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compare-elim.c: Fix head comment.

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* compare-elim.c: Fix head comment.
	(conforming_compare): Remove redundant test.
	(can_eliminate_compare): New function extracted from...
	(before_dom_children): ...here.  Use it, replace direct uses of
	flag_non_call_exceptions and tidy up.
	(maybe_select_cc_mode): Tidy up.

From-SVN: r218468
This commit is contained in:
Eric Botcazou 2014-12-07 21:55:47 +00:00 committed by Eric Botcazou
parent bbea402544
commit 6c6a593dc0
2 changed files with 62 additions and 54 deletions
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9
gcc/ChangeLog
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@ -1,3 +1,12 @@
2014-12-07 Eric Botcazou <ebotcazou@adacore.com>
* compare-elim.c: Fix head comment.
(conforming_compare): Remove redundant test.
(can_eliminate_compare): New function extracted from...
(before_dom_children): ...here. Use it, replace direct uses of
flag_non_call_exceptions and tidy up.
(maybe_select_cc_mode): Tidy up.
2014-12-07 Felix Yang <felix.yang@huawei.com>
Shanyao Chen <chenshanyao@huawei.com>

93
gcc/compare-elim.c
View File

@ -35,7 +35,7 @@ along with GCC; see the file COPYING3. If not see
(1) All comparison patterns are represented as
[(set (reg:CC) (compare:CC (reg) (immediate)))]
[(set (reg:CC) (compare:CC (reg) (reg_or_immediate)))]
(2) All insn patterns that modify the flags are represented as
@ -157,7 +157,6 @@ conforming_compare (rtx_insn *insn)
return NULL;
if (REG_P (XEXP (src, 0))
&& REG_P (XEXP (src, 0))
&& (REG_P (XEXP (src, 1)) || CONSTANT_P (XEXP (src, 1))))
return src;
@ -266,6 +265,45 @@ public:
virtual void before_dom_children (basic_block);
};
/* Return true if conforming COMPARE with EH_NOTE is redundant with comparison
CMP and can thus be eliminated. */
static bool
can_eliminate_compare (rtx compare, rtx eh_note, struct comparison *cmp)
{
/* Take care that it's in the same EH region. */
if (cfun->can_throw_non_call_exceptions
&& !rtx_equal_p (eh_note, cmp->eh_note))
return false;
/* Make sure the compare is redundant with the previous. */
if (!rtx_equal_p (XEXP (compare, 0), cmp->in_a)
|| !rtx_equal_p (XEXP (compare, 1), cmp->in_b))
return false;
/* New mode must be compatible with the previous compare mode. */
enum machine_mode new_mode
= targetm.cc_modes_compatible (GET_MODE (compare), cmp->orig_mode);
if (new_mode == VOIDmode)
return false;
if (cmp->orig_mode != new_mode)
{
/* Generate new comparison for substitution. */
rtx flags = gen_rtx_REG (new_mode, targetm.flags_regnum);
rtx x = gen_rtx_COMPARE (new_mode, cmp->in_a, cmp->in_b);
x = gen_rtx_SET (VOIDmode, flags, x);
if (!validate_change (cmp->insn, &PATTERN (cmp->insn), x, false))
return false;
cmp->orig_mode = new_mode;
}
return true;
}
/* Identify comparison instructions within BB. If the flags from the last
compare in the BB is live at the end of the block, install the compare
in BB->AUX. Called via dom_walker.walk (). */
@ -317,62 +355,26 @@ find_comparison_dom_walker::before_dom_children (basic_block bb)
src = conforming_compare (insn);
if (src)
{
machine_mode src_mode = GET_MODE (src);
rtx eh_note = NULL;
if (flag_non_call_exceptions)
if (cfun->can_throw_non_call_exceptions)
eh_note = find_reg_note (insn, REG_EH_REGION, NULL);
if (!last_cmp_valid)
goto dont_delete;
/* Take care that it's in the same EH region. */
if (flag_non_call_exceptions
&& !rtx_equal_p (eh_note, last_cmp->eh_note))
goto dont_delete;
/* Make sure the compare is redundant with the previous. */
if (!rtx_equal_p (last_cmp->in_a, XEXP (src, 0))
|| !rtx_equal_p (last_cmp->in_b, XEXP (src, 1)))
goto dont_delete;
/* New mode must be compatible with the previous compare mode. */
if (last_cmp_valid && can_eliminate_compare (src, eh_note, last_cmp))
{
machine_mode new_mode
= targetm.cc_modes_compatible (last_cmp->orig_mode, src_mode);
if (new_mode == VOIDmode)
goto dont_delete;
if (new_mode != last_cmp->orig_mode)
{
rtx x, flags = gen_rtx_REG (src_mode, targetm.flags_regnum);
/* Generate new comparison for substitution. */
x = gen_rtx_COMPARE (new_mode, XEXP (src, 0), XEXP (src, 1));
x = gen_rtx_SET (VOIDmode, flags, x);
if (!validate_change (last_cmp->insn,
&PATTERN (last_cmp->insn), x, false))
goto dont_delete;
last_cmp->orig_mode = new_mode;
}
}
/* All tests and substitutions succeeded! */
if (eh_note)
need_purge = true;
delete_insn (insn);
continue;
}
dont_delete:
last_cmp = XCNEW (struct comparison);
last_cmp->insn = insn;
last_cmp->prev_clobber = last_clobber;
last_cmp->in_a = XEXP (src, 0);
last_cmp->in_b = XEXP (src, 1);
last_cmp->eh_note = eh_note;
last_cmp->orig_mode = src_mode;
last_cmp->orig_mode = GET_MODE (src);
all_compares.safe_push (last_cmp);
/* It's unusual, but be prepared for comparison patterns that
@ -391,7 +393,6 @@ find_comparison_dom_walker::before_dom_children (basic_block bb)
/* In either case, the previous compare is no longer valid. */
last_cmp = NULL;
last_cmp_valid = false;
continue;
}
/* Notice if this instruction uses the flags register. */
@ -425,8 +426,7 @@ find_comparison_dom_walker::before_dom_children (basic_block bb)
FOR_EACH_EDGE (e, ei, bb->succs)
{
basic_block dest = e->dest;
if (bitmap_bit_p (df_get_live_in (bb),
targetm.flags_regnum)
if (bitmap_bit_p (df_get_live_in (bb), targetm.flags_regnum)
&& !single_pred_p (dest))
{
last_cmp->missing_uses = true;
@ -498,8 +498,7 @@ maybe_select_cc_mode (struct comparison *cmp, rtx a ATTRIBUTE_UNUSED,
sel_mode = SELECT_CC_MODE (cmp->uses[0].code, a, b);
for (i = 1; i < n; ++i)
{
machine_mode new_mode;
new_mode = SELECT_CC_MODE (cmp->uses[i].code, a, b);
machine_mode new_mode = SELECT_CC_MODE (cmp->uses[i].code, a, b);
if (new_mode != sel_mode)
{
sel_mode = targetm.cc_modes_compatible (sel_mode, new_mode);