tree-ssa-ccp.c (valid_lattice_transition): Clarify comment about transition from invariant to known bits.

* tree-ssa-ccp.c (valid_lattice_transition): Clarify comment
	about transition from invariant to known bits.
	(likely_value): Addresses with UNDEFINED components are UNDEFINED.

Co-Authored-By: Eric Botcazou <ebotcazou@adacore.com>

From-SVN: r189679

gcc/ChangeLog

@@ -1,3 +1,10 @@
+2012-07-19  Richard Guenther  <rguenther@suse.de>
+	    Eric Botcazou  <ebotcazou@adacore.com>
+
+	* tree-ssa-ccp.c (valid_lattice_transition): Clarify comment
+	about transition from invariant to known bits.
+	(likely_value): Addresses with UNDEFINED components are UNDEFINED.
+
 2012-07-19  Jakub Jelinek  <jakub@redhat.com>
 
 	PR middle-end/54017

gcc/testsuite/ChangeLog

@@ -1,3 +1,9 @@
+2012-07-19  Richard Guenther  <rguenther@suse.de>
+	    Eric Botcazou  <ebotcazou@adacore.com>
+
+	* gnat.dg/loop_optimization11.adb: New testcase.
+	* gnat.dg/loop_optimization11_pkg.ads: Likewise.
+
 2012-07-19  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* gnat.dg/discr38.adb: New test.

gcc/testsuite/gnat.dg/loop_optimization11.adb

@@ -0,0 +1,19 @@
+-- { dg-do compile }
+-- { dg-options "-O" }
+
+with Loop_Optimization11_Pkg; use Loop_Optimization11_Pkg;
+
+procedure Loop_Optimization11 is
+   Arr : array (Prot, Mem) of Integer := (others => (others => 0));
+begin
+   Put_Line (Img (0) & " ");
+   for I in Arr'Range (1) loop
+      for J in Arr'Range (2) loop
+         declare
+            Elem : Integer renames Arr (I, J);
+         begin
+            Put_Line (Img (Elem));
+         end;
+      end loop;
+   end loop;
+end;

gcc/testsuite/gnat.dg/loop_optimization11_pkg.ads

@@ -0,0 +1,11 @@
+package Loop_Optimization11_Pkg is
+
+   function Img (X : Integer) return String;
+
+   procedure Put_Line (Data : String);
+
+   type Prot is (Execute, Execute_Read, Execute_Read_Write);
+
+   type Mem is (Mem_Image, Mem_Mapped, Mem_Private, Unknown);
+
+end Loop_Optimization11_Pkg;

gcc/tree-ssa-ccp.c

@@ -409,7 +409,8 @@ valid_lattice_transition (prop_value_t old_val, prop_value_t new_val)
 
   /* Now both lattice values are CONSTANT.  */
 
-  /* Allow transitioning from &x to &x & ~3.  */
+  /* Allow transitioning from PHI <&x, not executable> == &x
+     to PHI <&x, &y> == common alignment.  */
   if (TREE_CODE (old_val.value) != INTEGER_CST
       && TREE_CODE (new_val.value) == INTEGER_CST)
     return true;
@@ -652,6 +653,11 @@ likely_value (gimple stmt)
 	     the undefined operand may be promoted.  */
 	  return UNDEFINED;
 
+	case ADDR_EXPR:
+	  /* If any part of an address is UNDEFINED, like the index
+	     of an ARRAY_EXPR, then treat the result as UNDEFINED.  */
+	  return UNDEFINED;
+
 	default:
 	  ;
 	}