[PATCH v2] Fix PR tree-optimization/103228 and 103228: folding of (type) X op CST where type is a nop convert

apinski@marvell.com apinski@marvell.com
Wed Nov 17 23:39:25 GMT 2021


From: Andrew Pinski <apinski@marvell.com>

Currently we fold (type) X op CST into (type) (X op ((type-x) CST)) when the conversion widens
but not when the conversion is a nop. For the same reason why we move the widening conversion
(the possibility of removing an extra conversion), we should do the same if the conversion is a
nop.

Committed as approved with the comment change.

	PR tree-optimization/103228
	PR tree-optimization/55177

gcc/ChangeLog:

	* match.pd ((type) X bitop CST): Also do this
	transformation for nop conversions.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/pr103228-1.c: New test.
	* gcc.dg/tree-ssa/pr55177-1.c: New test.
---
 gcc/match.pd                               |  6 ++++--
 gcc/testsuite/gcc.dg/tree-ssa/pr103228-1.c | 11 +++++++++++
 gcc/testsuite/gcc.dg/tree-ssa/pr55177-1.c  | 14 ++++++++++++++
 3 files changed, 29 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr103228-1.c
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr55177-1.c

diff --git a/gcc/match.pd b/gcc/match.pd
index cd8f349f618..4dc66fb47f2 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -1616,8 +1616,10 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 	  Restrict it to GIMPLE to avoid endless recursions.  */
        && (bitop != BIT_AND_EXPR || GIMPLE)
        && (/* That's a good idea if the conversion widens the operand, thus
-	      after hoisting the conversion the operation will be narrower.  */
-	   TYPE_PRECISION (TREE_TYPE (@0)) < TYPE_PRECISION (type)
+	      after hoisting the conversion the operation will be narrower.
+	      It is also a good if the conversion is a nop as moves the
+	      conversion to one side; allowing for combining of the conversions.  */
+	   TYPE_PRECISION (TREE_TYPE (@0)) <= TYPE_PRECISION (type)
 	   /* It's also a good idea if the conversion is to a non-integer
 	      mode.  */
 	   || GET_MODE_CLASS (TYPE_MODE (type)) != MODE_INT
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr103228-1.c b/gcc/testsuite/gcc.dg/tree-ssa/pr103228-1.c
new file mode 100644
index 00000000000..a7539819cf2
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr103228-1.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+int f(int a, int b)
+{
+  b|=1u;
+  b|=2;
+  return b;
+}
+/* { dg-final { scan-tree-dump-times "\\\| 3" 1 "optimized"} } */
+/* { dg-final { scan-tree-dump-times "\\\| 1" 0 "optimized"} } */
+/* { dg-final { scan-tree-dump-times "\\\| 2" 0 "optimized"} } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr55177-1.c b/gcc/testsuite/gcc.dg/tree-ssa/pr55177-1.c
new file mode 100644
index 00000000000..de1a264345c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr55177-1.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+extern int x;
+
+void foo(void)
+{
+  int a = __builtin_bswap32(x);
+  a &= 0x5a5b5c5d;
+  x = __builtin_bswap32(a);
+}
+
+/* { dg-final { scan-tree-dump-times "__builtin_bswap32" 0 "optimized"} } */
+/* { dg-final { scan-tree-dump-times "& 1566333786" 1 "optimized"} } */
+/* { dg-final { scan-tree-dump-times "& 1515936861" 0 "optimized"} } */
-- 
2.17.1



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