1 /* Redundant Extension Elimination pass for the GNU compiler.
2 Copyright (C) 2010, 2011, 2012 Free Software Foundation, Inc.
3 Contributed by Ilya Enkovich (ilya.enkovich@intel.com)
5 Based on the Redundant Zero-extension elimination pass contributed by
6 Sriraman Tallam (tmsriram@google.com) and Silvius Rus (rus@google.com).
8 This file is part of GCC.
10 GCC is free software; you can redistribute it and/or modify it under
11 the terms of the GNU General Public License as published by the Free
12 Software Foundation; either version 3, or (at your option) any later
15 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
16 WARRANTY; without even the implied warranty of MERCHANTABILITY or
17 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
20 You should have received a copy of the GNU General Public License
21 along with GCC; see the file COPYING3. If not see
22 <http://www.gnu.org/licenses/>. */
25 /* Problem Description :
27 This pass is intended to remove redundant extension instructions.
28 Such instructions appear for different reasons. We expect some of
29 them due to implicit zero-extension in 64-bit registers after writing
30 to their lower 32-bit half (e.g. for the x86-64 architecture).
31 Another possible reason is a type cast which follows a load (for
32 instance a register restore) and which can be combined into a single
33 instruction, and for which earlier local passes, e.g. the combiner,
34 weren't able to optimize.
36 How does this pass work ?
37 --------------------------
39 This pass is run after register allocation. Hence, all registers that
40 this pass deals with are hard registers. This pass first looks for an
41 extension instruction that could possibly be redundant. Such extension
42 instructions show up in RTL with the pattern :
43 (set (reg:<SWI248> x) (any_extend:<SWI248> (reg:<SWI124> x))),
44 where x can be any hard register.
45 Now, this pass tries to eliminate this instruction by merging the
46 extension with the definitions of register x. For instance, if
47 one of the definitions of register x was :
48 (set (reg:SI x) (plus:SI (reg:SI z1) (reg:SI z2))),
49 followed by extension :
50 (set (reg:DI x) (zero_extend:DI (reg:SI x)))
51 then the combination converts this into :
52 (set (reg:DI x) (zero_extend:DI (plus:SI (reg:SI z1) (reg:SI z2)))).
53 If all the merged definitions are recognizable assembly instructions,
54 the extension is effectively eliminated.
56 For example, for the x86-64 architecture, implicit zero-extensions
57 are captured with appropriate patterns in the i386.md file. Hence,
58 these merged definition can be matched to a single assembly instruction.
59 The original extension instruction is then deleted if all the
60 definitions can be merged.
62 However, there are cases where the definition instruction cannot be
63 merged with an extension. Examples are CALL instructions. In such
64 cases, the original extension is not redundant and this pass does
67 Handling conditional moves :
68 ----------------------------
70 Architectures like x86-64 support conditional moves whose semantics for
71 extension differ from the other instructions. For instance, the
72 instruction *cmov ebx, eax*
73 zero-extends eax onto rax only when the move from ebx to eax happens.
74 Otherwise, eax may not be zero-extended. Consider conditional moves as
75 RTL instructions of the form
76 (set (reg:SI x) (if_then_else (cond) (reg:SI y) (reg:SI z))).
77 This pass tries to merge an extension with a conditional move by
78 actually merging the definitions of y and z with an extension and then
79 converting the conditional move into :
80 (set (reg:DI x) (if_then_else (cond) (reg:DI y) (reg:DI z))).
81 Since registers y and z are extended, register x will also be extended
82 after the conditional move. Note that this step has to be done
83 transitively since the definition of a conditional copy can be
84 another conditional copy.
86 Motivating Example I :
89 **********************************************
102 **********************************************
106 400315: b8 4e 00 00 00 mov $0x4e,%eax
107 40031a: 0f af f8 imul %eax,%edi
108 40031d: 89 ff mov %edi,%edi - useless extension
109 40031f: 8b 04 bd 60 19 40 00 mov 0x401960(,%rdi,4),%eax
112 400330: ba 2d 00 00 00 mov $0x2d,%edx
113 400335: 0f af fa imul %edx,%edi
114 400338: 89 ff mov %edi,%edi - useless extension
115 40033a: 8b 04 bd 60 19 40 00 mov 0x401960(,%rdi,4),%eax
118 $ gcc -O2 -free bad_code.c
120 400315: 6b ff 4e imul $0x4e,%edi,%edi
121 400318: 8b 04 bd 40 19 40 00 mov 0x401940(,%rdi,4),%eax
123 400320: 6b ff 2d imul $0x2d,%edi,%edi
124 400323: 8b 04 bd 40 19 40 00 mov 0x401940(,%rdi,4),%eax
127 Motivating Example II :
128 ---------------------
130 Here is an example with a conditional move.
133 **********************************************
135 unsigned long long foo(unsigned x , unsigned y)
142 return (unsigned long long)(z);
147 400360: 8d 14 3e lea (%rsi,%rdi,1),%edx
148 400363: 89 f8 mov %edi,%eax
149 400365: 29 f0 sub %esi,%eax
150 400367: 83 ff 65 cmp $0x65,%edi
151 40036a: 0f 43 c2 cmovae %edx,%eax
152 40036d: 89 c0 mov %eax,%eax - useless extension
155 $ gcc -O2 -free bad_code.c
157 400360: 89 fa mov %edi,%edx
158 400362: 8d 04 3e lea (%rsi,%rdi,1),%eax
159 400365: 29 f2 sub %esi,%edx
160 400367: 83 ff 65 cmp $0x65,%edi
161 40036a: 89 d6 mov %edx,%esi
162 40036c: 48 0f 42 c6 cmovb %rsi,%rax
165 Motivating Example III :
166 ---------------------
168 Here is an example with a type cast.
171 **********************************************
173 void test(int size, unsigned char *in, unsigned char *out)
176 unsigned char xr, xg, xy=0;
178 for (i = 0; i < size; i++) {
181 xy = (unsigned char) ((19595*xr + 38470*xg) >> 16);
188 10: 0f b6 0e movzbl (%rsi),%ecx
189 13: 0f b6 46 01 movzbl 0x1(%rsi),%eax
190 17: 48 83 c6 02 add $0x2,%rsi
191 1b: 0f b6 c9 movzbl %cl,%ecx - useless extension
192 1e: 0f b6 c0 movzbl %al,%eax - useless extension
193 21: 69 c9 8b 4c 00 00 imul $0x4c8b,%ecx,%ecx
194 27: 69 c0 46 96 00 00 imul $0x9646,%eax,%eax
196 $ gcc -O2 -free bad_code.c
198 10: 0f b6 0e movzbl (%rsi),%ecx
199 13: 0f b6 46 01 movzbl 0x1(%rsi),%eax
200 17: 48 83 c6 02 add $0x2,%rsi
201 1b: 69 c9 8b 4c 00 00 imul $0x4c8b,%ecx,%ecx
202 21: 69 c0 46 96 00 00 imul $0x9646,%eax,%eax
207 The original redundant zero-extension elimination pass reported reduction
208 of the dynamic instruction count of a compression benchmark by 2.8% and
209 improvement of its run time by about 1%.
211 The additional performance gain with the enhanced pass is mostly expected
212 on in-order architectures where redundancy cannot be compensated by out of
213 order execution. Measurements showed up to 10% performance gain (reduced
214 run time) on EEMBC 2.0 benchmarks on Atom processor with geomean performance
220 #include "coretypes.h"
227 #include "hard-reg-set.h"
228 #include "basic-block.h"
229 #include "insn-config.h"
230 #include "function.h"
232 #include "insn-attr.h"
234 #include "diagnostic-core.h"
238 #include "insn-codes.h"
239 #include "rtlhooks-def.h"
240 /* Include output.h for dump_file. */
244 #include "tree-pass.h"
248 /* This structure represents a candidate for elimination. */
250 typedef struct GTY(()) ext_cand
252 /* The expression. */
255 /* The kind of extension. */
258 /* The destination mode. */
259 enum machine_mode mode
;
261 /* The instruction where it lives. */
266 DEF_VEC_ALLOC_O(ext_cand
, heap
);
268 static int max_insn_uid
;
270 /* Given a insn (CURR_INSN), an extension candidate for removal (CAND)
271 and a pointer to the SET rtx (ORIG_SET) that needs to be modified,
272 this code modifies the SET rtx to a new SET rtx that extends the
273 right hand expression into a register on the left hand side. Note
274 that multiple assumptions are made about the nature of the set that
275 needs to be true for this to work and is called from merge_def_and_ext.
278 (set (reg a) (expression))
281 (set (reg a) (any_extend (expression)))
284 If the expression is a constant or another extension, then directly
285 assign it to the register. */
288 combine_set_extension (ext_cand
*cand
, rtx curr_insn
, rtx
*orig_set
)
290 rtx orig_src
= SET_SRC (*orig_set
);
291 rtx new_reg
= gen_rtx_REG (cand
->mode
, REGNO (SET_DEST (*orig_set
)));
294 /* Merge constants by directly moving the constant into the register under
295 some conditions. Recall that RTL constants are sign-extended. */
296 if (GET_CODE (orig_src
) == CONST_INT
297 && HOST_BITS_PER_WIDE_INT
>= GET_MODE_BITSIZE (cand
->mode
))
299 if (INTVAL (orig_src
) >= 0 || cand
->code
== SIGN_EXTEND
)
300 new_set
= gen_rtx_SET (VOIDmode
, new_reg
, orig_src
);
303 /* Zero-extend the negative constant by masking out the bits outside
305 enum machine_mode src_mode
= GET_MODE (SET_DEST (*orig_set
));
307 = GEN_INT (INTVAL (orig_src
) & GET_MODE_MASK (src_mode
));
308 new_set
= gen_rtx_SET (VOIDmode
, new_reg
, new_const_int
);
311 else if (GET_MODE (orig_src
) == VOIDmode
)
313 /* This is mostly due to a call insn that should not be optimized. */
316 else if (GET_CODE (orig_src
) == cand
->code
)
318 /* Here is a sequence of two extensions. Try to merge them. */
320 = gen_rtx_fmt_e (cand
->code
, cand
->mode
, XEXP (orig_src
, 0));
321 rtx simplified_temp_extension
= simplify_rtx (temp_extension
);
322 if (simplified_temp_extension
)
323 temp_extension
= simplified_temp_extension
;
324 new_set
= gen_rtx_SET (VOIDmode
, new_reg
, temp_extension
);
326 else if (GET_CODE (orig_src
) == IF_THEN_ELSE
)
328 /* Only IF_THEN_ELSE of phi-type copies are combined. Otherwise,
329 in general, IF_THEN_ELSE should not be combined. */
334 /* This is the normal case. */
336 = gen_rtx_fmt_e (cand
->code
, cand
->mode
, orig_src
);
337 rtx simplified_temp_extension
= simplify_rtx (temp_extension
);
338 if (simplified_temp_extension
)
339 temp_extension
= simplified_temp_extension
;
340 new_set
= gen_rtx_SET (VOIDmode
, new_reg
, temp_extension
);
343 /* This change is a part of a group of changes. Hence,
344 validate_change will not try to commit the change. */
345 if (validate_change (curr_insn
, orig_set
, new_set
, true))
350 "Tentatively merged extension with definition:\n");
351 print_rtl_single (dump_file
, curr_insn
);
359 /* Treat if_then_else insns, where the operands of both branches
360 are registers, as copies. For instance,
362 (set (reg:SI a) (if_then_else (cond) (reg:SI b) (reg:SI c)))
364 (set (reg:DI a) (if_then_else (cond) (reg:DI b) (reg:DI c)))
365 DEF_INSN is the if_then_else insn. */
368 transform_ifelse (ext_cand
*cand
, rtx def_insn
)
370 rtx set_insn
= PATTERN (def_insn
);
371 rtx srcreg
, dstreg
, srcreg2
;
372 rtx map_srcreg
, map_dstreg
, map_srcreg2
;
377 gcc_assert (GET_CODE (set_insn
) == SET
);
379 cond
= XEXP (SET_SRC (set_insn
), 0);
380 dstreg
= SET_DEST (set_insn
);
381 srcreg
= XEXP (SET_SRC (set_insn
), 1);
382 srcreg2
= XEXP (SET_SRC (set_insn
), 2);
383 /* If the conditional move already has the right or wider mode,
384 there is nothing to do. */
385 if (GET_MODE_SIZE (GET_MODE (dstreg
)) >= GET_MODE_SIZE (cand
->mode
))
388 map_srcreg
= gen_rtx_REG (cand
->mode
, REGNO (srcreg
));
389 map_srcreg2
= gen_rtx_REG (cand
->mode
, REGNO (srcreg2
));
390 map_dstreg
= gen_rtx_REG (cand
->mode
, REGNO (dstreg
));
391 ifexpr
= gen_rtx_IF_THEN_ELSE (cand
->mode
, cond
, map_srcreg
, map_srcreg2
);
392 new_set
= gen_rtx_SET (VOIDmode
, map_dstreg
, ifexpr
);
394 if (validate_change (def_insn
, &PATTERN (def_insn
), new_set
, true))
399 "Mode of conditional move instruction extended:\n");
400 print_rtl_single (dump_file
, def_insn
);
408 /* Get all the reaching definitions of an instruction. The definitions are
409 desired for REG used in INSN. Return the definition list or NULL if a
410 definition is missing. If DEST is non-NULL, additionally push the INSN
411 of the definitions onto DEST. */
413 static struct df_link
*
414 get_defs (rtx insn
, rtx reg
, VEC (rtx
,heap
) **dest
)
416 df_ref reg_info
, *uses
;
417 struct df_link
*ref_chain
, *ref_link
;
421 for (uses
= DF_INSN_USES (insn
); *uses
; uses
++)
424 if (GET_CODE (DF_REF_REG (reg_info
)) == SUBREG
)
426 if (REGNO (DF_REF_REG (reg_info
)) == REGNO (reg
))
430 gcc_assert (reg_info
!= NULL
&& uses
!= NULL
);
432 ref_chain
= DF_REF_CHAIN (reg_info
);
434 for (ref_link
= ref_chain
; ref_link
; ref_link
= ref_link
->next
)
436 /* Problem getting some definition for this instruction. */
437 if (ref_link
->ref
== NULL
)
439 if (DF_REF_INSN_INFO (ref_link
->ref
) == NULL
)
444 for (ref_link
= ref_chain
; ref_link
; ref_link
= ref_link
->next
)
445 VEC_safe_push (rtx
, heap
, *dest
, DF_REF_INSN (ref_link
->ref
));
450 /* Return true if INSN is
451 (SET (reg REGNO (def_reg)) (if_then_else (cond) (REG x1) (REG x2)))
452 and store x1 and x2 in REG_1 and REG_2. */
455 is_cond_copy_insn (rtx insn
, rtx
*reg1
, rtx
*reg2
)
457 rtx expr
= single_set (insn
);
460 && GET_CODE (expr
) == SET
461 && GET_CODE (SET_DEST (expr
)) == REG
462 && GET_CODE (SET_SRC (expr
)) == IF_THEN_ELSE
463 && GET_CODE (XEXP (SET_SRC (expr
), 1)) == REG
464 && GET_CODE (XEXP (SET_SRC (expr
), 2)) == REG
)
466 *reg1
= XEXP (SET_SRC (expr
), 1);
467 *reg2
= XEXP (SET_SRC (expr
), 2);
474 enum ext_modified_kind
476 /* The insn hasn't been modified by ree pass yet. */
478 /* Changed into zero extension. */
480 /* Changed into sign extension. */
486 /* Mode from which ree has zero or sign extended the destination. */
487 ENUM_BITFIELD(machine_mode
) mode
: 8;
489 /* Kind of modification of the insn. */
490 ENUM_BITFIELD(ext_modified_kind
) kind
: 2;
492 /* True if the insn is scheduled to be deleted. */
493 unsigned int deleted
: 1;
496 /* Vectors used by combine_reaching_defs and its helpers. */
497 typedef struct ext_state
499 /* In order to avoid constant VEC_alloc/VEC_free, we keep these
500 4 vectors live through the entire find_and_remove_re and just
501 VEC_truncate them each time. */
502 VEC (rtx
, heap
) *defs_list
;
503 VEC (rtx
, heap
) *copies_list
;
504 VEC (rtx
, heap
) *modified_list
;
505 VEC (rtx
, heap
) *work_list
;
507 /* For instructions that have been successfully modified, this is
508 the original mode from which the insn is extending and
509 kind of extension. */
510 struct ext_modified
*modified
;
513 /* Reaching Definitions of the extended register could be conditional copies
514 or regular definitions. This function separates the two types into two
515 lists, STATE->DEFS_LIST and STATE->COPIES_LIST. This is necessary because,
516 if a reaching definition is a conditional copy, merging the extension with
517 this definition is wrong. Conditional copies are merged by transitively
518 merging their definitions. The defs_list is populated with all the reaching
519 definitions of the extension instruction (EXTEND_INSN) which must be merged
520 with an extension. The copies_list contains all the conditional moves that
521 will later be extended into a wider mode conditional move if all the merges
522 are successful. The function returns false upon failure, true upon
526 make_defs_and_copies_lists (rtx extend_insn
, const_rtx set_pat
,
529 rtx src_reg
= XEXP (SET_SRC (set_pat
), 0);
530 bool *is_insn_visited
;
533 VEC_truncate (rtx
, state
->work_list
, 0);
535 /* Initialize the work list. */
536 if (!get_defs (extend_insn
, src_reg
, &state
->work_list
))
539 is_insn_visited
= XCNEWVEC (bool, max_insn_uid
);
541 /* Perform transitive closure for conditional copies. */
542 while (!VEC_empty (rtx
, state
->work_list
))
544 rtx def_insn
= VEC_pop (rtx
, state
->work_list
);
547 gcc_assert (INSN_UID (def_insn
) < max_insn_uid
);
549 if (is_insn_visited
[INSN_UID (def_insn
)])
551 is_insn_visited
[INSN_UID (def_insn
)] = true;
553 if (is_cond_copy_insn (def_insn
, ®1
, ®2
))
555 /* Push it onto the copy list first. */
556 VEC_safe_push (rtx
, heap
, state
->copies_list
, def_insn
);
558 /* Now perform the transitive closure. */
559 if (!get_defs (def_insn
, reg1
, &state
->work_list
)
560 || !get_defs (def_insn
, reg2
, &state
->work_list
))
567 VEC_safe_push (rtx
, heap
, state
->defs_list
, def_insn
);
570 XDELETEVEC (is_insn_visited
);
575 /* Merge the DEF_INSN with an extension. Calls combine_set_extension
576 on the SET pattern. */
579 merge_def_and_ext (ext_cand
*cand
, rtx def_insn
, ext_state
*state
)
581 enum machine_mode ext_src_mode
;
587 ext_src_mode
= GET_MODE (XEXP (SET_SRC (cand
->expr
), 0));
588 code
= GET_CODE (PATTERN (def_insn
));
591 if (code
== PARALLEL
)
593 for (i
= 0; i
< XVECLEN (PATTERN (def_insn
), 0); i
++)
595 s_expr
= XVECEXP (PATTERN (def_insn
), 0, i
);
596 if (GET_CODE (s_expr
) != SET
)
600 sub_rtx
= &XVECEXP (PATTERN (def_insn
), 0, i
);
603 /* PARALLEL with multiple SETs. */
608 else if (code
== SET
)
609 sub_rtx
= &PATTERN (def_insn
);
612 /* It is not a PARALLEL or a SET, what could it be ? */
616 gcc_assert (sub_rtx
!= NULL
);
618 if (REG_P (SET_DEST (*sub_rtx
))
619 && (GET_MODE (SET_DEST (*sub_rtx
)) == ext_src_mode
620 || ((state
->modified
[INSN_UID (def_insn
)].kind
621 == (cand
->code
== ZERO_EXTEND
622 ? EXT_MODIFIED_ZEXT
: EXT_MODIFIED_SEXT
))
623 && state
->modified
[INSN_UID (def_insn
)].mode
626 if (GET_MODE_SIZE (GET_MODE (SET_DEST (*sub_rtx
)))
627 >= GET_MODE_SIZE (cand
->mode
))
629 /* If def_insn is already scheduled to be deleted, don't attempt
631 if (state
->modified
[INSN_UID (def_insn
)].deleted
)
633 if (combine_set_extension (cand
, def_insn
, sub_rtx
))
635 if (state
->modified
[INSN_UID (def_insn
)].kind
== EXT_MODIFIED_NONE
)
636 state
->modified
[INSN_UID (def_insn
)].mode
= ext_src_mode
;
644 /* This function goes through all reaching defs of the source
645 of the candidate for elimination (CAND) and tries to combine
646 the extension with the definition instruction. The changes
647 are made as a group so that even if one definition cannot be
648 merged, all reaching definitions end up not being merged.
649 When a conditional copy is encountered, merging is attempted
650 transitively on its definitions. It returns true upon success
651 and false upon failure. */
654 combine_reaching_defs (ext_cand
*cand
, const_rtx set_pat
, ext_state
*state
)
657 bool merge_successful
= true;
662 VEC_truncate (rtx
, state
->defs_list
, 0);
663 VEC_truncate (rtx
, state
->copies_list
, 0);
665 outcome
= make_defs_and_copies_lists (cand
->insn
, set_pat
, state
);
670 merge_successful
= true;
672 /* Go through the defs vector and try to merge all the definitions
674 VEC_truncate (rtx
, state
->modified_list
, 0);
675 FOR_EACH_VEC_ELT (rtx
, state
->defs_list
, defs_ix
, def_insn
)
677 if (merge_def_and_ext (cand
, def_insn
, state
))
678 VEC_safe_push (rtx
, heap
, state
->modified_list
, def_insn
);
681 merge_successful
= false;
686 /* Now go through the conditional copies vector and try to merge all
687 the copies in this vector. */
688 if (merge_successful
)
690 FOR_EACH_VEC_ELT (rtx
, state
->copies_list
, i
, def_insn
)
692 if (transform_ifelse (cand
, def_insn
))
693 VEC_safe_push (rtx
, heap
, state
->modified_list
, def_insn
);
696 merge_successful
= false;
702 if (merge_successful
)
704 /* Commit the changes here if possible
705 FIXME: It's an all-or-nothing scenario. Even if only one definition
706 cannot be merged, we entirely give up. In the future, we should allow
707 extensions to be partially eliminated along those paths where the
708 definitions could be merged. */
709 if (apply_change_group ())
712 fprintf (dump_file
, "All merges were successful.\n");
714 FOR_EACH_VEC_ELT (rtx
, state
->modified_list
, i
, def_insn
)
715 if (state
->modified
[INSN_UID (def_insn
)].kind
== EXT_MODIFIED_NONE
)
716 state
->modified
[INSN_UID (def_insn
)].kind
717 = (cand
->code
== ZERO_EXTEND
718 ? EXT_MODIFIED_ZEXT
: EXT_MODIFIED_SEXT
);
724 /* Changes need not be cancelled explicitly as apply_change_group
725 does it. Print list of definitions in the dump_file for debug
726 purposes. This extension cannot be deleted. */
730 "Merge cancelled, non-mergeable definitions:\n");
731 FOR_EACH_VEC_ELT (rtx
, state
->modified_list
, i
, def_insn
)
732 print_rtl_single (dump_file
, def_insn
);
738 /* Cancel any changes that have been made so far. */
745 /* Add an extension pattern that could be eliminated. */
748 add_removable_extension (const_rtx expr
, rtx insn
,
749 VEC (ext_cand
, heap
) **insn_list
,
753 enum machine_mode mode
;
757 /* We are looking for SET (REG N) (ANY_EXTEND (REG N)). */
758 if (GET_CODE (expr
) != SET
)
761 src
= SET_SRC (expr
);
762 code
= GET_CODE (src
);
763 dest
= SET_DEST (expr
);
764 mode
= GET_MODE (dest
);
767 && (code
== SIGN_EXTEND
|| code
== ZERO_EXTEND
)
768 && REG_P (XEXP (src
, 0))
769 && REGNO (dest
) == REGNO (XEXP (src
, 0)))
771 struct df_link
*defs
, *def
;
774 /* First, make sure we can get all the reaching definitions. */
775 defs
= get_defs (insn
, XEXP (src
, 0), NULL
);
780 fprintf (dump_file
, "Cannot eliminate extension:\n");
781 print_rtl_single (dump_file
, insn
);
782 fprintf (dump_file
, " because of missing definition(s)\n");
787 /* Second, make sure the reaching definitions don't feed another and
788 different extension. FIXME: this obviously can be improved. */
789 for (def
= defs
; def
; def
= def
->next
)
790 if ((idx
= def_map
[INSN_UID(DF_REF_INSN (def
->ref
))])
791 && (cand
= VEC_index (ext_cand
, *insn_list
, idx
- 1))
792 && (cand
->code
!= code
|| cand
->mode
!= mode
))
796 fprintf (dump_file
, "Cannot eliminate extension:\n");
797 print_rtl_single (dump_file
, insn
);
798 fprintf (dump_file
, " because of other extension\n");
803 /* Then add the candidate to the list and insert the reaching definitions
804 into the definition map. */
805 cand
= VEC_safe_push (ext_cand
, heap
, *insn_list
, NULL
);
810 idx
= VEC_length (ext_cand
, *insn_list
);
812 for (def
= defs
; def
; def
= def
->next
)
813 def_map
[INSN_UID(DF_REF_INSN (def
->ref
))] = idx
;
817 /* Traverse the instruction stream looking for extensions and return the
818 list of candidates. */
820 static VEC (ext_cand
, heap
)*
821 find_removable_extensions (void)
823 VEC (ext_cand
, heap
) *insn_list
= NULL
;
826 unsigned *def_map
= XCNEWVEC (unsigned, max_insn_uid
);
829 FOR_BB_INSNS (bb
, insn
)
831 if (!NONDEBUG_INSN_P (insn
))
834 set
= single_set (insn
);
837 add_removable_extension (set
, insn
, &insn_list
, def_map
);
840 XDELETEVEC (def_map
);
845 /* This is the main function that checks the insn stream for redundant
846 extensions and tries to remove them if possible. */
849 find_and_remove_re (void)
852 rtx curr_insn
= NULL_RTX
;
853 int num_re_opportunities
= 0, num_realized
= 0, i
;
854 VEC (ext_cand
, heap
) *reinsn_list
;
855 VEC (rtx
, heap
) *reinsn_del_list
;
858 /* Construct DU chain to get all reaching definitions of each
859 extension instruction. */
860 df_chain_add_problem (DF_UD_CHAIN
+ DF_DU_CHAIN
);
862 df_set_flags (DF_DEFER_INSN_RESCAN
);
864 max_insn_uid
= get_max_uid ();
865 reinsn_del_list
= NULL
;
866 reinsn_list
= find_removable_extensions ();
867 state
.defs_list
= NULL
;
868 state
.copies_list
= NULL
;
869 state
.modified_list
= NULL
;
870 state
.work_list
= NULL
;
871 if (VEC_empty (ext_cand
, reinsn_list
))
872 state
.modified
= NULL
;
874 state
.modified
= XCNEWVEC (struct ext_modified
, max_insn_uid
);
876 FOR_EACH_VEC_ELT (ext_cand
, reinsn_list
, i
, curr_cand
)
878 num_re_opportunities
++;
880 /* Try to combine the extension with the definition. */
883 fprintf (dump_file
, "Trying to eliminate extension:\n");
884 print_rtl_single (dump_file
, curr_cand
->insn
);
887 if (combine_reaching_defs (curr_cand
, curr_cand
->expr
, &state
))
890 fprintf (dump_file
, "Eliminated the extension.\n");
892 VEC_safe_push (rtx
, heap
, reinsn_del_list
, curr_cand
->insn
);
893 state
.modified
[INSN_UID (curr_cand
->insn
)].deleted
= 1;
897 /* Delete all useless extensions here in one sweep. */
898 FOR_EACH_VEC_ELT (rtx
, reinsn_del_list
, i
, curr_insn
)
899 delete_insn (curr_insn
);
901 VEC_free (ext_cand
, heap
, reinsn_list
);
902 VEC_free (rtx
, heap
, reinsn_del_list
);
903 VEC_free (rtx
, heap
, state
.defs_list
);
904 VEC_free (rtx
, heap
, state
.copies_list
);
905 VEC_free (rtx
, heap
, state
.modified_list
);
906 VEC_free (rtx
, heap
, state
.work_list
);
907 XDELETEVEC (state
.modified
);
909 if (dump_file
&& num_re_opportunities
> 0)
910 fprintf (dump_file
, "Elimination opportunities = %d realized = %d\n",
911 num_re_opportunities
, num_realized
);
913 df_finish_pass (false);
916 /* Find and remove redundant extensions. */
919 rest_of_handle_ree (void)
921 timevar_push (TV_REE
);
922 find_and_remove_re ();
923 timevar_pop (TV_REE
);
927 /* Run REE pass when flag_ree is set at optimization level > 0. */
930 gate_handle_ree (void)
932 return (optimize
> 0 && flag_ree
);
935 struct rtl_opt_pass pass_ree
=
940 gate_handle_ree
, /* gate */
941 rest_of_handle_ree
, /* execute */
944 0, /* static_pass_number */
946 0, /* properties_required */
947 0, /* properties_provided */
948 0, /* properties_destroyed */
949 0, /* todo_flags_start */
951 TODO_verify_rtl_sharing
, /* todo_flags_finish */