FFI: Fix pseudo type conversions for type punning.

src/lj_opt_mem.c

@@ -740,21 +740,19 @@ retry:
     case ALIAS_MUST:
       /* Emit conversion if the loaded type doesn't match the forwarded type. */
       if (!irt_sametype(fins->t, IR(store->op2)->t)) {
-	IRType st = irt_type(fins->t);
-	if (st == IRT_I8 || st == IRT_I16) {  /* Trunc + sign-extend. */
-	  st |= IRCONV_SEXT;
-	} else if (st == IRT_U8 || st == IRT_U16) {  /* Trunc + zero-extend. */
-	} else if (st == IRT_INT) {
-	  st = irt_type(IR(store->op2)->t);  /* Needs dummy CONV.int.*. */
-	} else {  /* I64/U64 are boxed, U32 is hidden behind a CONV.num.u32. */
-	  goto store_fwd;
+	IRType dt = irt_type(fins->t), st = irt_type(IR(store->op2)->t);
+	if (dt == IRT_I8 || dt == IRT_I16) {  /* Trunc + sign-extend. */
+	  st = dt | IRCONV_SEXT;
+	  dt = IRT_INT;
+	} else if (dt == IRT_U8 || dt == IRT_U16) {  /* Trunc + zero-extend. */
+	  st = dt;
+	  dt = IRT_INT;
 	}
-	fins->ot = IRTI(IR_CONV);
+	fins->ot = IRT(IR_CONV, dt);
 	fins->op1 = store->op2;
-	fins->op2 = (IRT_INT<<5)|st;
+	fins->op2 = (dt<<5)|st;
 	return RETRYFOLD;
       }
-    store_fwd:
       return store->op2;  /* Store forwarding. */
     }
     ref = store->prev;