[turbofan] Fix Math.sign.

src/compiler/simplified-lowering.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/simplified-lowering.h"
 
 #include <limits>
 
 #include "src/address-map.h"
 #include "src/base/bits.h"
@@ skipping 2831 matching lines @@
   Node* const one = jsgraph()->Float64Constant(1.0);
 
   Node* const input = node->InputAt(0);
 
   return graph()->NewNode(
       common()->Select(MachineRepresentation::kFloat64),
       graph()->NewNode(machine()->Float64LessThan(), input, zero), minus_one,
       graph()->NewNode(
           common()->Select(MachineRepresentation::kFloat64),
           graph()->NewNode(machine()->Float64LessThan(), zero, input), one,
-          zero));
+          input));
 }
 
 Node* SimplifiedLowering::Int32Abs(Node* const node) {
   Node* const input = node->InputAt(0);
 
   // Generate case for absolute integer value.
   //
   //    let sign = input >> 31 in
   //    (input ^ sign) - sign
 
@@ skipping 332 matching lines @@
         isolate(), graph()->zone(), callable.descriptor(), 0, flags,
         Operator::kNoProperties);
     to_number_operator_.set(common()->Call(desc));
   }
   return to_number_operator_.get();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8