fix the type of value that is returned by bit-shift expression.

src/opcode.h

@@ -20,17 +20,17 @@
 #define GETARG_C(i)   ((int)((((mrb_code)(i)) >>  7) & 0x7f))
 #define GETARG_Bx(i)  ((int)((((mrb_code)(i)) >>  7) & 0xffff))
 #define GETARG_sBx(i) ((int)(GETARG_Bx(i)-MAXARG_sBx))
-#define GETARG_Ax(i)  ((int)((((mrb_code)(i)) >>  7) & 0x1ffffff))
+#define GETARG_Ax(i)  ((int32_t)((((mrb_code)(i)) >>  7) & 0x1ffffff))
 #define GETARG_UNPACK_b(i,n1,n2) ((int)((((mrb_code)(i)) >> (7+n2)) & (((1<<n1)-1))))
 #define GETARG_UNPACK_c(i,n1,n2) ((int)((((mrb_code)(i)) >> 7) & (((1<<n2)-1))))
 #define GETARG_b(i)   GETARG_UNPACK_b(i,14,2)
 #define GETARG_c(i)   GETARG_UNPACK_c(i,14,2)
 
 #define MKOPCODE(op)  ((op) & 0x7f)
-#define MKARG_A(c)    (((c) & 0x1ff) << 23)
-#define MKARG_B(c)    (((c) & 0x1ff) << 14)
+#define MKARG_A(c)    ((mrb_code)((c) & 0x1ff) << 23)
+#define MKARG_B(c)    ((mrb_code)((c) & 0x1ff) << 14)
 #define MKARG_C(c)    (((c) & 0x7f) <<  7)
-#define MKARG_Bx(v)   (((v) & 0xffff) << 7)
+#define MKARG_Bx(v)   ((mrb_code)((v) & 0xffff) << 7)
 #define MKARG_sBx(v)  MKARG_Bx((v)+MAXARG_sBx)
 #define MKARG_Ax(v)   (((v) & 0x1ffffff) << 7)
 #define MKARG_PACK(b,n1,c,n2) ((((b) & ((1<<n1)-1)) << (7+n2))|(((c) & ((1<<n2)-1)) << 7))