Re: [PATCH target/89071] Fix false dependence of scalar operations vrcp/vsqrt/vrsqrt/vrndscale

[Uros Bizjak <ubizjak@gmail.com>]

On Wed, Oct 23, 2019 at 7:48 AM Hongtao Liu <crazylht@gmail.com> wrote:
>
> Update patch:
> Add m constraint to define_insn (sse_1_round<ssescalaemodesuffix,
> *sse_1_round<ssescalaemodesuffix)  to fix some unrecognized insn error
> when under sse4 but not avx512f.

It looks to me that the original insn is incompletely defined. It
should use nonimmediate_operand, "m" constraint and <iptr> pointer
size modifier. Something like:

(define_insn "sse4_1_round<ssescalarmodesuffix>"
  [(set (match_operand:VF_128 0 "register_operand" "=Yr,*x,x,v")
    (vec_merge:VF_128
      (unspec:VF_128
        [(match_operand:VF_128 2 "nonimmediate_operand" "Yrm,*xm,xm,vm")
         (match_operand:SI 3 "const_0_to_15_operand" "n,n,n,n")]
        UNSPEC_ROUND)
      (match_operand:VF_128 1 "register_operand" "0,0,x,v")
      (const_int 1)))]
  "TARGET_SSE4_1"
  "@
   round<ssescalarmodesuffix>\t{%3, %2, %0|%0, %<iptr>2, %3}
   round<ssescalarmodesuffix>\t{%3, %2, %0|%0, %<iptr>2, %3}
   vround<ssescalarmodesuffix>\t{%3, %2, %1, %0|%0, %1, %<iptr>2, %3}
   vrndscale<ssescalarmodesuffix>\t{%3, %2, %1, %0|%0, %1, %<iptr>2, %3}"

>
> Changelog:
> gcc/
>         * config/i386/sse.md:  (sse4_1_round<ssescalarmodesuffix>):
> Change constraint x to xm
>         since vround support memory operand.
>         * (*sse4_1_round<ssescalarmodesuffix>): Ditto.
>
> Bootstrap and regression test ok.
>
> On Wed, Oct 23, 2019 at 9:56 AM Hongtao Liu <crazylht@gmail.com> wrote:
> >
> > Hi uros:
> >   This patch fixes false dependence of scalar operations
> > vrcp/vsqrt/vrsqrt/vrndscale.
> >   Bootstrap ok, regression test on i386/x86 ok.
> >
> >   It does something like this:
> > -----
> > For scalar instructions with both xmm operands:
> >
> > op %xmmN,%xmmQ,%xmmQ ----> op %xmmN, %xmmN, %xmmQ
> >
> > for scalar instructions with one mem  or gpr operand:
> >
> > op mem/gpr, %xmmQ, %xmmQ
> >
> > --->  using pass rpad ---->
> >
> > xorps %xmmN, %xmmN, %xxN
> > op mem/gpr, %xmmN, %xmmQ
> >
> > Performance influence of SPEC2017 fprate which is tested on SKX
> >
> > 503.bwaves_r -0.03%
> > 507.cactuBSSN_r -0.22%
> > 508.namd_r -0.02%
> > 510.parest_r 0.37%
> > 511.povray_r 0.74%
> > 519.lbm_r 0.24%
> > 521.wrf_r 2.35%
> > 526.blender_r 0.71%
> > 527.cam4_r 0.65%
> > 538.imagick_r 0.95%
> > 544.nab_r -0.37
> > 549.fotonik3d_r 0.24%
> > 554.roms_r 0.90%
> > fprate geomean 0.50%
> > -----
> >
> > Changelog
> > gcc/
> >         * config/i386/i386.md (*rcpsf2_sse): Add
> >         avx_partial_xmm_update, prefer m constraint for TARGET_AVX.
> >         (*rsqrtsf2_sse): Ditto.
> >         (*sqrt<mode>2_sse): Ditto.
> >         (sse4_1_round<mode>2): separate constraint vm, add
> >         avx_partail_xmm_update, prefer m constraint for TARGET_AVX.
> >         * config/i386/sse.md (*sse_vmrcpv4sf2"): New define_insn used
> >         by pass rpad.
> >         (*<sse>_vmsqrt<mode>2<mask_scalar_name><round_scalar_name>*):
> >         Ditto.
> >         (*sse_vmrsqrtv4sf2): Ditto.
> >         (*avx512f_rndscale<mode><round_saeonly_name>): Ditto.
> >         (*sse4_1_round<ssescalarmodesuffix>): Ditto.
> >
> > gcc/testsuite
> >         * gcc.target/i386/pr87007-4.c: New test.
> >         * gcc.target/i386/pr87007-5.c: Ditto.
> >
> >
> > --
> > BR,
> > Hongtao

    (set (attr "preferred_for_speed")
      (cond [(eq_attr "alternative" "1")
           (symbol_ref "TARGET_AVX || !TARGET_SSE_PARTIAL_REG_DEPENDENCY")
        (eq_attr "alternative" "2")
-          (symbol_ref "!TARGET_SSE_PARTIAL_REG_DEPENDENCY")
+          (symbol_ref "TARGET_AVX || !TARGET_SSE_PARTIAL_REG_DEPENDENCY")
        ]
        (symbol_ref "true")))])

This can be written as:

    (set (attr "preferred_for_speed")
      (cond [(match_test "TARGET_AVX")
           (symbol_ref "true")
        (eq_attr "alternative" "1,2")
          (symbol_ref "!TARGET_SSE_PARTIAL_REG_DEPENDENCY")
        ]
        (symbol_ref "true")))])

Uros.