Fix ACATS c64106c at -O2 on SPARC64

Fix ACATS c64106c at -O2 on SPARC64

[Eric Botcazou]

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This is the outcome of the discussion started at
  http://gcc.gnu.org/ml/gcc/2009-10/msg00457.html
which was pre-approved by Richard.

Bootstrapped/regested on x86_64-suse-linux, applied on the mainline.


2009-10-24  Eric Botcazou  <ebotcazou@adacore.com>

	* tree-ssa-alias.c (nonaliasing_component_refs_p): Rename into...
	(aliasing_component_refs_p): ...this.  Return true if there is no
	common base and the base access types have the same alias set.
	(indirect_ref_may_alias_decl_p): Adjust for above renaming.
	(indirect_refs_may_alias_p): Likewise.


2009-10-24  Eric Botcazou  <ebotcazou@adacore.com>

	* gnat.dg/opt4.adb: New test.


-- 
Eric Botcazou

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Index: tree-ssa-alias.c
===================================================================
--- tree-ssa-alias.c	(revision 153447)
+++ tree-ssa-alias.c	(working copy)
@@ -553,10 +553,10 @@ same_type_for_tbaa (tree type1, tree typ
    on an indirect reference may alias.  */
 
 static bool
-nonaliasing_component_refs_p (tree ref1, tree type1,
-			      HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
-			      tree ref2, tree type2,
-			      HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2)
+aliasing_component_refs_p (tree ref1, tree type1,
+			   HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
+			   tree ref2, tree type2,
+			   HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2)
 {
   /* If one reference is a component references through pointers try to find a
      common base and apply offset based disambiguation.  This handles
@@ -600,9 +600,19 @@ nonaliasing_component_refs_p (tree ref1,
       offset1 -= offadj;
       return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
     }
-  /* If we have two type access paths B1.path1 and B2.path2 they may
-     only alias if either B1 is in B2.path2 or B2 is in B1.path1.  */
-  return false;
+
+  /* We haven't found any common base to apply offset-based disambiguation.
+     There are two cases:
+       1. The base access types have the same alias set.  This can happen
+	  in Ada when a function with an unconstrained parameter passed by
+	  reference is called on a constrained object and inlined: the types
+	  have the same alias set but aren't equivalent.  The references may
+	  alias in this case.
+       2. The base access types don't have the same alias set, i.e. one set
+	  is a subset of the other.  We have proved that B1 is not in the
+	  access path B2.path and that B2 is not in the access path B1.path
+	  so the references may not alias.  */
+  return get_alias_set (type1) == get_alias_set (type2);
 }
 
 /* Return true if two memory references based on the variables BASE1
@@ -681,10 +691,10 @@ indirect_ref_may_alias_decl_p (tree ref1
   if (ref1 && ref2
       && handled_component_p (ref1)
       && handled_component_p (ref2))
-    return nonaliasing_component_refs_p (ref1, TREE_TYPE (TREE_TYPE (ptr1)),
-					 offset1, max_size1,
-					 ref2, TREE_TYPE (base2),
-					 offset2, max_size2);
+    return aliasing_component_refs_p (ref1, TREE_TYPE (TREE_TYPE (ptr1)),
+				      offset1, max_size1,
+				      ref2, TREE_TYPE (base2),
+				      offset2, max_size2);
 
   return true;
 }
@@ -742,10 +752,10 @@ indirect_refs_may_alias_p (tree ref1, tr
   if (ref1 && ref2
       && handled_component_p (ref1)
       && handled_component_p (ref2))
-    return nonaliasing_component_refs_p (ref1, TREE_TYPE (TREE_TYPE (ptr1)),
-					 offset1, max_size1,
-					 ref2, TREE_TYPE (TREE_TYPE (ptr2)),
-					 offset2, max_size2);
+    return aliasing_component_refs_p (ref1, TREE_TYPE (TREE_TYPE (ptr1)),
+				      offset1, max_size1,
+				      ref2, TREE_TYPE (TREE_TYPE (ptr2)),
+				      offset2, max_size2);
 
   return true;
 }

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-- { dg-do run }
-- { dg-options "-O2" }

procedure Opt4 is

  type Rec (D : Natural) is record
    S : String (1..D);
  end record;

  procedure Test (R : Rec) is
  begin
    if R.D /= 9 then
      raise Program_Error;
    end if;
  end;

  R : Rec(9);

begin
  R := (9, "123456789");
  Test (R);
end;