[arm64] Use exclusive instructions in exchange

src/arm64/assembler-arm64.h

Index: src/arm64/assembler-arm64.h
diff --git a/src/arm64/assembler-arm64.h b/src/arm64/assembler-arm64.h
index 1072b76caec4ddb4b1c0df4e0e22b2cdc94c0ab9..bdd4ced5f900ea61cf1480f50e5e4795da541c86 100644
--- a/src/arm64/assembler-arm64.h
+++ b/src/arm64/assembler-arm64.h
@@ -1359,6 +1359,24 @@ class Assembler : public AssemblerBase {
   // Load literal to register.
   void ldr(const CPURegister& rt, const Immediate& imm);
 
+  // Load exclusive byte.
+  void ldxrb(const Register& rt, const Register& rn);
+
+  // Store exclusive byte.
+  void stxrb(const Register& rs, const Register& rt, const Register& rn);
+
+  // Load exclusive half-word.
+  void ldxrh(const Register& rt, const Register& rn);
+
+  // Store exclusive half-word.
+  void stxrh(const Register& rs, const Register& rt, const Register& rn);
+
+  // Load exclusive word.
+  void ldxr(const Register& rt, const Register& rn);
+
+  // Store exclusive word.
+  void stxr(const Register& rs, const Register& rt, const Register& rn);
+
   // Load-acquire word.
   void ldar(const Register& rt, const Register& rn);