https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93183
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Blocks| |26163, 53947
Summary|SVE only makes the last |SVE does not use neg as
|thing conditional with |conditional
|ifconversion |
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Actually it looks more like conditional neg does not work.
Take:
typedef unsigned char uint8_t;
static inline uint8_t x264_clip_uint8( uint8_t x )
{
uint8_t t = -x;
uint8_t t1 = x&(~63);
return t1 ? t : x;
}
void mc_weight( uint8_t *__restrict dst, uint8_t *__restrict src, int n)
{
for( int x = 0; x < n*16; x++ )
dst[x] = x264_clip_uint8(src[x]);
}
--- CUT ---
We get:
.L3:
ld1b z0.b, p0/z, [x1, x3]
movprfx z2, z0
and z2.b, z2.b, #0xc0
neg z1.b, p1/m, z0.b ;;; <<<< THIS
cmpeq p2.b, p1/z, z2.b, #0
sel z0.b, p2, z0.b, z1.b ;;;; <<<< AND THIS
st1b z0.b, p0, [x0, x3]
incb x3
whilelo p0.b, w3, w2
b.any .L3
The two instructions marked should be combined.
NOTE this does show up in real code in SPEC CPU, see PR 92492.
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=26163
[Bug 26163] [meta-bug] missed optimization in SPEC (2k17, 2k and 2k6 and 95)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53947
[Bug 53947] [meta-bug] vectorizer missed-optimizations
