===================================================================
@@ -100,17 +100,17 @@ along with GCC; see the file COPYING3.
}
**********************************************
- $ gcc -O2 -fsee bad_code.c (Turned on existing sign-extension elimination.)
+ $ gcc -O2 -fsee bad_code.c (Turned on existing sign-extension elimination)
........
400315: b8 4e 00 00 00 mov $0x4e,%eax
40031a: 0f af f8 imul %eax,%edi
- 40031d: 89 ff mov %edi,%edi ---> Useless extend.
+ 40031d: 89 ff mov %edi,%edi --> Useless extend
40031f: 8b 04 bd 60 19 40 00 mov 0x401960(,%rdi,4),%eax
400326: c3 retq
......
400330: ba 2d 00 00 00 mov $0x2d,%edx
400335: 0f af fa imul %edx,%edi
- 400338: 89 ff mov %edi,%edi ---> Useless extend.
+ 400338: 89 ff mov %edi,%edi --> Useless extend
40033a: 8b 04 bd 60 19 40 00 mov 0x401960(,%rdi,4),%eax
400341: c3 retq
@@ -141,14 +141,14 @@ along with GCC; see the file COPYING3.
return (unsigned long long)(z);
}
- $ gcc -O2 -fsee bad_code.c (Turned on existing sign-extension elimination.)
+ $ gcc -O2 -fsee bad_code.c (Turned on existing sign-extension elimination)
............
400360: 8d 14 3e lea (%rsi,%rdi,1),%edx
400363: 89 f8 mov %edi,%eax
400365: 29 f0 sub %esi,%eax
400367: 83 ff 65 cmp $0x65,%edi
40036a: 0f 43 c2 cmovae %edx,%eax
- 40036d: 89 c0 mov %eax,%eax ---> Useless extend.
+ 40036d: 89 c0 mov %eax,%eax --> Useless extend
40036f: c3 retq
$ gcc -O2 -fzee bad_code.c
@@ -165,16 +165,13 @@ along with GCC; see the file COPYING3.
Usefulness :
----------
- This pass reduces the dynamic instruction count of a compression benchmark by
- 2.8% and improves its run-time by about 1%. The compression benchmark had the
- following code sequence in a very hot region of code before ZEE optimized it :
+ This pass reduces the dynamic instruction count of a compression benchmark
+ by 2.8% and improves its run time by about 1%. The compression benchmark
+ had the following code sequence in a very hot region of code before ZEE
+ optimized it :
shr $0x5, %edx
- mov %edx, %edx --> Useless zero-extend.
-
- How to turn on ?
- ----------------
- -fzee -O2. */
+ mov %edx, %edx --> Useless zero-extend */
#include "config.h"
@@ -240,31 +237,6 @@ set_insn_status (rtx insn, enum insn_mer
is_insn_merge_attempted[INSN_UID (insn)] = code;
}
-/* Check to see if this zero-extend matches a pattern
- that could be eliminated. This is called via
- for_each_rtx in function find_and_remove_ze. */
-
-static int
-is_set_with_extension_DI (rtx *expr, void *data)
-{
- /* Looking only for patterns of the type :
- SET (REG:DI X) (ZERO_EXTEND (REG:SI x))
- */
-
- if (GET_CODE (*expr) == SET
- && GET_MODE (SET_DEST (*expr)) == DImode
- && GET_CODE (SET_DEST (*expr)) == REG
- && GET_CODE (SET_SRC (*expr)) == ZERO_EXTEND
- && GET_CODE (XEXP (SET_SRC (*expr),0)) == REG
- && GET_MODE (XEXP (SET_SRC (*expr),0)) == SImode
- && REGNO (SET_DEST (*expr)) == REGNO (XEXP (SET_SRC (*expr),0)))
- {
- *(rtx **)(data) = expr;
- return 1;
- }
- return 0;
-}
-
/* Given a insn (CURR_INSN) and a pointer to the SET rtx (ORIG_SET)
that needs to be modified, this code modifies the SET rtx to a
new SET rtx that zero_extends the right hand expression into a DImode
@@ -737,7 +709,7 @@ combine_reaching_defs (rtx zero_extend_i
VEC_free (rtx, heap, defs_list);
VEC_free (rtx, heap, copies_list);
if (dump_file)
- fprintf (dump_file, "All definitions have been merged previously...\n");
+ fprintf (dump_file, "All definitions have been merged previously.\n");
return true;
}
@@ -812,8 +784,8 @@ combine_reaching_defs (rtx zero_extend_i
}
else
{
- /* Changes need not be cancelled explicitly as apply_change_group ()
- does it. Print list of definitions in the dump_file for debug
+ /* Changes need not be cancelled explicitly as apply_change_group
+ does it. Print list of definitions in the dump_file for debug
purposes. This zero-extension cannot be deleted. */
if (dump_file)
@@ -838,50 +810,74 @@ combine_reaching_defs (rtx zero_extend_i
return false;
}
-/* Goes through the instruction stream looking for zero-extends. If the zero
- extension instruction has atleast one def it adds it to a list of possible
- candidates for deletion. It returns the list of candidates. */
+/* Carry information about zero-extensions while walking the RTL. */
-static VEC (rtx,heap)*
-find_removable_zero_extends (void)
+struct zero_extend_info
{
- VEC (rtx, heap) *zeinsn_list;
- basic_block curr_block;
- rtx curr_insn;
- rtx *set_insn;
- rtx which_reg;
- int type ;
- int has_defs;
+ /* The insn where the zero-extension is. */
+ rtx insn;
- zeinsn_list = VEC_alloc (rtx, heap, 8);
- FOR_EACH_BB (curr_block)
- {
- FOR_BB_INSNS (curr_block, curr_insn)
- {
- if (!NONDEBUG_INSN_P (curr_insn))
- continue;
+ /* The list of candidates. */
+ VEC (rtx, heap) *insn_list;
+};
- type = for_each_rtx (&PATTERN (curr_insn),
- is_set_with_extension_DI,
- (void *)&set_insn);
+/* Add a zero-extend pattern that could be eliminated. This is called via
+ note_stores from find_removable_zero_extends. */
- if (!type)
- continue;
+static void
+add_removable_zero_extend (rtx x ATTRIBUTE_UNUSED, const_rtx expr, void *data)
+{
+ struct zero_extend_info *zei = (struct zero_extend_info *)data;
+ rtx src, dest;
- which_reg = XEXP (SET_SRC (*set_insn), 0);
- has_defs = get_defs (curr_insn, which_reg, NULL);
- if (has_defs)
- VEC_safe_push (rtx, heap, zeinsn_list, curr_insn);
- else if (dump_file)
- {
- fprintf (dump_file, "Cannot eliminate zero extension : \n");
- print_rtl_single (dump_file, curr_insn);
- fprintf (dump_file,
- "This has no defs. Could be extending parameters.\n");
- }
- }
+ /* We are looking for SET (REG:DI N) (ZERO_EXTEND (REG:SI N)). */
+ if (GET_CODE (expr) != SET)
+ return;
+
+ src = SET_SRC (expr);
+ dest = SET_DEST (expr);
+
+ if (REG_P (dest)
+ && GET_MODE (dest) == DImode
+ && GET_CODE (src) == ZERO_EXTEND
+ && REG_P (XEXP (src, 0))
+ && GET_MODE (XEXP (src, 0)) == SImode
+ && REGNO (dest) == REGNO (XEXP (src, 0)))
+ {
+ if (get_defs (zei->insn, XEXP (src, 0), NULL))
+ VEC_safe_push (rtx, heap, zei->insn_list, zei->insn);
+ else if (dump_file)
+ {
+ fprintf (dump_file, "Cannot eliminate zero-extension: \n");
+ print_rtl_single (dump_file, zei->insn);
+ fprintf (dump_file, "No defs. Could be extending parameters.\n");
+ }
}
- return zeinsn_list;
+}
+
+/* Traverse the instruction stream looking for zero-extends and return the
+ list of candidates. */
+
+static VEC (rtx,heap)*
+find_removable_zero_extends (void)
+{
+ struct zero_extend_info zei;
+ basic_block bb;
+ rtx insn;
+
+ zei.insn_list = VEC_alloc (rtx, heap, 8);
+
+ FOR_EACH_BB (bb)
+ FOR_BB_INSNS (bb, insn)
+ {
+ if (!NONDEBUG_INSN_P (insn))
+ continue;
+
+ zei.insn = insn;
+ note_stores (PATTERN (insn), add_removable_zero_extend, &zei);
+ }
+
+ return zei.insn_list;
}
/* This is the main function that checks the insn stream for redundant
@@ -906,13 +902,12 @@ find_and_remove_ze (void)
max_insn_uid = get_max_uid ();
- is_insn_merge_attempted = XNEWVEC (enum insn_merge_code,
- sizeof (enum insn_merge_code)* max_insn_uid);
+ is_insn_merge_attempted
+ = XNEWVEC (enum insn_merge_code,
+ sizeof (enum insn_merge_code) * max_insn_uid);
for (i = 0; i < max_insn_uid; i++)
- {
- is_insn_merge_attempted[i] = MERGE_NOT_ATTEMPTED;
- }
+ is_insn_merge_attempted[i] = MERGE_NOT_ATTEMPTED;
num_ze_opportunities = num_realized = 0;
@@ -942,9 +937,7 @@ find_and_remove_ze (void)
/* Delete all useless zero extensions here in one sweep. */
for (ix = 0; VEC_iterate (rtx, zeinsn_del_list, ix, curr_insn); ix++)
- {
- delete_insn (curr_insn);
- }
+ delete_insn (curr_insn);
free (is_insn_merge_attempted);
VEC_free (rtx, heap, zeinsn_list);