PR tree-optimization/18291

	* tree-ssa-copy.c (merge_alias_info): Fix merging of
	flow-sensitive alias information.  If the new pointer has no
	name tag, copy it from the original pointer.  Otherwise, make
	sure that the pointed-to sets have a common intersection.

testsuite/ChangeLog

	PR tree-optimization/18291
	* testsuite/gcc.c-torture/compile/pr18291.c: New test.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@91574 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 35 insertions, 13 deletions

diff --git a/gcc/tree-ssa-copy.c b/gcc/tree-ssa-copy.c
index ff497a8ae0a..8a03c2435d1 100644
--- a/gcc/tree-ssa-copy.c
+++ b/gcc/tree-ssa-copy.c
@@ -178,7 +178,6 @@ merge_alias_info (tree orig, tree new)
   tree orig_sym = SSA_NAME_VAR (orig);
   var_ann_t new_ann = var_ann (new_sym);
   var_ann_t orig_ann = var_ann (orig_sym);
-  struct ptr_info_def *new_ptr_info;
   struct ptr_info_def *orig_ptr_info;
 
   gcc_assert (POINTER_TYPE_P (TREE_TYPE (orig)));
@@ -203,18 +202,41 @@ merge_alias_info (tree orig, tree new)
   else
     gcc_assert (new_ann->type_mem_tag == orig_ann->type_mem_tag);
 
-  /* Synchronize flow sensitive alias information.  If both pointers
-     had flow information and they are inconsistent, then something
-     has gone wrong.  */
-  new_ptr_info = get_ptr_info (new);
-  orig_ptr_info = get_ptr_info (orig);
-
-  if (new_ptr_info->name_mem_tag == NULL_TREE)
-    memcpy (new_ptr_info, orig_ptr_info, sizeof (*new_ptr_info));
-  else if (orig_ptr_info->name_mem_tag == NULL_TREE)
-    memcpy (orig_ptr_info, new_ptr_info, sizeof (*orig_ptr_info));
-  else if (orig_ptr_info->name_mem_tag != new_ptr_info->name_mem_tag)
-    abort ();
+  orig_ptr_info = SSA_NAME_PTR_INFO (orig);
+  if (orig_ptr_info && orig_ptr_info->name_mem_tag)
+    {
+      struct ptr_info_def *new_ptr_info = get_ptr_info (new);
+
+      if (new_ptr_info->name_mem_tag == NULL_TREE)
+	{
+	  /* If ORIG had a name tag, it means that was dereferenced in
+	     the code, and since pointer NEW will now replace every
+	     occurrence of ORIG, we have to make sure that NEW has an
+	     appropriate tag.  If, NEW did not have a name tag, get it
+	     from ORIG.  */
+	  memcpy (new_ptr_info, orig_ptr_info, sizeof (*new_ptr_info));
+	  new_ptr_info->pt_vars = BITMAP_GGC_ALLOC ();
+	  bitmap_copy (new_ptr_info->pt_vars, orig_ptr_info->pt_vars);
+	  new_ptr_info->name_mem_tag = orig_ptr_info->name_mem_tag;
+	}
+      else
+	{
+	  /* If NEW already had a name tag, nothing needs to be done.
+	     Note that pointer NEW may actually have a different set of
+	     pointed-to variables.
+	     
+	     However, since NEW is being copy-propagated into ORIG, it must
+	     always be true that the pointed-to set for pointer NEW is the
+	     same, or a subset, of the pointed-to set for pointer ORIG.  If
+	     this isn't the case, we shouldn't have been able to do the
+	     propagation of NEW into ORIG.  */
+#if defined ENABLE_CHECKING
+	  if (orig_ptr_info->pt_vars && new_ptr_info->pt_vars)
+	    gcc_assert (bitmap_intersect_p (new_ptr_info->pt_vars,
+					    orig_ptr_info->pt_vars));
+#endif
+	}
+    }
 }