想请教下JamVM的JIT编译器部分，patchExternalJumps函数里面跳转到外部块的疑惑？
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sundreams2009
2013-12-09
void patchExternalJumps(TestCodeBlock *test_block, CodeBlockHeader *new_block) {
BasicBlock *patchers = test_block->patchers;
char *test_addr = (char*)(test_block + 1);
char *new_addr = (char*)(new_block + 1);
for(; patchers; patchers = patchers->u.patch.next) {
Instruction *target = patchers->start[patchers->length - 1].operand.pntr;
char *handler = (char*)target->handler;
if(handler < min_entry_point || handler > max_entry_point) {
char *addr = patchers->u.patch.addr - test_addr + new_addr;
if(GEN_REL_JMP(handler, addr, goto_len)) {
TRACE("Patched branch to external block %p\n", handler);
}
}
}
}
if(handler < min_entry_point || handler > max_entry_point)这句话不太理解，外部块可能会是什么地方？刚大概看了下这部分的代码，感觉handler就是取自handler表中的，这个判断条件应该肯定能满足的吧，我搜了下对operand.pntr赋值的地方，就是在prepare函数里面进行了赋值，其他地方看着不像，这里的外部块应该是其他的拼凑的代码块吧？ |
