https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102811
--- Comment #7 from Uroš Bizjak <ubizjak at gmail dot com> ---
The improvement with patch from comment #6:
The testcase:
_Float16 test (_Float16 a, _Float16 b)
{
return a + b;
}
compiles with unpatched gcc -O2 -mf16c to:
vmovss %xmm0, %xmm0, %xmm2 # 27 [c=4 l=4] *movhf_internal/3
pextrw $0, %xmm1, -4(%rsp) # 28 [c=4 l=6] *movhf_internal/5
vpxor %xmm0, %xmm0, %xmm0 # 7 [c=4 l=4] movv8hf_internal/0
vpxor %xmm1, %xmm1, %xmm1 # 11 [c=4 l=4] movv8hf_internal/0
pextrw $0, %xmm2, -2(%rsp) # 30 [c=4 l=6] *movhf_internal/5
vpinsrw $0, -4(%rsp), %xmm1, %xmm1 # 12 [c=4 l=8]
sse4_1_pinsrph/3
vpinsrw $0, -2(%rsp), %xmm0, %xmm0 # 8 [c=4 l=8]
sse4_1_pinsrph/3
vcvtph2ps %xmm1, %xmm1 # 13 [c=4 l=4] vcvtph2ps
vcvtph2ps %xmm0, %xmm0 # 9 [c=4 l=4] vcvtph2ps
vaddss %xmm1, %xmm0, %xmm0 # 15 [c=12 l=4] *fop_sf_comm/2
vinsertps $0xe, %xmm0, %xmm0, %xmm0 # 17 [c=4 l=4]
vec_setv4sf_0/2
vcvtps2ph $4, %xmm0, %xmm0 # 18 [c=4 l=4] *vcvtps2ph
ret # 35 [c=0 l=1] simple_return_internal
with unpatched gcc -O2 -mf16c -mavx2:
vpbroadcastw %xmm0, %xmm0 # 8 [c=4 l=5] *vec_dupv8hf/1
vpxor %xmm2, %xmm2, %xmm2 # 7 [c=4 l=4] movv8hf_internal/0
vpbroadcastw %xmm1, %xmm1 # 13 [c=4 l=5] *vec_dupv8hf/1
vpblendw $1, %xmm0, %xmm2, %xmm2 # 9 [c=4 l=6]
sse4_1_pblendph/2
vpxor %xmm0, %xmm0, %xmm0 # 12 [c=4 l=4] movv8hf_internal/0
vpblendw $1, %xmm1, %xmm0, %xmm0 # 14 [c=4 l=6]
sse4_1_pblendph/2
vcvtph2ps %xmm2, %xmm2 # 10 [c=4 l=4] vcvtph2ps
vcvtph2ps %xmm0, %xmm0 # 15 [c=4 l=4] vcvtph2ps
vaddss %xmm0, %xmm2, %xmm0 # 17 [c=12 l=4] *fop_sf_comm/2
vinsertps $0xe, %xmm0, %xmm0, %xmm0 # 19 [c=4 l=4]
vec_setv4sf_0/2
vcvtps2ph $4, %xmm0, %xmm0 # 20 [c=4 l=4] *vcvtps2ph
ret # 36 [c=0 l=1] simple_return_internal
And with patched gcc -O2 -mf16c:
vpxor %xmm2, %xmm2, %xmm2 # 32 [c=4 l=4] movv8hf_internal/0
vpblendw $1, %xmm0, %xmm2, %xmm0 # 9 [c=4 l=6]
*vec_setv8hf_0/8
vpblendw $1, %xmm1, %xmm2, %xmm1 # 14 [c=4 l=6]
*vec_setv8hf_0/8
vcvtph2ps %xmm1, %xmm1 # 15 [c=4 l=4] vcvtph2ps
vcvtph2ps %xmm0, %xmm0 # 10 [c=4 l=4] vcvtph2ps
vaddss %xmm1, %xmm0, %xmm0 # 17 [c=12 l=4] *fop_sf_comm/2
vinsertps $0xe, %xmm0, %xmm0, %xmm0 # 19 [c=4 l=4]
vec_setv4sf_0/2
vcvtps2ph $4, %xmm0, %xmm0 # 20 [c=4 l=4] *vcvtps2ph
ret # 40 [c=0 l=1] simple_return_internal
The above dumps show inconsistendy for PEXTRW (it should be VPEXTRW) and also
open a question, why unpatched gcc prefers memory temp instead of GPR temp for
PEXTRW/PINSRW.
The patch improves HI/HFmode inserts to element 0 in general.
