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Simplify symbol table: now a stack with locals on top hiding globals … #28

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Simplify symbol table: now a stack with locals on top hiding globals … #28

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e6f5253
Simplify symbol table: now a stack with locals on top hiding globals …
tfisher98 Mar 7, 2017
7fe448a
Fix bugs in modified symbol table
tfisher98 Mar 8, 2017
1910e0c
Improve comments and tighten code slightly.
tfisher98 Mar 8, 2017
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49 changes: 23 additions & 26 deletions c4.c
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,8 @@ char *p, *lp, // current position in source code

int *e, *le, // current position in emitted code
*id, // currently parsed identifier
*sym, // symbol table (simple list of identifiers)
*sym, // symbol table (stack of identifiers, locals on top)
*symtop, // next empty entry in symbol table
tk, // current token
ival, // current token value
ty, // current expression type
Expand All @@ -42,7 +43,7 @@ enum { LEA ,IMM ,JMP ,JSR ,BZ ,BNZ ,ENT ,ADJ ,LEV ,LI ,LC ,SI ,SC ,PSH ,
enum { CHAR, INT, PTR };

// identifier offsets (since we can't create an ident struct)
enum { Tk, Hash, Name, Class, Type, Val, HClass, HType, HVal, Idsz };
enum { Tk, Hash, Name, Class, Type, Val, Idsz };

void next()
{
Expand Down Expand Up @@ -70,15 +71,16 @@ void next()
pp = p - 1;
while ((*p >= 'a' && *p <= 'z') || (*p >= 'A' && *p <= 'Z') || (*p >= '0' && *p <= '9') || *p == '_')
tk = tk * 147 + *p++;
tk = (tk << 6) + (p - pp);
id = sym;
while (id[Tk]) {
if (tk == id[Hash] && !memcmp((char *)id[Name], pp, p - pp)) { tk = id[Tk]; return; }
id = id + Idsz;
symtop[Hash] = ival = (tk << 6) + (p - pp);
symtop[Tk] = tk = Id;
symtop[Name] = (int)pp;
symtop[Class] = 0;
id = symtop - Idsz;
while (id >= sym) {
if (ival == id[Hash] && !memcmp((char *)id[Name], pp, p - pp)) { tk = id[Tk]; return; }
id = id - Idsz;
}
id[Name] = (int)pp;
id[Hash] = tk;
tk = id[Tk] = Id;
id = symtop; symtop = symtop + Idsz;
return;
}
else if (tk >= '0' && tk <= '9') {
Expand Down Expand Up @@ -343,7 +345,7 @@ int main(int argc, char **argv)
if ((fd = open(*argv, 0)) < 0) { printf("could not open(%s)\n", *argv); return -1; }

poolsz = 256*1024; // arbitrary size
if (!(sym = malloc(poolsz))) { printf("could not malloc(%d) symbol area\n", poolsz); return -1; }
if (!(symtop = sym = malloc(poolsz))) { printf("could not malloc(%d) symbol area\n", poolsz); return -1; }
if (!(le = e = malloc(poolsz))) { printf("could not malloc(%d) text area\n", poolsz); return -1; }
if (!(data = malloc(poolsz))) { printf("could not malloc(%d) data area\n", poolsz); return -1; }
if (!(sp = malloc(poolsz))) { printf("could not malloc(%d) stack area\n", poolsz); return -1; }
Expand Down Expand Up @@ -400,6 +402,7 @@ int main(int argc, char **argv)
next();
id[Type] = ty;
if (tk == '(') { // function
t = symtop;
id[Class] = Fun;
id[Val] = (int)(e + 1);
next(); i = 0;
Expand All @@ -410,9 +413,10 @@ int main(int argc, char **argv)
while (tk == Mul) { next(); ty = ty + PTR; }
if (tk != Id) { printf("%d: bad parameter declaration\n", line); return -1; }
if (id[Class] == Loc) { printf("%d: duplicate parameter definition\n", line); return -1; }
id[HClass] = id[Class]; id[Class] = Loc;
id[HType] = id[Type]; id[Type] = ty;
id[HVal] = id[Val]; id[Val] = i++;
if (id[Class] == Glo) { id = symtop; symtop = symtop + Idsz; }
id[Class] = Loc;
id[Type] = ty;
id[Val] = i++;
next();
if (tk == ',') next();
}
Expand All @@ -428,9 +432,10 @@ int main(int argc, char **argv)
while (tk == Mul) { next(); ty = ty + PTR; }
if (tk != Id) { printf("%d: bad local declaration\n", line); return -1; }
if (id[Class] == Loc) { printf("%d: duplicate local definition\n", line); return -1; }
id[HClass] = id[Class]; id[Class] = Loc;
id[HType] = id[Type]; id[Type] = ty;
id[HVal] = id[Val]; id[Val] = ++i;
if (id[Class] == Glo) { id = symtop; symtop = symtop + Idsz; }
id[Class] = Loc;
id[Type] = ty;
id[Val] = ++i;
next();
if (tk == ',') next();
}
Expand All @@ -439,15 +444,7 @@ int main(int argc, char **argv)
*++e = ENT; *++e = i - loc;
while (tk != '}') stmt();
*++e = LEV;
id = sym; // unwind symbol table locals
while (id[Tk]) {
if (id[Class] == Loc) {
id[Class] = id[HClass];
id[Type] = id[HType];
id[Val] = id[HVal];
}
id = id + Idsz;
}
symtop = t; // unwind symbol table locals
}
else {
id[Class] = Glo;
Expand Down