https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114428
Bug ID: 114428
Summary: [x86] psrad xmm, xmm, 16 and pand xmm, const_vector
(0xffff x4) can be optimized to psrld
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: liuhongt at gcc dot gnu.org
Target Milestone: ---
typedef unsigned short uint16_t;
typedef short int16_t;
#define QUANT_ONE( coef, mf, f ) \
{ \
if( (coef) > 0 ) \
(coef) = (f + (coef)) * (mf) >> 16; \
else \
(coef) = - ((f - (coef)) * (mf) >> 16); \
nz |= (coef); \
}
int quant_4x4( int16_t dct[16], uint16_t mf[16], uint16_t bias[16] )
{
int nz = 0;
for( int i = 0; i < 16; i++ )
QUANT_ONE( dct[i], mf[i], bias[i] );
return !!nz;
}
gcc -O2 -march=x86-64-v3 -S
mov edx, 65535
vmovd xmm4, edx
vpbroadcastd ymm4, xmm4
...
vpsrad ymm2, ymm2, 16
vpsrad ymm6, ymm6, 16
vpsrad ymm0, ymm0, 16
vpand ymm2, ymm4, ymm2
vpsrad ymm1, ymm1, 16
vpand ymm6, ymm4, ymm6
vpand ymm0, ymm4, ymm0
vpand ymm4, ymm4, ymm1
vpackusdw ymm2, ymm2, ymm6
vpackusdw ymm0, ymm0, ymm4
vpermq ymm2, ymm2, 216
vpermq ymm0, ymm0, 216
...
it can be optimized to below.
vpsrld ymm2, ymm2, 16
vpsrld ymm6, ymm6, 16
vpsrld ymm0, ymm0, 16
vpsrld ymm1, ymm1, 16
vpackusdw ymm2, ymm2, ymm6
vpackusdw ymm0, ymm0, ymm4
vpermq ymm2, ymm2, 216
vpermq ymm0, ymm0, 216
The optimization opportunity is exposed after vec_pack_trunk_expr is expanded
to vpand + vpackusdw.
