1 | # The new bytecode
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2 |
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3 | We will reimplement VM to use 8bit instruction code. By
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4 | bytecode, we mean real byte code. The whole purpose is
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5 | reducing the memory consumption of mruby VM.
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6 |
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7 | # Instructions
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8 |
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9 | Instructions are bytes. There can be 256 instructions. Currently we
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10 | have 94 instructions. Instructions can take 0 to 3 operands.
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11 |
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12 | ## operands
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13 |
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14 | The size of operands can be either 8bits, 16bits or 24bits.
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15 | In the table.1 below, the second field describes the size (and
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16 | sign) of operands.
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17 |
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18 | * B: 8bit
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19 | * sB: signed 8bit
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20 | * S: 16bit
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21 | * sS: signed 16bit
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22 | * W: 24bit
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23 |
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24 | First two byte operands may be extended to 16bit. When those byte
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25 | operands are bigger than 256, the instruction will be prefixed by
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26 | `OP_EXT1` (means 1st operand is 16bit) or `OP_EXT2` (means 2nd operand
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27 | is 16bit) or `OP_EXT3` (means 1st and 2nd operands are 16bit).
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28 |
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29 | For instructions marked by `'`, `OP_EXT1` can be prefixed. For those
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30 | with `"`, either `OP_EXT1` or `OP_EXT2` or `OP_EXT2` can be prefixed.
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31 |
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32 | ## table.1 Instruction Table
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33 |
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34 | | Instruction Name | Operand type | Semantics |
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35 | |:-----------------|--------------|---------------------|
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36 | | OP_NOP | - | |
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37 | | OP_MOVE" | BB | R(a) = R(b)
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38 | | OP_LOADL" | BB | R(a) = Pool(b)
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39 | | OP_LOADI" | BsB | R(a) = mrb_int(b)
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40 | | OP_LOADI_0' | B | R(a) = 0
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41 | | OP_LOADI_1' | B | R(a) = 1
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42 | | OP_LOADI_2' | B | R(a) = 2
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43 | | OP_LOADI_3' | B | R(a) = 3
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44 | | OP_LOADSYM" | BB | R(a) = Syms(b)
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45 | | OP_LOADNIL' | B | R(a) = nil
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46 | | OP_LOADSELF' | B | R(a) = self
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47 | | OP_LOADT' | B | R(a) = true
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48 | | OP_LOADF' | B | R(a) = false
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49 | | OP_GETGV" | BB | R(a) = getglobal(Syms(b))
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50 | | OP_SETGV" | BB | setglobal(Syms(b), R(a))
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51 | | OP_GETSV" | BB | R(a) = Special[b]
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52 | | OP_SETSV" | BB | Special[b] = R(a)
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53 | | OP_GETIV" | BB | R(a) = ivget(Syms(b))
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54 | | OP_SETIV" | BB | ivset(Syms(b),R(a))
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55 | | OP_GETCV" | BB | R(a) = cvget(Syms(b))
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56 | | OP_SETCV" | BB | cvset(Syms(b),R(a))
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57 | | OP_GETCONST" | BB | R(a) = constget(Syms(b))
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58 | | OP_SETCONST" | BB | constset(Syms(b),R(a))
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59 | | OP_GETMCNST" | BB | R(a) = R(a)::Syms(b)
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60 | | OP_SETMCNST" | BB | R(a+1)::Syms(b) = R(a)
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61 | | OP_GETUPVAR' | BBB | R(a) = uvget(b,c)
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62 | | OP_SETUPVAR' | BBB | uvset(b,c,R(a))
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63 | | OP_JMP | S | pc+=a
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64 | | OP_JMPIF' | SB | if R(b) pc+=a
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65 | | OP_JMPNOT' | SB | if !R(b) pc+=a
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66 | | OP_ONERR | sS | rescue_push(pc+a)
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67 | | OP_EXCEPT' | B | R(a) = exc
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68 | | OP_RESCUE" | BB | R(b) = R(a).isa?(R(b))
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69 | | OP_POPERR | B | a.times{rescue_pop()}
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70 | | OP_RAISE' | B | raise(R(a))
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71 | | OP_EPUSH' | B | ensure_push(SEQ[a])
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72 | | OP_EPOP | B | A.times{ensure_pop().call}
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73 | | OP_SENDV" | BB | R(a) = call(R(a),Syms(b),*R(a+1))
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74 | | OP_SENDVB" | BB | R(a) = call(R(a),Syms(b),*R(a+1),&R(a+2))
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75 | | OP_SEND" | BBB | R(a) = call(R(a),Syms(b),R(a+1),...,R(a+c))
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76 | | OP_SENDB" | BBB | R(a) = call(R(a),Syms(Bx),R(a+1),...,R(a+c),&R(a+c+1))
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77 | | OP_CALL' | B | R(a) = self.call(frame.argc, frame.argv)
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78 | | OP_SUPER' | BB | R(a) = super(R(a+1),... ,R(a+b+1))
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79 | | OP_ARGARY' | BS | R(a) = argument array (16=5:1:5:1:4)
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80 | | OP_ENTER | W | arg setup according to flags (23=5:5:1:5:5:1:1)
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81 | | OP_KARG" | BB | R(a) = kdict[Syms(Bx)] # todo
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82 | | OP_KARG2" | BB | R(a) = kdict[Syms(Bx)]; kdict.rm(Syms(b)) # todo
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83 | | OP_RETURN' | B | return R(a) (normal)
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84 | | OP_RETURN_BLK' | B | return R(a) (in-block return)
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85 | | OP_BREAK' | B | break R(a)
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86 | | OP_BLKPUSH' | BS | R(a) = block (16=5:1:5:1:4)
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87 | | OP_ADD" | BB | R(a) = R(a)+R(a+1)
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88 | | OP_ADDI" | BBB | R(a) = R(a)+mrb_int(c)
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89 | | OP_SUB" | BB | R(a) = R(a)-R(a+1)
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90 | | OP_SUBI" | BB | R(a) = R(a)-C
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91 | | OP_MUL" | BB | R(a) = R(a)*R(a+1)
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92 | | OP_DIV" | BB | R(a) = R(a)/R(a+1)
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93 | | OP_EQ" | BB | R(a) = R(a)==R(a+1)
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94 | | OP_LT" | BB | R(a) = R(a)<R(a+1)
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95 | | OP_LE" | BB | R(a) = R(a)<=R(a+1)
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96 | | OP_GT" | BB | R(a) = R(a)>R(a+1)
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97 | | OP_GE" | BB | R(a) = R(a)>=R(a+1)
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98 | | OP_ARRAY' | BB | R(a) = ary_new(R(a),R(a+1)..R(a+b))
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99 | | OP_ARRAY2" | BB | R(a) = ary_new(R(b),R(b+1)..R(b+c))
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100 | | OP_ARYCAT' | B | ary_cat(R(a),R(a+1))
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101 | | OP_ARYPUSH' | B | ary_push(R(a),R(a+1))
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102 | | OP_AREF' | BB | R(a) = R(a)[b]
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103 | | OP_ASET' | BB | R(a)[b] = R(a+1)
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104 | | OP_APOST' | BB | *R(a),R(A+1)..R(A+C) = R(a)[B..]
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105 | | OP_STRING" | BB | R(a) = str_dup(Lit(b))
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106 | | OP_STRCAT' | B | str_cat(R(a),R(a+1))
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107 | | OP_HASH' | BB | R(a) = hash_new(R(a),R(a+1)..R(a+b))
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108 | | OP_HASHADD' | BB | R(a) = hash_push(R(a),R(a+1)..R(a+b))
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109 | | OP_LAMBDA" | BB | R(a) = lambda(SEQ[b],OP_L_LAMBDA)
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110 | | OP_BLOCK" | BB | R(a) = lambda(SEQ[b],OP_L_BLOCK)
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111 | | OP_METHOD" | BB | R(a) = lambda(SEQ[b],OP_L_METHOD)
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112 | | OP_RANGE_INC' | B | R(a) = range_new(R(a),R(a+1),FALSE)
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113 | | OP_RANGE_EXC' | B | R(a) = range_new(R(a),R(a+1),TRUE)
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114 | | OP_OCLASS' | B | R(a) = ::Object
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115 | | OP_CLASS" | BB | R(a) = newclass(R(a),Syms(b),R(a+1))
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116 | | OP_MODULE" | BB | R(a) = newmodule(R(a),Syms(b))
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117 | | OP_EXEC" | BB | R(a) = blockexec(R(a),SEQ[b])
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118 | | OP_DEF" | BB | R(a).newmethod(Syms(b),R(a+1))
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119 | | OP_ALIAS' | B | alias_method(R(a),R(a+1),R(a+2))
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120 | | OP_UNDEF" | BB | undef_method(R(a),Syms(b))
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121 | | OP_SCLASS' | B | R(a) = R(a).singleton_class
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122 | | OP_TCLASS' | B | R(a) = target_class
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123 | | OP_ERR' | B | raise(RuntimeError, Lit(Bx))
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124 | | OP_EXT1 | - | make 1st operand 16bit
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125 | | OP_EXT2 | - | make 2nd operand 16bit
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126 | | OP_EXT3 | - | make 1st and 2nd operands 16bit
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127 | | OP_STOP | - | stop VM
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