Use SSE2 instructions when available on ia32 platform.

src/ia32/assembler-ia32.h

Index: src/ia32/assembler-ia32.h
===================================================================
--- src/ia32/assembler-ia32.h	(revision 2860)
+++ src/ia32/assembler-ia32.h	(working copy)
@@ -539,6 +539,7 @@
   void cmp(Register reg, Handle<Object> handle);
   void cmp(Register reg, const Operand& op);
   void cmp(const Operand& op, const Immediate& imm);
+  void cmp(const Operand& op, Handle<Object> handle);
 
   void dec_b(Register dst);
 
@@ -719,6 +720,8 @@
   void mulsd(XMMRegister dst, XMMRegister src);
   void divsd(XMMRegister dst, XMMRegister src);
 
+  void comisd(XMMRegister dst, XMMRegister src);
+
   // Use either movsd or movlpd.
   void movdbl(XMMRegister dst, const Operand& src);
   void movdbl(const Operand& dst, XMMRegister src);