d70720c238
This turns an inversion of the sign bit + arithmetic right shift into a
comparison with 0.
i.e.
void fun1(int32_t *x, int n)
{
for (int i = 0; i < (n & -16); i++)
x[i] = (-x[i]) >> 31;
}
now generates:
.L3:
ldr q0, [x0]
cmgt v0.4s, v0.4s, #0
str q0, [x0], 16
cmp x0, x1
bne .L3
instead of:
.L3:
ldr q0, [x0]
neg v0.4s, v0.4s
sshr v0.4s, v0.4s, 31
str q0, [x0], 16
cmp x0, x1
bne .L3
gcc/ChangeLog:
* match.pd: New negate+shift pattern.
gcc/testsuite/ChangeLog:
* gcc.dg/signbit-2.c: New test.
* gcc.dg/signbit-3.c: New test.
* gcc.dg/signbit-4.c: New test.
* gcc.dg/signbit-5.c: New test.
* gcc.dg/signbit-6.c: New test.
* gcc.target/aarch64/signbit-1.c: New test.
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