# The new bytecode We will reimplement VM to use 8bit instruction code. By bytecode, we mean real byte code. The whole purpose is reducing the memory consumption of mruby VM. # Instructions Instructions are bytes. There can be 256 instructions. Currently we have 94 instructions. Instructions can take 0 to 3 operands. ## operands The size of operands can be either 8bits, 16bits or 24bits. In the table.1 below, the second field describes the size (and sign) of operands. * B: 8bit * sB: signed 8bit * S: 16bit * sS: signed 16bit * W: 24bit First two byte operands may be extended to 16bit. When those byte operands are bigger than 256, the instruction will be prefixed by `OP_EXT1` (means 1st operand is 16bit) or `OP_EXT2` (means 2nd operand is 16bit) or `OP_EXT3` (means 1st and 2nd operands are 16bit). For instructions marked by `'`, `OP_EXT1` can be prefixed. For those with `"`, either `OP_EXT1` or `OP_EXT2` or `OP_EXT2` can be prefixed. ## table.1 Instruction Table | Instruction Name | Operand type | Semantics | |:-----------------|--------------|---------------------| | OP_NOP | - | | | OP_MOVE" | BB | R(a) = R(b) | OP_LOADL" | BB | R(a) = Pool(b) | OP_LOADI" | BsB | R(a) = mrb_int(b) | OP_LOADI_0' | B | R(a) = 0 | OP_LOADI_1' | B | R(a) = 1 | OP_LOADI_2' | B | R(a) = 2 | OP_LOADI_3' | B | R(a) = 3 | OP_LOADSYM" | BB | R(a) = Syms(b) | OP_LOADNIL' | B | R(a) = nil | OP_LOADSELF' | B | R(a) = self | OP_LOADT' | B | R(a) = true | OP_LOADF' | B | R(a) = false | OP_GETGV" | BB | R(a) = getglobal(Syms(b)) | OP_SETGV" | BB | setglobal(Syms(b), R(a)) | OP_GETSV" | BB | R(a) = Special[b] | OP_SETSV" | BB | Special[b] = R(a) | OP_GETIV" | BB | R(a) = ivget(Syms(b)) | OP_SETIV" | BB | ivset(Syms(b),R(a)) | OP_GETCV" | BB | R(a) = cvget(Syms(b)) | OP_SETCV" | BB | cvset(Syms(b),R(a)) | OP_GETCONST" | BB | R(a) = constget(Syms(b)) | OP_SETCONST" | BB | constset(Syms(b),R(a)) | OP_GETMCNST" | BB | R(a) = R(a)::Syms(b) | OP_SETMCNST" | BB | R(a+1)::Syms(b) = R(a) | OP_GETUPVAR' | BBB | R(a) = uvget(b,c) | OP_SETUPVAR' | BBB | uvset(b,c,R(a)) | OP_JMP | S | pc+=a | OP_JMPIF' | SB | if R(b) pc+=a | OP_JMPNOT' | SB | if !R(b) pc+=a | OP_ONERR | sS | rescue_push(pc+a) | OP_EXCEPT' | B | R(a) = exc | OP_RESCUE" | BB | R(b) = R(a).isa?(R(b)) | OP_POPERR | B | a.times{rescue_pop()} | OP_RAISE' | B | raise(R(a)) | OP_EPUSH' | B | ensure_push(SEQ[a]) | OP_EPOP | B | A.times{ensure_pop().call} | OP_SENDV" | BB | R(a) = call(R(a),Syms(b),*R(a+1)) | OP_SENDVB" | BB | R(a) = call(R(a),Syms(b),*R(a+1),&R(a+2)) | OP_SEND" | BBB | R(a) = call(R(a),Syms(b),R(a+1),...,R(a+c)) | OP_SENDB" | BBB | R(a) = call(R(a),Syms(Bx),R(a+1),...,R(a+c),&R(a+c+1)) | OP_CALL' | B | R(a) = self.call(frame.argc, frame.argv) | OP_SUPER' | BB | R(a) = super(R(a+1),... ,R(a+b+1)) | OP_ARGARY' | BS | R(a) = argument array (16=5:1:5:1:4) | OP_ENTER | W | arg setup according to flags (23=5:5:1:5:5:1:1) | OP_KARG" | BB | R(a) = kdict[Syms(Bx)] # todo | OP_KARG2" | BB | R(a) = kdict[Syms(Bx)]; kdict.rm(Syms(b)) # todo | OP_RETURN' | B | return R(a) (normal) | OP_RETURN_BLK' | B | return R(a) (in-block return) | OP_BREAK' | B | break R(a) | OP_BLKPUSH' | BS | R(a) = block (16=5:1:5:1:4) | OP_ADD" | BB | R(a) = R(a)+R(a+1) | OP_ADDI" | BBB | R(a) = R(a)+mrb_int(c) | OP_SUB" | BB | R(a) = R(a)-R(a+1) | OP_SUBI" | BB | R(a) = R(a)-C | OP_MUL" | BB | R(a) = R(a)*R(a+1) | OP_DIV" | BB | R(a) = R(a)/R(a+1) | OP_EQ" | BB | R(a) = R(a)==R(a+1) | OP_LT" | BB | R(a) = R(a)R(a+1) | OP_GE" | BB | R(a) = R(a)>=R(a+1) | OP_ARRAY' | BB | R(a) = ary_new(R(a),R(a+1)..R(a+b)) | OP_ARRAY2" | BB | R(a) = ary_new(R(b),R(b+1)..R(b+c)) | OP_ARYCAT' | B | ary_cat(R(a),R(a+1)) | OP_ARYPUSH' | B | ary_push(R(a),R(a+1)) | OP_AREF' | BB | R(a) = R(a)[b] | OP_ASET' | BB | R(a)[b] = R(a+1) | OP_APOST' | BB | *R(a),R(A+1)..R(A+C) = R(a)[B..] | OP_STRING" | BB | R(a) = str_dup(Lit(b)) | OP_STRCAT' | B | str_cat(R(a),R(a+1)) | OP_HASH' | BB | R(a) = hash_new(R(a),R(a+1)..R(a+b)) | OP_HASHADD' | BB | R(a) = hash_push(R(a),R(a+1)..R(a+b)) | OP_LAMBDA" | BB | R(a) = lambda(SEQ[b],OP_L_LAMBDA) | OP_BLOCK" | BB | R(a) = lambda(SEQ[b],OP_L_BLOCK) | OP_METHOD" | BB | R(a) = lambda(SEQ[b],OP_L_METHOD) | OP_RANGE_INC' | B | R(a) = range_new(R(a),R(a+1),FALSE) | OP_RANGE_EXC' | B | R(a) = range_new(R(a),R(a+1),TRUE) | OP_OCLASS' | B | R(a) = ::Object | OP_CLASS" | BB | R(a) = newclass(R(a),Syms(b),R(a+1)) | OP_MODULE" | BB | R(a) = newmodule(R(a),Syms(b)) | OP_EXEC" | BB | R(a) = blockexec(R(a),SEQ[b]) | OP_DEF" | BB | R(a).newmethod(Syms(b),R(a+1)) | OP_ALIAS' | B | alias_method(R(a),R(a+1),R(a+2)) | OP_UNDEF" | BB | undef_method(R(a),Syms(b)) | OP_SCLASS' | B | R(a) = R(a).singleton_class | OP_TCLASS' | B | R(a) = target_class | OP_ERR' | B | raise(RuntimeError, Lit(Bx)) | OP_EXT1 | - | make 1st operand 16bit | OP_EXT2 | - | make 2nd operand 16bit | OP_EXT3 | - | make 1st and 2nd operands 16bit | OP_STOP | - | stop VM