target-mips: fix translation of MT instructions

The translation of dmt/emt/dvpe/evpe was doing the moral equivalent of:

  int x;
  ...		/* no initialization of x */
  x = f (x);

which confused later bits of TCG rather badly, leading to crashes.

Fix the helpers to only return results (those instructions have no
inputs), and fix the translation code accordingly.
Signed-off-by: NNathan Froyd <froydnj@codesourcery.com>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

target-mips/helper.h

@@ -154,10 +154,10 @@ DEF_HELPER_2(mttlo, void, tl, i32)
 DEF_HELPER_2(mtthi, void, tl, i32)
 DEF_HELPER_2(mttacx, void, tl, i32)
 DEF_HELPER_1(mttdsp, void, tl)
-DEF_HELPER_1(dmt, tl, tl)
-DEF_HELPER_1(emt, tl, tl)
-DEF_HELPER_1(dvpe, tl, tl)
-DEF_HELPER_1(evpe, tl, tl)
+DEF_HELPER_0(dmt, tl)
+DEF_HELPER_0(emt, tl)
+DEF_HELPER_0(dvpe, tl)
+DEF_HELPER_0(evpe, tl)
 #endif /* !CONFIG_USER_ONLY */
 
 /* microMIPS functions */

target-mips/op_helper.c

@@ -1554,40 +1554,28 @@ void helper_mttdsp(target_ulong arg1)
 }
 
 /* MIPS MT functions */
-target_ulong helper_dmt(target_ulong arg1)
+target_ulong helper_dmt(void)
 {
     // TODO
-    arg1 = 0;
-    // rt = arg1
-
-    return arg1;
+     return 0;
 }
 
-target_ulong helper_emt(target_ulong arg1)
+target_ulong helper_emt(void)
 {
     // TODO
-    arg1 = 0;
-    // rt = arg1
-
-    return arg1;
+    return 0;
 }
 
-target_ulong helper_dvpe(target_ulong arg1)
+target_ulong helper_dvpe(void)
 {
     // TODO
-    arg1 = 0;
-    // rt = arg1
-
-    return arg1;
+    return 0;
 }
 
-target_ulong helper_evpe(target_ulong arg1)
+target_ulong helper_evpe(void)
 {
     // TODO
-    arg1 = 0;
-    // rt = arg1
-
-    return arg1;
+    return 0;
 }
 #endif /* !CONFIG_USER_ONLY */
 

target-mips/translate.c

@@ -12033,22 +12033,22 @@ static void decode_opc (CPUState *env, DisasContext *ctx, int *is_branch)
                 switch (op2) {
                 case OPC_DMT:
                     check_insn(env, ctx, ASE_MT);
-                    gen_helper_dmt(t0, t0);
+                    gen_helper_dmt(t0);
                     gen_store_gpr(t0, rt);
                     break;
                 case OPC_EMT:
                     check_insn(env, ctx, ASE_MT);
-                    gen_helper_emt(t0, t0);
+                    gen_helper_emt(t0);
                     gen_store_gpr(t0, rt);
                     break;
                 case OPC_DVPE:
                     check_insn(env, ctx, ASE_MT);
-                    gen_helper_dvpe(t0, t0);
+                    gen_helper_dvpe(t0);
                     gen_store_gpr(t0, rt);
                     break;
                 case OPC_EVPE:
                     check_insn(env, ctx, ASE_MT);
-                    gen_helper_evpe(t0, t0);
+                    gen_helper_evpe(t0);
                     gen_store_gpr(t0, rt);
                     break;
                 case OPC_DI: