Hi!
On Mon, Sep 06, 2021 at 02:10:58PM +0800, HAO CHEN GUI wrote:
> The patch optimized expansion for long long or double vec_reve builtin.
>
> Bootstrapped and tested on powerpc64le-linux with no regressions.
> Is this okay for trunk? Any recommendations? Thanks a lot.
In the future, please say something about what you changed, something
about the new code?
"Use xxswapd instead of <whatever we did before>" or even "Use xxswapd".
It doesn't have to be long, but something to guide the reader helps a
lot :-)
> * config/rs6000/altivec.md (altivec_vreve<mode>2):
> Modify the expansion when number of elements is 2.
* config/rs6000/altivec.md (altivec_vreve<mode>2): Modify the expansion
when num_elements is 2.
But "Modify" does not say what you changed it to. So something like
* config/rs6000/altivec.md (altivec_vreve<mode>2): Use xxswapd if
num_elements is 2.
But, there are multiple patterns with that name. So this would be
* config/rs6000/altivec.md (altivec_vreve<mode>2 for VEC_A): Use xxswapd
if num_elements is 2.
That check is a bit nasty, so maybe you should just split this pattern
into one for VEC_K and one for VEC_64?
> --- a/gcc/config/rs6000/altivec.md
> +++ b/gcc/config/rs6000/altivec.md
> @@ -4063,6 +4063,13 @@ (define_expand "altivec_vreve<mode>2"
> size = GET_MODE_UNIT_SIZE (<MODE>mode);
> num_elements = GET_MODE_NUNITS (<MODE>mode);
>
> + if (num_elements == 2)
> + {
> + emit_insn (gen_vsx_xxpermdi_<mode> (operands[0], operands[1],
> + operands[1], GEN_INT (2)));
> + DONE;
> + }
emit_insn (gen_xxswapd_<mode> (operands[0], operands[1]));
If this doesn't compile like this, it will need some "parameterized
names" magic (for xxswapd), a bit more work (but one-time work, and it
is worth it).
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/powerpc/vec_reve.c
> @@ -0,0 +1,17 @@
> +/* { dg-do compile { target { powerpc*-*-* } } } */
That is the only allowed target in gcc.target/powerpc anyway. Just
write
/* { dg-do compile } */
and nothing more (this (compile) is the default as well, you can just
leave it out completely if you want).
Finally: should whatever the old code generated have been optimised
better?
Segher
