[PATCH v3, rs6000] Add a combine pattern for CA minus one [PR95737]

[PATCH v3, rs6000] Add a combine pattern for CA minus one [PR95737]

[HAO CHEN GUI]

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
2022-01-20 Haochen Gui <guihaoc@linux.ibm.com>

gcc/
	* config/rs6000/rs6000.md (extenddi_ca_minus_one): Define.

gcc/testsuite/
	* gcc.target/powerpc/pr95737.c: New.


patch.diff
diff --git a/gcc/config/rs6000/rs6000.md b/gcc/config/rs6000/rs6000.md
index 6ecb0bd6142..1d8b212962f 100644
--- a/gcc/config/rs6000/rs6000.md
+++ b/gcc/config/rs6000/rs6000.md
@@ -2358,6 +2358,19 @@ (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" } */
+/* { dg-final { scan-assembler-not {\mextsw\M} } } */
+
+
+unsigned long negativeLessThan (unsigned long a, unsigned long b)
+{
+   return -(a < b);
+}

Ping^1 [PATCH v3, rs6000] Add a combine pattern for CA minus one [PR95737]

[HAO CHEN GUI]

Hi,
  Gentle ping this:
https://gcc.gnu.org/pipermail/gcc-patches/2022-January/589006.html
Thanks

On 21/1/2022 下午 5:28, 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
> 2022-01-20 Haochen Gui <guihaoc@linux.ibm.com>
> 
> gcc/
> 	* config/rs6000/rs6000.md (extenddi_ca_minus_one): Define.
> 
> gcc/testsuite/
> 	* gcc.target/powerpc/pr95737.c: New.
> 
> 
> patch.diff
> diff --git a/gcc/config/rs6000/rs6000.md b/gcc/config/rs6000/rs6000.md
> index 6ecb0bd6142..1d8b212962f 100644
> --- a/gcc/config/rs6000/rs6000.md
> +++ b/gcc/config/rs6000/rs6000.md
> @@ -2358,6 +2358,19 @@ (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" } */
> +/* { dg-final { scan-assembler-not {\mextsw\M} } } */
> +
> +
> +unsigned long negativeLessThan (unsigned long a, unsigned long b)
> +{
> +   return -(a < b);
> +}