target-i386: emulate XCHG using atomic helper

Signed-off-by: NEmilio G. Cota <cota@braap.org>
Message-Id: <1467054136-10430-19-git-send-email-cota@braap.org>
Signed-off-by: NRichard Henderson <rth@twiddle.net>

target-i386/translate.c

@@ -5564,12 +5564,8 @@ static target_ulong disas_insn(CPUX86State *env, DisasContext *s,
             gen_lea_modrm(env, s, modrm);
             gen_op_mov_v_reg(ot, cpu_T0, reg);
             /* for xchg, lock is implicit */
-            if (!(prefixes & PREFIX_LOCK))
-                gen_helper_lock();
-            gen_op_ld_v(s, ot, cpu_T1, cpu_A0);
-            gen_op_st_v(s, ot, cpu_T0, cpu_A0);
-            if (!(prefixes & PREFIX_LOCK))
-                gen_helper_unlock();
+            tcg_gen_atomic_xchg_tl(cpu_T1, cpu_A0, cpu_T0,
+                                   s->mem_index, ot | MO_LE);
             gen_op_mov_reg_v(ot, reg, cpu_T1);
         }
         break;