From 165ba2e9c7a6a86dbb12182486359edefba1dd9d Mon Sep 17 00:00:00 2001
From: Jakub Jelinek <jakub@redhat.com>
Date: Wed, 4 Jan 2017 10:07:33 +0100
Subject: [PATCH] re PR tree-optimization/71563 (Regression in GCC-7.0.0's
optimizer.)
PR tree-optimization/71563
* match.pd: Simplify X << Y into X if Y is known to be 0 or
out of range value - has low bits known to be zero.
* gcc.dg/tree-ssa/pr71563.c: New test.
From-SVN: r244050
---
gcc/ChangeLog | 6 ++++++
gcc/match.pd | 15 +++++++++++++++
gcc/testsuite/ChangeLog | 5 +++++
gcc/testsuite/gcc.dg/tree-ssa/pr71563.c | 23 +++++++++++++++++++++++
4 files changed, 49 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr71563.c
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 06021eed5def..864c30b9ccd2 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2017-01-04 Jakub Jelinek <jakub@redhat.com>
+
+ PR tree-optimization/71563
+ * match.pd: Simplify X << Y into X if Y is known to be 0 or
+ out of range value - has low bits known to be zero.
+
2017-01-04 Alan Modra <amodra@gmail.com>
* Makefile.in (aclocal_deps): Update and order as per aclocal.m4.
diff --git a/gcc/match.pd b/gcc/match.pd
index 8791e57ea212..7b9680094730 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -1515,6 +1515,21 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
(if (tem)
(shiftrotate @0 { tem; }))))))
+/* Simplify X << Y where Y's low width bits are 0 to X, as only valid
+ Y is 0. Similarly for X >> Y. */
+#if GIMPLE
+(for shift (lshift rshift)
+ (simplify
+ (shift @0 SSA_NAME@1)
+ (if (INTEGRAL_TYPE_P (TREE_TYPE (@1)))
+ (with {
+ int width = ceil_log2 (element_precision (TREE_TYPE (@0)));
+ int prec = TYPE_PRECISION (TREE_TYPE (@1));
+ }
+ (if ((get_nonzero_bits (@1) & wi::mask (width, false, prec)) == 0)
+ @0)))))
+#endif
+
/* Rewrite an LROTATE_EXPR by a constant into an
RROTATE_EXPR by a new constant. */
(simplify
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 4a1caa7bb04f..9e7cae414195 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2017-01-04 Jakub Jelinek <jakub@redhat.com>
+
+ PR tree-optimization/71563
+ * gcc.dg/tree-ssa/pr71563.c: New test.
+
2017-01-04 Janne Blomqvist <jb@gcc.gnu.org>
PR fortran/78534
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr71563.c b/gcc/testsuite/gcc.dg/tree-ssa/pr71563.c
new file mode 100644
index 000000000000..f01291d25dca
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr71563.c
@@ -0,0 +1,23 @@
+/* PR tree-optimization/71563 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+void link_error (void);
+
+void
+foo (int k)
+{
+ int t = 1 << ((1 / k) << 8);
+ if (t != 1)
+ link_error ();
+}
+
+void
+bar (int k, int l)
+{
+ int t = l << (k << 8);
+ if (t != l)
+ link_error ();
+}
+
+/* { dg-final { scan-tree-dump-not "link_error" "optimized" } } */
--
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