bytecode of YARV, Rubinius and JRuby

這應該是目前三大 Ruby VM 吧，其他勉強能提的大概是 IronRuby,
不過完成度好像還低於其他三者不少，先略過不提。要搞 mono 也比較麻煩。

暫時沒找到 JRuby 比較輕便的 compile 法，好像是 JRuby.compile 會產生
JRuby::CompiledScript, 一個完整可以執行的 script, 而 YARV 只是單純
產生 RubyVM::InstructionSequence, 而 Rubinius 則是 CompiledMethod,
介於 JRuby 與 YARV 之間吧。

短評：
YARV:
1. 用 instruction sequence 來 compile 有一點奇怪
2. 閱讀起來滿清楚的

Rubinius:
1. 用法最有彈性，可取得的資訊最多
2. 有點失望 constants 不是放在 Rubinius 下，如 JRuby 或 YARV

JRuby:
1. 用起來最清楚的一個，命名乾淨，沒試幾次就有結果了
2. bytecode 也未免 verbose 過頭了些......

接下來就是希望可以 decompile, 像是 Ruby2Ruby 的 to_ruby 那樣。
不過這個就不抱太大的期望了，畢竟如果能簡單的轉換，那 compile 就失去意義了。

godfat ~> irb1.9 -r pp

irb(main):001:0> pp RubyVM::InstructionSequence.compile('1 + 2').to_a
["YARVInstructionSequence/SimpleDataFormat",
 1,
 1,
 1,
 {:arg_size=>0, :local_size=>1, :stack_max=>2},
 "",
 "",
 :top,
 [],
 0,
 [],
 [1, [:trace, 1], [:putobject, 1], [:putobject, 2], [:opt_plus], [:leave]]]

或是：

irb(main):002:0> puts RubyVM::InstructionSequence.compile('1 + 2').disassemble
== disasm: <RubyVM::InstructionSequence:<compiled>@<compiled>>==========
0000 trace            1                                               (   1)
0002 putobject        1
0004 putobject        2
0006 opt_plus         
0007 leave

Rubinius:

godfat ~/p/g/rubinius> bin/rbx

irb(main):001:0> Compiler.compile_string('1 + 2', binding.context).iseq.decode
=> [[:meta_push_1], [:meta_push_2], [:meta_send_op_plus], [:ret]]

或是：

irb(main):002:0> Compiler.compile_string('1 + 2', binding.context).iseq.opcodes
=> #<Tuple: 72, 73, 74, 12>

或是：

irb(main):003:0> require 'pp'
=> true
irb(main):004:0> pp Compiler.compile_string('1 + 2', binding.context).decode
[#<CompiledMethod::Instruction:0x110 @ip=0 @args=[] @stack_consumed=[0, true] @op=#<InstructionSet::OpCode:0xc2 @opcode_info={:opcode=>:meta_push_1, :bytecode=>72, :args=>[], :stack=>[0, 1]}> @line=1 @stack_produced=[1, true] @comment=nil>,
 #<CompiledMethod::Instruction:0x118 @ip=1 @args=[] @stack_consumed=[0, true] @op=#<InstructionSet::OpCode:0xd2 @opcode_info={:opcode=>:meta_push_2, :bytecode=>73, :args=>[], :stack=>[0, 1]}> @line=1 @stack_produced=[1, true] @comment=nil>,
 #<CompiledMethod::Instruction:0x120 @ip=2 @args=[] @stack_consumed=[2, true] @op=#<InstructionSet::OpCode:0xe2 @opcode_info={:opcode=>:meta_send_op_plus, :vm_flags=>[:check_interrupts], :bytecode=>74, :flow=>:send, :args=>[], :stack=>[2, 1]}> @line=1 @stack_produced=[1, true] @comment=nil>,
 #<CompiledMethod::Instruction:0x128 @ip=3 @args=[] @stack_consumed=[0, true] @op=#<InstructionSet::OpCode:0xf4 @opcode_info={:opcode=>:ret, :vm_flags=>[:terminator], :bytecode=>12, :flow=>:return, :args=>[], :stack=>[0, 0]}> @line=1 @stack_produced=[0, true] @comment=nil>]

JRuby:

godfat ~> jirb

irb(main):001:0> puts JRuby.compile('1 + 2').inspect_bytecode
// class version 49.0 (49)
// access flags 33
public class _dash_ extends org/jruby/ast/executable/AbstractScript  {


  // access flags 18
  private final Ljava/lang/Class; $class

  // access flags 1
  public ()V
    ALOAD 0
    INVOKESPECIAL org/jruby/ast/executable/AbstractScript. ()V
    ALOAD 0
    LDC "_dash_"
    INVOKESTATIC java/lang/Class.forName (Ljava/lang/String;)Ljava/lang/Class;
    PUTFIELD _dash_.$class : Ljava/lang/Class;
    ALOAD 0
    LDC "+"
    INVOKESTATIC org/jruby/runtime/MethodIndex.getCallSite (Ljava/lang/String;)Lorg/jruby/runtime/CallSite;
    PUTFIELD _dash_.site0 : Lorg/jruby/runtime/CallSite;
    RETURN
    MAXSTACK = 2
    MAXLOCALS = 1

  // access flags 9
  public static ()V
    RETURN
    MAXSTACK = 0
    MAXLOCALS = 0

  // access flags 1
  public __file__(Lorg/jruby/runtime/ThreadContext;Lorg/jruby/runtime/builtin/IRubyObject;Lorg/jruby/runtime/Block;)Lorg/jruby/runtime/builtin/IRubyObject;
    ALOAD 1
    INVOKEVIRTUAL org/jruby/runtime/ThreadContext.getRuntime ()Lorg/jruby/Ruby;
    DUP
    ASTORE 5
    INVOKEVIRTUAL org/jruby/Ruby.getNil ()Lorg/jruby/runtime/builtin/IRubyObject;
    ASTORE 7
    NOP
    ALOAD 1
    ICONST_0
    INVOKESTATIC _dash_.setPosition (Lorg/jruby/runtime/ThreadContext;I)V
    ALOAD 0
    GETFIELD _dash_.site0 : Lorg/jruby/runtime/CallSite;
    ALOAD 1
    ALOAD 0
    ALOAD 5
    LDC 1
    INVOKEVIRTUAL _dash_.getFixnum0 (Lorg/jruby/Ruby;J)Lorg/jruby/RubyFixnum;
    ALOAD 0
    ALOAD 5
    LDC 2
    INVOKEVIRTUAL _dash_.getFixnum1 (Lorg/jruby/Ruby;J)Lorg/jruby/RubyFixnum;
    INVOKEVIRTUAL org/jruby/runtime/CallSite.call (Lorg/jruby/runtime/ThreadContext;Lorg/jruby/runtime/builtin/IRubyObject;Lorg/jruby/runtime/builtin/IRubyObject;)Lorg/jruby/runtime/builtin/IRubyObject;
    ARETURN
    MAXSTACK = 7
    MAXLOCALS = 8

  // access flags 1
  public __file__(Lorg/jruby/runtime/ThreadContext;Lorg/jruby/runtime/builtin/IRubyObject;[Lorg/jruby/runtime/builtin/IRubyObject;Lorg/jruby/runtime/Block;)Lorg/jruby/runtime/builtin/IRubyObject;
    ALOAD 1
    INVOKEVIRTUAL org/jruby/runtime/ThreadContext.getRuntime ()Lorg/jruby/Ruby;
    ALOAD 3
    ICONST_0
    ICONST_0
    INVOKESTATIC org/jruby/runtime/Arity.checkArgumentCount (Lorg/jruby/Ruby;[Lorg/jruby/runtime/builtin/IRubyObject;II)I
    POP
    ALOAD 0
    ALOAD 1
    ALOAD 2
    ALOAD 4
    INVOKEVIRTUAL _dash_.__file__ (Lorg/jruby/runtime/ThreadContext;Lorg/jruby/runtime/builtin/IRubyObject;Lorg/jruby/runtime/Block;)Lorg/jruby/runtime/builtin/IRubyObject;
    ARETURN
    MAXSTACK = 4
    MAXLOCALS = 5

  // access flags 1
  public load(Lorg/jruby/runtime/ThreadContext;Lorg/jruby/runtime/builtin/IRubyObject;[Lorg/jruby/runtime/builtin/IRubyObject;Lorg/jruby/runtime/Block;)Lorg/jruby/runtime/builtin/IRubyObject;
    TRYCATCHBLOCK L0 L1 L1 null
   L0
   FRAME FULL [] []
    ALOAD 1
    ICONST_0
    ANEWARRAY java/lang/String
    INVOKESTATIC org/jruby/javasupport/util/RuntimeHelpers.preLoad (Lorg/jruby/runtime/ThreadContext;[Ljava/lang/String;)V
    ALOAD 0
    ALOAD 1
    ALOAD 2
    ALOAD 3
    ALOAD 4
    INVOKEVIRTUAL _dash_.__file__ (Lorg/jruby/runtime/ThreadContext;Lorg/jruby/runtime/builtin/IRubyObject;[Lorg/jruby/runtime/builtin/IRubyObject;Lorg/jruby/runtime/Block;)Lorg/jruby/runtime/builtin/IRubyObject;
    ALOAD 1
    INVOKESTATIC org/jruby/javasupport/util/RuntimeHelpers.postLoad (Lorg/jruby/runtime/ThreadContext;)V
    ARETURN
   L1
   FRAME FULL [_dash_ org/jruby/runtime/ThreadContext org/jruby/runtime/builtin/IRubyObject [Lorg/jruby/runtime/builtin/IRubyObject; org/jruby/runtime/Block] [java/lang/Throwable]
    ALOAD 1
    INVOKESTATIC org/jruby/javasupport/util/RuntimeHelpers.postLoad (Lorg/jruby/runtime/ThreadContext;)V
    ATHROW
    MAXSTACK = 5
    MAXLOCALS = 5

  // access flags 9
  public static main([Ljava/lang/String;)V
    NEW _dash_
    DUP
    INVOKESPECIAL _dash_. ()V
    NEW org/jruby/RubyInstanceConfig
    DUP
    INVOKESPECIAL org/jruby/RubyInstanceConfig. ()V
    DUP
    ALOAD 0
    INVOKEVIRTUAL org/jruby/RubyInstanceConfig.setArgv ([Ljava/lang/String;)V
    INVOKESTATIC org/jruby/Ruby.newInstance (Lorg/jruby/RubyInstanceConfig;)Lorg/jruby/Ruby;
    DUP
    INVOKEVIRTUAL org/jruby/Ruby.getCurrentContext ()Lorg/jruby/runtime/ThreadContext;
    SWAP
    INVOKEVIRTUAL org/jruby/Ruby.getTopSelf ()Lorg/jruby/runtime/builtin/IRubyObject;
    GETSTATIC org/jruby/runtime/builtin/IRubyObject.NULL_ARRAY : [Lorg/jruby/runtime/builtin/IRubyObject;
    GETSTATIC org/jruby/runtime/Block.NULL_BLOCK : Lorg/jruby/runtime/Block;
    INVOKEVIRTUAL _dash_.load (Lorg/jruby/runtime/ThreadContext;Lorg/jruby/runtime/builtin/IRubyObject;[Lorg/jruby/runtime/builtin/IRubyObject;Lorg/jruby/runtime/Block;)Lorg/jruby/runtime/builtin/IRubyObject;
    RETURN
    MAXSTACK = 5
    MAXLOCALS = 1

  // access flags 4106
  private static setPosition(Lorg/jruby/runtime/ThreadContext;I)V
    ALOAD 0
    LDC "-"
    ILOAD 1
    INVOKEVIRTUAL org/jruby/runtime/ThreadContext.setFileAndLine (Ljava/lang/String;I)V
    RETURN
    MAXSTACK = 3
    MAXLOCALS = 2
}