[Patch 3/2 ifcvt costs] Don't expand a conditional move between identical sources

gcc/

	* optabs.c (emit_condiitonal_move): Short circuit for identical
	sources.

From-SVN: r238595

gcc/ChangeLog

 2016-07-21  James Greenhalgh  <james.greenhalgh@arm.com>
 
+	* optabs.c (emit_condiitonal_move): Short circuit for identical
+	sources.
+
+2016-07-21  James Greenhalgh  <james.greenhalgh@arm.com>
+
 	* ifcvt.c (noce_if_info): New fields: speed_p, original_cost,
 	max_seq_cost.  Removed fields: then_cost, else_cost, branch_cost.
 	(noce_conversion_profitable_p): New.

gcc/optabs.c

@@ -4214,6 +4214,17 @@ emit_conditional_move (rtx target, enum rtx_code code, rtx op0, rtx op1,
   enum insn_code icode;
   enum rtx_code reversed;
 
+  /* If the two source operands are identical, that's just a move.  */
+
+  if (rtx_equal_p (op2, op3))
+    {
+      if (!target)
+	target = gen_reg_rtx (mode);
+
+      emit_move_insn (target, op3);
+      return target;
+    }
+
   /* If one operand is constant, make it the second one.  Only do this
      if the other operand is not constant as well.  */