X87: Add cmpxchg and lock instructions to x64 and ia32 {dis,}assemblers.

src/x87/assembler-x87.h

Index: src/x87/assembler-x87.h
diff --git a/src/x87/assembler-x87.h b/src/x87/assembler-x87.h
index eaf28e9a67ea2a6f6b0eb276917bfd9a560b4e37..4c37ee36f73c9eb9a6b9a20d289d79995f5a1603 100644
--- a/src/x87/assembler-x87.h
+++ b/src/x87/assembler-x87.h
@@ -654,6 +654,14 @@ class Assembler : public AssemblerBase {
   void xchg_b(Register reg, const Operand& op);
   void xchg_w(Register reg, const Operand& op);
 
+  // Lock prefix
+  void lock();
+
+  // CompareExchange
+  void cmpxchg(const Operand& dst, Register src);
+  void cmpxchg_b(const Operand& dst, Register src);
+  void cmpxchg_w(const Operand& dst, Register src);
+
   // Arithmetics
   void adc(Register dst, int32_t imm32);
   void adc(Register dst, const Operand& src);