fold-const.c (operand_equal_p): Add code matching empty constructors.

	* fold-const.c (operand_equal_p): Add code matching empty
	constructors.
	* gcc.dg/tree-ssa/operand-equal-1.c: Verify that empty constructors
	are matched.

From-SVN: r229147

gcc/ChangeLog

+2015-10-11  Jan Hubicka  <hubicka@ucw.cz>
+
+	* fold-const.c (operand_equal_p): Add code matching empty
+	constructors.
+
 2015-10-21  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* tree.def (CEIL_DIV_EXPR, FLOOR_DIV_EXPR, ROUND_DIV_EXPR): Tweak

gcc/fold-const.c

@@ -2891,6 +2891,11 @@ operand_equal_p (const_tree arg0, const_tree arg1, unsigned int flags)
 	return operand_equal_p (TREE_OPERAND (arg0, 0), TREE_OPERAND (arg1, 0),
 				flags | OEP_ADDRESS_OF
 				| OEP_CONSTANT_ADDRESS_OF);
+      case CONSTRUCTOR:
+	/* In GIMPLE empty constructors are allowed in initializers of
+	   aggregates.  */
+	return (!vec_safe_length (CONSTRUCTOR_ELTS (arg0))
+		&& !vec_safe_length (CONSTRUCTOR_ELTS (arg1)));
       default:
 	break;
       }

gcc/testsuite/ChangeLog

+2015-10-11  Jan Hubicka  <hubicka@ucw.cz>
+
+	* gcc.dg/tree-ssa/operand-equal-1.c: Verify that empty constructors
+	are matched.
+
 2015-10-21  Richard Sandiford  <richard.sandiford@arm.com>
 
 	* gcc.dg/lto/20110201-1_0.c: Restrict to sqrt_insn targets.
@@ -21,6 +26,7 @@
 
 2015-10-21  Marek Polacek  <polacek@redhat.com>
 
+
 	PR c/68024
 	* gcc.dg/pr68024.c: New test.
 

gcc/testsuite/gcc.dg/tree-ssa/operand-equal-1.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-pre" } */
+struct a {int a,b;};
+struct a ret(int val)
+{
+   return val? (struct a){} : (struct a){};
+}
+/* { dg-final { scan-tree-dump-not "if " "pre"} } */