Convert String array index/length hash to BitField

src/arm/macro-assembler-arm.cc

 // Copyright 2012 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 <limits.h>  // For LONG_MIN, LONG_MAX.
 
 #include "v8.h"
 
 #if V8_TARGET_ARCH_ARM
 
@@ skipping 2421 matching lines @@
 }
 
 
 void MacroAssembler::IndexFromHash(Register hash, Register index) {
   // If the hash field contains an array index pick it out. The assert checks
   // that the constants for the maximum number of digits for an array index
   // cached in the hash field and the number of bits reserved for it does not
   // conflict.
   ASSERT(TenToThe(String::kMaxCachedArrayIndexLength) <
          (1 << String::kArrayIndexValueBits));
-  // We want the smi-tagged index in key.  kArrayIndexValueMask has zeros in
-  // the low kHashShift bits.
-  Ubfx(hash, hash, String::kHashShift, String::kArrayIndexValueBits);
-  SmiTag(index, hash);
+  DecodeFieldToSmi<String::ArrayIndexValueBits>(index, hash);
 }
 
 
 void MacroAssembler::SmiToDouble(LowDwVfpRegister value, Register smi) {
   if (CpuFeatures::IsSupported(VFP3)) {
     vmov(value.low(), smi);
     vcvt_f64_s32(value, 1);
   } else {
     SmiUntag(ip, smi);
     vmov(value.low(), ip);
@@ skipping 1587 matching lines @@
     sub(result, result, Operand(dividend));
   }
   if (ms.shift() > 0) mov(result, Operand(result, ASR, ms.shift()));
   add(result, result, Operand(dividend, LSR, 31));
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM