target/arm: use gen_goto_tb for ISB handling

While an ISB will ensure any raised IRQs happen on the next
instruction it doesn't cause any to get raised by itself. We can
therefore use a simple tb exit for ISB instructions and rely on the
exit_request check at the top of each TB to deal with exiting if
needed.
Signed-off-by: NAlex Bennée <alex.bennee@linaro.org>
Reviewed-by: NRichard Henderson <rth@twiddle.net>
Message-id: 20170713141928.25419-6-alex.bennee@linaro.org
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

target/arm/translate-a64.c

@@ -1393,7 +1393,7 @@ static void handle_sync(DisasContext *s, uint32_t insn,
          * a self-modified code correctly and also to take
          * any pending interrupts immediately.
          */
-        s->is_jmp = DISAS_UPDATE;
+        gen_goto_tb(s, 0, s->pc);
         return;
     default:
         unallocated_encoding(s);

target/arm/translate.c

@@ -8169,7 +8169,7 @@ static void disas_arm_insn(DisasContext *s, unsigned int insn)
                  * self-modifying code correctly and also to take
                  * any pending interrupts immediately.
                  */
-                gen_lookup_tb(s);
+                gen_goto_tb(s, 0, s->pc & ~1);
                 return;
             default:
                 goto illegal_op;
@@ -10562,7 +10562,7 @@ static int disas_thumb2_insn(CPUARMState *env, DisasContext *s, uint16_t insn_hw
                              * and also to take any pending interrupts
                              * immediately.
                              */
-                            gen_lookup_tb(s);
+                            gen_goto_tb(s, 0, s->pc & ~1);
                             break;
                         default:
                             goto illegal_op;