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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