re PR tree-optimization/45704 (load byte instruction is used for volatile int)

2010-09-20  Richard Guenther  <rguenther@suse.de>

	PR middle-end/45704
	* gimplify.c (gimplify_modify_expr_rhs): Preserve volatileness.

	* gcc.dg/torture/pr45704.c: New testcase.

From-SVN: r164439

gcc/ChangeLog

+2010-09-20  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/45704
+	* gimplify.c (gimplify_modify_expr_rhs): Preserve volatileness.
+
 2010-09-20  Jan Hubicka  <jh@suse.cz>
 
 	PR tree-optimize/45605

gcc/gimplify.c

@@ -4200,9 +4200,18 @@ gimplify_modify_expr_rhs (tree *expr_p, tree *from_p, tree *to_p,
 	     This kind of code arises in C++ when an object is bound
 	     to a const reference, and if "x" is a TARGET_EXPR we want
 	     to take advantage of the optimization below.  */
+	    bool volatile_p = TREE_THIS_VOLATILE (*from_p);
 	    tree t = gimple_fold_indirect_ref_rhs (TREE_OPERAND (*from_p, 0));
 	    if (t)
 	      {
+		if (TREE_THIS_VOLATILE (t) != volatile_p)
+		  {
+		    if (TREE_CODE_CLASS (TREE_CODE (t)) == tcc_declaration)
+		      t = build_simple_mem_ref_loc (EXPR_LOCATION (*from_p),
+						    build_fold_addr_expr (t));
+		    if (REFERENCE_CLASS_P (t))
+		      TREE_THIS_VOLATILE (t) = volatile_p;
+		  }
 		*from_p = t;
 		ret = GS_OK;
 		changed = true;

gcc/testsuite/ChangeLog

+2010-09-20  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/45704
+	* gcc.dg/torture/pr45704.c: New testcase.
+
 2010-09-20  Jan Hubicka  <jh@suse.cz>
 
 	PR tree-optimize/45605

gcc/testsuite/gcc.dg/torture/pr45704.c

+/* { dg-do compile } */
+/* { dg-options "-fdump-tree-optimized" } */
+
+struct st {
+    int ptr;
+};
+
+int foo(struct st *st)
+{
+  int v = *(volatile int *)&st->ptr;
+  return v & 0xff;
+}
+
+/* { dg-final { scan-tree-dump-times "={v}" 1 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */