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Fix PR 110386: backprop vs ABSU_EXPR

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The issue here is that when backprop tries to go
and strip sign ops, it skips over ABSU_EXPR but
ABSU_EXPR not only does an ABS, it also changes the
type to unsigned.
Since strip_sign_op_1 is only supposed to strip off
sign changing operands and not ones that change types,
removing ABSU_EXPR here is correct. We don't handle
nop conversions so this does cause any missed optimizations either.

OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

	PR tree-optimization/110386

gcc/ChangeLog:

	* gimple-ssa-backprop.cc (strip_sign_op_1): Remove ABSU_EXPR.

gcc/testsuite/ChangeLog:

	* gcc.c-torture/compile/pr110386-1.c: New test.
	* gcc.c-torture/compile/pr110386-2.c: New test.
This commit is contained in:
Andrew Pinski
2023-09-23 21:53:09 -07:00
committed by Andrew Pinski
parent 9d5f20fc4a
commit 2bbac12ea7
3 changed files with 20 additions and 1 deletions
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1
gcc/gimple-ssa-backprop.cc
View File

@@ -694,7 +694,6 @@ strip_sign_op_1 (tree rhs)
switch (gimple_assign_rhs_code (assign))
{
case ABS_EXPR:
case ABSU_EXPR:
case NEGATE_EXPR:
return gimple_assign_rhs1 (assign);

9
gcc/testsuite/gcc.c-torture/compile/pr110386-1.c Normal file
View File

@@ -0,0 +1,9 @@
int f(int a)
{
int c = c < 0 ? c : -c;
c = -c;
unsigned b = c;
unsigned t = b*a;
return t*t;
}

11
gcc/testsuite/gcc.c-torture/compile/pr110386-2.c Normal file
View File

@@ -0,0 +1,11 @@
/* { dg-do compile { target i?86-*-* x86_64-*-* } } */
/* { dg-options "-mavx" } */
#include <immintrin.h>
__m128i do_stuff(__m128i XMM0) {
__m128i ABS0 = _mm_abs_epi32(XMM0);
__m128i MUL0 = _mm_mullo_epi32(ABS0, XMM0);
__m128i MUL1 = _mm_mullo_epi32(MUL0, MUL0);
return MUL1;
}