gdbstub: add MIPS16 support

The only thing to do here is to expose the current processor mode to GDB
and to set the processor mode properly when we change the PC.
Signed-off-by: NNathan Froyd <froydnj@codesourcery.com>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

gdbstub.c

@@ -1053,7 +1053,7 @@ static int cpu_gdb_read_register(CPUState *env, uint8_t *mem_buf, int n)
     case 34: GET_REGL(env->active_tc.HI[0]);
     case 35: GET_REGL(env->CP0_BadVAddr);
     case 36: GET_REGL((int32_t)env->CP0_Cause);
-    case 37: GET_REGL(env->active_tc.PC);
+    case 37: GET_REGL(env->active_tc.PC | !!(env->hflags & MIPS_HFLAG_M16));
     case 72: GET_REGL(0); /* fp */
     case 89: GET_REGL((int32_t)env->CP0_PRid);
     }
@@ -1114,7 +1114,14 @@ static int cpu_gdb_write_register(CPUState *env, uint8_t *mem_buf, int n)
     case 34: env->active_tc.HI[0] = tmp; break;
     case 35: env->CP0_BadVAddr = tmp; break;
     case 36: env->CP0_Cause = tmp; break;
-    case 37: env->active_tc.PC = tmp; break;
+    case 37:
+        env->active_tc.PC = tmp & ~(target_ulong)1;
+        if (tmp & 1) {
+            env->hflags |= MIPS_HFLAG_M16;
+        } else {
+            env->hflags &= ~(MIPS_HFLAG_M16);
+        }
+        break;
     case 72: /* fp, ignored */ break;
     default: 
 	if (n > 89)
@@ -1658,7 +1665,12 @@ static void gdb_set_cpu_pc(GDBState *s, target_ulong pc)
 #elif defined (TARGET_SH4)
     s->c_cpu->pc = pc;
 #elif defined (TARGET_MIPS)
-    s->c_cpu->active_tc.PC = pc;
+    s->c_cpu->active_tc.PC = pc & ~(target_ulong)1;
+    if (pc & 1) {
+        s->c_cpu->hflags |= MIPS_HFLAG_M16;
+    } else {
+        s->c_cpu->hflags &= ~(MIPS_HFLAG_M16);
+    }
 #elif defined (TARGET_MICROBLAZE)
     s->c_cpu->sregs[SR_PC] = pc;
 #elif defined (TARGET_CRIS)