[arm][arm64] Improve CountTrailingZero implementation.

src/compiler/arm/instruction-selector-arm.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/base/bits.h"
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 
@@ skipping 742 matching lines @@
 
 
 void InstructionSelector::VisitWord32Clz(Node* node) {
   VisitRR(this, kArmClz, node);
 }
 
 
 void InstructionSelector::VisitWord32Ctz(Node* node) { UNREACHABLE(); }
 
 
+void InstructionSelector::VisitWord32ReverseBits(Node* node) {
+  DCHECK(IsSupported(ARMv7));
+  VisitRR(this, kArmRbit, node);
+}
+
+
 void InstructionSelector::VisitWord32Popcnt(Node* node) { UNREACHABLE(); }
 
 
 void InstructionSelector::VisitInt32Add(Node* node) {
   ArmOperandGenerator g(this);
   Int32BinopMatcher m(node);
   if (CanCover(node, m.left().node())) {
     switch (m.left().opcode()) {
       case IrOpcode::kInt32Mul: {
         Int32BinopMatcher mleft(m.left().node());
@@ skipping 865 matching lines @@
        g.UseRegister(right));
 }
 
 
 // static
 MachineOperatorBuilder::Flags
 InstructionSelector::SupportedMachineOperatorFlags() {
   MachineOperatorBuilder::Flags flags =
       MachineOperatorBuilder::kInt32DivIsSafe |
       MachineOperatorBuilder::kUint32DivIsSafe;
+  if (CpuFeatures::IsSupported(ARMv7)) {
+    flags |= MachineOperatorBuilder::kWord32ReverseBits;
+  }
   if (CpuFeatures::IsSupported(ARMv8)) {
     flags |= MachineOperatorBuilder::kFloat32RoundDown |
              MachineOperatorBuilder::kFloat64RoundDown |
              MachineOperatorBuilder::kFloat32RoundUp |
              MachineOperatorBuilder::kFloat64RoundUp |
              MachineOperatorBuilder::kFloat32RoundTruncate |
              MachineOperatorBuilder::kFloat64RoundTruncate |
              MachineOperatorBuilder::kFloat64RoundTiesAway |
              MachineOperatorBuilder::kFloat32RoundTiesEven |
              MachineOperatorBuilder::kFloat64RoundTiesEven;
   }
   return flags;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8