reaching". E.g. if EXPR is generated in blocks
2787 2 and 3, INSN is in block 4, and 2->3->4, we treat the expression in block
2788 2 as not reaching. The intent is to improve the probability of finding
2789 only one reaching expression and to reduce register lifetimes by picking
2790 the closest such expression. */
2793 expr_reaches_here_p_work (occr, expr, bb, check_self_loop, visited)
2797 int check_self_loop;
2802 for (pred = BASIC_BLOCK(bb)->pred; pred != NULL; pred = pred->pred_next)
2804 int pred_bb = pred->src->index;
2806 if (visited[pred_bb])
2807 /* This predecessor has already been visited. Nothing to do. */
2809 else if (pred_bb == bb)
2811 /* BB loops on itself. */
2813 && TEST_BIT (ae_gen[pred_bb], expr->bitmap_index)
2814 && BLOCK_NUM (occr->insn) == pred_bb)
2817 visited[pred_bb] = 1;
2820 /* Ignore this predecessor if it kills the expression. */
2821 else if (TEST_BIT (ae_kill[pred_bb], expr->bitmap_index))
2822 visited[pred_bb] = 1;
2824 /* Does this predecessor generate this expression? */
2825 else if (TEST_BIT (ae_gen[pred_bb], expr->bitmap_index))
2827 /* Is this the occurrence we're looking for?
2828 Note that there's only one generating occurrence per block
2829 so we just need to check the block number. */
2830 if (BLOCK_NUM (occr->insn) == pred_bb)
2833 visited[pred_bb] = 1;
2836 /* Neither gen nor kill. */
2839 visited[pred_bb] = 1;
2840 if (expr_reaches_here_p_work (occr, expr, pred_bb, check_self_loop,
2847 /* All paths have been checked. */
2851 /* This wrapper for expr_reaches_here_p_work() is to ensure that any
2852 memory allocated for that function is returned. */
2855 expr_reaches_here_p (occr, expr, bb, check_self_loop)
2859 int check_self_loop;
2862 char *visited = (char *) xcalloc (n_basic_blocks, 1);
2864 rval = expr_reaches_here_p_work (occr, expr, bb, check_self_loop, visited);
2870 /* Return the instruction that computes EXPR that reaches INSN's basic block.
2871 If there is more than one such instruction, return NULL.
2873 Called only by handle_avail_expr. */
2876 computing_insn (expr, insn)
2880 int bb = BLOCK_NUM (insn);
2882 if (expr->avail_occr->next == NULL)
2884 if (BLOCK_NUM (expr->avail_occr->insn) == bb)
2885 /* The available expression is actually itself
2886 (i.e. a loop in the flow graph) so do nothing. */
2889 /* (FIXME) Case that we found a pattern that was created by
2890 a substitution that took place. */
2891 return expr->avail_occr->insn;
2895 /* Pattern is computed more than once.
2896 Search backwards from this insn to see how many of these
2897 computations actually reach this insn. */
2899 rtx insn_computes_expr = NULL;
2902 for (occr = expr->avail_occr; occr != NULL; occr = occr->next)
2904 if (BLOCK_NUM (occr->insn) == bb)
2906 /* The expression is generated in this block.
2907 The only time we care about this is when the expression
2908 is generated later in the block [and thus there's a loop].
2909 We let the normal cse pass handle the other cases. */
2910 if (INSN_CUID (insn) < INSN_CUID (occr->insn)
2911 && expr_reaches_here_p (occr, expr, bb, 1))
2917 insn_computes_expr = occr->insn;
2920 else if (expr_reaches_here_p (occr, expr, bb, 0))
2926 insn_computes_expr = occr->insn;
2930 if (insn_computes_expr == NULL)
2933 return insn_computes_expr;
2937 /* Return non-zero if the definition in DEF_INSN can reach INSN.
2938 Only called by can_disregard_other_sets. */
2941 def_reaches_here_p (insn, def_insn)
2946 if (TEST_BIT (reaching_defs[BLOCK_NUM (insn)], INSN_CUID (def_insn)))
2949 if (BLOCK_NUM (insn) == BLOCK_NUM (def_insn))
2951 if (INSN_CUID (def_insn) < INSN_CUID (insn))
2953 if (GET_CODE (PATTERN (def_insn)) == PARALLEL)
2955 else if (GET_CODE (PATTERN (def_insn)) == CLOBBER)
2956 reg = XEXP (PATTERN (def_insn), 0);
2957 else if (GET_CODE (PATTERN (def_insn)) == SET)
2958 reg = SET_DEST (PATTERN (def_insn));
2962 return ! reg_set_between_p (reg, NEXT_INSN (def_insn), insn);
2971 /* Return non-zero if *ADDR_THIS_REG can only have one value at INSN. The
2972 value returned is the number of definitions that reach INSN. Returning a
2973 value of zero means that [maybe] more than one definition reaches INSN and
2974 the caller can't perform whatever optimization it is trying. i.e. it is
2975 always safe to return zero. */
2978 can_disregard_other_sets (addr_this_reg, insn, for_combine)
2979 struct reg_set **addr_this_reg;
2983 int number_of_reaching_defs = 0;
2984 struct reg_set *this_reg;
2986 for (this_reg = *addr_this_reg; this_reg != 0; this_reg = this_reg->next)
2987 if (def_reaches_here_p (insn, this_reg->insn))
2989 number_of_reaching_defs++;
2990 /* Ignore parallels for now. */
2991 if (GET_CODE (PATTERN (this_reg->insn)) == PARALLEL)
2995 && (GET_CODE (PATTERN (this_reg->insn)) == CLOBBER
2996 || ! rtx_equal_p (SET_SRC (PATTERN (this_reg->insn)),
2997 SET_SRC (PATTERN (insn)))))
2998 /* A setting of the reg to a different value reaches INSN. */
3001 if (number_of_reaching_defs > 1)
3003 /* If in this setting the value the register is being set to is
3004 equal to the previous value the register was set to and this
3005 setting reaches the insn we are trying to do the substitution
3006 on then we are ok. */
3007 if (GET_CODE (PATTERN (this_reg->insn)) == CLOBBER)
3009 else if (! rtx_equal_p (SET_SRC (PATTERN (this_reg->insn)),
3010 SET_SRC (PATTERN (insn))))
3014 *addr_this_reg = this_reg;
3017 return number_of_reaching_defs;
3020 /* Expression computed by insn is available and the substitution is legal,
3021 so try to perform the substitution.
3023 The result is non-zero if any changes were made. */
3026 handle_avail_expr (insn, expr)
3030 rtx pat, insn_computes_expr;
3032 struct reg_set *this_reg;
3033 int found_setting, use_src;
3036 /* We only handle the case where one computation of the expression
3037 reaches this instruction. */
3038 insn_computes_expr = computing_insn (expr, insn);
3039 if (insn_computes_expr == NULL)
3045 /* At this point we know only one computation of EXPR outside of this
3046 block reaches this insn. Now try to find a register that the
3047 expression is computed into. */
3048 if (GET_CODE (SET_SRC (PATTERN (insn_computes_expr))) == REG)
3050 /* This is the case when the available expression that reaches
3051 here has already been handled as an available expression. */
3052 unsigned int regnum_for_replacing
3053 = REGNO (SET_SRC (PATTERN (insn_computes_expr)));
3055 /* If the register was created by GCSE we can't use `reg_set_table',
3056 however we know it's set only once. */
3057 if (regnum_for_replacing >= max_gcse_regno
3058 /* If the register the expression is computed into is set only once,
3059 or only one set reaches this insn, we can use it. */
3060 || (((this_reg = reg_set_table[regnum_for_replacing]),
3061 this_reg->next == NULL)
3062 || can_disregard_other_sets (&this_reg, insn, 0)))
3071 unsigned int regnum_for_replacing
3072 = REGNO (SET_DEST (PATTERN (insn_computes_expr)));
3074 /* This shouldn't happen. */
3075 if (regnum_for_replacing >= max_gcse_regno)
3078 this_reg = reg_set_table[regnum_for_replacing];
3080 /* If the register the expression is computed into is set only once,
3081 or only one set reaches this insn, use it. */
3082 if (this_reg->next == NULL
3083 || can_disregard_other_sets (&this_reg, insn, 0))
3089 pat = PATTERN (insn);
3091 to = SET_SRC (PATTERN (insn_computes_expr));
3093 to = SET_DEST (PATTERN (insn_computes_expr));
3094 changed = validate_change (insn, &SET_SRC (pat), to, 0);
3096 /* We should be able to ignore the return code from validate_change but
3097 to play it safe we check. */
3101 if (gcse_file != NULL)
3103 fprintf (gcse_file, "GCSE: Replacing the source in insn %d with",
3105 fprintf (gcse_file, " reg %d %s insn %d\n",
3106 REGNO (to), use_src ? "from" : "set in",
3107 INSN_UID (insn_computes_expr));
3112 /* The register that the expr is computed into is set more than once. */
3113 else if (1 /*expensive_op(this_pattrn->op) && do_expensive_gcse)*/)
3115 /* Insert an insn after insnx that copies the reg set in insnx
3116 into a new pseudo register call this new register REGN.
3117 From insnb until end of basic block or until REGB is set
3118 replace all uses of REGB with REGN. */
3121 to = gen_reg_rtx (GET_MODE (SET_DEST (PATTERN (insn_computes_expr))));
3123 /* Generate the new insn. */
3124 /* ??? If the change fails, we return 0, even though we created
3125 an insn. I think this is ok. */
3127 = emit_insn_after (gen_rtx_SET (VOIDmode, to,
3129 (insn_computes_expr))),
3130 insn_computes_expr);
3132 /* Keep block number table up to date. */
3133 set_block_num (new_insn, BLOCK_NUM (insn_computes_expr));
3135 /* Keep register set table up to date. */
3136 record_one_set (REGNO (to), new_insn);
3138 gcse_create_count++;
3139 if (gcse_file != NULL)
3141 fprintf (gcse_file, "GCSE: Creating insn %d to copy value of reg %d",
3142 INSN_UID (NEXT_INSN (insn_computes_expr)),
3143 REGNO (SET_SRC (PATTERN (NEXT_INSN (insn_computes_expr)))));
3144 fprintf (gcse_file, ", computed in insn %d,\n",
3145 INSN_UID (insn_computes_expr));
3146 fprintf (gcse_file, " into newly allocated reg %d\n",
3150 pat = PATTERN (insn);
3152 /* Do register replacement for INSN. */
3153 changed = validate_change (insn, &SET_SRC (pat),
3155 (NEXT_INSN (insn_computes_expr))),
3158 /* We should be able to ignore the return code from validate_change but
3159 to play it safe we check. */
3163 if (gcse_file != NULL)
3166 "GCSE: Replacing the source in insn %d with reg %d ",
3168 REGNO (SET_DEST (PATTERN (NEXT_INSN
3169 (insn_computes_expr)))));
3170 fprintf (gcse_file, "set in insn %d\n",
3171 INSN_UID (insn_computes_expr));
3179 /* Perform classic GCSE. This is called by one_classic_gcse_pass after all
3180 the dataflow analysis has been done.
3182 The result is non-zero if a change was made. */
3190 /* Note we start at block 1. */
3193 for (bb = 1; bb < n_basic_blocks; bb++)
3195 /* Reset tables used to keep track of what's still valid [since the
3196 start of the block]. */
3197 reset_opr_set_tables ();
3199 for (insn = BLOCK_HEAD (bb);
3200 insn != NULL && insn != NEXT_INSN (BLOCK_END (bb));
3201 insn = NEXT_INSN (insn))
3203 /* Is insn of form (set (pseudo-reg) ...)? */
3204 if (GET_CODE (insn) == INSN
3205 && GET_CODE (PATTERN (insn)) == SET
3206 && GET_CODE (SET_DEST (PATTERN (insn))) == REG
3207 && REGNO (SET_DEST (PATTERN (insn))) >= FIRST_PSEUDO_REGISTER)
3209 rtx pat = PATTERN (insn);
3210 rtx src = SET_SRC (pat);
3213 if (want_to_gcse_p (src)
3214 /* Is the expression recorded? */
3215 && ((expr = lookup_expr (src)) != NULL)
3216 /* Is the expression available [at the start of the
3218 && TEST_BIT (ae_in[bb], expr->bitmap_index)
3219 /* Are the operands unchanged since the start of the
3221 && oprs_not_set_p (src, insn))
3222 changed |= handle_avail_expr (insn, expr);
3225 /* Keep track of everything modified by this insn. */
3226 /* ??? Need to be careful w.r.t. mods done to INSN. */
3227 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
3228 mark_oprs_set (insn);
3235 /* Top level routine to perform one classic GCSE pass.
3237 Return non-zero if a change was made. */
3240 one_classic_gcse_pass (pass)
3245 gcse_subst_count = 0;
3246 gcse_create_count = 0;
3248 alloc_expr_hash_table (max_cuid);
3249 alloc_rd_mem (n_basic_blocks, max_cuid);
3250 compute_expr_hash_table ();
3252 dump_hash_table (gcse_file, "Expression", expr_hash_table,
3253 expr_hash_table_size, n_exprs);
3259 alloc_avail_expr_mem (n_basic_blocks, n_exprs);
3261 compute_ae_kill (ae_gen, ae_kill);
3262 compute_available (ae_gen, ae_kill, ae_out, ae_in);
3263 changed = classic_gcse ();
3264 free_avail_expr_mem ();
3268 free_expr_hash_table ();
3272 fprintf (gcse_file, "\n");
3273 fprintf (gcse_file, "GCSE of %s, pass %d: %d bytes needed, %d substs,",
3274 current_function_name, pass, bytes_used, gcse_subst_count);
3275 fprintf (gcse_file, "%d insns created\n", gcse_create_count);
3281 /* Compute copy/constant propagation working variables. */
3283 /* Local properties of assignments. */
3284 static sbitmap *cprop_pavloc;
3285 static sbitmap *cprop_absaltered;
3287 /* Global properties of assignments (computed from the local properties). */
3288 static sbitmap *cprop_avin;
3289 static sbitmap *cprop_avout;
3291 /* Allocate vars used for copy/const propagation. N_BLOCKS is the number of
3292 basic blocks. N_SETS is the number of sets. */
3295 alloc_cprop_mem (n_blocks, n_sets)
3296 int n_blocks, n_sets;
3298 cprop_pavloc = sbitmap_vector_alloc (n_blocks, n_sets);
3299 cprop_absaltered = sbitmap_vector_alloc (n_blocks, n_sets);
3301 cprop_avin = sbitmap_vector_alloc (n_blocks, n_sets);
3302 cprop_avout = sbitmap_vector_alloc (n_blocks, n_sets);
3305 /* Free vars used by copy/const propagation. */
3310 free (cprop_pavloc);
3311 free (cprop_absaltered);
3316 /* For each block, compute whether X is transparent. X is either an
3317 expression or an assignment [though we don't care which, for this context
3318 an assignment is treated as an expression]. For each block where an
3319 element of X is modified, set (SET_P == 1) or reset (SET_P == 0) the INDX
3323 compute_transp (x, indx, bmap, set_p)
3334 /* repeat is used to turn tail-recursion into iteration since GCC
3335 can't do it when there's no return value. */
3341 code = GET_CODE (x);
3347 if (REGNO (x) < FIRST_PSEUDO_REGISTER)
3349 for (bb = 0; bb < n_basic_blocks; bb++)
3350 if (TEST_BIT (reg_set_in_block[bb], REGNO (x)))
3351 SET_BIT (bmap[bb], indx);
3355 for (r = reg_set_table[REGNO (x)]; r != NULL; r = r->next)
3356 SET_BIT (bmap[BLOCK_NUM (r->insn)], indx);
3361 if (REGNO (x) < FIRST_PSEUDO_REGISTER)
3363 for (bb = 0; bb < n_basic_blocks; bb++)
3364 if (TEST_BIT (reg_set_in_block[bb], REGNO (x)))
3365 RESET_BIT (bmap[bb], indx);
3369 for (r = reg_set_table[REGNO (x)]; r != NULL; r = r->next)
3370 RESET_BIT (bmap[BLOCK_NUM (r->insn)], indx);
3379 for (bb = 0; bb < n_basic_blocks; bb++)
3380 if (mem_set_in_block[bb])
3381 SET_BIT (bmap[bb], indx);
3385 for (bb = 0; bb < n_basic_blocks; bb++)
3386 if (mem_set_in_block[bb])
3387 RESET_BIT (bmap[bb], indx);
3408 for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
3412 /* If we are about to do the last recursive call
3413 needed at this level, change it into iteration.
3414 This function is called enough to be worth it. */
3421 compute_transp (XEXP (x, i), indx, bmap, set_p);
3423 else if (fmt[i] == 'E')
3424 for (j = 0; j < XVECLEN (x, i); j++)
3425 compute_transp (XVECEXP (x, i, j), indx, bmap, set_p);
3429 /* Top level routine to do the dataflow analysis needed by copy/const
3433 compute_cprop_data ()
3435 compute_local_properties (cprop_absaltered, cprop_pavloc, NULL, 1);
3436 compute_available (cprop_pavloc, cprop_absaltered,
3437 cprop_avout, cprop_avin);
3440 /* Copy/constant propagation. */
3442 /* Maximum number of register uses in an insn that we handle. */
3445 /* Table of uses found in an insn.
3446 Allocated statically to avoid alloc/free complexity and overhead. */
3447 static struct reg_use reg_use_table[MAX_USES];
3449 /* Index into `reg_use_table' while building it. */
3450 static int reg_use_count;
3452 /* Set up a list of register numbers used in INSN. The found uses are stored
3453 in `reg_use_table'. `reg_use_count' is initialized to zero before entry,
3454 and contains the number of uses in the table upon exit.
3456 ??? If a register appears multiple times we will record it multiple times.
3457 This doesn't hurt anything but it will slow things down. */
3467 /* repeat is used to turn tail-recursion into iteration since GCC
3468 can't do it when there's no return value. */
3474 code = GET_CODE (x);
3478 if (reg_use_count == MAX_USES)
3481 reg_use_table[reg_use_count].reg_rtx = x;
3499 case ASM_INPUT: /*FIXME*/
3503 if (GET_CODE (SET_DEST (x)) == MEM)
3504 find_used_regs (SET_DEST (x));
3512 /* Recursively scan the operands of this expression. */
3514 for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
3518 /* If we are about to do the last recursive call
3519 needed at this level, change it into iteration.
3520 This function is called enough to be worth it. */
3527 find_used_regs (XEXP (x, i));
3529 else if (fmt[i] == 'E')
3530 for (j = 0; j < XVECLEN (x, i); j++)
3531 find_used_regs (XVECEXP (x, i, j));
3535 /* Try to replace all non-SET_DEST occurrences of FROM in INSN with TO.
3536 Returns non-zero is successful. */
3539 try_replace_reg (from, to, insn)
3547 note = find_reg_note (insn, REG_EQUAL, NULL_RTX);
3550 note = find_reg_note (insn, REG_EQUIV, NULL_RTX);
3552 /* If this fails we could try to simplify the result of the
3553 replacement and attempt to recognize the simplified insn.
3555 But we need a general simplify_rtx that doesn't have pass
3556 specific state variables. I'm not aware of one at the moment. */
3558 success = validate_replace_src (from, to, insn);
3559 set = single_set (insn);
3561 /* We've failed to do replacement. Try to add REG_EQUAL note to not loose
3563 if (!success && !note)
3568 note = REG_NOTES (insn) = gen_rtx_EXPR_LIST (REG_EQUAL,
3569 copy_rtx (SET_SRC (set)),
3573 /* Always do the replacement in REQ_EQUAL and REG_EQUIV notes. Also
3574 try to simplify them. */
3579 src = XEXP (note, 0);
3580 replace_rtx (src, from, to);
3582 /* Try to simplify resulting note. */
3583 simplified = simplify_rtx (src);
3587 XEXP (note, 0) = src;
3590 /* REG_EQUAL may get simplified into register.
3591 We don't allow that. Remove that note. This code ought
3592 not to hapen, because previous code ought to syntetize
3593 reg-reg move, but be on the safe side. */
3594 else if (REG_P (src))
3595 remove_note (insn, note);
3600 /* Find a set of REGNOs that are available on entry to INSN's block. Returns
3601 NULL no such set is found. */
3603 static struct expr *
3604 find_avail_set (regno, insn)
3608 /* SET1 contains the last set found that can be returned to the caller for
3609 use in a substitution. */
3610 struct expr *set1 = 0;
3612 /* Loops are not possible here. To get a loop we would need two sets
3613 available at the start of the block containing INSN. ie we would
3614 need two sets like this available at the start of the block:
3616 (set (reg X) (reg Y))
3617 (set (reg Y) (reg X))
3619 This can not happen since the set of (reg Y) would have killed the
3620 set of (reg X) making it unavailable at the start of this block. */
3624 struct expr *set = lookup_set (regno, NULL_RTX);
3626 /* Find a set that is available at the start of the block
3627 which contains INSN. */
3630 if (TEST_BIT (cprop_avin[BLOCK_NUM (insn)], set->bitmap_index))
3632 set = next_set (regno, set);
3635 /* If no available set was found we've reached the end of the
3636 (possibly empty) copy chain. */
3640 if (GET_CODE (set->expr) != SET)
3643 src = SET_SRC (set->expr);
3645 /* We know the set is available.
3646 Now check that SRC is ANTLOC (i.e. none of the source operands
3647 have changed since the start of the block).
3649 If the source operand changed, we may still use it for the next
3650 iteration of this loop, but we may not use it for substitutions. */
3652 if (CONSTANT_P (src) || oprs_not_set_p (src, insn))
3655 /* If the source of the set is anything except a register, then
3656 we have reached the end of the copy chain. */
3657 if (GET_CODE (src) != REG)
3660 /* Follow the copy chain, ie start another iteration of the loop
3661 and see if we have an available copy into SRC. */
3662 regno = REGNO (src);
3665 /* SET1 holds the last set that was available and anticipatable at
3670 /* Subroutine of cprop_insn that tries to propagate constants into
3671 JUMP_INSNS. INSN must be a conditional jump; COPY is a copy of it
3672 that we can use for substitutions.
3673 REG_USED is the use we will try to replace, SRC is the constant we
3674 will try to substitute for it.
3675 Returns nonzero if a change was made. */
3678 cprop_jump (insn, copy, reg_used, src)
3680 struct reg_use *reg_used;
3683 rtx set = PATTERN (copy);
3686 /* Replace the register with the appropriate constant. */
3687 replace_rtx (SET_SRC (set), reg_used->reg_rtx, src);
3689 temp = simplify_ternary_operation (GET_CODE (SET_SRC (set)),
3690 GET_MODE (SET_SRC (set)),
3691 GET_MODE (XEXP (SET_SRC (set), 0)),
3692 XEXP (SET_SRC (set), 0),
3693 XEXP (SET_SRC (set), 1),
3694 XEXP (SET_SRC (set), 2));
3696 /* If no simplification can be made, then try the next
3701 SET_SRC (set) = temp;
3703 /* That may have changed the structure of TEMP, so
3704 force it to be rerecognized if it has not turned
3705 into a nop or unconditional jump. */
3707 INSN_CODE (copy) = -1;
3708 if ((SET_DEST (set) == pc_rtx
3709 && (SET_SRC (set) == pc_rtx
3710 || GET_CODE (SET_SRC (set)) == LABEL_REF))
3711 || recog (PATTERN (copy), copy, NULL) >= 0)
3713 /* This has either become an unconditional jump
3714 or a nop-jump. We'd like to delete nop jumps
3715 here, but doing so confuses gcse. So we just
3716 make the replacement and let later passes
3718 PATTERN (insn) = set;
3719 INSN_CODE (insn) = -1;
3721 /* One less use of the label this insn used to jump to
3722 if we turned this into a NOP jump. */
3723 if (SET_SRC (set) == pc_rtx && JUMP_LABEL (insn) != 0)
3724 --LABEL_NUSES (JUMP_LABEL (insn));
3726 /* If this has turned into an unconditional jump,
3727 then put a barrier after it so that the unreachable
3728 code will be deleted. */
3729 if (GET_CODE (SET_SRC (set)) == LABEL_REF)
3730 emit_barrier_after (insn);
3732 run_jump_opt_after_gcse = 1;
3735 if (gcse_file != NULL)
3738 "CONST-PROP: Replacing reg %d in insn %d with constant ",
3739 REGNO (reg_used->reg_rtx), INSN_UID (insn));
3740 print_rtl (gcse_file, src);
3741 fprintf (gcse_file, "\n");
3751 /* Subroutine of cprop_insn that tries to propagate constants into JUMP_INSNS
3752 for machines that have CC0. INSN is a single set that stores into CC0;
3753 the insn following it is a conditional jump. REG_USED is the use we will
3754 try to replace, SRC is the constant we will try to substitute for it.
3755 Returns nonzero if a change was made. */
3758 cprop_cc0_jump (insn, reg_used, src)
3760 struct reg_use *reg_used;
3763 rtx jump = NEXT_INSN (insn);
3764 rtx copy = copy_rtx (jump);
3765 rtx set = PATTERN (copy);
3767 /* We need to copy the source of the cc0 setter, as cprop_jump is going to
3768 substitute into it. */
3769 replace_rtx (SET_SRC (set), cc0_rtx, copy_rtx (SET_SRC (PATTERN (insn))));
3770 if (! cprop_jump (jump, copy, reg_used, src))
3773 /* If we succeeded, delete the cc0 setter. */
3774 PUT_CODE (insn, NOTE);
3775 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
3776 NOTE_SOURCE_FILE (insn) = 0;
3781 /* Perform constant and copy propagation on INSN.
3782 The result is non-zero if a change was made. */
3785 cprop_insn (insn, alter_jumps)
3789 struct reg_use *reg_used;
3793 /* Only propagate into SETs. Note that a conditional jump is a
3794 SET with pc_rtx as the destination. */
3795 if ((GET_CODE (insn) != INSN
3796 && GET_CODE (insn) != JUMP_INSN)
3797 || GET_CODE (PATTERN (insn)) != SET)
3801 find_used_regs (PATTERN (insn));
3803 note = find_reg_note (insn, REG_EQUIV, NULL_RTX);
3805 note = find_reg_note (insn, REG_EQUAL, NULL_RTX);
3807 /* We may win even when propagating constants into notes. */
3809 find_used_regs (XEXP (note, 0));
3811 for (reg_used = ®_use_table[0]; reg_use_count > 0;
3812 reg_used++, reg_use_count--)
3814 unsigned int regno = REGNO (reg_used->reg_rtx);
3818 /* Ignore registers created by GCSE.
3819 We do this because ... */
3820 if (regno >= max_gcse_regno)
3823 /* If the register has already been set in this block, there's
3824 nothing we can do. */
3825 if (! oprs_not_set_p (reg_used->reg_rtx, insn))
3828 /* Find an assignment that sets reg_used and is available
3829 at the start of the block. */
3830 set = find_avail_set (regno, insn);
3835 /* ??? We might be able to handle PARALLELs. Later. */
3836 if (GET_CODE (pat) != SET)
3839 src = SET_SRC (pat);
3841 /* Constant propagation. */
3842 if (GET_CODE (src) == CONST_INT || GET_CODE (src) == CONST_DOUBLE
3843 || GET_CODE (src) == SYMBOL_REF)
3845 /* Handle normal insns first. */
3846 if (GET_CODE (insn) == INSN
3847 && try_replace_reg (reg_used->reg_rtx, src, insn))
3851 if (gcse_file != NULL)
3853 fprintf (gcse_file, "CONST-PROP: Replacing reg %d in ",
3855 fprintf (gcse_file, "insn %d with constant ",
3857 print_rtl (gcse_file, src);
3858 fprintf (gcse_file, "\n");
3861 /* The original insn setting reg_used may or may not now be
3862 deletable. We leave the deletion to flow. */
3865 /* Try to propagate a CONST_INT into a conditional jump.
3866 We're pretty specific about what we will handle in this
3867 code, we can extend this as necessary over time.
3869 Right now the insn in question must look like
3870 (set (pc) (if_then_else ...)) */
3871 else if (alter_jumps
3872 && GET_CODE (insn) == JUMP_INSN
3873 && condjump_p (insn)
3874 && ! simplejump_p (insn))
3875 changed |= cprop_jump (insn, copy_rtx (insn), reg_used, src);
3877 /* Similar code for machines that use a pair of CC0 setter and
3878 conditional jump insn. */
3879 else if (alter_jumps
3880 && GET_CODE (PATTERN (insn)) == SET
3881 && SET_DEST (PATTERN (insn)) == cc0_rtx
3882 && GET_CODE (NEXT_INSN (insn)) == JUMP_INSN
3883 && condjump_p (NEXT_INSN (insn))
3884 && ! simplejump_p (NEXT_INSN (insn)))
3885 changed |= cprop_cc0_jump (insn, reg_used, src);
3888 else if (GET_CODE (src) == REG
3889 && REGNO (src) >= FIRST_PSEUDO_REGISTER
3890 && REGNO (src) != regno)
3892 if (try_replace_reg (reg_used->reg_rtx, src, insn))
3896 if (gcse_file != NULL)
3898 fprintf (gcse_file, "COPY-PROP: Replacing reg %d in insn %d",
3899 regno, INSN_UID (insn));
3900 fprintf (gcse_file, " with reg %d\n", REGNO (src));
3903 /* The original insn setting reg_used may or may not now be
3904 deletable. We leave the deletion to flow. */
3905 /* FIXME: If it turns out that the insn isn't deletable,
3906 then we may have unnecessarily extended register lifetimes
3907 and made things worse. */
3915 /* Forward propagate copies. This includes copies and constants. Return
3916 non-zero if a change was made. */
3925 /* Note we start at block 1. */
3928 for (bb = 1; bb < n_basic_blocks; bb++)
3930 /* Reset tables used to keep track of what's still valid [since the
3931 start of the block]. */
3932 reset_opr_set_tables ();
3934 for (insn = BLOCK_HEAD (bb);
3935 insn != NULL && insn != NEXT_INSN (BLOCK_END (bb));
3936 insn = NEXT_INSN (insn))
3938 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
3940 changed |= cprop_insn (insn, alter_jumps);
3942 /* Keep track of everything modified by this insn. */
3943 /* ??? Need to be careful w.r.t. mods done to INSN. Don't
3944 call mark_oprs_set if we turned the insn into a NOTE. */
3945 if (GET_CODE (insn) != NOTE)
3946 mark_oprs_set (insn);
3951 if (gcse_file != NULL)
3952 fprintf (gcse_file, "\n");
3957 /* Perform one copy/constant propagation pass.
3958 F is the first insn in the function.
3959 PASS is the pass count. */
3962 one_cprop_pass (pass, alter_jumps)
3968 const_prop_count = 0;
3969 copy_prop_count = 0;
3971 alloc_set_hash_table (max_cuid);
3972 compute_set_hash_table ();
3974 dump_hash_table (gcse_file, "SET", set_hash_table, set_hash_table_size,
3978 alloc_cprop_mem (n_basic_blocks, n_sets);
3979 compute_cprop_data ();
3980 changed = cprop (alter_jumps);
3984 free_set_hash_table ();
3988 fprintf (gcse_file, "CPROP of %s, pass %d: %d bytes needed, ",
3989 current_function_name, pass, bytes_used);
3990 fprintf (gcse_file, "%d const props, %d copy props\n\n",
3991 const_prop_count, copy_prop_count);
3997 /* Compute PRE+LCM working variables. */
3999 /* Local properties of expressions. */
4000 /* Nonzero for expressions that are transparent in the block. */
4001 static sbitmap *transp;
4003 /* Nonzero for expressions that are transparent at the end of the block.
4004 This is only zero for expressions killed by abnormal critical edge
4005 created by a calls. */
4006 static sbitmap *transpout;
4008 /* Nonzero for expressions that are computed (available) in the block. */
4009 static sbitmap *comp;
4011 /* Nonzero for expressions that are locally anticipatable in the block. */
4012 static sbitmap *antloc;
4014 /* Nonzero for expressions where this block is an optimal computation
4016 static sbitmap *pre_optimal;
4018 /* Nonzero for expressions which are redundant in a particular block. */
4019 static sbitmap *pre_redundant;
4021 /* Nonzero for expressions which should be inserted on a specific edge. */
4022 static sbitmap *pre_insert_map;
4024 /* Nonzero for expressions which should be deleted in a specific block. */
4025 static sbitmap *pre_delete_map;
4027 /* Contains the edge_list returned by pre_edge_lcm. */
4028 static struct edge_list *edge_list;
4030 /* Redundant insns. */
4031 static sbitmap pre_redundant_insns;
4033 /* Allocate vars used for PRE analysis. */
4036 alloc_pre_mem (n_blocks, n_exprs)
4037 int n_blocks, n_exprs;
4039 transp = sbitmap_vector_alloc (n_blocks, n_exprs);
4040 comp = sbitmap_vector_alloc (n_blocks, n_exprs);
4041 antloc = sbitmap_vector_alloc (n_blocks, n_exprs);
4044 pre_redundant = NULL;
4045 pre_insert_map = NULL;
4046 pre_delete_map = NULL;
4049 ae_kill = sbitmap_vector_alloc (n_blocks, n_exprs);
4051 /* pre_insert and pre_delete are allocated later. */
4054 /* Free vars used for PRE analysis. */
4062 /* ANTLOC and AE_KILL are freed just after pre_lcm finishes. */
4067 free (pre_redundant);
4069 free (pre_insert_map);
4071 free (pre_delete_map);
4078 transp = comp = NULL;
4079 pre_optimal = pre_redundant = pre_insert_map = pre_delete_map = NULL;
4080 ae_in = ae_out = NULL;
4083 /* Top level routine to do the dataflow analysis needed by PRE. */
4090 compute_local_properties (transp, comp, antloc, 0);
4091 sbitmap_vector_zero (ae_kill, n_basic_blocks);
4093 /* Compute ae_kill for each basic block using:
4097 This is significantly faster than compute_ae_kill. */
4099 for (i = 0; i < n_basic_blocks; i++)
4101 sbitmap_a_or_b (ae_kill[i], transp[i], comp[i]);
4102 sbitmap_not (ae_kill[i], ae_kill[i]);
4105 edge_list = pre_edge_lcm (gcse_file, n_exprs, transp, comp, antloc,
4106 ae_kill, &pre_insert_map, &pre_delete_map);
4115 /* Return non-zero if an occurrence of expression EXPR in OCCR_BB would reach
4118 VISITED is a pointer to a working buffer for tracking which BB's have
4119 been visited. It is NULL for the top-level call.
4121 We treat reaching expressions that go through blocks containing the same
4122 reaching expression as "not reaching". E.g. if EXPR is generated in blocks
4123 2 and 3, INSN is in block 4, and 2->3->4, we treat the expression in block
4124 2 as not reaching. The intent is to improve the probability of finding
4125 only one reaching expression and to reduce register lifetimes by picking
4126 the closest such expression. */
4129 pre_expr_reaches_here_p_work (occr_bb, expr, bb, visited)
4137 for (pred = BASIC_BLOCK (bb)->pred; pred != NULL; pred = pred->pred_next)
4139 int pred_bb = pred->src->index;
4141 if (pred->src == ENTRY_BLOCK_PTR
4142 /* Has predecessor has already been visited? */
4143 || visited[pred_bb])
4144 ;/* Nothing to do. */
4146 /* Does this predecessor generate this expression? */
4147 else if (TEST_BIT (comp[pred_bb], expr->bitmap_index))
4149 /* Is this the occurrence we're looking for?
4150 Note that there's only one generating occurrence per block
4151 so we just need to check the block number. */
4152 if (occr_bb == pred_bb)
4155 visited[pred_bb] = 1;
4157 /* Ignore this predecessor if it kills the expression. */
4158 else if (! TEST_BIT (transp[pred_bb], expr->bitmap_index))
4159 visited[pred_bb] = 1;
4161 /* Neither gen nor kill. */
4164 visited[pred_bb] = 1;
4165 if (pre_expr_reaches_here_p_work (occr_bb, expr, pred_bb, visited))
4170 /* All paths have been checked. */
4174 /* The wrapper for pre_expr_reaches_here_work that ensures that any
4175 memory allocated for that function is returned. */
4178 pre_expr_reaches_here_p (occr_bb, expr, bb)
4184 char *visited = (char *) xcalloc (n_basic_blocks, 1);
4186 rval = pre_expr_reaches_here_p_work(occr_bb, expr, bb, visited);
4193 /* Given an expr, generate RTL which we can insert at the end of a BB,
4194 or on an edge. Set the block number of any insns generated to
4198 process_insert_insn (expr)
4201 rtx reg = expr->reaching_reg;
4202 rtx pat, copied_expr;
4206 copied_expr = copy_rtx (expr->expr);
4207 emit_move_insn (reg, copied_expr);
4208 first_new_insn = get_insns ();
4209 pat = gen_sequence ();
4215 /* Add EXPR to the end of basic block BB.
4217 This is used by both the PRE and code hoisting.
4219 For PRE, we want to verify that the expr is either transparent
4220 or locally anticipatable in the target block. This check makes
4221 no sense for code hoisting. */
4224 insert_insn_end_bb (expr, bb, pre)
4229 rtx insn = BLOCK_END (bb);
4231 rtx reg = expr->reaching_reg;
4232 int regno = REGNO (reg);
4236 pat = process_insert_insn (expr);
4238 /* If the last insn is a jump, insert EXPR in front [taking care to
4239 handle cc0, etc. properly]. */
4241 if (GET_CODE (insn) == JUMP_INSN)
4247 /* If this is a jump table, then we can't insert stuff here. Since
4248 we know the previous real insn must be the tablejump, we insert
4249 the new instruction just before the tablejump. */
4250 if (GET_CODE (PATTERN (insn)) == ADDR_VEC
4251 || GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC)
4252 insn = prev_real_insn (insn);
4255 /* FIXME: 'twould be nice to call prev_cc0_setter here but it aborts
4256 if cc0 isn't set. */
4257 note = find_reg_note (insn, REG_CC_SETTER, NULL_RTX);
4259 insn = XEXP (note, 0);
4262 rtx maybe_cc0_setter = prev_nonnote_insn (insn);
4263 if (maybe_cc0_setter
4264 && GET_RTX_CLASS (GET_CODE (maybe_cc0_setter)) == 'i'
4265 && sets_cc0_p (PATTERN (maybe_cc0_setter)))
4266 insn = maybe_cc0_setter;
4269 /* FIXME: What if something in cc0/jump uses value set in new insn? */
4270 new_insn = emit_block_insn_before (pat, insn, BASIC_BLOCK (bb));
4273 /* Likewise if the last insn is a call, as will happen in the presence
4274 of exception handling. */
4275 else if (GET_CODE (insn) == CALL_INSN)
4277 HARD_REG_SET parm_regs;
4281 /* Keeping in mind SMALL_REGISTER_CLASSES and parameters in registers,
4282 we search backward and place the instructions before the first
4283 parameter is loaded. Do this for everyone for consistency and a
4284 presumtion that we'll get better code elsewhere as well.
4286 It should always be the case that we can put these instructions
4287 anywhere in the basic block with performing PRE optimizations.
4291 && !TEST_BIT (antloc[bb], expr->bitmap_index)
4292 && !TEST_BIT (transp[bb], expr->bitmap_index))
4295 /* Since different machines initialize their parameter registers
4296 in different orders, assume nothing. Collect the set of all
4297 parameter registers. */
4298 CLEAR_HARD_REG_SET (parm_regs);
4300 for (p = CALL_INSN_FUNCTION_USAGE (insn); p ; p = XEXP (p, 1))
4301 if (GET_CODE (XEXP (p, 0)) == USE
4302 && GET_CODE (XEXP (XEXP (p, 0), 0)) == REG)
4304 if (REGNO (XEXP (XEXP (p, 0), 0)) >= FIRST_PSEUDO_REGISTER)
4307 SET_HARD_REG_BIT (parm_regs, REGNO (XEXP (XEXP (p, 0), 0)));
4311 /* Search backward for the first set of a register in this set. */
4312 while (nparm_regs && BLOCK_HEAD (bb) != insn)
4314 insn = PREV_INSN (insn);
4315 p = single_set (insn);
4316 if (p && GET_CODE (SET_DEST (p)) == REG
4317 && REGNO (SET_DEST (p)) < FIRST_PSEUDO_REGISTER
4318 && TEST_HARD_REG_BIT (parm_regs, REGNO (SET_DEST (p))))
4320 CLEAR_HARD_REG_BIT (parm_regs, REGNO (SET_DEST (p)));
4325 /* If we found all the parameter loads, then we want to insert
4326 before the first parameter load.
4328 If we did not find all the parameter loads, then we might have
4329 stopped on the head of the block, which could be a CODE_LABEL.
4330 If we inserted before the CODE_LABEL, then we would be putting
4331 the insn in the wrong basic block. In that case, put the insn
4332 after the CODE_LABEL. Also, respect NOTE_INSN_BASIC_BLOCK. */
4333 while (GET_CODE (insn) == CODE_LABEL
4334 || NOTE_INSN_BASIC_BLOCK_P (insn))
4335 insn = NEXT_INSN (insn);
4337 new_insn = emit_block_insn_before (pat, insn, BASIC_BLOCK (bb));
4341 new_insn = emit_insn_after (pat, insn);
4342 BLOCK_END (bb) = new_insn;
4345 /* Keep block number table up to date.
4346 Note, PAT could be a multiple insn sequence, we have to make
4347 sure that each insn in the sequence is handled. */
4348 if (GET_CODE (pat) == SEQUENCE)
4350 for (i = 0; i < XVECLEN (pat, 0); i++)
4352 rtx insn = XVECEXP (pat, 0, i);
4354 set_block_num (insn, bb);
4355 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
4356 add_label_notes (PATTERN (insn), new_insn);
4358 note_stores (PATTERN (insn), record_set_info, insn);
4363 add_label_notes (SET_SRC (pat), new_insn);
4364 set_block_num (new_insn, bb);
4366 /* Keep register set table up to date. */
4367 record_one_set (regno, new_insn);
4370 gcse_create_count++;
4374 fprintf (gcse_file, "PRE/HOIST: end of bb %d, insn %d, ",
4375 bb, INSN_UID (new_insn));
4376 fprintf (gcse_file, "copying expression %d to reg %d\n",
4377 expr->bitmap_index, regno);
4381 /* Insert partially redundant expressions on edges in the CFG to make
4382 the expressions fully redundant. */
4385 pre_edge_insert (edge_list, index_map)
4386 struct edge_list *edge_list;
4387 struct expr **index_map;
4389 int e, i, j, num_edges, set_size, did_insert = 0;
4392 /* Where PRE_INSERT_MAP is nonzero, we add the expression on that edge
4393 if it reaches any of the deleted expressions. */
4395 set_size = pre_insert_map[0]->size;
4396 num_edges = NUM_EDGES (edge_list);
4397 inserted = sbitmap_vector_alloc (num_edges, n_exprs);
4398 sbitmap_vector_zero (inserted, num_edges);
4400 for (e = 0; e < num_edges; e++)
4403 basic_block pred = INDEX_EDGE_PRED_BB (edge_list, e);
4404 int bb = pred->index;
4406 for (i = indx = 0; i < set_size; i++, indx += SBITMAP_ELT_BITS)
4408 SBITMAP_ELT_TYPE insert = pre_insert_map[e]->elms[i];
4410 for (j = indx; insert && j < n_exprs; j++, insert >>= 1)
4411 if ((insert & 1) != 0 && index_map[j]->reaching_reg != NULL_RTX)
4413 struct expr *expr = index_map[j];
4416 /* Now look at each deleted occurence of this expression. */
4417 for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
4419 if (! occr->deleted_p)
4422 /* Insert this expression on this edge if if it would
4423 reach the deleted occurence in BB. */
4424 if (!TEST_BIT (inserted[e], j))
4427 edge eg = INDEX_EDGE (edge_list, e);
4429 /* We can't insert anything on an abnormal and
4430 critical edge, so we insert the insn at the end of
4431 the previous block. There are several alternatives
4432 detailed in Morgans book P277 (sec 10.5) for
4433 handling this situation. This one is easiest for
4436 if ((eg->flags & EDGE_ABNORMAL) == EDGE_ABNORMAL)
4437 insert_insn_end_bb (index_map[j], bb, 0);
4440 insn = process_insert_insn (index_map[j]);
4441 insert_insn_on_edge (insn, eg);
4446 fprintf (gcse_file, "PRE/HOIST: edge (%d,%d), ",
4448 INDEX_EDGE_SUCC_BB (edge_list, e)->index);
4449 fprintf (gcse_file, "copy expression %d\n",
4450 expr->bitmap_index);
4453 SET_BIT (inserted[e], j);
4455 gcse_create_count++;
4466 /* Copy the result of INSN to REG. INDX is the expression number. */
4469 pre_insert_copy_insn (expr, insn)
4473 rtx reg = expr->reaching_reg;
4474 int regno = REGNO (reg);
4475 int indx = expr->bitmap_index;
4476 rtx set = single_set (insn);
4478 int bb = BLOCK_NUM (insn);
4483 new_insn = emit_insn_after (gen_rtx_SET (VOIDmode, reg, SET_DEST (set)),
4486 /* Keep block number table up to date. */
4487 set_block_num (new_insn, bb);
4489 /* Keep register set table up to date. */
4490 record_one_set (regno, new_insn);
4491 if (insn == BLOCK_END (bb))
4492 BLOCK_END (bb) = new_insn;
4494 gcse_create_count++;
4498 "PRE: bb %d, insn %d, copy expression %d in insn %d to reg %d\n",
4499 BLOCK_NUM (insn), INSN_UID (new_insn), indx,
4500 INSN_UID (insn), regno);
4503 /* Copy available expressions that reach the redundant expression
4504 to `reaching_reg'. */
4507 pre_insert_copies ()
4514 /* For each available expression in the table, copy the result to
4515 `reaching_reg' if the expression reaches a deleted one.
4517 ??? The current algorithm is rather brute force.
4518 Need to do some profiling. */
4520 for (i = 0; i < expr_hash_table_size; i++)
4521 for (expr = expr_hash_table[i]; expr != NULL; expr = expr->next_same_hash)
4523 /* If the basic block isn't reachable, PPOUT will be TRUE. However,
4524 we don't want to insert a copy here because the expression may not
4525 really be redundant. So only insert an insn if the expression was
4526 deleted. This test also avoids further processing if the
4527 expression wasn't deleted anywhere. */
4528 if (expr->reaching_reg == NULL)
4531 for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
4533 if (! occr->deleted_p)
4536 for (avail = expr->avail_occr; avail != NULL; avail = avail->next)
4538 rtx insn = avail->insn;
4540 /* No need to handle this one if handled already. */
4541 if (avail->copied_p)
4544 /* Don't handle this one if it's a redundant one. */
4545 if (TEST_BIT (pre_redundant_insns, INSN_CUID (insn)))
4548 /* Or if the expression doesn't reach the deleted one. */
4549 if (! pre_expr_reaches_here_p (BLOCK_NUM (avail->insn), expr,
4550 BLOCK_NUM (occr->insn)))
4553 /* Copy the result of avail to reaching_reg. */
4554 pre_insert_copy_insn (expr, insn);
4555 avail->copied_p = 1;
4561 /* Delete redundant computations.
4562 Deletion is done by changing the insn to copy the `reaching_reg' of
4563 the expression into the result of the SET. It is left to later passes
4564 (cprop, cse2, flow, combine, regmove) to propagate the copy or eliminate it.
4566 Returns non-zero if a change is made. */
4577 for (i = 0; i < expr_hash_table_size; i++)
4578 for (expr = expr_hash_table[i]; expr != NULL; expr = expr->next_same_hash)
4580 int indx = expr->bitmap_index;
4582 /* We only need to search antic_occr since we require
4585 for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
4587 rtx insn = occr->insn;
4589 int bb = BLOCK_NUM (insn);
4591 if (TEST_BIT (pre_delete_map[bb], indx))
4593 set = single_set (insn);
4597 /* Create a pseudo-reg to store the result of reaching
4598 expressions into. Get the mode for the new pseudo from
4599 the mode of the original destination pseudo. */
4600 if (expr->reaching_reg == NULL)
4602 = gen_reg_rtx (GET_MODE (SET_DEST (set)));
4604 /* In theory this should never fail since we're creating
4607 However, on the x86 some of the movXX patterns actually
4608 contain clobbers of scratch regs. This may cause the
4609 insn created by validate_change to not match any pattern
4610 and thus cause validate_change to fail. */
4611 if (validate_change (insn, &SET_SRC (set),
4612 expr->reaching_reg, 0))
4614 occr->deleted_p = 1;
4615 SET_BIT (pre_redundant_insns, INSN_CUID (insn));
4623 "PRE: redundant insn %d (expression %d) in ",
4624 INSN_UID (insn), indx);
4625 fprintf (gcse_file, "bb %d, reaching reg is %d\n",
4626 bb, REGNO (expr->reaching_reg));
4635 /* Perform GCSE optimizations using PRE.
4636 This is called by one_pre_gcse_pass after all the dataflow analysis
4639 This is based on the original Morel-Renvoise paper Fred Chow's thesis, and
4640 lazy code motion from Knoop, Ruthing and Steffen as described in Advanced
4641 Compiler Design and Implementation.
4643 ??? A new pseudo reg is created to hold the reaching expression. The nice
4644 thing about the classical approach is that it would try to use an existing
4645 reg. If the register can't be adequately optimized [i.e. we introduce
4646 reload problems], one could add a pass here to propagate the new register
4649 ??? We don't handle single sets in PARALLELs because we're [currently] not
4650 able to copy the rest of the parallel when we insert copies to create full
4651 redundancies from partial redundancies. However, there's no reason why we
4652 can't handle PARALLELs in the cases where there are no partial
4659 int did_insert, changed;
4660 struct expr **index_map;
4663 /* Compute a mapping from expression number (`bitmap_index') to
4664 hash table entry. */
4666 index_map = (struct expr **) xcalloc (n_exprs, sizeof (struct expr *));
4667 for (i = 0; i < expr_hash_table_size; i++)
4668 for (expr = expr_hash_table[i]; expr != NULL; expr = expr->next_same_hash)
4669 index_map[expr->bitmap_index] = expr;
4671 /* Reset bitmap used to track which insns are redundant. */
4672 pre_redundant_insns = sbitmap_alloc (max_cuid);
4673 sbitmap_zero (pre_redundant_insns);
4675 /* Delete the redundant insns first so that
4676 - we know what register to use for the new insns and for the other
4677 ones with reaching expressions
4678 - we know which insns are redundant when we go to create copies */
4680 changed = pre_delete ();
4682 did_insert = pre_edge_insert (edge_list, index_map);
4684 /* In other places with reaching expressions, copy the expression to the
4685 specially allocated pseudo-reg that reaches the redundant expr. */
4686 pre_insert_copies ();
4689 commit_edge_insertions ();
4694 free (pre_redundant_insns);
4698 /* Top level routine to perform one PRE GCSE pass.
4700 Return non-zero if a change was made. */
4703 one_pre_gcse_pass (pass)
4708 gcse_subst_count = 0;
4709 gcse_create_count = 0;
4711 alloc_expr_hash_table (max_cuid);
4712 add_noreturn_fake_exit_edges ();
4713 compute_expr_hash_table ();
4715 dump_hash_table (gcse_file, "Expression", expr_hash_table,
4716 expr_hash_table_size, n_exprs);
4720 alloc_pre_mem (n_basic_blocks, n_exprs);
4721 compute_pre_data ();
4722 changed |= pre_gcse ();
4723 free_edge_list (edge_list);
4727 remove_fake_edges ();
4728 free_expr_hash_table ();
4732 fprintf (gcse_file, "\nPRE GCSE of %s, pass %d: %d bytes needed, ",
4733 current_function_name, pass, bytes_used);
4734 fprintf (gcse_file, "%d substs, %d insns created\n",
4735 gcse_subst_count, gcse_create_count);
4741 /* If X contains any LABEL_REF's, add REG_LABEL notes for them to INSN.
4742 We have to add REG_LABEL notes, because the following loop optimization
4743 pass requires them. */
4745 /* ??? This is very similar to the loop.c add_label_notes function. We
4746 could probably share code here. */
4748 /* ??? If there was a jump optimization pass after gcse and before loop,
4749 then we would not need to do this here, because jump would add the
4750 necessary REG_LABEL notes. */
4753 add_label_notes (x, insn)
4757 enum rtx_code code = GET_CODE (x);
4761 if (code == LABEL_REF && !LABEL_REF_NONLOCAL_P (x))
4763 /* This code used to ignore labels that referred to dispatch tables to
4764 avoid flow generating (slighly) worse code.
4766 We no longer ignore such label references (see LABEL_REF handling in
4767 mark_jump_label for additional information). */
4769 REG_NOTES (insn) = gen_rtx_EXPR_LIST (REG_LABEL, XEXP (x, 0),
4774 for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
4777 add_label_notes (XEXP (x, i), insn);
4778 else if (fmt[i] == 'E')
4779 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
4780 add_label_notes (XVECEXP (x, i, j), insn);
4784 /* Compute transparent outgoing information for each block.
4786 An expression is transparent to an edge unless it is killed by
4787 the edge itself. This can only happen with abnormal control flow,
4788 when the edge is traversed through a call. This happens with
4789 non-local labels and exceptions.
4791 This would not be necessary if we split the edge. While this is
4792 normally impossible for abnormal critical edges, with some effort
4793 it should be possible with exception handling, since we still have
4794 control over which handler should be invoked. But due to increased
4795 EH table sizes, this may not be worthwhile. */
4798 compute_transpout ()
4804 sbitmap_vector_ones (transpout, n_basic_blocks);
4806 for (bb = 0; bb < n_basic_blocks; ++bb)
4808 /* Note that flow inserted a nop a the end of basic blocks that
4809 end in call instructions for reasons other than abnormal
4811 if (GET_CODE (BLOCK_END (bb)) != CALL_INSN)
4814 for (i = 0; i < expr_hash_table_size; i++)
4815 for (expr = expr_hash_table[i]; expr ; expr = expr->next_same_hash)
4816 if (GET_CODE (expr->expr) == MEM)
4818 if (GET_CODE (XEXP (expr->expr, 0)) == SYMBOL_REF
4819 && CONSTANT_POOL_ADDRESS_P (XEXP (expr->expr, 0)))
4822 /* ??? Optimally, we would use interprocedural alias
4823 analysis to determine if this mem is actually killed
4825 RESET_BIT (transpout[bb], expr->bitmap_index);
4830 /* Removal of useless null pointer checks */
4832 /* Called via note_stores. X is set by SETTER. If X is a register we must
4833 invalidate nonnull_local and set nonnull_killed. DATA is really a
4834 `null_pointer_info *'.
4836 We ignore hard registers. */
4839 invalidate_nonnull_info (x, setter, data)
4841 rtx setter ATTRIBUTE_UNUSED;
4845 struct null_pointer_info *npi = (struct null_pointer_info *) data;
4847 while (GET_CODE (x) == SUBREG)
4850 /* Ignore anything that is not a register or is a hard register. */
4851 if (GET_CODE (x) != REG
4852 || REGNO (x) < npi->min_reg
4853 || REGNO (x) >= npi->max_reg)
4856 regno = REGNO (x) - npi->min_reg;
4858 RESET_BIT (npi->nonnull_local[npi->current_block], regno);
4859 SET_BIT (npi->nonnull_killed[npi->current_block], regno);
4862 /* Do null-pointer check elimination for the registers indicated in
4863 NPI. NONNULL_AVIN and NONNULL_AVOUT are pre-allocated sbitmaps;
4864 they are not our responsibility to free. */
4867 delete_null_pointer_checks_1 (block_reg, nonnull_avin, nonnull_avout, npi)
4868 unsigned int *block_reg;
4869 sbitmap *nonnull_avin;
4870 sbitmap *nonnull_avout;
4871 struct null_pointer_info *npi;
4875 sbitmap *nonnull_local = npi->nonnull_local;
4876 sbitmap *nonnull_killed = npi->nonnull_killed;
4878 /* Compute local properties, nonnull and killed. A register will have
4879 the nonnull property if at the end of the current block its value is
4880 known to be nonnull. The killed property indicates that somewhere in
4881 the block any information we had about the register is killed.
4883 Note that a register can have both properties in a single block. That
4884 indicates that it's killed, then later in the block a new value is
4886 sbitmap_vector_zero (nonnull_local, n_basic_blocks);
4887 sbitmap_vector_zero (nonnull_killed, n_basic_blocks);
4889 for (current_block = 0; current_block < n_basic_blocks; current_block++)
4891 rtx insn, stop_insn;
4893 /* Set the current block for invalidate_nonnull_info. */
4894 npi->current_block = current_block;
4896 /* Scan each insn in the basic block looking for memory references and
4898 stop_insn = NEXT_INSN (BLOCK_END (current_block));
4899 for (insn = BLOCK_HEAD (current_block);
4901 insn = NEXT_INSN (insn))
4906 /* Ignore anything that is not a normal insn. */
4907 if (GET_RTX_CLASS (GET_CODE (insn)) != 'i')
4910 /* Basically ignore anything that is not a simple SET. We do have
4911 to make sure to invalidate nonnull_local and set nonnull_killed
4912 for such insns though. */
4913 set = single_set (insn);
4916 note_stores (PATTERN (insn), invalidate_nonnull_info, npi);
4920 /* See if we've got a useable memory load. We handle it first
4921 in case it uses its address register as a dest (which kills
4922 the nonnull property). */
4923 if (GET_CODE (SET_SRC (set)) == MEM
4924 && GET_CODE ((reg = XEXP (SET_SRC (set), 0))) == REG
4925 && REGNO (reg) >= npi->min_reg
4926 && REGNO (reg) < npi->max_reg)
4927 SET_BIT (nonnull_local[current_block],
4928 REGNO (reg) - npi->min_reg);
4930 /* Now invalidate stuff clobbered by this insn. */
4931 note_stores (PATTERN (insn), invalidate_nonnull_info, npi);
4933 /* And handle stores, we do these last since any sets in INSN can
4934 not kill the nonnull property if it is derived from a MEM
4935 appearing in a SET_DEST. */
4936 if (GET_CODE (SET_DEST (set)) == MEM
4937 && GET_CODE ((reg = XEXP (SET_DEST (set), 0))) == REG
4938 && REGNO (reg) >= npi->min_reg
4939 && REGNO (reg) < npi->max_reg)
4940 SET_BIT (nonnull_local[current_block],
4941 REGNO (reg) - npi->min_reg);
4945 /* Now compute global properties based on the local properties. This
4946 is a classic global availablity algorithm. */
4947 compute_available (nonnull_local, nonnull_killed,
4948 nonnull_avout, nonnull_avin);
4950 /* Now look at each bb and see if it ends with a compare of a value
4952 for (bb = 0; bb < n_basic_blocks; bb++)
4954 rtx last_insn = BLOCK_END (bb);
4955 rtx condition, earliest;
4956 int compare_and_branch;
4958 /* Since MIN_REG is always at least FIRST_PSEUDO_REGISTER, and
4959 since BLOCK_REG[BB] is zero if this block did not end with a
4960 comparison against zero, this condition works. */
4961 if (block_reg[bb] < npi->min_reg
4962 || block_reg[bb] >= npi->max_reg)
4965 /* LAST_INSN is a conditional jump. Get its condition. */
4966 condition = get_condition (last_insn, &earliest);
4968 /* If we can't determine the condition then skip. */
4972 /* Is the register known to have a nonzero value? */
4973 if (!TEST_BIT (nonnull_avout[bb], block_reg[bb] - npi->min_reg))
4976 /* Try to compute whether the compare/branch at the loop end is one or
4977 two instructions. */
4978 if (earliest == last_insn)
4979 compare_and_branch = 1;
4980 else if (earliest == prev_nonnote_insn (last_insn))
4981 compare_and_branch = 2;
4985 /* We know the register in this comparison is nonnull at exit from
4986 this block. We can optimize this comparison. */
4987 if (GET_CODE (condition) == NE)
4991 new_jump = emit_jump_insn_before (gen_jump (JUMP_LABEL (last_insn)),
4993 JUMP_LABEL (new_jump) = JUMP_LABEL (last_insn);
4994 LABEL_NUSES (JUMP_LABEL (new_jump))++;
4995 emit_barrier_after (new_jump);
4997 delete_insn (last_insn);
4998 if (compare_and_branch == 2)
4999 delete_insn (earliest);
5001 /* Don't check this block again. (Note that BLOCK_END is
5002 invalid here; we deleted the last instruction in the
5008 /* Find EQ/NE comparisons against zero which can be (indirectly) evaluated
5011 This is conceptually similar to global constant/copy propagation and
5012 classic global CSE (it even uses the same dataflow equations as cprop).
5014 If a register is used as memory address with the form (mem (reg)), then we
5015 know that REG can not be zero at that point in the program. Any instruction
5016 which sets REG "kills" this property.
5018 So, if every path leading to a conditional branch has an available memory
5019 reference of that form, then we know the register can not have the value
5020 zero at the conditional branch.
5022 So we merely need to compute the local properies and propagate that data
5023 around the cfg, then optimize where possible.
5025 We run this pass two times. Once before CSE, then again after CSE. This
5026 has proven to be the most profitable approach. It is rare for new
5027 optimization opportunities of this nature to appear after the first CSE
5030 This could probably be integrated with global cprop with a little work. */
5033 delete_null_pointer_checks (f)
5034 rtx f ATTRIBUTE_UNUSED;
5036 sbitmap *nonnull_avin, *nonnull_avout;
5037 unsigned int *block_reg;
5042 struct null_pointer_info npi;
5044 /* If we have only a single block, then there's nothing to do. */
5045 if (n_basic_blocks <= 1)
5048 /* Trying to perform global optimizations on flow graphs which have
5049 a high connectivity will take a long time and is unlikely to be
5050 particularly useful.
5052 In normal circumstances a cfg should have about twice has many edges
5053 as blocks. But we do not want to punish small functions which have
5054 a couple switch statements. So we require a relatively large number
5055 of basic blocks and the ratio of edges to blocks to be high. */
5056 if (n_basic_blocks > 1000 && n_edges / n_basic_blocks >= 20)
5059 /* We need four bitmaps, each with a bit for each register in each
5061 max_reg = max_reg_num ();
5062 regs_per_pass = get_bitmap_width (4, n_basic_blocks, max_reg);
5064 /* Allocate bitmaps to hold local and global properties. */
5065 npi.nonnull_local = sbitmap_vector_alloc (n_basic_blocks, regs_per_pass);
5066 npi.nonnull_killed = sbitmap_vector_alloc (n_basic_blocks, regs_per_pass);
5067 nonnull_avin = sbitmap_vector_alloc (n_basic_blocks, regs_per_pass);
5068 nonnull_avout = sbitmap_vector_alloc (n_basic_blocks, regs_per_pass);
5070 /* Go through the basic blocks, seeing whether or not each block
5071 ends with a conditional branch whose condition is a comparison
5072 against zero. Record the register compared in BLOCK_REG. */
5073 block_reg = (unsigned int *) xcalloc (n_basic_blocks, sizeof (int));
5074 for (bb = 0; bb < n_basic_blocks; bb++)
5076 rtx last_insn = BLOCK_END (bb);
5077 rtx condition, earliest, reg;
5079 /* We only want conditional branches. */
5080 if (GET_CODE (last_insn) != JUMP_INSN
5081 || !any_condjump_p (last_insn)
5082 || !onlyjump_p (last_insn))
5085 /* LAST_INSN is a conditional jump. Get its condition. */
5086 condition = get_condition (last_insn, &earliest);
5088 /* If we were unable to get the condition, or it is not a equality
5089 comparison against zero then there's nothing we can do. */
5091 || (GET_CODE (condition) != NE && GET_CODE (condition) != EQ)
5092 || GET_CODE (XEXP (condition, 1)) != CONST_INT
5093 || (XEXP (condition, 1)
5094 != CONST0_RTX (GET_MODE (XEXP (condition, 0)))))
5097 /* We must be checking a register against zero. */
5098 reg = XEXP (condition, 0);
5099 if (GET_CODE (reg) != REG)
5102 block_reg[bb] = REGNO (reg);
5105 /* Go through the algorithm for each block of registers. */
5106 for (reg = FIRST_PSEUDO_REGISTER; reg < max_reg; reg += regs_per_pass)
5109 npi.max_reg = MIN (reg + regs_per_pass, max_reg);
5110 delete_null_pointer_checks_1 (block_reg, nonnull_avin,
5111 nonnull_avout, &npi);
5114 /* Free the table of registers compared at the end of every block. */
5118 free (npi.nonnull_local);
5119 free (npi.nonnull_killed);
5120 free (nonnull_avin);
5121 free (nonnull_avout);
5124 /* Code Hoisting variables and subroutines. */
5126 /* Very busy expressions. */
5127 static sbitmap *hoist_vbein;
5128 static sbitmap *hoist_vbeout;
5130 /* Hoistable expressions. */
5131 static sbitmap *hoist_exprs;
5133 /* Dominator bitmaps. */
5134 static sbitmap *dominators;
5136 /* ??? We could compute post dominators and run this algorithm in
5137 reverse to to perform tail merging, doing so would probably be
5138 more effective than the tail merging code in jump.c.
5140 It's unclear if tail merging could be run in parallel with
5141 code hoisting. It would be nice. */
5143 /* Allocate vars used for code hoisting analysis. */
5146 alloc_code_hoist_mem (n_blocks, n_exprs)
5147 int n_blocks, n_exprs;
5149 antloc = sbitmap_vector_alloc (n_blocks, n_exprs);
5150 transp = sbitmap_vector_alloc (n_blocks, n_exprs);
5151 comp = sbitmap_vector_alloc (n_blocks, n_exprs);
5153 hoist_vbein = sbitmap_vector_alloc (n_blocks, n_exprs);
5154 hoist_vbeout = sbitmap_vector_alloc (n_blocks, n_exprs);
5155 hoist_exprs = sbitmap_vector_alloc (n_blocks, n_exprs);
5156 transpout = sbitmap_vector_alloc (n_blocks, n_exprs);
5158 dominators = sbitmap_vector_alloc (n_blocks, n_blocks);
5161 /* Free vars used for code hoisting analysis. */
5164 free_code_hoist_mem ()
5171 free (hoist_vbeout);
5178 /* Compute the very busy expressions at entry/exit from each block.
5180 An expression is very busy if all paths from a given point
5181 compute the expression. */
5184 compute_code_hoist_vbeinout ()
5186 int bb, changed, passes;
5188 sbitmap_vector_zero (hoist_vbeout, n_basic_blocks);
5189 sbitmap_vector_zero (hoist_vbein, n_basic_blocks);
5198 /* We scan the blocks in the reverse order to speed up
5200 for (bb = n_basic_blocks - 1; bb >= 0; bb--)
5202 changed |= sbitmap_a_or_b_and_c (hoist_vbein[bb], antloc[bb],
5203 hoist_vbeout[bb], transp[bb]);
5204 if (bb != n_basic_blocks - 1)
5205 sbitmap_intersection_of_succs (hoist_vbeout[bb], hoist_vbein, bb);
5212 fprintf (gcse_file, "hoisting vbeinout computation: %d passes\n", passes);
5215 /* Top level routine to do the dataflow analysis needed by code hoisting. */
5218 compute_code_hoist_data ()
5220 compute_local_properties (transp, comp, antloc, 0);
5221 compute_transpout ();
5222 compute_code_hoist_vbeinout ();
5223 compute_flow_dominators (dominators, NULL);
5225 fprintf (gcse_file, "\n");
5228 /* Determine if the expression identified by EXPR_INDEX would
5229 reach BB unimpared if it was placed at the end of EXPR_BB.
5231 It's unclear exactly what Muchnick meant by "unimpared". It seems
5232 to me that the expression must either be computed or transparent in
5233 *every* block in the path(s) from EXPR_BB to BB. Any other definition
5234 would allow the expression to be hoisted out of loops, even if
5235 the expression wasn't a loop invariant.
5237 Contrast this to reachability for PRE where an expression is
5238 considered reachable if *any* path reaches instead of *all*
5242 hoist_expr_reaches_here_p (expr_bb, expr_index, bb, visited)
5249 int visited_allocated_locally = 0;
5252 if (visited == NULL)
5254 visited_allocated_locally = 1;
5255 visited = xcalloc (n_basic_blocks, 1);
5258 visited[expr_bb] = 1;
5259 for (pred = BASIC_BLOCK (bb)->pred; pred != NULL; pred = pred->pred_next)
5261 int pred_bb = pred->src->index;
5263 if (pred->src == ENTRY_BLOCK_PTR)
5265 else if (visited[pred_bb])
5268 /* Does this predecessor generate this expression? */
5269 else if (TEST_BIT (comp[pred_bb], expr_index))
5271 else if (! TEST_BIT (transp[pred_bb], expr_index))
5277 visited[pred_bb] = 1;
5278 if (! hoist_expr_reaches_here_p (expr_bb, expr_index,
5283 if (visited_allocated_locally)
5286 return (pred == NULL);
5289 /* Actually perform code hoisting. */
5296 struct expr **index_map;
5299 sbitmap_vector_zero (hoist_exprs, n_basic_blocks);
5301 /* Compute a mapping from expression number (`bitmap_index') to
5302 hash table entry. */
5304 index_map = (struct expr **) xcalloc (n_exprs, sizeof (struct expr *));
5305 for (i = 0; i < expr_hash_table_size; i++)
5306 for (expr = expr_hash_table[i]; expr != NULL; expr = expr->next_same_hash)
5307 index_map[expr->bitmap_index] = expr;
5309 /* Walk over each basic block looking for potentially hoistable
5310 expressions, nothing gets hoisted from the entry block. */
5311 for (bb = 0; bb < n_basic_blocks; bb++)
5314 int insn_inserted_p;
5316 /* Examine each expression that is very busy at the exit of this
5317 block. These are the potentially hoistable expressions. */
5318 for (i = 0; i < hoist_vbeout[bb]->n_bits; i++)
5322 if (TEST_BIT (hoist_vbeout[bb], i) && TEST_BIT (transpout[bb], i))
5324 /* We've found a potentially hoistable expression, now
5325 we look at every block BB dominates to see if it
5326 computes the expression. */
5327 for (dominated = 0; dominated < n_basic_blocks; dominated++)
5329 /* Ignore self dominance. */
5331 || ! TEST_BIT (dominators[dominated], bb))
5334 /* We've found a dominated block, now see if it computes
5335 the busy expression and whether or not moving that
5336 expression to the "beginning" of that block is safe. */
5337 if (!TEST_BIT (antloc[dominated], i))
5340 /* Note if the expression would reach the dominated block
5341 unimpared if it was placed at the end of BB.
5343 Keep track of how many times this expression is hoistable
5344 from a dominated block into BB. */
5345 if (hoist_expr_reaches_here_p (bb, i, dominated, NULL))
5349 /* If we found more than one hoistable occurence of this
5350 expression, then note it in the bitmap of expressions to
5351 hoist. It makes no sense to hoist things which are computed
5352 in only one BB, and doing so tends to pessimize register
5353 allocation. One could increase this value to try harder
5354 to avoid any possible code expansion due to register
5355 allocation issues; however experiments have shown that
5356 the vast majority of hoistable expressions are only movable
5357 from two successors, so raising this threshhold is likely
5358 to nullify any benefit we get from code hoisting. */
5361 SET_BIT (hoist_exprs[bb], i);
5367 /* If we found nothing to hoist, then quit now. */
5371 /* Loop over all the hoistable expressions. */
5372 for (i = 0; i < hoist_exprs[bb]->n_bits; i++)
5374 /* We want to insert the expression into BB only once, so
5375 note when we've inserted it. */
5376 insn_inserted_p = 0;
5378 /* These tests should be the same as the tests above. */
5379 if (TEST_BIT (hoist_vbeout[bb], i))
5381 /* We've found a potentially hoistable expression, now
5382 we look at every block BB dominates to see if it
5383 computes the expression. */
5384 for (dominated = 0; dominated < n_basic_blocks; dominated++)
5386 /* Ignore self dominance. */
5388 || ! TEST_BIT (dominators[dominated], bb))
5391 /* We've found a dominated block, now see if it computes
5392 the busy expression and whether or not moving that
5393 expression to the "beginning" of that block is safe. */
5394 if (!TEST_BIT (antloc[dominated], i))
5397 /* The expression is computed in the dominated block and
5398 it would be safe to compute it at the start of the
5399 dominated block. Now we have to determine if the
5400 expresion would reach the dominated block if it was
5401 placed at the end of BB. */
5402 if (hoist_expr_reaches_here_p (bb, i, dominated, NULL))
5404 struct expr *expr = index_map[i];
5405 struct occr *occr = expr->antic_occr;
5409 /* Find the right occurence of this expression. */
5410 while (BLOCK_NUM (occr->insn) != dominated && occr)
5413 /* Should never happen. */
5419 set = single_set (insn);
5423 /* Create a pseudo-reg to store the result of reaching
5424 expressions into. Get the mode for the new pseudo
5425 from the mode of the original destination pseudo. */
5426 if (expr->reaching_reg == NULL)
5428 = gen_reg_rtx (GET_MODE (SET_DEST (set)));
5430 /* In theory this should never fail since we're creating
5433 However, on the x86 some of the movXX patterns
5434 actually contain clobbers of scratch regs. This may
5435 cause the insn created by validate_change to not
5436 match any pattern and thus cause validate_change to
5438 if (validate_change (insn, &SET_SRC (set),
5439 expr->reaching_reg, 0))
5441 occr->deleted_p = 1;
5442 if (!insn_inserted_p)
5444 insert_insn_end_bb (index_map[i], bb, 0);
5445 insn_inserted_p = 1;
5457 /* Top level routine to perform one code hoisting (aka unification) pass
5459 Return non-zero if a change was made. */
5462 one_code_hoisting_pass ()
5466 alloc_expr_hash_table (max_cuid);
5467 compute_expr_hash_table ();
5469 dump_hash_table (gcse_file, "Code Hosting Expressions", expr_hash_table,
5470 expr_hash_table_size, n_exprs);
5474 alloc_code_hoist_mem (n_basic_blocks, n_exprs);
5475 compute_code_hoist_data ();
5477 free_code_hoist_mem ();
5480 free_expr_hash_table ();