Re: [PATCH V5 2/2] rs6000: use mtvsrws to move sf from si p9

[David Edelsohn <dje.gcc@gmail.com>]

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On Thu, Oct 5, 2023 at 12:14 AM Jiufu Guo <guojiufu@linux.ibm.com> wrote:

> Hi,
>
> As mentioned in PR108338, on p9, we could use mtvsrws to implement
> the bitcast from SI to SF (or lowpart DI to SF).
>
> For example:
>   *(long long*)buff = di;
>   float f = *(float*)(buff);
>
> "sldi 9,3,32 ; mtvsrd 1,9 ; xscvspdpn 1,1" is generated.
> A better one would be "mtvsrws 1,3 ; xscvspdpn 1,1".
>
> Compare with previous patch:
> https://gcc.gnu.org/pipermail/gcc-patches/2023-August/628791.html
> According to review comments, this version refines commit message
> and words in comments, also updates the test case
>
> Pass bootstrap and regtest on ppc64{,le}.
> Is this ok for trunk?
>

Okay.

Thanks, David


>
> BR,
> Jeff (Jiufu Guo)
>
>         PR target/108338
>
> gcc/ChangeLog:
>
>         * config/rs6000/rs6000.md (movsf_from_si): Update to generate
> mtvsrws
>         for P9.
>
> gcc/testsuite/ChangeLog:
>
>         * gcc.target/powerpc/pr108338.c: Updated to check mtvsrws for p9.
>
> ---
>  gcc/config/rs6000/rs6000.md                 | 25 ++++++++++++++++-----
>  gcc/testsuite/gcc.target/powerpc/pr108338.c | 21 ++++++++++++++---
>  2 files changed, 37 insertions(+), 9 deletions(-)
>
> diff --git a/gcc/config/rs6000/rs6000.md b/gcc/config/rs6000/rs6000.md
> index 56bd8bc1147..d6dfb25cea0 100644
> --- a/gcc/config/rs6000/rs6000.md
> +++ b/gcc/config/rs6000/rs6000.md
> @@ -8283,13 +8283,26 @@ (define_insn_and_split "movsf_from_si"
>  {
>    rtx op0 = operands[0];
>    rtx op1 = operands[1];
> -  rtx op2 = operands[2];
> -  rtx op1_di = gen_rtx_REG (DImode, REGNO (op1));
>
> -  /* Move SF value to upper 32-bits for xscvspdpn.  */
> -  emit_insn (gen_ashldi3 (op2, op1_di, GEN_INT (32)));
> -  emit_insn (gen_p8_mtvsrd_sf (op0, op2));
> -  emit_insn (gen_vsx_xscvspdpn_directmove (op0, op0));
> +  /* Move lowpart 32-bits from register for SFmode.  */
> +  if (TARGET_P9_VECTOR)
> +    {
> +      /* Using mtvsrws;xscvspdpn.  */
> +      rtx op0_v = gen_rtx_REG (V4SImode, REGNO (op0));
> +      emit_insn (gen_vsx_splat_v4si (op0_v, op1));
> +      emit_insn (gen_vsx_xscvspdpn_directmove (op0, op0));
> +    }
> +  else
> +    {
> +      rtx op2 = operands[2];
> +      rtx op1_di = gen_rtx_REG (DImode, REGNO (op1));
> +
> +      /* Using sldi;mtvsrd;xscvspdpn.  */
> +      emit_insn (gen_ashldi3 (op2, op1_di, GEN_INT (32)));
> +      emit_insn (gen_p8_mtvsrd_sf (op0, op2));
> +      emit_insn (gen_vsx_xscvspdpn_directmove (op0, op0));
> +    }
> +
>    DONE;
>  }
>    [(set_attr "length"
> diff --git a/gcc/testsuite/gcc.target/powerpc/pr108338.c
> b/gcc/testsuite/gcc.target/powerpc/pr108338.c
> index bd83c0b3ad8..5f2f62866ee 100644
> --- a/gcc/testsuite/gcc.target/powerpc/pr108338.c
> +++ b/gcc/testsuite/gcc.target/powerpc/pr108338.c
> @@ -3,9 +3,12 @@
>  /* { dg-options "-O2 -save-temps" } */
>
>  /* Under lp64, parameter 'v' is in DI regs, then bitcast sub DI to SF. */
> -/* { dg-final { scan-assembler-times {\mxscvspdpn\M} 1 { target { lp64 &&
> has_arch_pwr8 } } } } */
> -/* { dg-final { scan-assembler-times {\mmtvsrd\M} 1 { target { lp64 &&
> has_arch_pwr8 } } } } */
> +/* { dg-final { scan-assembler-times {\mxscvspdpn\M} 2 { target { lp64 &&
> has_arch_pwr8 } } } } */
> +/* { dg-final { scan-assembler-times {\mmtvsrd\M} 2 { target { lp64 && {
> has_arch_pwr8 && { ! has_arch_pwr9 } } } } } } */
> +/* { dg-final { scan-assembler-times {\mmtvsrd\M} 1 { target { lp64 &&
> has_arch_pwr9 } } } } */
> +/* { dg-final { scan-assembler-times {\mmtvsrws\M} 1 { target { lp64 &&
> has_arch_pwr9 } } } } */
>  /* { dg-final { scan-assembler-times {\mrldicr\M} 1 { target { lp64 &&
> has_arch_pwr8 } } } } */
> +/* { dg-final { scan-assembler-times {\msldi\M} 1 { target { lp64 && {
> has_arch_pwr8 && { ! has_arch_pwr9 } } } } } } */
>
>  struct di_sf_sf
>  {
> @@ -22,16 +25,28 @@ sf_from_high32bit_di (struct di_sf_sf v)
>  #endif
>  }
>
> +float __attribute__ ((noipa))
> +sf_from_low32bit_di (struct di_sf_sf v)
> +{
> +#ifdef __LITTLE_ENDIAN__
> +  return v.f1;
> +#else
> +  return v.f2;
> +#endif
> +}
> +
>  int main()
>  {
>    struct di_sf_sf v;
>    v.f1 = v.f2 = 0.0f;
>  #ifdef __LITTLE_ENDIAN__
> +  v.f1 = 1.0f;
>    v.f2 = 2.0f;
>  #else
>    v.f1 = 2.0f;
> +  v.f2 = 1.0f;
>  #endif
> -  if (sf_from_high32bit_di (v) != 2.0f)
> +  if (sf_from_high32bit_di (v) != 2.0f || sf_from_low32bit_di (v) != 1.0f)
>      __builtin_abort ();
>    return 0;
>  }
> --
> 2.25.1
>
>