RegExp: Remove use of 16-bit immediates on ia32/x64.

src/x64/regexp-macro-assembler-x64.h

Index: src/x64/regexp-macro-assembler-x64.h
diff --git a/src/x64/regexp-macro-assembler-x64.h b/src/x64/regexp-macro-assembler-x64.h
index 490326971fb0e2cd888d2df0403dd76dbc908401..3bcc3ac16506c9a14829b6880326ea5ec3672a2f 100644
--- a/src/x64/regexp-macro-assembler-x64.h
+++ b/src/x64/regexp-macro-assembler-x64.h
@@ -173,10 +173,9 @@ class RegExpMacroAssemblerX64: public NativeRegExpMacroAssembler {
   // the frame in GetCode.
   static const int kInputStartMinusOne =
       kLastCalleeSaveRegister - kPointerSize;
-  static const int kAtStart = kInputStartMinusOne - kPointerSize;
 
   // First register address. Following registers are below it on the stack.
-  static const int kRegisterZero = kAtStart - kPointerSize;
+  static const int kRegisterZero = kInputStartMinusOne - kPointerSize;
 
   // Initial size of code buffer.
   static const size_t kRegExpCodeSize = 1024;