1 files changed, 37 insertions, 20 deletions

diff --git a/lopcodes.h b/lopcodes.h
index 494cb84c..1e3b9ee9 100644
--- a/lopcodes.h
+++ b/lopcodes.h
@@ -24,34 +24,51 @@
   is the usigned value minus 2^23.
 ===========================================================================*/
 
-#define EXCESS_S        (1<<23)         /* == 2^23 */
+#define SIZE_OP         8
+#define SIZE_U          24
+#define POS_U           8
+#define SIZE_S          24
+#define POS_S           8
+#define SIZE_A          16
+#define POS_A           16
+#define SIZE_B          8
+#define POS_B           8
+
+#define EXCESS_S        (1<<(SIZE_S-1))         /* == 2^23 */
+
+
+/* creates a mask with `n' 1 bits at position `p' */
+#define MASK1(n,p)      ((~((~0ul)<<n))<<p)
+
+/* creates a mask with `n' 0 bits at position `p' */
+#define MASK0(n,p)      (~MASK1(n,p))
 
 /*
 ** the following macros help to manipulate instructions
 */
 
-#define MAXARG_U        ((1<<24)-1)
-#define MAXARG_S        ((1<<23)-1)
-#define MAXARG_A        ((1<<16)-1)
-#define MAXARG_B        ((1<<8)-1)
+#define MAXARG_U        ((1<<SIZE_U)-1)
+#define MAXARG_S        ((1<<(SIZE_S-1))-1)  /* `S' is signed */
+#define MAXARG_A        ((1<<SIZE_A)-1)
+#define MAXARG_B        ((1<<SIZE_B)-1)
 
-#define GET_OPCODE(i)   ((OpCode)((i)&0xFF))
-#define GETARG_U(i)     ((int)((i)>>8))
-#define GETARG_S(i)     ((int)((i)>>8)-EXCESS_S)
-#define GETARG_A(i)     ((int)((i)>>16))
-#define GETARG_B(i)     ((int)(((i)>>8) & 0xFF))
+#define GET_OPCODE(i)   ((OpCode)((i)&MASK1(SIZE_OP,0)))
+#define GETARG_U(i)     ((int)((i)>>POS_U))
+#define GETARG_S(i)     ((int)((i)>>POS_S)-EXCESS_S)
+#define GETARG_A(i)     ((int)((i)>>POS_A))
+#define GETARG_B(i)     ((int)(((i)>>POS_B) & MASK1(SIZE_B,0)))
 
-#define SET_OPCODE(i,o) (((i)&0xFFFFFF00u) | (Instruction)(o))
-#define SETARG_U(i,u)   (((i)&0x000000FFu) | ((Instruction)(u)<<8))
-#define SETARG_S(i,s)   (((i)&0x000000FFu) | ((Instruction)((s)+EXCESS_S)<<8))
-#define SETARG_A(i,a)   (((i)&0x0000FFFFu) | ((Instruction)(a)<<16))
-#define SETARG_B(i,b)   (((i)&0xFFFF00FFu) | ((Instruction)(b)<<8))
+#define SET_OPCODE(i,o) (((i)&MASK0(SIZE_OP,0)) | (Instruction)(o))
+#define SETARG_U(i,u)   (((i)&MASK0(SIZE_U,POS_U)) | ((Instruction)(u)<<POS_U))
+#define SETARG_S(i,s)   (((i)&MASK0(SIZE_S,POS_S)) | ((Instruction)((s)+EXCESS_S)<<POS_S))
+#define SETARG_A(i,a)   (((i)&MASK0(SIZE_A,POS_A)) | ((Instruction)(a)<<POS_A))
+#define SETARG_B(i,b)   (((i)&MASK0(SIZE_B,POS_B)) | ((Instruction)(b)<<POS_B))
 
 #define CREATE_0(o)      ((Instruction)(o))
-#define CREATE_U(o,u)    ((Instruction)(o) | (Instruction)(u)<<8)
-#define CREATE_S(o,s)    ((Instruction)(o) | ((Instruction)(s)+EXCESS_S)<<8)
-#define CREATE_AB(o,a,b) ((Instruction)(o) | ((Instruction)(a)<<16) \
-                                           |  ((Instruction)(b)<<8))
+#define CREATE_U(o,u)    ((Instruction)(o) | (Instruction)(u)<<POS_U)
+#define CREATE_S(o,s)    ((Instruction)(o) | ((Instruction)(s)+EXCESS_S)<<POS_S)
+#define CREATE_AB(o,a,b) ((Instruction)(o) | ((Instruction)(a)<<POS_A) \
+                                           |  ((Instruction)(b)<<POS_B))
 
 
 /*
@@ -111,7 +128,7 @@ SUBOP,/*	-	y x		x-y				*/
 MULTOP,/*       -       y x             x*y                             */
 DIVOP,/*        -       y x             x/y                             */
 POWOP,/*        -       y x             x^y                             */
-CONCOP,/*       -       y x             x..y                            */
+CONCOP,/*       U       v_u-v_1         v1..-..v_u                      */
 MINUSOP,/*      -       x               -x                              */
 NOTOP,/*        -       x               (x==nil)? 1 : nil               */