diff mbox

[3/2] Fix PR77768

Message ID alpine.LSU.2.11.1609291429270.26629@t29.fhfr.qr
State New
Headers show

Commit Message

Richard Biener Sept. 29, 2016, 12:30 p.m. UTC 
Another one - this time with the testcase from the other PR.

Bootstrapped / tested on x86_64-unknown-linux-gnu, applied.

Richard.

2016-09-29  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/77768
	* tree-ssa-pre.c (eliminate_dom_walker::before_dom_children):
	Handle stores to readonly memory when removing redundant stores.

	* gcc.dg/torture/pr77768.c: New testcase.
diff mbox

Patch

Index: gcc/tree-ssa-pre.c
===================================================================
--- gcc/tree-ssa-pre.c	(revision 240609)
+++ gcc/tree-ssa-pre.c	(working copy)
@@ -4443,9 +4443,11 @@  eliminate_dom_walker::before_dom_childre
 	      && operand_equal_p (val, rhs, 0))
 	    {
 	      /* We can only remove the later store if the former aliases
-		 at least all accesses the later one does.  */
+		 at least all accesses the later one does or if the store
+		 was to readonly memory storing the same value.  */
 	      alias_set_type set = get_alias_set (lhs);
-	      if (vnresult->set == set
+	      if (! vnresult
+		  || vnresult->set == set
 		  || alias_set_subset_of (set, vnresult->set))
 		{
 		  if (dump_file && (dump_flags & TDF_DETAILS))
Index: gcc/testsuite/gcc.dg/torture/pr77768.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr77768.c	(revision 0)
+++ gcc/testsuite/gcc.dg/torture/pr77768.c	(working copy)
@@ -0,0 +1,13 @@ 
+/* { dg-do run } */
+
+static const int a;
+int b;
+int *c, *d;
+int main()
+{
+  c = (int *)&a;
+  c == d ?: __builtin_exit(0); 
+  for (; b; b++ >= (*d = a))
+    ;
+  return 0;
+}