https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105033
Bug ID: 105033
Summary: Suboptimal for vec_concat lower halves of two vectors.
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: crazylht at gmail dot com
Target Milestone: ---
typedef _Float16 v8hf __attribute__((vector_size (16)));
typedef _Float16 v4hf __attribute__((vector_size (8)));
v8hf foov (v4hf a, v4hf b)
{
return __builtin_shufflevector (a, b, 0, 1, 2, 3, 4, 5, 6, 7);
}
typedef short v8hi __attribute__((vector_size (16)));
typedef short v4hi __attribute__((vector_size (8)));
v8hi foov (v4hi a, v4hi b)
{
return __builtin_shufflevector (a, b, 0, 1, 2, 3, 4, 5, 6, 7);
}
with -march=skylake-avx512 -O2
_Z4foovDv4_DF16_S_:
vmovq xmm2, xmm0
vmovdqa xmm0, XMMWORD PTR .LC0[rip]
vmovq xmm1, xmm1
vpermi2w xmm0, xmm2, xmm1
ret
foov(short __vector(4), short __vector(4)):
vmovq xmm2, xmm0
vmovdqa xmm0, XMMWORD PTR .LC0[rip]
vmovq xmm1, xmm1
vpermi2w xmm0, xmm2, xmm1
ret
.LC0:
.value 0
.value 1
.value 2
.value 3
.value 8
.value 9
.value 10
.value 11
But with -march=skylake -O2
It can be optimized to
_Z4foovDv4_DF16_S_:
vmovq xmm1, xmm1
vmovq xmm0, xmm0
vpunpcklqdq xmm0, xmm0, xmm1
ret
foov(short __vector(4), short __vector(4)):
vmovq xmm1, xmm1
vmovq xmm0, xmm0
vpunpcklqdq xmm0, xmm0, xmm1
ret
