From: Pat Haugen <pthaugen@linux.ibm.com>
Date: Thu, 23 Mar 2023 19:08:00 +0000 (-0500)
Subject: Don't force target of modulo into a distinct register.
X-Git-Tag: basepoints/gcc-14~370
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=f58cbbb7c90d8cfea87dc4490b575a368e1e2c82;p=thirdparty%2Fgcc.git

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.

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.
---

diff --git a/gcc/config/rs6000/rs6000.md b/gcc/config/rs6000/rs6000.md
index 81bffb04ceb0..44f7dd509cb4 100644
--- a/gcc/config/rs6000/rs6000.md
+++ b/gcc/config/rs6000/rs6000.md
@@ -3437,9 +3437,9 @@
 ;; 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 "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 000000000000..c55e486ee9b9
--- /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 000000000000..7517fbc397c9
--- /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} } } */