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re PR target/77881 (Non-optimal signed comparison on x86_64 since r146817)

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PR missed-optimization/77881
	* combine.c (simplify_comparison): Remove useless subregs
	also inside the loop, not just after it.
	(make_compound_operation): Recognize some subregs as being
	masking as well.

testsuite/
	* gcc.target/i386/pr77881.c: New test.

From-SVN: r242414
This commit is contained in:
Michael Matz 2016-11-15 14:02:28 +00:00 • committed by Michael Matz
parent aa806c3be7
commit b229ab2a71
4 changed files with 60 additions and 0 deletions
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8
gcc/ChangeLog
View file

@ -1,3 +1,11 @@
2016-11-15 Michael Matz <matz@suse.de>
PR missed-optimization/77881
* combine.c (simplify_comparison): Remove useless subregs
also inside the loop, not just after it.
(make_compound_operation): Recognize some subregs as being
masking as well.
2016-11-15 Richard Sandiford <richard.sandiford@arm.com>
Alan Hayward <alan.hayward@arm.com>
David Sherwood <david.sherwood@arm.com>

35
gcc/combine.c
View file

@ -8102,6 +8102,18 @@ make_compound_operation (rtx x, enum rtx_code in_code)
rtx inner = SUBREG_REG (x), simplified;
enum rtx_code subreg_code = in_code;
/* If the SUBREG is masking of a logical right shift,
make an extraction. */
if (GET_CODE (inner) == LSHIFTRT
&& GET_MODE_SIZE (mode) < GET_MODE_SIZE (GET_MODE (inner))
&& subreg_lowpart_p (x))
{
new_rtx = make_compound_operation (XEXP (inner, 0), next_code);
new_rtx = make_extraction (mode, new_rtx, 0, XEXP (inner, 1),
mode_width, 1, 0, in_code == COMPARE);
break;
}
/* If in_code is COMPARE, it isn't always safe to pass it through
to the recursive make_compound_operation call. */
if (subreg_code == COMPARE
@ -11994,6 +12006,29 @@ simplify_comparison (enum rtx_code code, rtx *pop0, rtx *pop1)
if (subreg_lowpart_p (op0)
&& GET_MODE_PRECISION (GET_MODE (SUBREG_REG (op0))) < mode_width)
;
else if (subreg_lowpart_p (op0)
&& GET_MODE_CLASS (GET_MODE (op0)) == MODE_INT
&& GET_MODE_CLASS (GET_MODE (SUBREG_REG (op0))) == MODE_INT
&& (code == NE || code == EQ)
&& (GET_MODE_PRECISION (GET_MODE (SUBREG_REG (op0)))
<= HOST_BITS_PER_WIDE_INT)
&& !paradoxical_subreg_p (op0)
&& (nonzero_bits (SUBREG_REG (op0),
GET_MODE (SUBREG_REG (op0)))
& ~GET_MODE_MASK (GET_MODE (op0))) == 0)
{
/* Remove outer subregs that don't do anything. */
tem = gen_lowpart (GET_MODE (SUBREG_REG (op0)), op1);
if ((nonzero_bits (tem, GET_MODE (SUBREG_REG (op0)))
& ~GET_MODE_MASK (GET_MODE (op0))) == 0)
{
op0 = SUBREG_REG (op0);
op1 = tem;
continue;
}
break;
}
else
break;

5
gcc/testsuite/ChangeLog
View file

@ -1,3 +1,8 @@
2016-11-15 Michael Matz <matz@suse.de>
PR missed-optimization/77881
* gcc.target/i386/pr77881.c: New test.
2016-11-15 Jakub Jelinek <jakub@redhat.com>
PR middle-end/78295

12
gcc/testsuite/gcc.target/i386/pr77881.c Normal file
View file

@ -0,0 +1,12 @@
/* { dg-do compile } */
/* { dg-require-effective-target pie } */
/* { dg-options "-O2" } */
extern void baz(void);
int
foo (long long int a, long long int a2, int b)
{
if (a < 0 || b)
baz ();
}
/* { dg-final { scan-assembler "js\[ \t\]\.L" } } */
/* { dg-final { scan-assembler "jne\[ \t\]\.L" } } */