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

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

 // Copyright 2014 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.
 
 #include "src/compiler/machine-operator-reducer.h"
 #include "src/base/bits.h"
 #include "src/base/division-by-constant.h"
 #include "src/base/ieee754.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/typer.h"
@@ skipping 1576 matching lines @@
   }
   {
     Reduction r = Reduce(
         graph()->NewNode(machine()->Float64Mul(), Float64Constant(-1.0), p0));
     ASSERT_TRUE(r.Changed());
     EXPECT_THAT(r.replacement(),
                 IsFloat64Sub(IsFloat64Constant(BitEq(-0.0)), p0));
   }
 }
 
+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
 
 TEST_F(MachineOperatorReducerTest, Float64AcosWithConstant) {
   TRACED_FOREACH(double, x, kFloat64Values) {
     Reduction const r =
         Reduce(graph()->NewNode(machine()->Float64Acos(), Float64Constant(x)));
     ASSERT_TRUE(r.Changed());
     EXPECT_THAT(
         r.replacement(),
@@ skipping 469 matching lines @@
     Reduction r = Reduce(node);
     ASSERT_TRUE(r.Changed());
     EXPECT_THAT(r.replacement(),
                 IsStore(rep, base, index, value, effect, control));
   }
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8