lopcodes.h

Go to the documentation of this file.

/*
** $Id: lopcodes.h,v 1.125.1.1 2007/12/27 13:02:25 roberto Exp $
** Opcodes for Lua virtual machine
** See Copyright Notice in lua.h
*/

#ifndef lopcodes_h
#define lopcodes_h

#include "llimits.h"


/*===========================================================================
  We assume that instructions are unsigned numbers.
  All instructions have an opcode in the first 6 bits.
  Instructions can have the following fields:
  `A' : 8 bits
  `B' : 9 bits
  `C' : 9 bits
  `Bx' : 18 bits (`B' and `C' together)
  `sBx' : signed Bx

  A signed argument is represented in excess K; that is, the number
  value is the unsigned value minus K. K is exactly the maximum value
  for that argument (so that -max is represented by 0, and +max is
  represented by 2*max), which is half the maximum for the corresponding
  unsigned argument.
===========================================================================*/


enum OpMode {iABC, iABx, iAsBx};  /* basic instruction format */


/*
** size and position of opcode arguments.
*/
#define SIZE_C    9
#define SIZE_B    9
#define SIZE_Bx   (SIZE_C + SIZE_B)
#define SIZE_A    8

#define SIZE_OP   6

#define POS_OP    0
#define POS_A   (POS_OP + SIZE_OP)
#define POS_C   (POS_A + SIZE_A)
#define POS_B   (POS_C + SIZE_C)
#define POS_Bx    POS_C


/*
** limits for opcode arguments.
** we use (signed) int to manipulate most arguments,
** so they must fit in LUAI_BITSINT-1 bits (-1 for sign)
*/
#if SIZE_Bx < LUAI_BITSINT-1
#define MAXARG_Bx        ((1<<SIZE_Bx)-1)
#define MAXARG_sBx        (MAXARG_Bx>>1)         /* `sBx' is signed */
#else
#define MAXARG_Bx        MAX_INT
#define MAXARG_sBx        MAX_INT
#endif


#define MAXARG_A        ((1<<SIZE_A)-1)
#define MAXARG_B        ((1<<SIZE_B)-1)
#define MAXARG_C        ((1<<SIZE_C)-1)


/* creates a mask with `n' 1 bits at position `p' */
#define MASK1(n,p)  ((~((~(Instruction)0)<<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 GET_OPCODE(i) (cast(OpCode, ((i)>>POS_OP) & MASK1(SIZE_OP,0)))
#define SET_OPCODE(i,o) ((i) = (((i)&MASK0(SIZE_OP,POS_OP)) | \
    ((cast(Instruction, o)<<POS_OP)&MASK1(SIZE_OP,POS_OP))))

#define GETARG_A(i) (cast(int, ((i)>>POS_A) & MASK1(SIZE_A,0)))
#define SETARG_A(i,u) ((i) = (((i)&MASK0(SIZE_A,POS_A)) | \
    ((cast(Instruction, u)<<POS_A)&MASK1(SIZE_A,POS_A))))

#define GETARG_B(i) (cast(int, ((i)>>POS_B) & MASK1(SIZE_B,0)))
#define SETARG_B(i,b) ((i) = (((i)&MASK0(SIZE_B,POS_B)) | \
    ((cast(Instruction, b)<<POS_B)&MASK1(SIZE_B,POS_B))))

#define GETARG_C(i) (cast(int, ((i)>>POS_C) & MASK1(SIZE_C,0)))
#define SETARG_C(i,b) ((i) = (((i)&MASK0(SIZE_C,POS_C)) | \
    ((cast(Instruction, b)<<POS_C)&MASK1(SIZE_C,POS_C))))

#define GETARG_Bx(i)  (cast(int, ((i)>>POS_Bx) & MASK1(SIZE_Bx,0)))
#define SETARG_Bx(i,b)  ((i) = (((i)&MASK0(SIZE_Bx,POS_Bx)) | \
    ((cast(Instruction, b)<<POS_Bx)&MASK1(SIZE_Bx,POS_Bx))))

#define GETARG_sBx(i) (GETARG_Bx(i)-MAXARG_sBx)
#define SETARG_sBx(i,b) SETARG_Bx((i),cast(unsigned int, (b)+MAXARG_sBx))


#define CREATE_ABC(o,a,b,c) ((cast(Instruction, o)<<POS_OP) \
      | (cast(Instruction, a)<<POS_A) \
      | (cast(Instruction, b)<<POS_B) \
      | (cast(Instruction, c)<<POS_C))

#define CREATE_ABx(o,a,bc)  ((cast(Instruction, o)<<POS_OP) \
      | (cast(Instruction, a)<<POS_A) \
      | (cast(Instruction, bc)<<POS_Bx))


/*
** Macros to operate RK indices
*/

/* this bit 1 means constant (0 means register) */
#define BITRK   (1 << (SIZE_B - 1))

/* test whether value is a constant */
#define ISK(x)    ((x) & BITRK)

/* gets the index of the constant */
#define INDEXK(r) ((int)(r) & ~BITRK)

#define MAXINDEXRK  (BITRK - 1)

/* code a constant index as a RK value */
#define RKASK(x)  ((x) | BITRK)


/*
** invalid register that fits in 8 bits
*/
#define NO_REG    MAXARG_A


/*
** R(x) - register
** Kst(x) - constant (in constant table)
** RK(x) == if ISK(x) then Kst(INDEXK(x)) else R(x)
*/


/*
** grep "ORDER OP" if you change these enums
*/

typedef enum {
/*----------------------------------------------------------------------
name    args  description
------------------------------------------------------------------------*/
OP_MOVE,/*  A B R(A) := R(B)          */
OP_LOADK,/* A Bx  R(A) := Kst(Bx)         */
OP_LOADBOOL,/*  A B C R(A) := (Bool)B; if (C) pc++      */
OP_LOADNIL,/* A B R(A) := ... := R(B) := nil      */
OP_GETUPVAL,/*  A B R(A) := UpValue[B]        */

OP_GETGLOBAL,/* A Bx  R(A) := Gbl[Kst(Bx)]        */
OP_GETTABLE,/*  A B C R(A) := R(B)[RK(C)]       */

OP_SETGLOBAL,/* A Bx  Gbl[Kst(Bx)] := R(A)        */
OP_SETUPVAL,/*  A B UpValue[B] := R(A)        */
OP_SETTABLE,/*  A B C R(A)[RK(B)] := RK(C)        */

OP_NEWTABLE,/*  A B C R(A) := {} (size = B,C)       */

OP_SELF,/*  A B C R(A+1) := R(B); R(A) := R(B)[RK(C)]   */

OP_ADD,/* A B C R(A) := RK(B) + RK(C)       */
OP_SUB,/* A B C R(A) := RK(B) - RK(C)       */
OP_MUL,/* A B C R(A) := RK(B) * RK(C)       */
OP_DIV,/* A B C R(A) := RK(B) / RK(C)       */
OP_MOD,/* A B C R(A) := RK(B) % RK(C)       */
OP_POW,/* A B C R(A) := RK(B) ^ RK(C)       */
OP_UNM,/* A B R(A) := -R(B)         */
OP_NOT,/* A B R(A) := not R(B)        */
OP_LEN,/* A B R(A) := length of R(B)        */

OP_CONCAT,/*  A B C R(A) := R(B).. ... ..R(C)     */

OP_JMP,/* sBx pc+=sBx         */

OP_EQ,/*  A B C if ((RK(B) == RK(C)) ~= A) then pc++    */
OP_LT,/*  A B C if ((RK(B) <  RK(C)) ~= A) then pc++      */
OP_LE,/*  A B C if ((RK(B) <= RK(C)) ~= A) then pc++      */

OP_TEST,/*  A C if not (R(A) <=> C) then pc++     */ 
OP_TESTSET,/* A B C if (R(B) <=> C) then R(A) := R(B) else pc++ */ 

OP_CALL,/*  A B C R(A), ... ,R(A+C-2) := R(A)(R(A+1), ... ,R(A+B-1)) */
OP_TAILCALL,/*  A B C return R(A)(R(A+1), ... ,R(A+B-1))    */
OP_RETURN,/*  A B return R(A), ... ,R(A+B-2)  (see note)  */

OP_FORLOOP,/* A sBx R(A)+=R(A+2);
      if R(A) <?= R(A+1) then { pc+=sBx; R(A+3)=R(A) }*/
OP_FORPREP,/* A sBx R(A)-=R(A+2); pc+=sBx       */

OP_TFORLOOP,/*  A C R(A+3), ... ,R(A+2+C) := R(A)(R(A+1), R(A+2)); 
                        if R(A+3) ~= nil then R(A+2)=R(A+3) else pc++ */ 
OP_SETLIST,/* A B C R(A)[(C-1)*FPF+i] := R(A+i), 1 <= i <= B  */

OP_CLOSE,/* A   close all variables in the stack up to (>=) R(A)*/
OP_CLOSURE,/* A Bx  R(A) := closure(KPROTO[Bx], R(A), ... ,R(A+n))  */

OP_VARARG/* A B R(A), R(A+1), ..., R(A+B-1) = vararg    */
} OpCode;


#define NUM_OPCODES (cast(int, OP_VARARG) + 1)



/*===========================================================================
  Notes:
  (*) In OP_CALL, if (B == 0) then B = top. C is the number of returns - 1,
      and can be 0: OP_CALL then sets `top' to last_result+1, so
      next open instruction (OP_CALL, OP_RETURN, OP_SETLIST) may use `top'.

  (*) In OP_VARARG, if (B == 0) then use actual number of varargs and
      set top (like in OP_CALL with C == 0).

  (*) In OP_RETURN, if (B == 0) then return up to `top'

  (*) In OP_SETLIST, if (B == 0) then B = `top';
      if (C == 0) then next `instruction' is real C

  (*) For comparisons, A specifies what condition the test should accept
      (true or false).

  (*) All `skips' (pc++) assume that next instruction is a jump
===========================================================================*/


/*
** masks for instruction properties. The format is:
** bits 0-1: op mode
** bits 2-3: C arg mode
** bits 4-5: B arg mode
** bit 6: instruction set register A
** bit 7: operator is a test
*/  

enum OpArgMask {
  OpArgN,  /* argument is not used */
  OpArgU,  /* argument is used */
  OpArgR,  /* argument is a register or a jump offset */
  OpArgK   /* argument is a constant or register/constant */
};

LUAI_DATA const lu_byte luaP_opmodes[NUM_OPCODES];

#define getOpMode(m)  (cast(enum OpMode, luaP_opmodes[m] & 3))
#define getBMode(m) (cast(enum OpArgMask, (luaP_opmodes[m] >> 4) & 3))
#define getCMode(m) (cast(enum OpArgMask, (luaP_opmodes[m] >> 2) & 3))
#define testAMode(m)  (luaP_opmodes[m] & (1 << 6))
#define testTMode(m)  (luaP_opmodes[m] & (1 << 7))


LUAI_DATA const char *const luaP_opnames[NUM_OPCODES+1];  /* opcode names */


/* number of list items to accumulate before a SETLIST instruction */
#define LFIELDS_PER_FLUSH 50


#endif