diff mbox series

[V2,rs6000] Tweak modulo define_insns to eliminate register copy

Message ID 0e1a14ae-a16a-5af7-82be-c868d792d00d@linux.ibm.com
State New
Headers
Series [V2,rs6000] Tweak modulo define_insns to eliminate register copy |

Commit Message

Pat Haugen March 21, 2023, 12:10 p.m. UTC 
  Updated patch with review comments addressed: fixed up testcase and added
another testcase to verify peephole is functional.

Don't force target of modulo into a distinct register.

The define_insns for the modulo operation currently force the target 
register
to a distinct reg in preparation for a possible future peephole combining
div/mod. But this can lead to cases of a needless copy being inserted. Fixed
with the following patch.

Bootstrapped and regression tested on powerpc64le.
Ok for master?

-Pat


2023-03-21  Pat Haugen  <pthaugen@linux.ibm.com>

gcc/
	* config/rs6000/rs6000.md (*mod<mode>3, umod<mode>3): Add
	non-earlyclobber alternative.

gcc/testsuite/
	* gcc.target/powerpc/mod-no_copy.c: New.
	* gcc.target/powerpc/mod-peephole.c: New.

Comments

Segher Boessenkool March 21, 2023, 6:21 p.m. UTC | #1 
Hi!

On Tue, Mar 21, 2023 at 07:10:04AM -0500, Pat Haugen wrote:
> Updated patch with review comments addressed: fixed up testcase and added
> another testcase to verify peephole is functional.
> 
> Don't force target of modulo into a distinct register.
> 
> The define_insns for the modulo operation currently force the target 
> register
> to a distinct reg in preparation for a possible future peephole combining
> div/mod. But this can lead to cases of a needless copy being inserted. Fixed
> with the following patch.

> +/* { dg-final { scan-assembler-not {\mmodsd\M} } } */
> +/* { dg-final { scan-assembler-not {\mmodud\M} } } */

You can do
  /* { dg-final { scan-assembler-not {\mmod[su]d\M} } } */
if you want?

With or without that, okay for trunk.  Thanks!


Segher
diff mbox series

Patch

diff --git a/gcc/config/rs6000/rs6000.md b/gcc/config/rs6000/rs6000.md
index 81bffb04ceb..44f7dd509cb 100644
--- a/gcc/config/rs6000/rs6000.md
+++ b/gcc/config/rs6000/rs6000.md
@@ -3437,9 +3437,9 @@  (define_expand "mod<mode>3"
  ;; In order to enable using a peephole2 for combining div/mod to 
eliminate the
  ;; mod, prefer putting the result of mod into a different register
  (define_insn "*mod<mode>3"
-  [(set (match_operand:GPR 0 "gpc_reg_operand" "=&r")
-        (mod:GPR (match_operand:GPR 1 "gpc_reg_operand" "r")
-		 (match_operand:GPR 2 "gpc_reg_operand" "r")))]
+  [(set (match_operand:GPR 0 "gpc_reg_operand" "=&r,r")
+        (mod:GPR (match_operand:GPR 1 "gpc_reg_operand" "r,r")
+		 (match_operand:GPR 2 "gpc_reg_operand" "r,r")))]
    "TARGET_MODULO"
    "mods<wd> %0,%1,%2"
    [(set_attr "type" "div")
@@ -3447,9 +3447,9 @@  (define_insn "*mod<mode>3"


  (define_insn "umod<mode>3"
-  [(set (match_operand:GPR 0 "gpc_reg_operand" "=&r")
-        (umod:GPR (match_operand:GPR 1 "gpc_reg_operand" "r")
-		  (match_operand:GPR 2 "gpc_reg_operand" "r")))]
+  [(set (match_operand:GPR 0 "gpc_reg_operand" "=&r,r")
+        (umod:GPR (match_operand:GPR 1 "gpc_reg_operand" "r,r")
+		  (match_operand:GPR 2 "gpc_reg_operand" "r,r")))]
    "TARGET_MODULO"
    "modu<wd> %0,%1,%2"
    [(set_attr "type" "div")
diff --git a/gcc/testsuite/gcc.target/powerpc/mod-no_copy.c 
b/gcc/testsuite/gcc.target/powerpc/mod-no_copy.c
new file mode 100644
index 00000000000..c55e486ee9b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/mod-no_copy.c
@@ -0,0 +1,16 @@ 
+/* { dg-do compile } */
+/* { dg-options "-mdejagnu-cpu=power9 -O2" } */
+
+/* Verify r3 is used as source and target, no copy inserted. */
+
+long foo (long a, long b)
+{
+  return (a % b);
+}
+
+unsigned long foo2 (unsigned long a, unsigned long b)
+{
+  return (a % b);
+}
+
+/* { dg-final { scan-assembler-not {\mmr\M} } } */
diff --git a/gcc/testsuite/gcc.target/powerpc/mod-peephole.c 
b/gcc/testsuite/gcc.target/powerpc/mod-peephole.c
new file mode 100644
index 00000000000..7517fbc397c
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/mod-peephole.c
@@ -0,0 +1,25 @@ 
+/* { dg-do compile } */
+/* { dg-options "-mdejagnu-cpu=power9 -O2" } */
+
+/* Verify peephole fires to combine div/mod using same opnds. */
+
+long foo (long a, long b)
+{
+  long x, y;
+
+  x = a / b;
+  y = a % b;
+  return (x + y);
+}
+
+unsigned long foo2 (unsigned long a, unsigned long b)
+{
+  unsigned long x, y;
+
+  x = a / b;
+  y = a % b;
+  return (x + y);
+}
+
+/* { dg-final { scan-assembler-not {\mmodsd\M} } } */
+/* { dg-final { scan-assembler-not {\mmodud\M} } } */