[turbofan] Lower "-0.0 - x" in the MachineOperatorReducer.

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 e894bf95dd128f83d8d9a978d80503f8c595bb56..427ad16155db859ac4cea04101342f9483406301 100644
--- a/test/unittests/compiler/machine-operator-reducer-unittest.cc
+++ b/test/unittests/compiler/machine-operator-reducer-unittest.cc
@@ -1594,6 +1594,26 @@ TEST_F(MachineOperatorReducerTest, Float64MulWithMinusOne) {
   }
 }
 
+TEST_F(MachineOperatorReducerTest, Float64SubMinusZeroMinusX) {
+  Node* const p0 = Parameter(0);
+  {
+    Reduction r = Reduce(
+        graph()->NewNode(machine()->Float64Sub(), Float64Constant(-0.0), p0));
+    ASSERT_TRUE(r.Changed());
+    EXPECT_THAT(r.replacement(), IsFloat64Neg(p0));
+  }
+}
+
+TEST_F(MachineOperatorReducerTest, Float32SubMinusZeroMinusX) {
+  Node* const p0 = Parameter(0);
+  {
+    Reduction r = Reduce(
+        graph()->NewNode(machine()->Float32Sub(), Float32Constant(-0.0), p0));
+    ASSERT_TRUE(r.Changed());
+    EXPECT_THAT(r.replacement(), IsFloat32Neg(p0));
+  }
+}
+
 // -----------------------------------------------------------------------------
 // Float64Acos