[turbofan] Fix Math.sign.

Review-Url: https://codereview.chromium.org/2294143004
Cr-Commit-Position: refs/heads/master@{#39073}

src/compiler/simplified-lowering.cc

@@ -2849,7 +2849,7 @@ Node* SimplifiedLowering::Float64Sign(Node* const node) {
       graph()->NewNode(
           common()->Select(MachineRepresentation::kFloat64),
           graph()->NewNode(machine()->Float64LessThan(), zero, input), one,
-          zero));
+          input));
 }
 
 Node* SimplifiedLowering::Int32Abs(Node* const node) {

test/mjsunit/compiler/math-sign.js

+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax
+
+function signInt32(i) {
+  i = i|0;
+  return Math.sign(i);
+}
+
+signInt32(0);
+signInt32(2);
+%OptimizeFunctionOnNextCall(signInt32);
+assertEquals(1, signInt32(1));
+assertEquals(0, signInt32(0));
+assertEquals(-1, signInt32(-1));
+assertEquals(-1, signInt32(-1));
+assertEquals(1, signInt32(2147483647));
+assertEquals(-1, signInt32(2147483648));
+assertEquals(-1, signInt32(-2147483648));
+assertEquals(0, signInt32(NaN));
+assertEquals(0, signInt32(undefined));
+assertEquals(0, signInt32(-0));
+
+function signFloat64(i) {
+  return Math.sign(+i);
+}
+
+signFloat64(0.1);
+signFloat64(-0.1);
+%OptimizeFunctionOnNextCall(signFloat64);
+assertEquals(1, signFloat64(1));
+assertEquals(1, signFloat64(0.001));
+assertEquals(-1, signFloat64(-0.002));
+assertEquals(1, signFloat64(1e100));
+assertEquals(-1, signFloat64(-2e100));
+assertEquals(0, signFloat64(0));
+assertEquals(Infinity, 1/signFloat64(0));
+assertEquals(-1, signFloat64(-1));
+assertEquals(-1, signFloat64(-1));
+assertEquals(1, signFloat64(2147483647));
+assertEquals(1, signFloat64(2147483648));
+assertEquals(-1, signFloat64(-2147483647));
+assertEquals(-1, signFloat64(-2147483648));
+assertEquals(-1, signFloat64(-2147483649));
+assertEquals(-0, signFloat64(-0));
+assertEquals(NaN, signFloat64(NaN));
+assertEquals(NaN, signFloat64(undefined));
+assertEquals(1, signFloat64(Infinity));
+assertEquals(-1, signFloat64(-Infinity));