CTZ instruction implemented as optional operator.

src/compiler/ia32/instruction-selector-ia32.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/adapters.h"
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 
 namespace v8 {
@@ skipping 535 matching lines @@
   VisitShift(this, node, kIA32Ror);
 }
 
 
 void InstructionSelector::VisitWord32Clz(Node* node) {
   IA32OperandGenerator g(this);
   Emit(kIA32Lzcnt, g.DefineAsRegister(node), g.Use(node->InputAt(0)));
 }
 
 
+void InstructionSelector::VisitWord32Ctz(Node* node) {
+  IA32OperandGenerator g(this);
+  Emit(kIA32Tzcnt, g.DefineAsRegister(node), g.Use(node->InputAt(0)));
+}
+
+
 void InstructionSelector::VisitInt32Add(Node* node) {
   IA32OperandGenerator g(this);
 
   // Try to match the Add to a lea pattern
   BaseWithIndexAndDisplacement32Matcher m(node);
   if (m.matches() &&
       (m.displacement() == NULL || g.CanBeImmediate(m.displacement()))) {
     InstructionOperand inputs[4];
     size_t input_count = 0;
     AddressingMode mode = g.GenerateMemoryOperandInputs(
@@ skipping 784 matching lines @@
 
 
 // static
 MachineOperatorBuilder::Flags
 InstructionSelector::SupportedMachineOperatorFlags() {
   MachineOperatorBuilder::Flags flags =
       MachineOperatorBuilder::kFloat32Max |
       MachineOperatorBuilder::kFloat32Min |
       MachineOperatorBuilder::kFloat64Max |
       MachineOperatorBuilder::kFloat64Min |
-      MachineOperatorBuilder::kWord32ShiftIsSafe;
+      MachineOperatorBuilder::kWord32ShiftIsSafe |
+      MachineOperatorBuilder::kWord32Ctz;
   if (CpuFeatures::IsSupported(SSE4_1)) {
     flags |= MachineOperatorBuilder::kFloat64RoundDown |
              MachineOperatorBuilder::kFloat64RoundTruncate;
   }
   return flags;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8