From d41b097350d3c5d03824ea19520cd3b4430c9e62 Mon Sep 17 00:00:00 2001
From: Jakub Jelinek <jakub@redhat.com>
Date: Tue, 15 Dec 2020 22:43:46 +0100
Subject: [PATCH] match.pd: Optimize X / bool_range_Y to X [PR96094]
When the divisor is bool or has [0, 1] range, as division by
0 is UB, the only remaining option in valid programs is division by 1,
so we can optimize X / bool_range_Y into X.
2020-12-15 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/96094
* match.pd (X / bool_range_Y -> X): New simplification.
* gcc.dg/tree-ssa/pr96094.c: New test.
---
gcc/match.pd | 13 +++++++---
gcc/testsuite/gcc.dg/tree-ssa/pr96094.c | 34 +++++++++++++++++++++++++
2 files changed, 43 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr96094.c
diff --git a/gcc/match.pd b/gcc/match.pd
index 8f3edfa2fa62..c7ee57d4bc20 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -348,11 +348,16 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
/* But not for 0 / 0 so that we can get the proper warnings and errors. */
(if (!integer_zerop (@1))
@0))
- /* X / -1 is -X. */
+ /* X / -1 is -X. */
(simplify
- (div @0 integer_minus_onep@1)
- (if (!TYPE_UNSIGNED (type))
- (negate @0)))
+ (div @0 integer_minus_onep@1)
+ (if (!TYPE_UNSIGNED (type))
+ (negate @0)))
+ /* X / bool_range_Y is X. */
+ (simplify
+ (div @0 SSA_NAME@1)
+ (if (INTEGRAL_TYPE_P (type) && ssa_name_has_boolean_range (@1))
+ @0))
/* X / X is one. */
(simplify
(div @0 @0)
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr96094.c b/gcc/testsuite/gcc.dg/tree-ssa/pr96094.c
new file mode 100644
index 000000000000..fe9163dda3e4
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr96094.c
@@ -0,0 +1,34 @@
+/* PR tree-optimization/96094 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump-times "return 34;" 2 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "return y_\[0-9]*\\\(D\\\);" 2 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "return \[^\n\r;]*;" 4 "optimized" } } */
+
+int
+foo (int x)
+{
+ if (x >= 2U)
+ return 34;
+ return 34 / x;
+}
+
+int
+bar (int x, int y)
+{
+ if (x >= 2U)
+ return y;
+ return y / x;
+}
+
+int
+baz (_Bool x)
+{
+ return 34 / x;
+}
+
+int
+qux (_Bool x, int y)
+{
+ return y / x;
+}
--
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