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mruby-mruby/doc/internal/opcode.md
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# The new bytecode
We will reimplement the 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
## 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` | `BS` | `R(a) = mrb_int(b)` |
| `OP_LOADI32` | `BSS` | `R(a) = mrb_int((b<<16)+c)` |
| `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_GETIDX` | `B` | `R(a) = R(a)[R(a+1)]` |
| `OP_SETIDX` | `B` | `R(a)[R(a+1)] = R(a+2)` |
| `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_JMPUW` | `S` | `unwind_and_jump_to(a)` |
| `OP_EXCEPT` | `B` | `R(a) = exc` |
| `OP_RESCUE` | `BB` | `R(b) = R(a).isa?(R(b))` |
| `OP_RAISEIF` | `B` | `raise(R(a)) if R(a)` |
| `OP_SSEND` | `BBB` | `R(a) = self.send(Syms(b),R(a+1)..,R(a+n+1):R(a+n+2)..) (c=n|k<<4)` |
| `OP_SSENDB` | `BBB` | `R(a) = self.send(Syms(b),R(a+1)..,R(a+n+1):R(a+n+2)..,&R(a+n+2k+1))` |
| `OP_SEND` | `BBB` | `R(a) = R(a).send(Syms(b),R(a+1)..,R(a+n+1):R(a+n+2)..) (c=n|k<<4)` |
| `OP_SENDB` | `BBB` | `R(a) = R(a).send(Syms(b),R(a+1)..,R(a+n+1):R(a+n+2)..,&R(a+n+2k+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=m5:r1:m5:d1:lv4)` |
| `OP_ENTER` | `W` | `arg setup according to flags (23=m5:o5:r1:m5:k5:d1:b1)` |
| `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=m5:r1:m5:d1:lv4)` |
| `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_LE` | `B` | `R(a) = R(a)<=R(a+1)` |
| `OP_GT` | `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` | `BB` | `ary_push(R(a),R(a+1)..R(a+b))` |
| `OP_ARYSPLAT` | `B` | `R(a) = ary_splat(R(a))` |
| `OP_AREF` | `BBB` | `R(a) = R(b)[c]` |
| `OP_ASET` | `BBB` | `R(b)[c] = R(a)` |
| `OP_APOST` | `BBB` | `*R(a),R(a+1)..R(a+c) = R(a)[b..]` |
| `OP_INTERN` | `B` | `R(a) = intern(R(a))` |
| `OP_SYMBOL` | `BB` | `R(a) = intern(Pool(b))` |
| `OP_STRING` | `BB` | `R(a) = str_dup(Pool(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*2-1))` |
| `OP_HASHADD` | `BB` | `hash_push(R(a),R(a+1)..R(a+b*2))` |
| `OP_HASHCAT` | `B` | `R(a) = hash_cat(R(a),R(a+1))` |
| `OP_LAMBDA` | `BB` | `R(a) = lambda(Irep(b),OP_L_LAMBDA)` |
| `OP_BLOCK` | `BB` | `R(a) = lambda(Irep(b),OP_L_BLOCK)` |
| `OP_METHOD` | `BB` | `R(a) = lambda(Irep(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),Irep(b))` |
| `OP_DEF` | `BB` | `R(a).newmethod(Syms(b),R(a+1)); R(a) = Syms(b)` |
| `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, Pool(a))` |
| `OP_EXT1` | `-` | `make 1st operand (a) 16bit` |
| `OP_EXT2` | `-` | `make 2nd operand (b) 16bit` |
| `OP_EXT3` | `-` | `make 1st and 2nd operands 16bit` |
| `OP_STOP` | `-` | `stop VM` |