re PR tree-optimization/50078 (combine wrong code: volatile accesses optimized out)

	PR tree-optimization/50078
	* tree-ssa-forwprop.c (forward_propagate_addr_expr_1): Copy over
	TREE_THIS_VOLATILE also from the old to new lhs resp. rhs.

	* gcc.dg/pr50078.c: New test.

From-SVN: r181786

gcc/ChangeLog

 2011-11-28  Jakub Jelinek  <jakub@redhat.com>
 
+	PR tree-optimization/50078
+	* tree-ssa-forwprop.c (forward_propagate_addr_expr_1): Copy over
+	TREE_THIS_VOLATILE also from the old to new lhs resp. rhs.
+
 	PR tree-optimization/50682
 	* tree-eh.c (maybe_remove_unreachable_handlers): New function.
 	* tree-flow.h (maybe_remove_unreachable_handlers): New prototype.

gcc/testsuite/ChangeLog

 2011-11-28  Jakub Jelinek  <jakub@redhat.com>
 
+	PR tree-optimization/50078
+	* gcc.dg/pr50078.c: New test.
+
 	PR tree-optimization/50682
 	* g++.dg/opt/pr50682.C: New test.
 

gcc/testsuite/gcc.dg/pr50078.c

+/* PR tree-optimization/50078 */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+unsigned nonvolvar[2];
+
+void
+test (int arg)
+{
+  unsigned v = *(volatile unsigned *) (&nonvolvar[arg]);
+  *(volatile unsigned *) (&nonvolvar[arg]) = v;
+}
+
+/* { dg-final { scan-assembler-times "movl\[^\n\r\]*nonvolvar" 2 { target { { i?86-*-* x86_64-*-* } && nonpic } } } } */

gcc/tree-ssa-forwprop.c

@@ -910,7 +910,7 @@ forward_propagate_addr_expr_1 (tree name, tree def_rhs,
 		     TREE_TYPE (gimple_assign_rhs1 (use_stmt))))
 	{
 	  tree *def_rhs_basep = &TREE_OPERAND (def_rhs, 0);
-	  tree new_offset, new_base, saved;
+	  tree new_offset, new_base, saved, new_lhs;
 	  while (handled_component_p (*def_rhs_basep))
 	    def_rhs_basep = &TREE_OPERAND (*def_rhs_basep, 0);
 	  saved = *def_rhs_basep;
@@ -930,8 +930,9 @@ forward_propagate_addr_expr_1 (tree name, tree def_rhs,
 				   new_base, new_offset);
 	  TREE_THIS_VOLATILE (*def_rhs_basep) = TREE_THIS_VOLATILE (lhs);
 	  TREE_THIS_NOTRAP (*def_rhs_basep) = TREE_THIS_NOTRAP (lhs);
-	  gimple_assign_set_lhs (use_stmt,
-				 unshare_expr (TREE_OPERAND (def_rhs, 0)));
+	  new_lhs = unshare_expr (TREE_OPERAND (def_rhs, 0));
+	  gimple_assign_set_lhs (use_stmt, new_lhs);
+	  TREE_THIS_VOLATILE (new_lhs) = TREE_THIS_VOLATILE (lhs);
 	  *def_rhs_basep = saved;
 	  tidy_after_forward_propagate_addr (use_stmt);
 	  /* Continue propagating into the RHS if this was not the
@@ -991,7 +992,7 @@ forward_propagate_addr_expr_1 (tree name, tree def_rhs,
 		     TREE_TYPE (TREE_OPERAND (def_rhs, 0))))
 	{
 	  tree *def_rhs_basep = &TREE_OPERAND (def_rhs, 0);
-	  tree new_offset, new_base, saved;
+	  tree new_offset, new_base, saved, new_rhs;
 	  while (handled_component_p (*def_rhs_basep))
 	    def_rhs_basep = &TREE_OPERAND (*def_rhs_basep, 0);
 	  saved = *def_rhs_basep;
@@ -1011,8 +1012,9 @@ forward_propagate_addr_expr_1 (tree name, tree def_rhs,
 				   new_base, new_offset);
 	  TREE_THIS_VOLATILE (*def_rhs_basep) = TREE_THIS_VOLATILE (rhs);
 	  TREE_THIS_NOTRAP (*def_rhs_basep) = TREE_THIS_NOTRAP (rhs);
-	  gimple_assign_set_rhs1 (use_stmt,
-				  unshare_expr (TREE_OPERAND (def_rhs, 0)));
+	  new_rhs = unshare_expr (TREE_OPERAND (def_rhs, 0));
+	  gimple_assign_set_rhs1 (use_stmt, new_rhs);
+	  TREE_THIS_VOLATILE (new_rhs) = TREE_THIS_VOLATILE (rhs);
 	  *def_rhs_basep = saved;
 	  fold_stmt_inplace (use_stmt_gsi);
 	  tidy_after_forward_propagate_addr (use_stmt);