target-arm: Generate fences in ARMv7 frontend

Signed-off-by: NPranith Kumar <bobby.prani@gmail.com>
Message-Id: <20160714202026.9727-12-bobby.prani@gmail.com>
Signed-off-by: NRichard Henderson <rth@twiddle.net>

target-arm/translate.c

@@ -8083,7 +8083,7 @@ static void disas_arm_insn(DisasContext *s, unsigned int insn)
             case 4: /* dsb */
             case 5: /* dmb */
                 ARCH(7);
-                /* We don't emulate caches so these are a no-op.  */
+                tcg_gen_mb(TCG_MO_ALL | TCG_BAR_SC);
                 return;
             case 6: /* isb */
                 /* We need to break the TB after this insn to execute
@@ -10432,7 +10432,7 @@ static int disas_thumb2_insn(CPUARMState *env, DisasContext *s, uint16_t insn_hw
                             break;
                         case 4: /* dsb */
                         case 5: /* dmb */
-                            /* These execute as NOPs.  */
+                            tcg_gen_mb(TCG_MO_ALL | TCG_BAR_SC);
                             break;
                         case 6: /* isb */
                             /* We need to break the TB after this insn