Hi Haochen,
on 2022/5/13 09:07, HAO CHEN GUI wrote:
> Hi,
> This patch adds a combine pattern for "CA minus one". As CA only has two
> values (0 or 1), we could convert following pattern
> (sign_extend:DI (plus:SI (reg:SI 98 ca)
> (const_int -1 [0xffffffffffffffff]))))
> to
> (plus:DI (reg:DI 98 ca)
> (const_int -1 [0xffffffffffffffff])))
> With this patch, one unnecessary sign extend is eliminated.
>
> Bootstrapped and tested on powerpc64-linux BE and LE with no regressions.
> Is this okay for trunk? Any recommendations? Thanks a lot.
>
> ChangeLog
> 2022-05-13 Haochen Gui <guih...@linux.ibm.com>
>
> gcc/
> PR target/95737
> * config/rs6000/rs6000.md (extenddi_ca_minus_one): Define.
>
Nit: (*extenddi_ca_minus_one): New define_insn_and_split.
> gcc/testsuite/
> PR target/95737
> * gcc.target/powerpc/pr95737.c: New.
>
> patch.diff
> diff --git a/gcc/config/rs6000/rs6000.md b/gcc/config/rs6000/rs6000.md
> index 64049a6e521..483a93956f8 100644
> --- a/gcc/config/rs6000/rs6000.md
> +++ b/gcc/config/rs6000/rs6000.md
> @@ -2353,6 +2353,19 @@ (define_insn "subf<mode>3_carry_in_xx"
> "subfe %0,%0,%0"
> [(set_attr "type" "add")])
>
> +(define_insn_and_split "*extenddi_ca_minus_one"
> + [(set (match_operand:DI 0 "gpc_reg_operand" "=r")
> + (sign_extend:DI (plus:SI (reg:SI CA_REGNO)
> + (const_int -1))))]
> + ""
> + "#"
> + ""
> + [(parallel [(set (match_dup 0)
> + (plus:DI (reg:DI CA_REGNO)
> + (const_int -1)))
> + (clobber (reg:DI CA_REGNO))])]
> + ""
> +)
>
> (define_insn "@neg<mode>2"
> [(set (match_operand:GPR 0 "gpc_reg_operand" "=r")
> diff --git a/gcc/testsuite/gcc.target/powerpc/pr95737.c
> b/gcc/testsuite/gcc.target/powerpc/pr95737.c
> new file mode 100644
> index 00000000000..d4d6a4198cf
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/powerpc/pr95737.c
> @@ -0,0 +1,10 @@
> +/* PR target/95737 */
> +/* { dg-do compile { target lp64 } } */> +/* { dg-options "-O2 -mno-isel" }
> */
Nit: It seems good to put one comment for the reason why we need this
special -mno-isel, like something: Power9 leverages isel for this case,
force -mno-isel to keep the test point valid on Power9 and later."
> +/* { dg-final { scan-assembler-not {\mextsw\M} } } */
> +
> +
> +unsigned long negativeLessThan (unsigned long a, unsigned long b)
> +{
> + return -(a < b);
> +}
OK with those nits fixed, but please wait for a few days, just in case
Segher/David have more comments.
BR,
Kewen
