void block(unsigned long fsys) {
long tx0; // initial table index
long cx0; // initial code index
long tx1; // save current table index before processing nested procedures
long dx1; // save data allocation index
dx = 3; tx0 = tx; table[tx].addr = cx; gen(jmp, 0, 0);
if (lev > levmax) {
error(32);
}
do {
if (sym == constsym) {
getsym();
do {
constdeclaration();
while (sym == comma) {
getsym(); constdeclaration();
}
if (sym == semicolon) {
getsym();
}
else {
error(5);
}
} while (sym == ident);
}
if (sym == varsym) {
getsym();
do {
vardeclaration();
while (sym == comma) {
getsym(); vardeclaration();
}
if (sym == semicolon) {
getsym();
}
else {
error(5);
}
} while (sym == ident);
}
while (sym == procsym) {
getsym();
if (sym == ident) {
enter(proc); getsym();
}
else {
error(4);
}
if (sym == semicolon) {
getsym();
}
else {
error(5);
}
lev = lev + 1; tx1 = tx; dx1 = dx;
block(fsys | semicolon);
lev = lev - 1; tx = tx1; dx = dx1;
if (sym == semicolon) {
getsym();
//printf("this sym is %d\n",sym);
test(statbegsys | ident | procsym, fsys, 6);
}
else {
error(5);
}
}
test(statbegsys | ident, declbegsys, 7);
} while (sym&declbegsys);
code[table[tx0].addr].a = cx;
table[tx0].addr = cx; // start addr of code
cx0 = cx; gen(Int, 0, dx);
statement(fsys | semicolon | endsym);
gen(opr, 0, 0); // return
test(fsys, 0, 8);
listcode(cx0);
}
void block(unsigned long fsys)
{
long tx0; // 层初始符号表指针
long cx0; // 层初始code指针
// long tx1; // 调用前保留现场
long dx1;
dx = 3;
tx0 = tx;
table[tx].addr = cx;
gen(jmp, 0, 0);
if (lev>levmax)
{
error(32);
}
do
{
if (sym == constsym)
{
getsym();
constdeclaration(tx0);
while (sym == comma)
{
getsym();
constdeclaration(tx0);
}
if (sym == semicolon)
{
getsym();
}
else
{
error(5);
}
}
if (sym == varsym)
{
getsym();
vardeclaration(tx0);
while (sym == comma)
{
getsym();
vardeclaration(tx0);
}
if (sym == semicolon)
{
getsym();
}
else
{
error(5);
}
}
while (sym == procsym)
{
getsym();
if (sym == ident)
{
enter(proc,tx0);
getsym();
}
else
{
error(4);
}
if (sym == semicolon)
{
getsym();
}
else
{
error(5);
}
lev = lev + 1;
dx1 = dx;
block(fsys | semicolon);
lev = lev - 1;
dx = dx1;//问题
if (sym == semicolon)
{
getsym();
}
else
{
error(5);
if (sym == period)
{
getsym();
}
}
}
test(beginsym, statbegsys | ident| declbegsys, 7);//TODO 1
} while (sym&declbegsys);
code[table[tx0].addr].a = cx;//把前面生成的跳转语句的跳转位置改成当前位置
table[tx0].addr = cx;
cx0 = cx;
gen(Int, 0, dx);
statement(fsys | semicolon | endsym);
gen(opr, 0, 0); // return
test(fsys, 0, 8);
// listcode(cx0);
}
void block(unsigned long long fsys)
{
long tx0; // initial table index
long cx0; // initial code index
long tx1; // save current table index before processing nested procedures
long dx1; // save data allocation index
dx=3;
// 地址寄存器给出每层局部量当前已分配到的相对位置
// 置初始值为 3 的原因是：每一层最开始的位置有三个空间用于存放
// 静态链 SL、动态链 DL 和 返回地址 RA
tx0=tx; // 记录本层开始时符号表的位置
table[tx].addr=cx; // 符号表记下当前层代码的开始地址
gen(jmp,0,0); // block开始时首先写下一句跳转指令
// 地址到后面再补
if(lev>levmax)
{
error(32);
}
do
{
if(sym==constsym) // 常数定义
{
getsym();
do
{
constdeclaration();
while(sym==comma)
{
getsym(); constdeclaration();
}
if(sym==semicolon)
{
getsym();
}
else
{
error(5);
}
} while(sym==ident);
}
if(sym==varsym)
{
getsym();
do
{
vardeclaration();
} while(sym!=beginsym&&sym!=procsym);
}
while(sym==procsym)
{
getsym();
if(sym==ident)
{
enter(proc); getsym();
}
else
{
error(4);
}
if(sym==semicolon)
{
getsym();
}
else
{
error(5);
}
lev=lev+1; tx1=tx; dx1=dx;
block(fsys|semicolon);
lev=lev-1; tx=tx1; dx=dx1;
if(sym==semicolon)
{
getsym();
test(statbegsys|ident|procsym,fsys,6);
}
else
{
error(5);
}
}
test(statbegsys|ident,declbegsys,7);
} while(sym&declbegsys);
if (sym==beginsym)
{
code[table[tx0].addr].a=cx;// 把block开头写下的跳转指令的地址补上
table[tx0].addr=cx; // tx0的符号表存的是当前block的参数
cx0=cx;
gen(Int,0,dx);
getsym();
statement(fsys|semicolon|endsym);
while(sym==semicolon||(sym&statbegsys))
{
if(sym==semicolon) getsym();
else error(10);
statement(fsys|semicolon|endsym);
}
if(sym==endsym) getsym();
else error(17);
gen(opr,0,0); // block结束，加上一句返回指令
test(fsys,0,8);
//listcode(cx0);
} else error(37);
}
