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i386: Improve code generation for vector __builtin_signbit (x.x[i]) ? -1 : 0 [PR112816]

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On the testcase I've recently fixed I've noticed bad code generation,
we emit
        pxor    %xmm1, %xmm1
        psrld   $31, %xmm0
        pcmpeqd %xmm1, %xmm0
        pcmpeqd %xmm1, %xmm0
or
        vpxor   %xmm1, %xmm1, %xmm1
        vpsrld  $31, %xmm0, %xmm0
        vpcmpeqd        %xmm1, %xmm0, %xmm0
        vpcmpeqd        %xmm1, %xmm0, %xmm2
rather than
        psrad   $31, %xmm2
or
        vpsrad  $31, %xmm1, %xmm2
The following patch fixes that using a combiner splitter.

2023-12-05  Jakub Jelinek  <jakub@redhat.com>

	PR target/112816
	* config/i386/sse.md ((eq (eq (lshiftrt x elt_bits-1) 0) 0)): New
	splitter to turn psrld $31; pcmpeq; pcmpeq into psrad $31.

	* gcc.target/i386/pr112816.c: New test.
This commit is contained in:
Jakub Jelinek 2023-12-05 09:08:45 +01:00
parent 8b93a0f3eb
commit bf418db27c
2 changed files with 39 additions and 0 deletions
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12
gcc/config/i386/sse.md
View file

@ -16614,6 +16614,18 @@
DONE;
})
(define_split
[(set (match_operand:VI248_AVX2 0 "register_operand")
(eq:VI248_AVX2
(eq:VI248_AVX2
(lshiftrt:VI248_AVX2
(match_operand:VI248_AVX2 1 "register_operand")
(match_operand:SI 2 "const_int_operand"))
(match_operand:VI248_AVX2 3 "const0_operand"))
(match_operand:VI248_AVX2 4 "const0_operand")))]
"INTVAL (operands[2]) == GET_MODE_PRECISION (<ssescalarmode>mode) - 1"
[(set (match_dup 0) (ashiftrt:VI248_AVX2 (match_dup 1) (match_dup 2)))])
(define_expand "rotlv1ti3"
[(set (match_operand:V1TI 0 "register_operand")
(rotate:V1TI

27
gcc/testsuite/gcc.target/i386/pr112816.c Normal file
View file

@ -0,0 +1,27 @@
/* PR target/112816 */
/* { dg-do compile } */
/* { dg-options "-O2 -mno-avx512f -masm=att" } */
/* { dg-final { scan-assembler-times "psrad\t\\\$31," 2 } } */
/* { dg-final { scan-assembler-not "pcmpeqd\t" } } */
#define N 4
struct S { float x[N]; };
struct T { int x[N]; };
__attribute__((target ("no-sse3,sse2"))) struct T
foo (struct S x)
{
struct T res;
for (int i = 0; i < N; ++i)
res.x[i] = __builtin_signbit (x.x[i]) ? -1 : 0;
return res;
}
__attribute__((target ("avx2"))) struct T
bar (struct S x)
{
struct T res;
for (int i = 0; i < N; ++i)
res.x[i] = __builtin_signbit (x.x[i]) ? -1 : 0;
return res;
}