Re: [PATCH v2] x86: Remove __mmask intrinsics in strstr-avx512.c

[Sunil Pandey <skpgkp2@gmail.com>]

On Mon, Jul 11, 2022 at 3:52 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> On Mon, Jul 11, 2022 at 3:38 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> >
> > Using standard operators generates and the same code and __mmask
> > instrinsics are not available before GCC7.
> >
> > Removed:
> >     _cvtmask64_u64
> >     _kshiftri_mask64
> >     _kand_mask64
> > ---
> >  sysdeps/x86_64/multiarch/strstr-avx512.c | 16 ++++++++++------
> >  1 file changed, 10 insertions(+), 6 deletions(-)
> >
> > diff --git a/sysdeps/x86_64/multiarch/strstr-avx512.c b/sysdeps/x86_64/multiarch/strstr-avx512.c
> > index 2ab9e96db8..e44c1a05dc 100644
> > --- a/sysdeps/x86_64/multiarch/strstr-avx512.c
> > +++ b/sysdeps/x86_64/multiarch/strstr-avx512.c
> > @@ -26,6 +26,10 @@
> >  #define ZMM_SIZE_IN_BYTES 64
> >  #define PAGESIZE 4096
> >
> > +#define cvtmask64_u64(...) (uint64_t) (__VA_ARGS__)
> > +#define kshiftri_mask64(x, y) ((x) >> (y))
> > +#define kand_mask64(x, y) ((x) & (y))
> > +
> >  /*
> >   Returns the index of the first edge within the needle, returns 0 if no edge
> >   is found. Example: 'ab' is the first edge in 'aaaaaaaaaabaarddg'
> > @@ -133,15 +137,15 @@ __strstr_avx512 (const char *haystack, const char *ned)
> >    __m512i hay0 = _mm512_maskz_loadu_epi8 (loadmask, haystack + hay_index);
> >    /* Search for NULL and compare only till null char */
> >    uint64_t nullmask
> > -      = _cvtmask64_u64 (_mm512_mask_testn_epi8_mask (loadmask, hay0, hay0));
> > +      = cvtmask64_u64 (_mm512_mask_testn_epi8_mask (loadmask, hay0, hay0));
> >    uint64_t cmpmask = nullmask ^ (nullmask - ONE_64BIT);
> > -  cmpmask = cmpmask & _cvtmask64_u64 (loadmask);
> > +  cmpmask = cmpmask & cvtmask64_u64 (loadmask);
> >    /* Search for the 2 charaters of needle */
> >    __mmask64 k0 = _mm512_cmpeq_epi8_mask (hay0, ned0);
> >    __mmask64 k1 = _mm512_cmpeq_epi8_mask (hay0, ned1);
> > -  k1 = _kshiftri_mask64 (k1, 1);
> > +  k1 = kshiftri_mask64 (k1, 1);
> >    /* k2 masks tell us if both chars from needle match */
> > -  uint64_t k2 = _cvtmask64_u64 (_kand_mask64 (k0, k1)) & cmpmask;
> > +  uint64_t k2 = cvtmask64_u64 (kand_mask64 (k0, k1)) & cmpmask;
> >    /* For every match, search for the entire needle for a full match */
> >    while (k2)
> >      {
> > @@ -178,13 +182,13 @@ __strstr_avx512 (const char *haystack, const char *ned)
> >        hay0 = _mm512_loadu_si512 (haystack + hay_index);
> >        hay1 = _mm512_load_si512 (haystack + hay_index
> >                                  + 1); // Always 64 byte aligned
> > -      nullmask = _cvtmask64_u64 (_mm512_testn_epi8_mask (hay1, hay1));
> > +      nullmask = cvtmask64_u64 (_mm512_testn_epi8_mask (hay1, hay1));
> >        /* Compare only till null char */
> >        cmpmask = nullmask ^ (nullmask - ONE_64BIT);
> >        k0 = _mm512_cmpeq_epi8_mask (hay0, ned0);
> >        k1 = _mm512_cmpeq_epi8_mask (hay1, ned1);
> >        /* k2 masks tell us if both chars from needle match */
> > -      k2 = _cvtmask64_u64 (_kand_mask64 (k0, k1)) & cmpmask;
> > +      k2 = cvtmask64_u64 (kand_mask64 (k0, k1)) & cmpmask;
> >        /* For every match, compare full strings for potential match */
> >        while (k2)
> >          {
> > --
> > 2.34.1
> >
> Sunil,
> Does this work (v2 didn't get chained because I changed commit msg).

Yes, v2 works.

--Sunil