[x64] Smi zero can be used as an immediate.

src/compiler/x64/instruction-selector-x64.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 <algorithm>
 
 #include "src/base/adapters.h"
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 // Adds X64-specific methods for generating operands.
 class X64OperandGenerator final : public OperandGenerator {
  public:
   explicit X64OperandGenerator(InstructionSelector* selector)
       : OperandGenerator(selector) {}
 
   bool CanBeImmediate(Node* node) {
     switch (node->opcode()) {
       case IrOpcode::kInt32Constant:
         return true;
       case IrOpcode::kInt64Constant: {
         const int64_t value = OpParameter<int64_t>(node);
         return value == static_cast<int64_t>(static_cast<int32_t>(value));
       }
+      case IrOpcode::kNumberConstant: {
+        const double value = OpParameter<double>(node);
+        return bit_cast<int64_t>(value) == 0;
+      }
       default:
         return false;
     }
   }
 
   AddressingMode GenerateMemoryOperandInputs(Node* index, int scale_exponent,
                                              Node* base, Node* displacement,
                                              InstructionOperand inputs[],
                                              size_t* input_count) {
     AddressingMode mode = kMode_MRI;
@@ skipping 1592 matching lines @@
   if (CpuFeatures::IsSupported(SSE4_1)) {
     flags |= MachineOperatorBuilder::kFloat64RoundDown |
              MachineOperatorBuilder::kFloat64RoundTruncate;
   }
   return flags;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8