avoid the use of bit 'Bk' ('B' will lose this bit soon)

lcode.c

@@ -1,5 +1,5 @@
 /*
-** $Id: lcode.c,v 2.125 2017/09/26 18:14:45 roberto Exp roberto $
+** $Id: lcode.c,v 2.126 2017/09/28 16:53:29 roberto Exp roberto $
 ** Code generator for Lua
 ** See Copyright Notice in lua.h
 */
@@ -1068,7 +1068,7 @@ static int isKstr (FuncState *fs, expdesc *e) {
 */
 static int isKint (expdesc *e) {
   return (e->k == VKINT && !hasjumps(e) &&
-          l_castS2U(e->u.ival) <= l_castS2U(MAXARG_C));
+          l_castS2U(e->u.ival) <= l_castS2U(MAXARG_Cr));
 }
 
 
@@ -1178,8 +1178,8 @@ static void codebinexpval (FuncState *fs, OpCode op,
       v1 = luaK_exp2anyreg(fs, e1);
     }
     else {  /* exchange operands to make 2nd one a constant */
-      v2 = cast_int(e1->u.ival);
-      v1 = luaK_exp2anyreg(fs, e2) | BITRK;  /* K bit signal the exchange */
+      v2 = cast_int(e1->u.ival) | BITRK;  /* K bit signal the exchange */
+      v1 = luaK_exp2anyreg(fs, e2);
     }
     op = OP_ADDI;
   }

lopcodes.h

@@ -1,5 +1,5 @@
 /*
-** $Id: lopcodes.h,v 1.161 2017/09/26 18:14:45 roberto Exp roberto $
+** $Id: lopcodes.h,v 1.162 2017/09/28 16:53:29 roberto Exp roberto $
 ** Opcodes for Lua virtual machine
 ** See Copyright Notice in lua.h
 */
@@ -73,6 +73,7 @@ enum OpMode {iABC, iABx, iAsBx, iAx};  /* basic instruction format */
 #define MAXARG_A        ((1<<SIZE_A)-1)
 #define MAXARG_B        ((1<<SIZE_B)-1)
 #define MAXARG_C        ((1<<SIZE_C)-1)
+#define MAXARG_Cr        ((1<<(SIZE_C - 1))-1)
 
 
 /* creates a mask with 'n' 1 bits at position 'p' */
@@ -102,10 +103,6 @@ enum OpMode {iABC, iABx, iAsBx, iAx};  /* basic instruction format */
 #define GETARG_B(i)	check_exp(checkopm(i, iABC), getarg(i, POS_B, SIZE_B))
 #define SETARG_B(i,v)	setarg(i, v, POS_B, SIZE_B)
 
-#define GETARG_Br(i)  \
-	check_exp(checkopm(i, iABC), getarg(i, POS_B, SIZE_B - 1))
-#define GETARG_Bk(i)	getarg(i, (POS_B + SIZE_B - 1), 1)
-
 #define GETARG_C(i)	check_exp(checkopm(i, iABC), getarg(i, POS_C, SIZE_C))
 #define SETARG_C(i,v)	setarg(i, v, POS_C, SIZE_C)
 
@@ -142,7 +139,7 @@ enum OpMode {iABC, iABx, iAsBx, iAx};  /* basic instruction format */
 */
 
 /* this bit 1 means constant (0 means register) */
-#define BITRK		(1 << (SIZE_B - 1))
+#define BITRK		(1 << (SIZE_C - 1))
 
 /* test whether value is a constant */
 #define ISK(x)		((x) & BITRK)

lvm.c

@@ -1,5 +1,5 @@
 /*
-** $Id: lvm.c,v 2.295 2017/09/27 18:59:08 roberto Exp roberto $
+** $Id: lvm.c,v 2.296 2017/09/28 16:53:29 roberto Exp roberto $
 ** Lua virtual machine
 ** See Copyright Notice in lua.h
 */
@@ -733,7 +733,7 @@ void luaV_finishOp (lua_State *L) {
 
 
 #define RA(i)	(base+GETARG_A(i))
-#define RB(i)	(base+GETARG_Br(i))
+#define RB(i)	(base+GETARG_B(i))
 #define vRB(i)	s2v(RB(i))
 #define KB(i)	(k+GETARG_B(i))
 #define RC(i)	(base+GETARG_C(i))
@@ -989,7 +989,7 @@ void luaV_execute (lua_State *L) {
       }
       vmcase(OP_ADDI) {
         TValue *rb = vRB(i);
-        int ic = GETARG_C(i);
+        int ic = GETARG_Cr(i);
         lua_Number nb;
         if (ttisinteger(rb)) {
           setivalue(s2v(ra), intop(+, ivalue(rb), ic));
@@ -998,7 +998,7 @@ void luaV_execute (lua_State *L) {
           setfltvalue(s2v(ra), luai_numadd(L, nb, cast_num(ic)));
         }
         else
-          Protect(luaT_trybiniTM(L, rb, ic, GETARG_Bk(i), ra, TM_ADD));
+          Protect(luaT_trybiniTM(L, rb, ic, GETARG_Ck(i), ra, TM_ADD));
         vmbreak;
       }
       vmcase(OP_ADD) {