PR optimization/14511

	* tree-ssa-alias.c (compute_flow_insensitive_aliasing): Do not
	ignore read-only variables.
	(may_alias_p): Fix pointer-to-var calculation when 'var' is an
	array.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/tree-ssa-20020619-branch@79599 138bc75d-0d04-0410-961f-82ee72b054a4

5 files changed, 58 insertions, 5 deletions

diff --git a/gcc/ChangeLog.tree-ssa b/gcc/ChangeLog.tree-ssa
index bfa7439aeab..ae6223b2724 100644
--- a/gcc/ChangeLog.tree-ssa
+++ b/gcc/ChangeLog.tree-ssa
@@ -1,3 +1,11 @@
+2004-03-17  Diego Novillo  <dnovillo@redhat.com>
+
+	PR optimization/14511
+	* tree-ssa-alias.c (compute_flow_insensitive_aliasing): Do not
+	ignore read-only variables.
+	(may_alias_p): Fix pointer-to-var calculation when 'var' is an
+	array.
+
 2004-03-17  Jan Hubicka  <jh@suse.cz>
 
 	* tree-ssa.c (rewrite_into_ssa, compute_global_livein): Fix.
diff --git a/gcc/testsuite/ChangeLog.tree-ssa b/gcc/testsuite/ChangeLog.tree-ssa
index c3515108308..37d7e4be8d6 100644
--- a/gcc/testsuite/ChangeLog.tree-ssa
+++ b/gcc/testsuite/ChangeLog.tree-ssa
@@ -1,3 +1,8 @@
+2004-03-17  Diego Novillo  <dnovillo@redhat.com>
+
+	PR optimization/14511
+	* g++.dg/tree-ssa/20040317-1.C: New test.
+
 2004-03-13  Diego Novillo  <dnovillo@redhat.com>
 
 	PR optimization/14553
diff --git a/gcc/testsuite/g++.dg/README b/gcc/testsuite/g++.dg/README
index 27f6a5a80cf..d96e8990ee3 100644
--- a/gcc/testsuite/g++.dg/README
+++ b/gcc/testsuite/g++.dg/README
@@ -21,6 +21,7 @@ rtti	 Tests for run-time type identification (typeid, dynamic_cast, etc.)
 special	 Tests requiring individual processing.
 template Tests for templates.
 tls	 Tests for support of thread-local data.
+tree-ssa Tests for Tree SSA optimizations.
 warn	 Tests for compiler warnings.
 
 other	 Tests that don't fit into one of the other categories.
diff --git a/gcc/testsuite/g++.dg/tree-ssa/20040317-1.C b/gcc/testsuite/g++.dg/tree-ssa/20040317-1.C
new file mode 100644
index 00000000000..e2f3dcdceb8
--- /dev/null
+++ b/gcc/testsuite/g++.dg/tree-ssa/20040317-1.C
@@ -0,0 +1,38 @@
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+/* Test provided by Brian Ryner in PR 14511.  The alias analyzer was
+   not handling structures containing arrays properly.  In this case,
+   the static cast was introducing two assignments of the form
+
+	  this_6->_vptr.IFoo = &_ZTV4IFoo[2];
+	  this_4->_vptr.IFoo = &_ZTV3Bar[2];
+
+   which were not considered to alias each other because the alias
+   analyzer was not computing a proper pointer to array elements.
+   Another related bug was the type based alias analyzer not computing
+   alias relations to _ZTV4IFoo and _ZTV3Bar.  Since those variables
+   are read-only, it was disregarding alias information for them.
+   So, the memory tags for the two 'this' variables were not being
+   marked as aliased with these variables.  Resulting in the two
+   assignments not aliasing each other.
+
+   This was causing the optimizers to generate a call to the virtual
+   method Foo() instead of the overloaded version.  */
+
+struct IFoo
+{
+  virtual void Foo() = 0;
+};
+
+struct Bar : IFoo
+{
+  void Foo() { }
+};
+
+int main(int argc, char **argv)
+{
+  Bar* b = new Bar();
+  static_cast<IFoo*>(b)->Foo();
+  return 0;
+}
diff --git a/gcc/tree-ssa-alias.c b/gcc/tree-ssa-alias.c
index eabce62df5c..ff7ef9a6c9a 100644
--- a/gcc/tree-ssa-alias.c
+++ b/gcc/tree-ssa-alias.c
@@ -797,10 +797,6 @@ compute_flow_insensitive_aliasing (struct alias_info *ai)
 	  if (!tag_stored_p && !var_stored_p)
 	    continue;
 	     
-	  /* Skip memory tags which are written if the variable is readonly.  */
-	  if (tag_stored_p && TREE_READONLY (var))
-	    continue;
-
 	  if (may_alias_p (p_map->var, p_map->set, var, v_map->set))
 	    {
 	      size_t num_tag_refs = ai->num_references[tag_ann->uid];
@@ -1337,7 +1333,12 @@ may_alias_p (tree ptr, HOST_WIDE_INT mem_alias_set,
       if (AGGREGATE_TYPE_P (TREE_TYPE (mem))
 	  || AGGREGATE_TYPE_P (TREE_TYPE (var)))
 	{
-	  tree ptr_to_var = TYPE_POINTER_TO (TREE_TYPE (var));
+	  tree ptr_to_var;
+	  
+	  if (TREE_CODE (TREE_TYPE (var)) == ARRAY_TYPE)
+	    ptr_to_var = TYPE_POINTER_TO (TREE_TYPE (TREE_TYPE (var)));
+	  else
+	    ptr_to_var = TYPE_POINTER_TO (TREE_TYPE (var));
 
 	  /* If no pointer-to VAR exists, then MEM can't alias VAR.  */
 	  if (ptr_to_var == NULL_TREE)