# 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 * 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 | - | no operation | | OP_MOVE" | BB | R(a) = R(b) | | OP_LOADL" | BB | R(a) = Pool(b) | | OP_LOADI" | BB | R(a) = mrb_int(b) | | OP_LOADINEG" | BB | R(a) = mrb_int(-b) | | OP_LOADI__1' | B | R(a) = mrb_int(-1) | | OP_LOADI_0' | B | R(a) = mrb_int(0) | | OP_LOADI_1' | B | R(a) = mrb_int(1) | | OP_LOADI_2' | B | R(a) = mrb_int(2) | | OP_LOADI_3' | B | R(a) = mrb_int(3) | | OP_LOADI_4' | B | R(a) = mrb_int(4) | | OP_LOADI_5' | B | R(a) = mrb_int(5) | | OP_LOADI_6' | B | R(a) = mrb_int(6) | | OP_LOADI_7' | B | R(a) = mrb_int(7) | | OP_LOADI16' | BsS | R(a) = mrb_int(b) | | 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[Syms(b)] | | OP_SETSV" | BB | Special[Syms(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' | BS | if R(a) pc=b | | OP_JMPNOT' | BS | if !R(a) pc=b | | OP_JMPNIL' | BS | if R(a)==nil pc=b | | OP_ONERR | S | rescue_push(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(b),R(a+1),...,R(a+c),&R(a+c+1)) | | OP_CALL | - | R(0) = 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_KEY_P" | BB | R(a) = kdict.key?(Syms(b)) | | OP_KEYEND | - | raise unless kdict.empty? | | OP_KARG" | BB | R(a) = kdict[Syms(b)]; kdict.delete(Syms(b)) | | 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' | B | R(a) = R(a)+R(a+1) | | OP_ADDI" | BB | R(a) = R(a)+mrb_int(b) | | OP_SUB' | B | R(a) = R(a)-R(a+1) | | OP_SUBI" | BB | R(a) = R(a)-mrb_int(b) | | OP_MUL' | B | R(a) = R(a)*R(a+1) | | OP_DIV' | B | R(a) = R(a)/R(a+1) | | OP_EQ' | B | R(a) = R(a)==R(a+1) | | OP_LT' | B | R(a) = R(a)R(a+1) | | OP_GE' | B | R(a) = R(a)>=R(a+1) | | OP_ARRAY" | BB | R(a) = ary_new(R(a),R(a+1)..R(a+b)) | | OP_ARRAY2" | BBB | 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_ARYDUP' | B | R(a) = ary_dup(R(a)) | | OP_AREF" | BBB | R(a) = R(b)[c] | | OP_ASET" | BBB | R(a)[c] = R(b) | | OP_APOST" | BBB | *R(a),R(a+1)..R(a+c) = R(a)[b..] | | OP_INTERN' | B | R(a) = intern(R(a)) | | 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_HASHCAT' | B | R(a) = hash_cat(R(a),R(a+1)) | | 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" | BB | alias_method(target_class,Syms(a),Syms(b)) | | OP_UNDEF' | B | undef_method(target_class,Syms(a)) | | OP_SCLASS' | B | R(a) = R(a).singleton_class | | OP_TCLASS' | B | R(a) = target_class | | OP_DEBUG" | BBB | print a,b,c | | OP_ERR' | B | raise(LocalJumpError, Lit(a)) | | OP_EXT1 | - | make 1st operand 16bit | | OP_EXT2 | - | make 2nd operand 16bit | | OP_EXT3 | - | make 1st and 2nd operands 16bit | | OP_STOP | - | stop VM | |------------------|--------------|--------------------------------------------------------|