Hotspot源码解析-第十四章-字节码初始化

2024-01-08 19:13:03

14.1 字节码指令定义

14.1.1 bytecodes.cpp

14.1.1.1 Bytecodes::initialize

这个函数的入口是bytecodes_init()函数。

在讲解字节码指令定义前,先了解下def各参数的含义:

  • bytecode:字节码指令
  • bytecode name:字节码指令名称
  • format:这个属性能表达2个意思,首先能表达字节码的格式,另外还能表示字节码的长度
  • wide f(wide_format):表示字节码前面是否可以加wide,如果可以,则值为"wbii"
  • result tp:表示指令执行后的结果类型。如为T_ILLEGAL时,表示只参考当前字节码无法决定执行结果的类型,如_invokevirtual方法调用指令,结果类型应该为方法返回类型,但是此时只参考这个调用方法的字节码指令是无法决定的;再比如T_VOID和T_OBJECT,分别表示返回void和object类型
  • stk:表示对表达式栈深度的影响,如_nop指令不执行任何操作,所以对表达式栈的深度无影响,stk的值为0;当用_iconst_0向栈中压入0时,栈的深度增加1,所以stk的值为1。当为_lconst_0时,栈的深度会增加2;当为_lstore_0时,栈的深度会减少2;
  • traps:表示can_trap,这个比较重要,先把它理解成操作系统中的陷阱门,后面用到再细讲。

接下来我们讲一下format参数,有点汇编基础的都了解,一条指令是由操作码和操作数组成的,操作码可以想像成我们这里的bytecode这一列,操作数就是操作码要操作的数值,比如加1减1中的这个1就是操作数,format这个参数就表示字节码指令的格式,当这一列字符串中有一个字符时就表示该指令长度就是一个字节,当为2个字符时就表示指令长度为2个字节,依此类推。比如_iconst_0指令就占一个字节宽度,_store的format值是"bi",表示占2个字节。format也可能是空字符,为空时,表示当前的字节码指令不是Java虚拟机规范中定义的,_fast_agetfield、_fast_bgetfield这两个指令的format就是空字符,这一类字节码都是虚拟机内部定义的。另外,format还能表示字节码的格式,字符串中各个字符的含义如下:

  • b:表示指令是不可变长度
  • c:表示操作数是有符号的常量值,如bipush指令将byte带符号扩展为一个int类型的值,然后将这个值入栈到操作数栈中
  • i:表示操作数为无符号的局部变量表索引值,如iload指令从局部变量表加载一个int类型的值到操作数栈中
  • j:表示操作数是常量池缓存的索引值
  • k:表示操作数为无符号的常量池索引,如ldc指令就是从运行时常量池中根据对应的索引值提取数据并压入操作数栈
  • o:表示操作数为分支偏移,就把它想像成判断后的分支走向,如ifeq指令表示整数与零比较,如果整数为0,则结果为真,该操作数就是分支偏移量,也就是要进行跳转的地方
  • w:这个字符是wide f(wide_format)这一参数的,表示用来扩展局部变量表索引

以上这些描述,大家知道大概意思就行,无需深入研究。

// 字节码指令定义的函数
void Bytecodes::def(Code code, const char* name, const char* format, const char* wide_format, 			BasicType result_type, int depth, bool can_trap, Code java_code) {
  assert(wide_format == NULL || format != NULL, "short form must exist if there's a wide form");
  // 得出format字符占的长度
  int len  = (format      != NULL ? (int) strlen(format)      : 0);
    // 得出format字符占的长度
  int wlen = (wide_format != NULL ? (int) strlen(wide_format) : 0);
  // _name/_result_type/_depth/_lengths/_java_code 这些都是数组,这里的意思就是把字节码指令的相关属性都按字节数组存储起来,数组的index都是对应的字节码code
  _name          [code] = name;
  _result_type   [code] = result_type;
  _depth         [code] = depth;
   // 这里用1个字节存放了format(低4位)和wide_format(高4位)
  _lengths       [code] = (wlen << 4) | (len & 0xF);
  _java_code     [code] = java_code;
  int bc_flags = 0;
   // bc_flags 用低2位分别表示can_trap和can_rewrite
  if (can_trap)           bc_flags |= _bc_can_trap;
  if (java_code != code)  bc_flags |= _bc_can_rewrite;
  // 将bc_flags、format和wide_format通过位运算操作都整到一个整型值中,并存储到_flags数组中,用的时候再按位拆解出来
  _flags[(u1)code+0*(1<<BitsPerByte)] = compute_flags(format,      bc_flags);
  _flags[(u1)code+1*(1<<BitsPerByte)] = compute_flags(wide_format, bc_flags);
  assert(is_defined(code)      == (format != NULL),      "");
  assert(wide_is_defined(code) == (wide_format != NULL), "");
  assert(length_for(code)      == len, "");
  assert(wide_length_for(code) == wlen, "");
}

/*
* 总结一下字节码定义函数def做的事情:就是将所有字节码的信息按着字节码指令操作码(bytecode)
* 归整到对应的索引值的数组中,方便使用时,直接按bytecode索引值取出来就行
*/

void Bytecodes::initialize() {
  if (_is_initialized) return;  // 重复初始化判断
  // 字节码指令个数不能大于256,Java字节码指令都是精简指令,用一个字节表示,所以最多256个
  assert(number_of_codes <= 256, "too many bytecodes");

  //  Java bytecodes  下面都是Java规范中定义的字节码
  //  bytecode               bytecode name           format   wide f.   result tp  stk traps
  def(_nop                 , "nop"                 , "b"    , NULL    , T_VOID   ,  0, false);
  def(_aconst_null         , "aconst_null"         , "b"    , NULL    , T_OBJECT ,  1, false);
  def(_iconst_m1           , "iconst_m1"           , "b"    , NULL    , T_INT    ,  1, false);
  def(_iconst_0            , "iconst_0"            , "b"    , NULL    , T_INT    ,  1, false);
  def(_iconst_1            , "iconst_1"            , "b"    , NULL    , T_INT    ,  1, false);
  def(_iconst_2            , "iconst_2"            , "b"    , NULL    , T_INT    ,  1, false);
  def(_iconst_3            , "iconst_3"            , "b"    , NULL    , T_INT    ,  1, false);
  def(_iconst_4            , "iconst_4"            , "b"    , NULL    , T_INT    ,  1, false);
  def(_iconst_5            , "iconst_5"            , "b"    , NULL    , T_INT    ,  1, false);
  def(_lconst_0            , "lconst_0"            , "b"    , NULL    , T_LONG   ,  2, false);
  def(_lconst_1            , "lconst_1"            , "b"    , NULL    , T_LONG   ,  2, false);
  def(_fconst_0            , "fconst_0"            , "b"    , NULL    , T_FLOAT  ,  1, false);
  def(_fconst_1            , "fconst_1"            , "b"    , NULL    , T_FLOAT  ,  1, false);
  def(_fconst_2            , "fconst_2"            , "b"    , NULL    , T_FLOAT  ,  1, false);
  def(_dconst_0            , "dconst_0"            , "b"    , NULL    , T_DOUBLE ,  2, false);
  def(_dconst_1            , "dconst_1"            , "b"    , NULL    , T_DOUBLE ,  2, false);
  def(_bipush              , "bipush"              , "bc"   , NULL    , T_INT    ,  1, false);
  def(_sipush              , "sipush"              , "bcc"  , NULL    , T_INT    ,  1, false);
  def(_ldc                 , "ldc"                 , "bk"   , NULL    , T_ILLEGAL,  1, true );
  def(_ldc_w               , "ldc_w"               , "bkk"  , NULL    , T_ILLEGAL,  1, true );
  def(_ldc2_w              , "ldc2_w"              , "bkk"  , NULL    , T_ILLEGAL,  2, true );
  def(_iload               , "iload"               , "bi"   , "wbii"  , T_INT    ,  1, false);
  def(_lload               , "lload"               , "bi"   , "wbii"  , T_LONG   ,  2, false);
  def(_fload               , "fload"               , "bi"   , "wbii"  , T_FLOAT  ,  1, false);
  def(_dload               , "dload"               , "bi"   , "wbii"  , T_DOUBLE ,  2, false);
  def(_aload               , "aload"               , "bi"   , "wbii"  , T_OBJECT ,  1, false);
  def(_iload_0             , "iload_0"             , "b"    , NULL    , T_INT    ,  1, false);
  def(_iload_1             , "iload_1"             , "b"    , NULL    , T_INT    ,  1, false);
  def(_iload_2             , "iload_2"             , "b"    , NULL    , T_INT    ,  1, false);
  def(_iload_3             , "iload_3"             , "b"    , NULL    , T_INT    ,  1, false);
  def(_lload_0             , "lload_0"             , "b"    , NULL    , T_LONG   ,  2, false);
  def(_lload_1             , "lload_1"             , "b"    , NULL    , T_LONG   ,  2, false);
  def(_lload_2             , "lload_2"             , "b"    , NULL    , T_LONG   ,  2, false);
  def(_lload_3             , "lload_3"             , "b"    , NULL    , T_LONG   ,  2, false);
  def(_fload_0             , "fload_0"             , "b"    , NULL    , T_FLOAT  ,  1, false);
  def(_fload_1             , "fload_1"             , "b"    , NULL    , T_FLOAT  ,  1, false);
  def(_fload_2             , "fload_2"             , "b"    , NULL    , T_FLOAT  ,  1, false);
  def(_fload_3             , "fload_3"             , "b"    , NULL    , T_FLOAT  ,  1, false);
  def(_dload_0             , "dload_0"             , "b"    , NULL    , T_DOUBLE ,  2, false);
  def(_dload_1             , "dload_1"             , "b"    , NULL    , T_DOUBLE ,  2, false);
  def(_dload_2             , "dload_2"             , "b"    , NULL    , T_DOUBLE ,  2, false);
  def(_dload_3             , "dload_3"             , "b"    , NULL    , T_DOUBLE ,  2, false);
  def(_aload_0             , "aload_0"             , "b"    , NULL    , T_OBJECT ,  1, true ); // rewriting in interpreter
  def(_aload_1             , "aload_1"             , "b"    , NULL    , T_OBJECT ,  1, false);
  def(_aload_2             , "aload_2"             , "b"    , NULL    , T_OBJECT ,  1, false);
  def(_aload_3             , "aload_3"             , "b"    , NULL    , T_OBJECT ,  1, false);
  def(_iaload              , "iaload"              , "b"    , NULL    , T_INT    , -1, true );
  def(_laload              , "laload"              , "b"    , NULL    , T_LONG   ,  0, true );
  def(_faload              , "faload"              , "b"    , NULL    , T_FLOAT  , -1, true );
  def(_daload              , "daload"              , "b"    , NULL    , T_DOUBLE ,  0, true );
  def(_aaload              , "aaload"              , "b"    , NULL    , T_OBJECT , -1, true );
  def(_baload              , "baload"              , "b"    , NULL    , T_INT    , -1, true );
  def(_caload              , "caload"              , "b"    , NULL    , T_INT    , -1, true );
  def(_saload              , "saload"              , "b"    , NULL    , T_INT    , -1, true );
  def(_istore              , "istore"              , "bi"   , "wbii"  , T_VOID   , -1, false);
  def(_lstore              , "lstore"              , "bi"   , "wbii"  , T_VOID   , -2, false);
  def(_fstore              , "fstore"              , "bi"   , "wbii"  , T_VOID   , -1, false);
  def(_dstore              , "dstore"              , "bi"   , "wbii"  , T_VOID   , -2, false);
  def(_astore              , "astore"              , "bi"   , "wbii"  , T_VOID   , -1, false);
  def(_istore_0            , "istore_0"            , "b"    , NULL    , T_VOID   , -1, false);
  def(_istore_1            , "istore_1"            , "b"    , NULL    , T_VOID   , -1, false);
  def(_istore_2            , "istore_2"            , "b"    , NULL    , T_VOID   , -1, false);
  def(_istore_3            , "istore_3"            , "b"    , NULL    , T_VOID   , -1, false);
  def(_lstore_0            , "lstore_0"            , "b"    , NULL    , T_VOID   , -2, false);
  def(_lstore_1            , "lstore_1"            , "b"    , NULL    , T_VOID   , -2, false);
  def(_lstore_2            , "lstore_2"            , "b"    , NULL    , T_VOID   , -2, false);
  def(_lstore_3            , "lstore_3"            , "b"    , NULL    , T_VOID   , -2, false);
  def(_fstore_0            , "fstore_0"            , "b"    , NULL    , T_VOID   , -1, false);
  def(_fstore_1            , "fstore_1"            , "b"    , NULL    , T_VOID   , -1, false);
  def(_fstore_2            , "fstore_2"            , "b"    , NULL    , T_VOID   , -1, false);
  def(_fstore_3            , "fstore_3"            , "b"    , NULL    , T_VOID   , -1, false);
  def(_dstore_0            , "dstore_0"            , "b"    , NULL    , T_VOID   , -2, false);
  def(_dstore_1            , "dstore_1"            , "b"    , NULL    , T_VOID   , -2, false);
  def(_dstore_2            , "dstore_2"            , "b"    , NULL    , T_VOID   , -2, false);
  def(_dstore_3            , "dstore_3"            , "b"    , NULL    , T_VOID   , -2, false);
  def(_astore_0            , "astore_0"            , "b"    , NULL    , T_VOID   , -1, false);
  def(_astore_1            , "astore_1"            , "b"    , NULL    , T_VOID   , -1, false);
  def(_astore_2            , "astore_2"            , "b"    , NULL    , T_VOID   , -1, false);
  def(_astore_3            , "astore_3"            , "b"    , NULL    , T_VOID   , -1, false);
  def(_iastore             , "iastore"             , "b"    , NULL    , T_VOID   , -3, true );
  def(_lastore             , "lastore"             , "b"    , NULL    , T_VOID   , -4, true );
  def(_fastore             , "fastore"             , "b"    , NULL    , T_VOID   , -3, true );
  def(_dastore             , "dastore"             , "b"    , NULL    , T_VOID   , -4, true );
  def(_aastore             , "aastore"             , "b"    , NULL    , T_VOID   , -3, true );
  def(_bastore             , "bastore"             , "b"    , NULL    , T_VOID   , -3, true );
  def(_castore             , "castore"             , "b"    , NULL    , T_VOID   , -3, true );
  def(_sastore             , "sastore"             , "b"    , NULL    , T_VOID   , -3, true );
  def(_pop                 , "pop"                 , "b"    , NULL    , T_VOID   , -1, false);
  def(_pop2                , "pop2"                , "b"    , NULL    , T_VOID   , -2, false);
  def(_dup                 , "dup"                 , "b"    , NULL    , T_VOID   ,  1, false);
  def(_dup_x1              , "dup_x1"              , "b"    , NULL    , T_VOID   ,  1, false);
  def(_dup_x2              , "dup_x2"              , "b"    , NULL    , T_VOID   ,  1, false);
  def(_dup2                , "dup2"                , "b"    , NULL    , T_VOID   ,  2, false);
  def(_dup2_x1             , "dup2_x1"             , "b"    , NULL    , T_VOID   ,  2, false);
  def(_dup2_x2             , "dup2_x2"             , "b"    , NULL    , T_VOID   ,  2, false);
  def(_swap                , "swap"                , "b"    , NULL    , T_VOID   ,  0, false);
  def(_iadd                , "iadd"                , "b"    , NULL    , T_INT    , -1, false);
  def(_ladd                , "ladd"                , "b"    , NULL    , T_LONG   , -2, false);
  def(_fadd                , "fadd"                , "b"    , NULL    , T_FLOAT  , -1, false);
  def(_dadd                , "dadd"                , "b"    , NULL    , T_DOUBLE , -2, false);
  def(_isub                , "isub"                , "b"    , NULL    , T_INT    , -1, false);
  def(_lsub                , "lsub"                , "b"    , NULL    , T_LONG   , -2, false);
  def(_fsub                , "fsub"                , "b"    , NULL    , T_FLOAT  , -1, false);
  def(_dsub                , "dsub"                , "b"    , NULL    , T_DOUBLE , -2, false);
  def(_imul                , "imul"                , "b"    , NULL    , T_INT    , -1, false);
  def(_lmul                , "lmul"                , "b"    , NULL    , T_LONG   , -2, false);
  def(_fmul                , "fmul"                , "b"    , NULL    , T_FLOAT  , -1, false);
  def(_dmul                , "dmul"                , "b"    , NULL    , T_DOUBLE , -2, false);
  def(_idiv                , "idiv"                , "b"    , NULL    , T_INT    , -1, true );
  def(_ldiv                , "ldiv"                , "b"    , NULL    , T_LONG   , -2, true );
  def(_fdiv                , "fdiv"                , "b"    , NULL    , T_FLOAT  , -1, false);
  def(_ddiv                , "ddiv"                , "b"    , NULL    , T_DOUBLE , -2, false);
  def(_irem                , "irem"                , "b"    , NULL    , T_INT    , -1, true );
  def(_lrem                , "lrem"                , "b"    , NULL    , T_LONG   , -2, true );
  def(_frem                , "frem"                , "b"    , NULL    , T_FLOAT  , -1, false);
  def(_drem                , "drem"                , "b"    , NULL    , T_DOUBLE , -2, false);
  def(_ineg                , "ineg"                , "b"    , NULL    , T_INT    ,  0, false);
  def(_lneg                , "lneg"                , "b"    , NULL    , T_LONG   ,  0, false);
  def(_fneg                , "fneg"                , "b"    , NULL    , T_FLOAT  ,  0, false);
  def(_dneg                , "dneg"                , "b"    , NULL    , T_DOUBLE ,  0, false);
  def(_ishl                , "ishl"                , "b"    , NULL    , T_INT    , -1, false);
  def(_lshl                , "lshl"                , "b"    , NULL    , T_LONG   , -1, false);
  def(_ishr                , "ishr"                , "b"    , NULL    , T_INT    , -1, false);
  def(_lshr                , "lshr"                , "b"    , NULL    , T_LONG   , -1, false);
  def(_iushr               , "iushr"               , "b"    , NULL    , T_INT    , -1, false);
  def(_lushr               , "lushr"               , "b"    , NULL    , T_LONG   , -1, false);
  def(_iand                , "iand"                , "b"    , NULL    , T_INT    , -1, false);
  def(_land                , "land"                , "b"    , NULL    , T_LONG   , -2, false);
  def(_ior                 , "ior"                 , "b"    , NULL    , T_INT    , -1, false);
  def(_lor                 , "lor"                 , "b"    , NULL    , T_LONG   , -2, false);
  def(_ixor                , "ixor"                , "b"    , NULL    , T_INT    , -1, false);
  def(_lxor                , "lxor"                , "b"    , NULL    , T_LONG   , -2, false);
  def(_iinc                , "iinc"                , "bic"  , "wbiicc", T_VOID   ,  0, false);
  def(_i2l                 , "i2l"                 , "b"    , NULL    , T_LONG   ,  1, false);
  def(_i2f                 , "i2f"                 , "b"    , NULL    , T_FLOAT  ,  0, false);
  def(_i2d                 , "i2d"                 , "b"    , NULL    , T_DOUBLE ,  1, false);
  def(_l2i                 , "l2i"                 , "b"    , NULL    , T_INT    , -1, false);
  def(_l2f                 , "l2f"                 , "b"    , NULL    , T_FLOAT  , -1, false);
  def(_l2d                 , "l2d"                 , "b"    , NULL    , T_DOUBLE ,  0, false);
  def(_f2i                 , "f2i"                 , "b"    , NULL    , T_INT    ,  0, false);
  def(_f2l                 , "f2l"                 , "b"    , NULL    , T_LONG   ,  1, false);
  def(_f2d                 , "f2d"                 , "b"    , NULL    , T_DOUBLE ,  1, false);
  def(_d2i                 , "d2i"                 , "b"    , NULL    , T_INT    , -1, false);
  def(_d2l                 , "d2l"                 , "b"    , NULL    , T_LONG   ,  0, false);
  def(_d2f                 , "d2f"                 , "b"    , NULL    , T_FLOAT  , -1, false);
  def(_i2b                 , "i2b"                 , "b"    , NULL    , T_BYTE   ,  0, false);
  def(_i2c                 , "i2c"                 , "b"    , NULL    , T_CHAR   ,  0, false);
  def(_i2s                 , "i2s"                 , "b"    , NULL    , T_SHORT  ,  0, false);
  def(_lcmp                , "lcmp"                , "b"    , NULL    , T_VOID   , -3, false);
  def(_fcmpl               , "fcmpl"               , "b"    , NULL    , T_VOID   , -1, false);
  def(_fcmpg               , "fcmpg"               , "b"    , NULL    , T_VOID   , -1, false);
  def(_dcmpl               , "dcmpl"               , "b"    , NULL    , T_VOID   , -3, false);
  def(_dcmpg               , "dcmpg"               , "b"    , NULL    , T_VOID   , -3, false);
  def(_ifeq                , "ifeq"                , "boo"  , NULL    , T_VOID   , -1, false);
  def(_ifne                , "ifne"                , "boo"  , NULL    , T_VOID   , -1, false);
  def(_iflt                , "iflt"                , "boo"  , NULL    , T_VOID   , -1, false);
  def(_ifge                , "ifge"                , "boo"  , NULL    , T_VOID   , -1, false);
  def(_ifgt                , "ifgt"                , "boo"  , NULL    , T_VOID   , -1, false);
  def(_ifle                , "ifle"                , "boo"  , NULL    , T_VOID   , -1, false);
  def(_if_icmpeq           , "if_icmpeq"           , "boo"  , NULL    , T_VOID   , -2, false);
  def(_if_icmpne           , "if_icmpne"           , "boo"  , NULL    , T_VOID   , -2, false);
  def(_if_icmplt           , "if_icmplt"           , "boo"  , NULL    , T_VOID   , -2, false);
  def(_if_icmpge           , "if_icmpge"           , "boo"  , NULL    , T_VOID   , -2, false);
  def(_if_icmpgt           , "if_icmpgt"           , "boo"  , NULL    , T_VOID   , -2, false);
  def(_if_icmple           , "if_icmple"           , "boo"  , NULL    , T_VOID   , -2, false);
  def(_if_acmpeq           , "if_acmpeq"           , "boo"  , NULL    , T_VOID   , -2, false);
  def(_if_acmpne           , "if_acmpne"           , "boo"  , NULL    , T_VOID   , -2, false);
  def(_goto                , "goto"                , "boo"  , NULL    , T_VOID   ,  0, false);
  def(_jsr                 , "jsr"                 , "boo"  , NULL    , T_INT    ,  0, false);
  def(_ret                 , "ret"                 , "bi"   , "wbii"  , T_VOID   ,  0, false);
  def(_tableswitch         , "tableswitch"         , ""     , NULL    , T_VOID   , -1, false); // may have backward branches
  def(_lookupswitch        , "lookupswitch"        , ""     , NULL    , T_VOID   , -1, false); // rewriting in interpreter
  def(_ireturn             , "ireturn"             , "b"    , NULL    , T_INT    , -1, true);
  def(_lreturn             , "lreturn"             , "b"    , NULL    , T_LONG   , -2, true);
  def(_freturn             , "freturn"             , "b"    , NULL    , T_FLOAT  , -1, true);
  def(_dreturn             , "dreturn"             , "b"    , NULL    , T_DOUBLE , -2, true);
  def(_areturn             , "areturn"             , "b"    , NULL    , T_OBJECT , -1, true);
  def(_return              , "return"              , "b"    , NULL    , T_VOID   ,  0, true);
  def(_getstatic           , "getstatic"           , "bJJ"  , NULL    , T_ILLEGAL,  1, true );
  def(_putstatic           , "putstatic"           , "bJJ"  , NULL    , T_ILLEGAL, -1, true );
  def(_getfield            , "getfield"            , "bJJ"  , NULL    , T_ILLEGAL,  0, true );
  def(_putfield            , "putfield"            , "bJJ"  , NULL    , T_ILLEGAL, -2, true );
  def(_invokevirtual       , "invokevirtual"       , "bJJ"  , NULL    , T_ILLEGAL, -1, true);
  def(_invokespecial       , "invokespecial"       , "bJJ"  , NULL    , T_ILLEGAL, -1, true);
  def(_invokestatic        , "invokestatic"        , "bJJ"  , NULL    , T_ILLEGAL,  0, true);
  def(_invokeinterface     , "invokeinterface"     , "bJJ__", NULL    , T_ILLEGAL, -1, true);
  def(_invokedynamic       , "invokedynamic"       , "bJJJJ", NULL    , T_ILLEGAL,  0, true );
  def(_new                 , "new"                 , "bkk"  , NULL    , T_OBJECT ,  1, true );
  def(_newarray            , "newarray"            , "bc"   , NULL    , T_OBJECT ,  0, true );
  def(_anewarray           , "anewarray"           , "bkk"  , NULL    , T_OBJECT ,  0, true );
  def(_arraylength         , "arraylength"         , "b"    , NULL    , T_VOID   ,  0, true );
  def(_athrow              , "athrow"              , "b"    , NULL    , T_VOID   , -1, true );
  def(_checkcast           , "checkcast"           , "bkk"  , NULL    , T_OBJECT ,  0, true );
  def(_instanceof          , "instanceof"          , "bkk"  , NULL    , T_INT    ,  0, true );
  def(_monitorenter        , "monitorenter"        , "b"    , NULL    , T_VOID   , -1, true );
  def(_monitorexit         , "monitorexit"         , "b"    , NULL    , T_VOID   , -1, true );
  def(_wide                , "wide"                , ""     , NULL    , T_VOID   ,  0, false);
  def(_multianewarray      , "multianewarray"      , "bkkc" , NULL    , T_OBJECT ,  1, true );
  def(_ifnull              , "ifnull"              , "boo"  , NULL    , T_VOID   , -1, false);
  def(_ifnonnull           , "ifnonnull"           , "boo"  , NULL    , T_VOID   , -1, false);
  def(_goto_w              , "goto_w"              , "boooo", NULL    , T_VOID   ,  0, false);
  def(_jsr_w               , "jsr_w"               , "boooo", NULL    , T_INT    ,  0, false);
  def(_breakpoint          , "breakpoint"          , ""     , NULL    , T_VOID   ,  0, true);

  //  JVM bytecodes  下面这些都是JVM扩展定义的字节码
  //  bytecode               bytecode name           format   wide f.   result tp  stk traps  std code

  def(_fast_agetfield      , "fast_agetfield"      , "bJJ"  , NULL    , T_OBJECT ,  0, true , _getfield       );
  def(_fast_bgetfield      , "fast_bgetfield"      , "bJJ"  , NULL    , T_INT    ,  0, true , _getfield       );
  def(_fast_cgetfield      , "fast_cgetfield"      , "bJJ"  , NULL    , T_CHAR   ,  0, true , _getfield       );
  def(_fast_dgetfield      , "fast_dgetfield"      , "bJJ"  , NULL    , T_DOUBLE ,  0, true , _getfield       );
  def(_fast_fgetfield      , "fast_fgetfield"      , "bJJ"  , NULL    , T_FLOAT  ,  0, true , _getfield       );
  def(_fast_igetfield      , "fast_igetfield"      , "bJJ"  , NULL    , T_INT    ,  0, true , _getfield       );
  def(_fast_lgetfield      , "fast_lgetfield"      , "bJJ"  , NULL    , T_LONG   ,  0, true , _getfield       );
  def(_fast_sgetfield      , "fast_sgetfield"      , "bJJ"  , NULL    , T_SHORT  ,  0, true , _getfield       );

  def(_fast_aputfield      , "fast_aputfield"      , "bJJ"  , NULL    , T_OBJECT ,  0, true , _putfield       );
  def(_fast_bputfield      , "fast_bputfield"      , "bJJ"  , NULL    , T_INT    ,  0, true , _putfield       );
  def(_fast_zputfield      , "fast_zputfield"      , "bJJ"  , NULL    , T_INT    ,  0, true , _putfield       );
  def(_fast_cputfield      , "fast_cputfield"      , "bJJ"  , NULL    , T_CHAR   ,  0, true , _putfield       );
  def(_fast_dputfield      , "fast_dputfield"      , "bJJ"  , NULL    , T_DOUBLE ,  0, true , _putfield       );
  def(_fast_fputfield      , "fast_fputfield"      , "bJJ"  , NULL    , T_FLOAT  ,  0, true , _putfield       );
  def(_fast_iputfield      , "fast_iputfield"      , "bJJ"  , NULL    , T_INT    ,  0, true , _putfield       );
  def(_fast_lputfield      , "fast_lputfield"      , "bJJ"  , NULL    , T_LONG   ,  0, true , _putfield       );
  def(_fast_sputfield      , "fast_sputfield"      , "bJJ"  , NULL    , T_SHORT  ,  0, true , _putfield       );

  def(_fast_aload_0        , "fast_aload_0"        , "b"    , NULL    , T_OBJECT ,  1, true , _aload_0        );
  def(_fast_iaccess_0      , "fast_iaccess_0"      , "b_JJ" , NULL    , T_INT    ,  1, true , _aload_0        );
  def(_fast_aaccess_0      , "fast_aaccess_0"      , "b_JJ" , NULL    , T_OBJECT ,  1, true , _aload_0        );
  def(_fast_faccess_0      , "fast_faccess_0"      , "b_JJ" , NULL    , T_OBJECT ,  1, true , _aload_0        );

  def(_fast_iload          , "fast_iload"          , "bi"   , NULL    , T_INT    ,  1, false, _iload);
  def(_fast_iload2         , "fast_iload2"         , "bi_i" , NULL    , T_INT    ,  2, false, _iload);
  def(_fast_icaload        , "fast_icaload"        , "bi_"  , NULL    , T_INT    ,  0, false, _iload);

  // Faster method invocation.
  def(_fast_invokevfinal   , "fast_invokevfinal"   , "bJJ"  , NULL    , T_ILLEGAL, -1, true, _invokevirtual   );

  def(_fast_linearswitch   , "fast_linearswitch"   , ""     , NULL    , T_VOID   , -1, false, _lookupswitch   );
  def(_fast_binaryswitch   , "fast_binaryswitch"   , ""     , NULL    , T_VOID   , -1, false, _lookupswitch   );

  def(_return_register_finalizer , "return_register_finalizer" , "b"    , NULL    , T_VOID   ,  0, true, _return);

  def(_invokehandle        , "invokehandle"        , "bJJ"  , NULL    , T_ILLEGAL, -1, true, _invokevirtual   );

  def(_fast_aldc           , "fast_aldc"           , "bj"   , NULL    , T_OBJECT,   1, true,  _ldc   );
  def(_fast_aldc_w         , "fast_aldc_w"         , "bJJ"  , NULL    , T_OBJECT,   1, true,  _ldc_w );

  def(_shouldnotreachhere  , "_shouldnotreachhere" , "b"    , NULL    , T_VOID   ,  0, false);

  // platform specific JVM bytecodes
  // 针对JVM字节码的平台特性操作,默认这个函数未做实现
  pd_initialize();

  // compare can_trap information for each bytecode with the
  // can_trap information for the corresponding base bytecode
  // (if a rewritten bytecode can trap, so must the base bytecode)
  #ifdef ASSERT
    { for (int i = 0; i < number_of_codes; i++) {
        // 遍历检查定义后的字节码
        if (is_defined(i)) { // 判断是不是都定义了
          Code code = cast(i); // 类型转成枚举Code
          Code java = java_code(code);
          // 通过前面的def定义函数可以了解到,这里的code和java是同一个东西,如果不同,那就是错误
          if (can_trap(code) && !can_trap(java))
            // 打印出错信息的文件和代码行数
            fatal(err_msg("%s can trap => %s can trap, too", name(code),
                          name(java)));
        }
      }
    }
  #endif

  // 标记初始化成功,防止重复初始化
  _is_initialized = true;
}

文章来源:https://blog.csdn.net/zhang527294844/article/details/135462585
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