From: Diego Novillo <dnovillo@redhat.com>
Date: Wed, 15 Sep 2004 02:58:28 +0000 (+0000)
Subject: re PR tree-optimization/17252 (not marking char types as aliasing anything)
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=391f9afbd2d6ac8dd691c6d79a8817c63a637ca8;p=gcc.git

re PR tree-optimization/17252 (not marking char types as aliasing anything)


	PR tree-optimization/17252
	* tree-ssa-alias.c (may_alias_p): Don't assume that a
	pointer may not point to itself when using relaxed
	aliasing rules.

testsuite/ChangeLog

	PR tree-optimization/17252
	* gcc.c-torture/execute/pr17252.c: New test.

From-SVN: r87529
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index ff7e392a177..a2f169c575d 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2004-09-14  Diego Novillo  <dnovillo@redhat.com>
+
+	PR tree-optimization/17252
+	* tree-ssa-alias.c (may_alias_p): Don't assume that a
+	pointer may not point to itself when using relaxed
+	aliasing rules.
+
 2004-09-14  Richard Henderson  <rth@redhat.com>
 
 	PR middle-end/17397
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 78de08e73e3..61744bf33f7 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2004-09-14  Diego Novillo  <dnovillo@redhat.com>
+
+	PR tree-optimization/17252
+	* gcc.c-torture/execute/pr17252.c: New test.
+
 2004-09-14  Andrew Pinski  <apinski@apple.com>
 
 	* g++.dg/tree-ssa/pointer-reference-alias.C: New test.
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr17252.c b/gcc/testsuite/gcc.c-torture/execute/pr17252.c
new file mode 100644
index 00000000000..e31622fc7e0
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr17252.c
@@ -0,0 +1,24 @@
+/* PR 17252.  When a char * pointer P takes its own address, storing
+   into *P changes P itself.  */
+
+char *a;
+
+main ()
+{
+  int i;
+
+  /* Make 'a' point to itself.  */
+  a = (char *)&a;
+
+  /* Assign NULL to 'a' byte by byte.  */
+  for (i = 0; i < sizeof(char *); i++)
+    a[i] = 0;
+
+  /* If a's memory tag does not contain 'a' in its alias set, we will
+     think that this predicate is superfluous and change it to
+     'if (1)'.  */
+  if (a == (char *)&a)
+    abort ();
+
+  return 0;
+}
diff --git a/gcc/tree-ssa-alias.c b/gcc/tree-ssa-alias.c
index 65b0d7bc776..801de5bfaa5 100644
--- a/gcc/tree-ssa-alias.c
+++ b/gcc/tree-ssa-alias.c
@@ -1558,7 +1558,8 @@ may_alias_p (tree ptr, HOST_WIDE_INT mem_alias_set,
      for PTR's alias set here, not its pointed-to type.  We also can't
      do this check with relaxed aliasing enabled.  */
   if (POINTER_TYPE_P (TREE_TYPE (var))
-      && var_alias_set != 0)
+      && var_alias_set != 0
+      && mem_alias_set != 0)
     {
       HOST_WIDE_INT ptr_alias_set = get_alias_set (ptr);
       if (ptr_alias_set == var_alias_set)