From 2236cf7a503a24ef54b02a41ab3b7febf99bfc13 Mon Sep 17 00:00:00 2001
From: jakub <jakub@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Wed, 11 Jan 2017 08:40:59 +0000
Subject: [PATCH] 	PR middle-end/50199 	* lto-lang.c
 (lto_post_options): Force flag_merge_constants = 1 	if it was 0.

	* gcc.dg/lto/pr50199_0.c: New test.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@244304 138bc75d-0d04-0410-961f-82ee72b054a4
---
 gcc/lto/ChangeLog                    |  6 ++++++
 gcc/lto/lto-lang.c                   |  6 ++++++
 gcc/testsuite/ChangeLog              |  5 +++++
 gcc/testsuite/gcc.dg/lto/pr50199_0.c | 17 +++++++++++++++++
 4 files changed, 34 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/lto/pr50199_0.c

diff --git a/gcc/lto/ChangeLog b/gcc/lto/ChangeLog
index f94add55852..9bf6df01544 100644
--- a/gcc/lto/ChangeLog
+++ b/gcc/lto/ChangeLog
@@ -1,3 +1,9 @@
+2017-01-11  Jakub Jelinek  <jakub@redhat.com>
+
+	PR middle-end/50199
+	* lto-lang.c (lto_post_options): Force flag_merge_constants = 1
+	if it was 0.
+
 2017-01-09  Jakub Jelinek  <jakub@redhat.com>
 
 	PR translation/79019
diff --git a/gcc/lto/lto-lang.c b/gcc/lto/lto-lang.c
index c2b49dc44b6..fccb8c61f8f 100644
--- a/gcc/lto/lto-lang.c
+++ b/gcc/lto/lto-lang.c
@@ -857,6 +857,12 @@ lto_post_options (const char **pfilename ATTRIBUTE_UNUSED)
      support.  */
   flag_excess_precision_cmdline = EXCESS_PRECISION_FAST;
 
+  /* When partitioning, we can tear appart STRING_CSTs uses from the same
+     TU into multiple partitions.  Without constant merging the constants
+     might not be equal at runtime.  See PR50199.  */
+  if (!flag_merge_constants)
+    flag_merge_constants = 1;
+
   /* Initialize the compiler back end.  */
   return false;
 }
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index c332d9062e0..2b5f3b9dca0 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2017-01-11  Jakub Jelinek  <jakub@redhat.com>
+
+	PR middle-end/50199
+	* gcc.dg/lto/pr50199_0.c: New test.
+
 2017-01-10  Martin Sebor  <msebor@redhat.com>
 
 	PR testsuite/78960
diff --git a/gcc/testsuite/gcc.dg/lto/pr50199_0.c b/gcc/testsuite/gcc.dg/lto/pr50199_0.c
new file mode 100644
index 00000000000..61d0012be92
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/lto/pr50199_0.c
@@ -0,0 +1,17 @@
+/* PR middle-end/50199 */
+/* { dg-lto-options {{-O2 -flto -fno-merge-constants --param=lto-min-partition=1}} } */
+
+__attribute__ ((noinline)) const char *
+foo (const char *x)
+{
+  return x;
+}
+
+int
+main ()
+{
+  const char *a = "ab";
+  if (a != foo (a))
+    __builtin_abort ();
+  return 0;
+}
-- 
2.11.4.GIT