struct Fn {
Blk *start; // start block, Blk::link 构成了 Blk 链表
Tmp *tmp;
Con *con;
Mem *mem;
int ntmp;
int ncon;
int nmem;
uint nblk;
int retty; /* index in typ[], -1 if no aggregate return */
Ref retr;
Blk **rpo; // reverse post order
bits reg;
int slot;
int salign;
char vararg;
char dynalloc;
char leaf;
char name[NString];
Lnk lnk;
};