[simplify-rtx][2/2] Simplify - (y ? -x : x) -> (!y ? -x : x)

	* simplify-rtx.c (simplify_unary_operation_1, NEG case):
	(neg (x ? (neg y) : y)) -> !x ? (neg y) : y.

	* gcc.target/aarch64/neg_abs_1.c: New test.

From-SVN: r225997

gcc/ChangeLog

 2015-07-20  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
 
+	* simplify-rtx.c (simplify_unary_operation_1, NEG case):
+	(neg (x ? (neg y) : y)) -> !x ? (neg y) : y.
+
+2015-07-20  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
+
 	* combine.c (combine_simplify_rtx): Move simplification step
 	before various transformations/substitutions.
 

gcc/simplify-rtx.c

@@ -957,6 +957,32 @@ simplify_unary_operation_1 (enum rtx_code code, machine_mode mode, rtx op)
       if (GET_CODE (op) == NEG)
 	return XEXP (op, 0);
 
+      /* (neg (x ? (neg y) : y)) == !x ? (neg y) : y.
+	 If comparison is not reversible use
+	 x ? y : (neg y).  */
+      if (GET_CODE (op) == IF_THEN_ELSE)
+	{
+	  rtx cond = XEXP (op, 0);
+	  rtx true_rtx = XEXP (op, 1);
+	  rtx false_rtx = XEXP (op, 2);
+
+	  if ((GET_CODE (true_rtx) == NEG
+	       && rtx_equal_p (XEXP (true_rtx, 0), false_rtx))
+	       || (GET_CODE (false_rtx) == NEG
+		   && rtx_equal_p (XEXP (false_rtx, 0), true_rtx)))
+	    {
+	      if (reversed_comparison_code (cond, NULL_RTX) != UNKNOWN)
+		temp = reversed_comparison (cond, mode);
+	      else
+		{
+		  temp = cond;
+		  std::swap (true_rtx, false_rtx);
+		}
+	      return simplify_gen_ternary (IF_THEN_ELSE, mode,
+					    mode, temp, true_rtx, false_rtx);
+	    }
+	}
+
       /* (neg (plus X 1)) can become (not X).  */
       if (GET_CODE (op) == PLUS
 	  && XEXP (op, 1) == const1_rtx)

gcc/testsuite/ChangeLog

+2015-07-20  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
+
+	* gcc.target/aarch64/neg_abs_1.c: New test.
+
 2015-07-18  Uros Bizjak  <ubizjak@gmail.com>
 
 	PR target/66922

gcc/testsuite/gcc.target/aarch64/neg_abs_1.c

+/* { dg-do compile } */
+/* { dg-options "-save-temps -O2" } */
+
+int
+f1 (int x)
+{
+  return x < 0 ? x : -x;
+}
+
+long long
+f2 (long long x)
+{
+  return x < 0 ? x : -x;
+}
+
+/* { dg-final { scan-assembler-not "\tneg\tw\[0-9\]*.*" } } */
+/* { dg-final { scan-assembler-not "\tneg\tx\[0-9\]*.*" } } */