[Turbofan] Make the -0 deopt case more efficient in multiplication.

test/unittests/compiler/machine-operator-reducer-unittest.cc

Index: test/unittests/compiler/machine-operator-reducer-unittest.cc
diff --git a/test/unittests/compiler/machine-operator-reducer-unittest.cc b/test/unittests/compiler/machine-operator-reducer-unittest.cc
index 7de6c7d2f24a6beffe37f5a5ffa4ac9f4af6bfc9..ac39e0ca8aa6bda8445587709314fc3875d2431d 100644
--- a/test/unittests/compiler/machine-operator-reducer-unittest.cc
+++ b/test/unittests/compiler/machine-operator-reducer-unittest.cc
@@ -289,7 +289,6 @@ TEST_F(MachineOperatorReducerTest,
   EXPECT_EQ(value, reduction.replacement());
 }
 
-
 TEST_F(MachineOperatorReducerTest, ChangeFloat64ToInt32WithConstant) {
   TRACED_FOREACH(int32_t, x, kInt32Values) {
     Reduction reduction = Reduce(graph()->NewNode(
@@ -1506,6 +1505,27 @@ TEST_F(MachineOperatorReducerTest, Int32MulWithOverflowWithConstant) {
 }
 
 // -----------------------------------------------------------------------------
+// Int32LessThan
+
+TEST_F(MachineOperatorReducerTest, Int32LessThanWithWord32Or) {
+  // Node* control = graph()->start();

[Benedikt Meurer, 2016/07/20 17:37:44]

Nit: Remove this line.

+  Node* const p0 = Parameter(0);
+  TRACED_FOREACH(int32_t, x, kInt32Values) {
+    Node* word32_or =
+        graph()->NewNode(machine()->Word32Or(), p0, Int32Constant(x));
+    Node* less_than = graph()->NewNode(machine()->Int32LessThan(), word32_or,
+                                       Int32Constant(0));
+    Reduction r = Reduce(less_than);
+    if (x < 0) {
+      ASSERT_TRUE(r.Changed());
+      EXPECT_THAT(r.replacement(), IsInt32Constant(1));
+    } else {
+      ASSERT_FALSE(r.Changed());
+    }
+  }
+}
+
+// -----------------------------------------------------------------------------
 // Uint32LessThan
 
 TEST_F(MachineOperatorReducerTest, Uint32LessThanWithWord32Sar) {