https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97249
Bug ID: 97249
Summary: Missing vec_select and subreg optimization
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: crazylht at gmail dot com
CC: hjl.tools at gmail dot com, wwwhhhyyy333 at gmail dot com
Target Milestone: ---
Host: x86_64-pc-linux-gnu
Cat test.c
---
void
foo (unsigned char* p1, unsigned char* p2, short* __restrict p3)
{
for (int i = 0 ; i != 8; i++)
p3[i] = p1[i] + p2[i];
return;
}
---
gcc11 -Ofast -mavx2 test.c got
---
foo:
.LFB0:
.cfi_startproc
vmovq (%rdi), %xmm0
vmovq (%rsi), %xmm1
vpmovzxbw %xmm0, %xmm0
vpmovzxbw %xmm1, %xmm1
vpaddw %xmm1, %xmm0, %xmm0
vmovdqu %xmm0, (%rdx)
ret
.cfi_endproc
---
memory operand doesn't propagate into *vpmovzxbw* because rtl didn't simplify
---
(insn 9 8 10 2 (set (reg:V8HI 92 [ vect__33.6 ])
(zero_extend:V8HI (vec_select:V8QI (subreg:V16QI (reg:V8QI 91 [
vect__40.5 ]) 0)
(parallel [
(const_int 0 [0])
(const_int 1 [0x1])
(const_int 2 [0x2])
(const_int 3 [0x3])
(const_int 4 [0x4])
(const_int 5 [0x5])
(const_int 6 [0x6])
(const_int 7 [0x7])
])))) "test.c":5:16 4638 {sse4_1_zero_extendv8qiv8hi2}
(expr_list:REG_DEAD (reg:V8QI 91 [ vect__40.5 ])
(nil)))
---
to
---
(insn 9 8 10 2 (set (reg:V8HI 92 [ vect__33.6 ])
(zero_extend:V8HI (reg:V8QI 91 [ vect__40.5 ])))) "test.c":5:16 4638
{sse4_1_zero_extendv8qiv8hi2}
(expr_list:REG_DEAD (reg:V8QI 91 [ vect__40.5 ])
(nil)))
---
Similar for other vector modes.
