[arm][arm64] Improve CountTrailingZero implementation.

src/compiler/arm/code-generator-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/compiler/code-generator.h"
 
 #include "src/arm/macro-assembler-arm.h"
 #include "src/ast/scopes.h"
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/gap-resolver.h"
@@ skipping 652 matching lines @@
     case kArmUxtab:
       __ uxtab(i.OutputRegister(), i.InputRegister(0), i.InputRegister(1),
                i.InputInt32(2));
       DCHECK_EQ(LeaveCC, i.OutputSBit());
       break;
     case kArmUxtah:
       __ uxtah(i.OutputRegister(), i.InputRegister(0), i.InputRegister(1),
                i.InputInt32(2));
       DCHECK_EQ(LeaveCC, i.OutputSBit());
       break;
+    case kArmRbit: {
+      CpuFeatureScope scope(masm(), ARMv7);
+      __ rbit(i.OutputRegister(), i.InputRegister(0));
+      DCHECK_EQ(LeaveCC, i.OutputSBit());
+      break;
+    }
     case kArmClz:
       __ clz(i.OutputRegister(), i.InputRegister(0));
       DCHECK_EQ(LeaveCC, i.OutputSBit());
       break;
     case kArmCmp:
       __ cmp(i.InputRegister(0), i.InputOperand2(1));
       DCHECK_EQ(SetCC, i.OutputSBit());
       break;
     case kArmCmn:
       __ cmn(i.InputRegister(0), i.InputOperand2(1));
@@ skipping 734 matching lines @@
       padding_size -= v8::internal::Assembler::kInstrSize;
     }
   }
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8