[turbofan] Transform x * -1.0 to -0.0 - x.

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/base/bits.h"
 #include "src/base/division-by-constant.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/machine-operator-reducer.h"
 #include "src/compiler/typer.h"
 #include "test/unittests/compiler/graph-unittest.h"
@@ skipping 1089 matching lines @@
     Reduction r = Reduce(node);
     ASSERT_TRUE(r.Changed());
     EXPECT_THAT(r.replacement(),
                 IsUint32LessThan(
                     p0, IsInt32Constant(bit_cast<int32_t>(limit << shift))));
   }
 }
 
 
 // -----------------------------------------------------------------------------
+// Float64Mul
+
+
+TEST_F(MachineOperatorReducerTest, Float64MulWithMinusOne) {
+  Node* const p0 = Parameter(0);
+  {
+    Reduction r = Reduce(
+        graph()->NewNode(machine()->Float64Mul(), p0, Float64Constant(-1.0)));
+    ASSERT_TRUE(r.Changed());
+    EXPECT_THAT(r.replacement(), IsFloat64Sub(IsFloat64Constant(-0.0), p0));
+  }
+  {
+    Reduction r = Reduce(
+        graph()->NewNode(machine()->Float64Mul(), Float64Constant(-1.0), p0));
+    ASSERT_TRUE(r.Changed());
+    EXPECT_THAT(r.replacement(), IsFloat64Sub(IsFloat64Constant(-0.0), p0));
+  }
+}
+
+
+// -----------------------------------------------------------------------------
 // Store
 
 
 TEST_F(MachineOperatorReducerTest, StoreRepWord8WithWord32And) {
   const StoreRepresentation rep(kRepWord8, kNoWriteBarrier);
   Node* const base = Parameter(0);
   Node* const index = Parameter(1);
   Node* const value = Parameter(2);
   Node* const effect = graph()->start();
   Node* const control = graph()->start();
@@ skipping 77 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