target-i386: emulate LOCK'ed INC using atomic helper

[rth: Merge gen_inc_locked back into gen_inc to share cc update.]
Signed-off-by: NEmilio G. Cota <cota@braap.org>
Message-Id: <1467054136-10430-14-git-send-email-cota@braap.org>
Signed-off-by: NRichard Henderson <rth@twiddle.net>

target-i386/translate.c

@@ -1361,21 +1361,23 @@ static void gen_op(DisasContext *s1, int op, TCGMemOp ot, int d)
 /* if d == OR_TMP0, it means memory operand (address in A0) */
 static void gen_inc(DisasContext *s1, TCGMemOp ot, int d, int c)
 {
-    if (d != OR_TMP0) {
-        gen_op_mov_v_reg(ot, cpu_T0, d);
+    if (s1->prefix & PREFIX_LOCK) {
+        tcg_gen_movi_tl(cpu_T0, c > 0 ? 1 : -1);
+        tcg_gen_atomic_add_fetch_tl(cpu_T0, cpu_A0, cpu_T0,
+                                    s1->mem_index, ot | MO_LE);
     } else {
-        gen_op_ld_v(s1, ot, cpu_T0, cpu_A0);
+        if (d != OR_TMP0) {
+            gen_op_mov_v_reg(ot, cpu_T0, d);
+        } else {
+            gen_op_ld_v(s1, ot, cpu_T0, cpu_A0);
+        }
+        tcg_gen_addi_tl(cpu_T0, cpu_T0, (c > 0 ? 1 : -1));
+        gen_op_st_rm_T0_A0(s1, ot, d);
     }
+
     gen_compute_eflags_c(s1, cpu_cc_src);
-    if (c > 0) {
-        tcg_gen_addi_tl(cpu_T0, cpu_T0, 1);
-        set_cc_op(s1, CC_OP_INCB + ot);
-    } else {
-        tcg_gen_addi_tl(cpu_T0, cpu_T0, -1);
-        set_cc_op(s1, CC_OP_DECB + ot);
-    }
-    gen_op_st_rm_T0_A0(s1, ot, d);
     tcg_gen_mov_tl(cpu_cc_dst, cpu_T0);
+    set_cc_op(s1, (c > 0 ? CC_OP_INCB : CC_OP_DECB) + ot);
 }
 
 static void gen_shift_flags(DisasContext *s, TCGMemOp ot, TCGv result,