re PR c++/71372 (C++ FE drops TREE_THIS_VOLATILE in cp_fold on all tcc_reference trees)

	PR c++/71372
	* cp-gimplify.c (cp_fold): For INDIRECT_REF, if the folded expression
	is INDIRECT_REF or MEM_REF, copy over TREE_READONLY, TREE_SIDE_EFFECTS
	and TREE_THIS_VOLATILE flags.  For ARRAY_REF and ARRAY_RANGE_REF, copy
	over TREE_READONLY, TREE_SIDE_EFFECTS and TREE_THIS_VOLATILE flags
	to the newly built tree.

	* c-c++-common/pr71372.c: New test.

From-SVN: r237041

gcc/cp/ChangeLog

+2016-06-02  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/71372
+	* cp-gimplify.c (cp_fold): For INDIRECT_REF, if the folded expression
+	is INDIRECT_REF or MEM_REF, copy over TREE_READONLY, TREE_SIDE_EFFECTS
+	and TREE_THIS_VOLATILE flags.  For ARRAY_REF and ARRAY_RANGE_REF, copy
+	over TREE_READONLY, TREE_SIDE_EFFECTS and TREE_THIS_VOLATILE flags
+	to the newly built tree.
+
 2016-05-31  Jason Merrill  <jason@redhat.com>
 
 	* pt.c (instantiate_decl): Avoid recalculation.

gcc/cp/cp-gimplify.c

@@ -2035,7 +2035,16 @@ cp_fold (tree x)
 	  if (op0 == error_mark_node)
 	    x = error_mark_node;
 	  else
-	    x = fold_build1_loc (loc, code, TREE_TYPE (x), op0);
+	    {
+	      x = fold_build1_loc (loc, code, TREE_TYPE (x), op0);
+	      if (code == INDIRECT_REF
+		  && (INDIRECT_REF_P (x) || TREE_CODE (x) == MEM_REF))
+		{
+		  TREE_READONLY (x) = TREE_READONLY (org_x);
+		  TREE_SIDE_EFFECTS (x) = TREE_SIDE_EFFECTS (org_x);
+		  TREE_THIS_VOLATILE (x) = TREE_THIS_VOLATILE (org_x);
+		}
+	    }
 	}
       else
 	x = fold (x);
@@ -2312,7 +2321,12 @@ cp_fold (tree x)
 	      || op3 == error_mark_node)
 	    x = error_mark_node;
 	  else
-	    x = build4_loc (loc, code, TREE_TYPE (x), op0, op1, op2, op3);
+	    {
+	      x = build4_loc (loc, code, TREE_TYPE (x), op0, op1, op2, op3);
+	      TREE_READONLY (x) = TREE_READONLY (org_x);
+	      TREE_SIDE_EFFECTS (x) = TREE_SIDE_EFFECTS (org_x);
+	      TREE_THIS_VOLATILE (x) = TREE_THIS_VOLATILE (org_x);
+	    }
 	}
 
       x = fold (x);

gcc/testsuite/ChangeLog

 2016-06-02  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/71372
+	* c-c++-common/pr71372.c: New test.
+
 	* gcc.dg/cpp/source_date_epoch-1.c (main): Test __DATE__ and
 	__TIME__ strings with __builtin_strcmp instead of printf and
 	dg-output.

gcc/testsuite/c-c++-common/pr71372.c

+/* PR c++/71372 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+void
+foo (volatile int *p, int q)
+{
+  *(volatile int *)p = 0;
+  *(p + (q - q) + 1) = 0;
+  *(p + (q - q) + 2) = 0;
+  *(p + (q - q) + 3) = 0;
+}
+
+/* { dg-final { scan-tree-dump-times " ={v} " 4 "optimized" } } */