From: Richard Biener <rguenther@suse.de>
Date: Tue, 28 Mar 2017 10:10:01 +0000 (+0000)
Subject: re PR middle-end/80222 (may_alias folded away)
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=737f500a0bb2cfdf1e28975a27403e555ede633e;p=gcc.git

re PR middle-end/80222 (may_alias folded away)

2017-03-28  Richard Biener  <rguenther@suse.de>

	PR middle-end/80222
	* gimple-fold.c (gimple_fold_indirect_ref): Do not touch
	TYPE_REF_CAN_ALIAS_ALL references.
	* fold-const.c (fold_indirect_ref_1): Likewise.

	* g++.dg/pr80222.C: New testcase.

From-SVN: r246527
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 27e7b8f0a75..7274aa4e7a6 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2017-03-28  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/80222
+	* gimple-fold.c (gimple_fold_indirect_ref): Do not touch
+	TYPE_REF_CAN_ALIAS_ALL references.
+	* fold-const.c (fold_indirect_ref_1): Likewise.
+
 2017-03-28  Martin Liska  <mliska@suse.cz>
 
 	PR ipa/80104
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 6db16b514f1..fb54ffa0e5e 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -14006,7 +14006,8 @@ fold_indirect_ref_1 (location_t loc, tree type, tree op0)
 
   STRIP_NOPS (sub);
   subtype = TREE_TYPE (sub);
-  if (!POINTER_TYPE_P (subtype))
+  if (!POINTER_TYPE_P (subtype)
+      || TYPE_REF_CAN_ALIAS_ALL (TREE_TYPE (op0)))
     return NULL_TREE;
 
   if (TREE_CODE (sub) == ADDR_EXPR)
diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c
index 3094b54c109..a6a958cefa4 100644
--- a/gcc/gimple-fold.c
+++ b/gcc/gimple-fold.c
@@ -6539,8 +6539,8 @@ gimple_get_virt_method_for_binfo (HOST_WIDE_INT token, tree known_binfo,
   return gimple_get_virt_method_for_vtable (token, v, offset, can_refer);
 }
 
-/* Given a pointer value OP0, return a simplified version of an
-   indirection through OP0, or NULL_TREE if no simplification is
+/* Given a pointer value T, return a simplified version of an
+   indirection through T, or NULL_TREE if no simplification is
    possible.  Note that the resulting type may be different from
    the type pointed to in the sense that it is still compatible
    from the langhooks point of view. */
@@ -6554,7 +6554,8 @@ gimple_fold_indirect_ref (tree t)
 
   STRIP_NOPS (sub);
   subtype = TREE_TYPE (sub);
-  if (!POINTER_TYPE_P (subtype))
+  if (!POINTER_TYPE_P (subtype)
+      || TYPE_REF_CAN_ALIAS_ALL (ptype))
     return NULL_TREE;
 
   if (TREE_CODE (sub) == ADDR_EXPR)
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index a896f753719..4abe1dc0cfa 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2017-03-28  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/80222
+	* g++.dg/pr80222.C: New testcase.
+
 2017-03-28  Martin Liska  <mliska@suse.cz>
 
 	PR ipa/80104
diff --git a/gcc/testsuite/g++.dg/pr80222.C b/gcc/testsuite/g++.dg/pr80222.C
new file mode 100644
index 00000000000..ed1b37f5e37
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr80222.C
@@ -0,0 +1,13 @@
+// { dg-do compile }
+// { dg-options "-O2 -fdump-tree-optimized" } */
+
+struct C { int i; }__attribute__((may_alias)) ;
+
+C a, b;
+
+int main()
+{
+  a = static_cast <C&> (b);
+}
+
+// { dg-final { scan-tree-dump "{ref-all}\\\)&b\];" "optimized" } } */