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bc.b
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main(argc, argv) {
extrn printf, xprintf;
extrn fout, fin, nerror, eof;
printf = xprintf; /* hack */
if(argc<3) {
error("Arg count");
exit(1);
}
if((fin=open(argv[1],0))<0) {
error("Can't find %s", argv[1]);
exit(1);
}
if((fout=creat(argv[2], 0664))<0) {
error("Can't create %s", argv[2]);
exit(1);
}
keyw("auto", Auto);
keyw("extrn", Extern);
keyw("goto", Goto);
keyw("return", Return);
keyw("if", If);
keyw("while", While);
keyw("else", Else);
keyw("switch", Switch);
keyw("case", Case);
keyw("break", Break);
keyw("default", Default);
while(!eof) {
extdef();
enddef();
}
exit(nerror!=0);
}
keyw(s, t) {
extrn namsiz, symbuf;
auto n, i, j, c, sp;
n = namsiz;
i = j = 0;
while(n--) {
lchar(symbuf, i++, c = char(s, j++));
if(c == '*e')
j--;
}
sp = lookup();
sp[0] = KeyType;
sp[1] = t;
}
extdef() {
extrn csym, cval, loc;
auto t, cs, i, n;
if((t=token()) == 0 | t == Semi)
return;
if(t != Name)
goto syntax;
csym[0] = Extern;
cs = csym+2;
printf("g %p*n", cs);
switch(t = token()) {
/* Function */
case LParen:
printf("d*nl %p*nv 1f*n", cs);
func();
return;
/* Single word */
case Semi:
printf("b*nl %p*ns 1*n", cs);
return;
case Const:
printf("d*nl %p*nw %o*n", cs, cval);
semi:
if((t = token()) != Semi)
goto syntax;
return;
case String:
printf("d*nf %p*nv l%d*n", cs, cval);
goto semi;
case Name:
csym[0] = Extern;
printf("d*nf %p*nv %p*n", cs, csym+2);
goto semi;
/* Vector */
case LBrack:
n = 0;
if((t = token()) == Const) {
n = cval;
t = token();
}
if(t != RBrack)
goto syntax;
printf("d*nf %p*nv 1f*n", cs);
if((t = token()) == Semi) {
printf("b*nl 1*ns %d*n", n);
return;
}
printf("l 1*n");
while(t == Const | t == String | t == Name) {
switch(t) {
case Const:
printf("w %o*n", cval);
break;
case String:
i = loc++;
printf("d*nf l%d*nv l%d*n", i, cval);
break;
case Name:
i = loc++;
csym[0] = Extern;
printf("f l%d*nv %p*n*n", i, csym+2);
break;
}
n--;
if((t=token()) == Semi)
goto done;
if(t != Comma)
goto syntax;
t = token();
}
goto syntax;
done:
if(n > 0)
printf("s %d*n", n);
return;
case 0:
return;
}
syntax:
error("Definition syntax");
errflush(t);
}
setstack() {
extrn pop, stksym, dirty;
if(dirty) {
printf("*ts l%d*n", stksym);
pop = dirty = 0;
}
}
func() {
extrn loc, stksym, stack, dirty;
auto s;
/* Stack layout:
* auton
* ....
* auto0
* argn
* 3 ....
* 2 arg0
* 1 return address
* 0 old fp <- fp
*/
stack = 2;
stksym = loc++;
printf("t*nl 1*n", stksym);
decl(Param);
dirty = 1;
stmt();
printf("*tn11*nq l%d,%d*n", stksym, stack);
}
enddef() {
extrn loc, stksym, stack, dirty, symsz, symtab, stablen, symused;
auto s;
s = symtab;
while(s < &symtab[stablen]) {
if(s[2])
if(s[0] == 0)
error("%p undefined", s+2);
if(s[0] != KeyType) {
s[2] = 0;
symused--;
}
s =+ symsz;
}
printf("*n");
}
decl(kw) {
extrn csym, cval, stack;
auto t;
while((t = token()) == Name) {
if(csym[0] != 0)
error("%p redeclared", csym+2);
csym[0] = kw;
if(kw == Param | kw == Auto) {
csym[0] = Auto;
csym[1] = stack;
stack++;
}
t = token();
if(kw == Auto) {
/* Two ways to declare vectors */
if(t == LBrack) {
printf("*ty %d*n", csym[1]);
if((t = token()) == Const) {
stack =+ cval;
t = token();
}
if(t != RBrack)
goto syntax;
t = token();
} else if(t == Const) {
printf("*ty %d*n", csym[1]);
stack =+ cval;
t = token();
}
}
if(t != Comma)
break;
}
if(kw == Param & t == RParen |
kw != Param & t == Semi)
return;
syntax:
error("Declaration syntax");
errflush(t);
}
stmt() {
extrn pop, stksym, dirty, loc, csym, cval, eof, peekc, peektok,
brklab, deflab, swp, swtab, swsiz, nsw;
auto t, l1, l2, l3, p, sswp, snsw;
next:
switch(t = token()) {
case 0:
error("Unexpected EOF");
return;
case RBrace:
peektok = t;
case Semi:
return;
case LBrace:
while((t = token()) != RBrace) {
if(eof) {
error("Expected }");
break;
}
peektok = t;
stmt();
}
return;
case Keyword:
switch(cval) {
case Auto:
case Extern:
decl(cval);
goto next;
case Return:
if((peektok = token()) == LParen) {
gen(pexpr(), 0);
printf("*tn7*n");
goto semi;
}
printf("*tn11*n");
goto semi;
case Goto:
gen(expr(), 0);
printf("*tn6*n");
goto semi;
case If:
gen(pexpr(), l1=loc++);
stmt();
if((t=token()) == Keyword & cval == Else) {
jmp(l2=loc++);
label(l1);
stmt();
label(l2);
} else {
peektok = t;
label(l1);
}
return;
case While:
l1 = brklab;
brklab = loc++;
label(l2 = loc++);
gen(pexpr(), brklab);
stmt();
jmp(l2);
label(brklab);
brklab = l1;
return;
case Switch:
l1 = brklab;
brklab = loc++;
gen(pexpr(), 0);
printf("*tz l%d*n", l2=loc++);
sswp = swp;
snsw = nsw;
if(swp == 0)
swp = swtab;
p = swp;
nsw = 0;
l3 = deflab;
deflab = 0;
stmt();
jmp(brklab);
if(deflab == 0)
deflab = brklab;
/* PDP-11 runtime can't handle this */
if(nsw == 0)
error("No cases in switch");
printf("l l%d*nw %o*n", l2, nsw);
while(nsw--) {
printf("w %o*nv l%d*n", p[1], p[0]);
p =+ 2;
}
if(deflab != brklab)
jmp(deflab);
label(brklab);
deflab = l3;
swp = sswp;
nsw = snsw;
brklab = l1;
return;
case Case:
if((t = token()) != Const)
goto syntax;
if((t = token()) != Colon)
goto syntax;
if(swp == 0) {
error("Not in switch");
goto next;
}
if(swp >= swtab+swsiz) {
error("Switch table overflow");
} else {
*swp++ = loc;
*swp++ = cval;
nsw++;
label(loc++);
}
goto next;
case Break:
if(brklab == 0)
error("Nothing to break from");
jmp(brklab);
goto semi;
case Default:
if(swp == 0)
error("Default not in switch");
if(deflab)
error("Default case already defined");
if((t = token()) != Colon)
goto syntax;
label(deflab = loc++);
goto next;
}
error("Unknown keyword");
goto syntax;
case Name:
if(peekc == ':') {
peekc = 0;
if(csym[0] != 0) {
error("Redefinition");
goto next;
}
csym[0] = Intern;
if(csym[1] == 0)
csym[1] = loc++;
printf("d*nl l%d*nv 1f*nt*nl 1*n", csym[1]);
dirty = 1;
goto next;
}
}
/* Expression statement */
peektok = t;
gen(expr(), 0);
semi:
if((t = token()) == Semi)
return;
syntax:
error("Statement syntax");
errflush(t);
goto next;
}
gen(x, l) {
extrn pop;
setstack();
if(l == 0)
genxpr(x, 0);
else
cjmp(x, l);
pop = 1;
}
label(n) printf("l l%d*n", n);
jmp(n) printf("*tt l%d*n", n);
/* jump to label l if condition is false,
* fall through otherwise. */
cjmp(x, l) {
extrn pop, loc;
auto l1, l2;
if(x == 0) /* there has been a parse error */
return;
switch(x[0]) {
case And:
cjmp(x[1], l);
cjmp(x[2], l);
return;
case Or:
cjmp(x[1], l1=loc++);
jmp(l2=loc++);
label(l1);
cjmp(x[2], l);
label(l2);
return;
case Not:
cjmp(x[1], l1=loc++);
jmp(l);
label(l1);
}
genxpr(x, 0);
pop = 1;
printf("*tf l%d*n", l);
}
pexpr() {
auto t, n;
if((t = token()) != LParen)
goto syntax;
n = expr();
if((t = token()) != RParen)
goto syntax;
return(n);
syntax:
error("Statement syntax");
errflush(t);
return(0);
}
/* Parse an expression into a tree */
expr() {
extrn csym, cval, peekc, peektok, loc, opdope, cp, cmst,
space, ospace;
auto op, opst[20], pp, prst[20], andflg, o, p, os;
space = ospace;
op = opst;
pp = prst;
cp = cmst;
/* mark bottom of stack */
*op = 0;
*pp = 6; /* why exactly was this chosen? */
andflg = 0;
advanc:
switch(o = token()) {
/* operands */
case Name:
/* Have to be very careful here because token()
* can peek a token itself after a '='.
* In particular it can overwrite csym then.
* e.g. 'a =b' will return '=' and peek b,
* overwriting a's csym. */
if(csym[0] == 0) {
/* this is the best we can do to recognize a call */
if(peekc == '(')
csym[0] = Extern;
else
/* otherwise assume it's a label */
if(csym[1] == 0)
csym[1] = loc++;
}
*cp++ = block(1, o, csym);
goto tand;
case Const:
case String:
*cp++ = block(1, o, cval);
tand:
if(andflg)
goto syntax;
andflg = 1;
goto advanc;
/* unary operators */
case Preinc:
case Predec:
if(andflg)
o =+ 2;
goto oponst;
case Not:
if(andflg)
goto syntax;
goto oponst;
case Minus:
if(andflg)
andflg = 0;
else
o = Neg;
goto oponst;
case And:
case Times:
if(andflg)
andflg = 0;
else if(o == And)
o = Amp;
else
o = Star;
goto oponst;
/* special tokens */
case LParen:
if(andflg) {
/* function call */
if((o=token()) == RParen) {
/* empty call */
o = MCall;
} else {
peektok = o;
o = Call;
andflg = 0;
}
}
goto oponst;
case RParen:
case RBrack:
if(!andflg)
goto syntax;
goto oponst;
}
/* binary operators */
if(!andflg)
goto syntax;
andflg = 0;
oponst:
p = (opdope[o]>>6) & 077;
/* new op binds tighter, so push onto stack */
if(p > *pp | p == *pp & (opdope[o]&2)!=0) {
/* Make parens (and calls) such low precedence
* that only closing paren can pop. */
switch(o) {
case LParen:
case LBrack:
case Call:
p = 04;
}
if(op >= opst+20) {
error("expression overflow");
exit(1);
}
*++op = o;
*++pp = p;
goto advanc;
}
/* new op binds less tightly, so pop off stack */
--pp;
switch(os = *op--) {
case 0:
peektok = o;
return(*--cp);
case MCall:
*cp++ = 0;
os = Call;
break;
case Call:
if(o != RParen)
goto syntax;
build(os);
goto advanc;
case LParen:
if(o != RParen)
goto syntax;
goto advanc;
case LBrack:
if(o != RBrack)
goto syntax;
build(Vector);
goto advanc;
}
build(os);
goto oponst;
syntax:
error("Expression syntax");
errflush(o);
return(0);
}
block(n, op, p1, p2) {
extrn space, ossiz, ospace;
auto p, ap;
p = space;
ap = &op;
n++;
if(space+n >= ospace+ossiz) {
error("Expression overflow");
exit(1);
}
while(n--)
*space++ = *ap++;
return(p);
}
/* Combine operands on stack to a new tree node.
* Also simplify somewhat and check semantics here. */
build(op) {
extrn cp, opdope;
auto p1, p2;
/* convert a[b] to *(a+b) so we can take lvalue */
if(op == Vector) {
build(Plus);
op = Star;
}
if((opdope[op] & 1) != 0)
p2 = *--cp;
p1 = *--cp;
switch(op) {
case Quest:
if(p2[0] != Colon) {
error(": Expected");
return;
}
break;
case Neg:
if(p1[0] == Const) {
p1[1] = -p1[1];
*cp++ = p1;
return;
}
break;
case Star:
if(p1[0] == Amp) {
*cp++ = p1[1];
return;
}
break;
case Amp:
if(p1[0] == Star) {
*cp++ = p1[1];
return;
}
if(p1[0] != Name) {
error("Illegal lvalue");
return;
}
}
if((opdope[op] & 4)!=0)
if(p1[0] != Star & p1[0] != Name) {
error("Illegal lvalue");
return;
}
if((opdope[op] & 1) != 0)
*cp++ = block(2, op, p1, p2);
else
*cp++ = block(1, op, p1);
}
genxpr(x, lv) {
extrn opdope, pop, loc;
auto op, p1, p2, l1, l2;
if(x == 0) /* there has been a parse error */
return;
op = x[0];
p1 = x[1];
p2 = x[2];
switch(op) {
case Name:
case Const:
case String:
genleaf(x, lv);
return;
case Amp:
genleaf(p1, 1); /* p1 can only be Name */
return;
case Star:
if(lv) {
genxpr(p1, 0);
return;
}
/* turn *(a+b) back to a[b] */
if(p1[0] == Plus) {
p1[0] = Vector;
genxpr(p1, 0);
return;
}
break;
case Call:
genxpr(p1, 0);
if(p2 == 0) {
printf("*tn1*n");
return;
}
printf("*tn2*n");
while(p2[0] == Comma) {
genxpr(p2[1], 0);
p2 = p2[2];
}
genxpr(p2, 0);
printf("*tn3*n");
return;
case Comma:
while(x[0] == Comma) {
genxpr(x[1], 0);
x = x[2];
pop = 1;
}
genxpr(x, 0);
return;
case Quest:
cjmp(p1, l1=loc++);
pop = 1;
genxpr(p2[1], lv);
jmp(l2=loc++);
label(l1);
pop = 1;
genxpr(p2[2], lv);
label(l2);
return;
}
genxpr(p1, (opdope[op]&4)!=0);
if((opdope[op]&1)!=0)
genxpr(p2, 0);
if(op < Vector)
error("UNKNOWN OP %d", op);
else if(op == Vector)
printf("*tn4*n");
else if(op <= Div)
printf("*tb%o*n", op-Assign+1);
else if(op <= ADiv)
printf("*tb%o*n", op-AOr+0102);
else if(op <= Postdec)
printf("*tu%o*n", op-Amp+1);
}
genleaf(x, lv) {
extrn pop;
auto s;
putchar('*t');
if(pop) {
putchar('i');
pop = 0;
}
switch(x[0]) {
case Name:
s = x[1];
if(lv)
putchar('v');
switch(s[0]) {
case Extern:
printf("x %p*n", s+2);
return;
case 0: /* undefined label */
case Intern:
printf("x l%d*n", s[1]);
return;
case Auto:
printf("a %d*n", s[1]);
return;
}
error("invalid type*n");
exit(1);
case Const:
printf("c %o*n", x[1]);
return;
case String:
printf("vx l%d*n", x[1]);
return;
}
}
errflush(t) {
extrn peektok;
while(t != Semi & t != LBrace & t != RBrace)
t = token();
peektok = t;
}
/*
* Lexical analysis
*/
lookup() {
extrn symbuf, nwps, symtab, stabsz, stablen, symused, symsz;
auto i, j, np, sp, rp;
i = 0;
sp = symbuf;
j = nwps;
while(j--)
i =+ *sp++;
if(i < 0)
i = -i;
i =% stabsz;
i =* symsz;
while(*(np = &symtab[i+2])) {
sp = symbuf;
j = nwps;
while(j--)
if(*np++ != *sp++)
goto no;
return(&symtab[i]);
no:
if((i =+ symsz) >= stablen)
i = 0;
}
if(++symused >= stabsz) {
error("Symbol table overflow");
exit(1);
}
rp = np = &symtab[i];
sp = symbuf;
*np++ = 0;
*np++ = 0;
j = nwps;
while(j--)
*np++ = *sp++;
return(rp);
}
token() {
extrn peektok, eof, ctab;
auto c;
next:
if(peektok >= 0) {
c = peektok;
peektok = -1;
return(c);
}
c = getchr();
if(eof)
return(0);
if(c >= 128) {
error("unknown char <%c>", c);
goto next;
}
switch(ctab[c]) {
case Space:
goto next;
case Plus:
return(subseq('+', Plus, Preinc));
case Minus:
return(subseq('-', Minus, Predec));
case Not:
return(subseq('=', Not, Neq));
case Less:
if(subseq('<', 0, 1))
return(LShift);
return(subseq('=', Less, Leq));
case Greater:
if(subseq('>', 0, 1))
return(RShift);
return(subseq('=', Greater, Geq));
case Assign:
/* First handle ==, === to avoid recursion later */
if((c = getchr()) == '=')
return(subseq('=', Eq, AEq));
/* NB: does not handle comments! */
if(ctab[c] == Space)
return(Assign);
ungetchr(c);
/* BUG: this is a big kludge! */
c = token();
if(c >= Or & c <= Div)
return(c - Or + AOr);
if(peektok >= 0) error("OVERWRITING peeked token (%o %o)", peektok, c);
peektok = c;
return(Assign);
case Div:
if(subseq('**', 1, 0))
return(Div);
/* find end of comment */
while(1) {
c = getchr();
if(eof) {
error("Unterminated comment");
return(0);
}
if(c == '**') {
c = getchr();
if(c == '/')
goto next;
}
}
case Digit:
ungetchr(c);
return(number());
case Letter:
ungetchr(c);
return(symbol());
case SQuote:
return(getcc());
case DQuote:
return(getstr());
default:
return(ctab[c]);
}
return(0);
}
subseq(c,a,b) {
auto chr;
if((chr = getchr()) == c)
return(b);
ungetchr(chr);
return(a);
}
getstr() {
extrn cval, loc;
auto c, i, buf;
printf("a*nl l%d*n", cval=loc++);
i = 0;
buf = 0;
while((c = mapch('"')) >= 0) {
lchar(&buf, i++, c);
if(i == NCPW) {
printf("w %o*n", buf);
buf = 0;
i = 0;
}
}
printf("w %o*nt*n", buf);
return(String);
}
getcc() {
extrn cval;
auto c, i;