Using array index hash code for string-to-number conversion.

src/arm/macro-assembler-arm.cc

Index: src/arm/macro-assembler-arm.cc
===================================================================
--- src/arm/macro-assembler-arm.cc	(revision 5357)
+++ src/arm/macro-assembler-arm.cc	(working copy)
@@ -1337,6 +1337,21 @@
 }
 
 
+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.
+  STATIC_ASSERT(kSmiTag == 0);
+  Ubfx(hash, hash, String::kHashShift, String::kArrayIndexValueBits);
+  mov(index, Operand(hash, LSL, kSmiTagSize));
+}
+
+
 void MacroAssembler::IntegerToDoubleConversionWithVFP3(Register inReg,
                                                        Register outHighReg,
                                                        Register outLowReg) {