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 <rguent...@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.
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;
+}
