Lua Bytecode

lop.h

// from lopcodes.h

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

// Here, x can be three things
// x can be a variable denoting a register (its 8th bit is 0), in which case R(x) returns the value of the x-th register
// x can be a variable index to a constant (string or something, its 8th bit is 1), in which case INDEXK(x) returns the actual index
// x can be the actual index itself

// Each instruction may have up to 3 arguments. They are
// A - 8 bits
// B - 9 bits
// C - 9 bits
// Occasionally, a larger integer container is needed for some operands, which is done by concatenating the B and C arguments together
// Bx - 18 bytes, = B<<9|C

// The above arguments are all unsigned. There is a single signed argument sBx, which is just Bx-bias

// UpValues are known variables that escape the scope of the current function but are not global (see escape analysis)

/*
** 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++	Note that (Bool)B isn't the value of the register associated with B, but B itself		*/
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;