Convert String array index/length hash to BitField

src/ia32/macro-assembler-ia32.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 "v8.h"
 
 #if V8_TARGET_ARCH_IA32
 
 #include "bootstrapper.h"
 #include "codegen.h"
@@ skipping 2029 matching lines @@
   return has_frame_ || !stub->SometimesSetsUpAFrame();
 }
 
 
 void MacroAssembler::IndexFromHash(Register hash, Register index) {
   // 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.
-  and_(hash, String::kArrayIndexValueMask);
-  STATIC_ASSERT(String::kHashShift >= kSmiTagSize && kSmiTag == 0);
-  if (String::kHashShift > kSmiTagSize) {
-    shr(hash, String::kHashShift - kSmiTagSize);
-  }
   if (!index.is(hash)) {
     mov(index, hash);
   }
+  DecodeFieldToSmi<String::ArrayIndexValueBits>(index);
 }
 
 
 void MacroAssembler::CallRuntime(const Runtime::Function* f,
                                  int num_arguments,
                                  SaveFPRegsMode save_doubles) {
   // If the expected number of arguments of the runtime function is
   // constant, we check that the actual number of arguments match the
   // expectation.
   CHECK(f->nargs < 0 || f->nargs == num_arguments);
@@ skipping 1372 matching lines @@
   if (ms.shift() > 0) sar(edx, ms.shift());
   mov(eax, dividend);
   shr(eax, 31);
   add(edx, eax);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32