Re: [PATCH] rs6000: Remove unspecs for vec_mrghl[bhw]

[Segher Boessenkool <segher@kernel.crashing.org>]

On Mon, May 24, 2021 at 04:02:13AM -0500, Xionghu Luo wrote:
> vmrghb only accepts permute index {0, 16, 1, 17, 2, 18, 3, 19, 4, 20,
> 5, 21, 6, 22, 7, 23} no matter for BE or LE in ISA, similarly for vmrghlb.

(vmrglb)

> +  if (BYTES_BIG_ENDIAN)
> +    emit_insn (
> +      gen_altivec_vmrghb_direct (operands[0], operands[1], operands[2]));
> +  else
> +    emit_insn (
> +      gen_altivec_vmrglb_direct (operands[0], operands[2], operands[1]));

Please don't indent like that, it doesn't match what we do elsewhere.
For better or for worse (for worse imo), we use deep hanging indents.
If you have to, you can do something like

  rtx insn;
  if (BYTES_BIG_ENDIAN)
    insn = gen_altivec_vmrghb_direct (operands[0], operands[1], operands[2]);
  else
    insn = gen_altivec_vmrglb_direct (operands[0], operands[2], operands[1]);
  emit_insn (insn);

(this is better even, in that it has only one emit_insn), or even

  rtx (*fun) () = BYTES_BIG_ENDIAN ? gen_altivec_vmrghb_direct
				   : gen_altivec_vmrglb_direct;
  if (!BYTES_BIG_ENDIAN)
    std::swap (operands[1], operands[2]);
  emit_insn (fun (operands[0], operands[1], operands[2]));

Well, C++ does not allow that last example like that, sigh, so
  rtx (*fun) (rtx, rtx, rtx) = BYTES_BIG_ENDIAN ? gen_altivec_vmrghb_direct
						: gen_altivec_vmrglb_direct;

This is shorter than the other two options ;-)

> +(define_insn "altivec_vmrghb_direct"
>    [(set (match_operand:V16QI 0 "register_operand" "=v")
> +    (vec_select:V16QI

This should be indented one space more.

>    "TARGET_ALTIVEC"
>    "@
> -   xxmrghw %x0,%x1,%x2
> -   vmrghw %0,%1,%2"
> +  xxmrghw %x0,%x1,%x2
> +  vmrghw %0,%1,%2"

The original indent was correct, please restore.

> -      emit_insn (gen_altivec_vmrghw_direct (operands[0], ve, vo));
> +      emit_insn (gen_altivec_vmrghw_direct_v4si (operands[0], ve, vo));

When you see a mode as part of a pattern name, chances are that it will
be a good candidate for using parameterized names with.  (But don't do
that now, just keep it in mind as a nice cleanup to do).

> @@ -23022,8 +23022,8 @@ altivec_expand_vec_perm_const (rtx target, rtx op0, rtx op1,
>         : CODE_FOR_altivec_vmrglh_direct),
>        {  0,  1, 16, 17,  2,  3, 18, 19,  4,  5, 20, 21,  6,  7, 22, 23 } },
>      { OPTION_MASK_ALTIVEC,
> -      (BYTES_BIG_ENDIAN ? CODE_FOR_altivec_vmrghw_direct
> -       : CODE_FOR_altivec_vmrglw_direct),
> +      (BYTES_BIG_ENDIAN ? CODE_FOR_altivec_vmrghw_direct_v4si
> +       : CODE_FOR_altivec_vmrglw_direct_v4si),

The correct way is to align the ? and the : (or put everything on one
line of course, if that fits)

The parens around this are not needed btw, and are a distraction.

> --- a/gcc/testsuite/gcc.target/powerpc/builtins-1.c
> +++ b/gcc/testsuite/gcc.target/powerpc/builtins-1.c
> @@ -317,10 +317,10 @@ int main ()
>  /* { dg-final { scan-assembler-times "vctuxs" 2 } } */
>  
>  /* { dg-final { scan-assembler-times "vmrghb" 4 { target be } } } */
> -/* { dg-final { scan-assembler-times "vmrghb" 5 { target le } } } */
> +/* { dg-final { scan-assembler-times "vmrghb" 6 { target le } } } */
>  /* { dg-final { scan-assembler-times "vmrghh" 8 } } */
> -/* { dg-final { scan-assembler-times "xxmrghw" 8 } } */
> -/* { dg-final { scan-assembler-times "xxmrglw" 8 } } */
> +/* { dg-final { scan-assembler-times "xxmrghw" 4 } } */
> +/* { dg-final { scan-assembler-times "xxmrglw" 4 } } */
>  /* { dg-final { scan-assembler-times "vmrglh" 8 } } */
>  /* { dg-final { scan-assembler-times "xxlnor" 6 } } */
>  /* { dg-final { scan-assembler-times {\mvpkudus\M} 1 } } */
> @@ -347,7 +347,7 @@ int main ()
>  /* { dg-final { scan-assembler-times "vspltb" 6 } } */
>  /* { dg-final { scan-assembler-times "vspltw" 0 } } */
>  /* { dg-final { scan-assembler-times "vmrgow" 8 } } */
> -/* { dg-final { scan-assembler-times "vmrglb" 5 { target le } } } */
> +/* { dg-final { scan-assembler-times "vmrglb" 4 { target le } } } */
>  /* { dg-final { scan-assembler-times "vmrglb" 6 { target be } } } */
>  /* { dg-final { scan-assembler-times "vmrgew" 8 } } */
>  /* { dg-final { scan-assembler-times "vsplth" 8 } } */

Are those changes correct?  It looks like a vmrglb became a vmrghb, and
that 4 each of xxmrghw and xxmrglw disappeared?  Both seem wrong?


Segher