sub.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

#include	"cc.h"

Node*
new(int t, Node *l, Node *r)
{
	Node *n;

	n = alloc(sizeof(*n));
	n->op = t;
	n->left = l;
	n->right = r;
	if(l && t != OGOTO)
		n->lineno = l->lineno;
	else if(r)
		n->lineno = r->lineno;
	else
		n->lineno = lineno;
	newflag = 1;
	return n;
}

Node*
new1(int o, Node *l, Node *r)
{
	Node *n;

	n = new(o, l, r);
	n->lineno = nearln;
	return n;
}

void
prtree(Node *n, char *s)
{

	print(" == %s ==\n", s);
	prtree1(n, 0, 0);
	print("\n");
}

void
prtree1(Node *n, int d, int f)
{
	int i;

	if(f)
	for(i=0; i<d; i++)
		print("   ");
	if(n == Z) {
		print("Z\n");
		return;
	}
	if(n->op == OLIST) {
		prtree1(n->left, d, 0);
		prtree1(n->right, d, 1);
		return;
	}
	d++;
	print("%O", n->op);
	i = 3;
	switch(n->op)
	{
	case ONAME:
		print(" \"%F\"", n);
		print(" %ld", n->xoffset);
		i = 0;
		break;

	case OINDREG:
		print(" %ld(R%d)", n->xoffset, n->reg);
		i = 0;
		break;

	case OREGISTER:
		if(n->xoffset)
			print(" %ld+R%d", n->xoffset, n->reg);
		else
			print(" R%d", n->reg);
		i = 0;
		break;

	case OSTRING:
		print(" \"%s\"", n->cstring);
		i = 0;
		break;

	case OLSTRING:
		print(" \"%S\"", n->rstring);
		i = 0;
		break;

	case ODOT:
	case OELEM:
		print(" \"%F\"", n);
		break;

	case OCONST:
		if(typefd[n->type->etype])
			print(" \"%.8e\"", n->fconst);
		else
			print(" \"%lld\"", n->vconst);
		i = 0;
		break;
	}
	if(n->addable != 0)
		print(" <%d>", n->addable);
	if(n->type != T)
		print(" %T", n->type);
	if(n->complex != 0)
		print(" (%d)", n->complex);
	print(" %L\n", n->lineno);
	if(i & 2)
		prtree1(n->left, d, 1);
	if(i & 1)
		prtree1(n->right, d, 1);
}

Type*
typ(int et, Type *d)
{
	Type *t;

	t = alloc(sizeof(*t));
	t->etype = et;
	t->link = d;
	t->down = T;
	t->sym = S;
	t->width = ewidth[et];
	t->offset = 0;
	t->shift = 0;
	t->nbits = 0;
	t->garb = 0;
	return t;
}

Type*
copytyp(Type *t)
{
	Type *nt;

	nt = typ(TXXX, T);
	*nt = *t;
	return nt;
}

Type*
garbt(Type *t, long b)
{
	Type *t1;

	if(b & BGARB) {
		t1 = copytyp(t);
		t1->garb = simpleg(b);
		return t1;
	}
	return t;
}

int
simpleg(long b)
{

	b &= BGARB;
	switch(b) {
	case BCONSTNT:
		return GCONSTNT;
	case BVOLATILE:
		return GVOLATILE;
	case BVOLATILE|BCONSTNT:
		return GCONSTNT|GVOLATILE;
	}
	return GXXX;
}

int
simplec(long b)
{

	b &= BCLASS;
	switch(b) {
	case 0:
	case BREGISTER:
		return CXXX;
	case BAUTO:
	case BAUTO|BREGISTER:
		return CAUTO;
	case BEXTERN:
		return CEXTERN;
	case BEXTERN|BREGISTER:
		return CEXREG;
	case BSTATIC:
		return CSTATIC;
	case BTYPEDEF:
		return CTYPEDEF;
	case BTYPESTR:
		return CTYPESTR;
	}
	diag(Z, "illegal combination of classes %Q", b);
	return CXXX;
}

Type*
simplet(long b)
{

	b &= ~BCLASS & ~BGARB;
	switch(b) {
	case BCHAR:
	case BCHAR|BSIGNED:
		return types[TCHAR];

	case BCHAR|BUNSIGNED:
		return types[TUCHAR];

	case BSHORT:
	case BSHORT|BINT:
	case BSHORT|BSIGNED:
	case BSHORT|BINT|BSIGNED:
		return types[TSHORT];

	case BUNSIGNED|BSHORT:
	case BUNSIGNED|BSHORT|BINT:
		return types[TUSHORT];

	case 0:
	case BINT:
	case BINT|BSIGNED:
	case BSIGNED:
		return types[TINT];

	case BUNSIGNED:
	case BUNSIGNED|BINT:
		return types[TUINT];

	case BLONG:
	case BLONG|BINT:
	case BLONG|BSIGNED:
	case BLONG|BINT|BSIGNED:
		return types[TLONG];

	case BUNSIGNED|BLONG:
	case BUNSIGNED|BLONG|BINT:
		return types[TULONG];

	case BVLONG|BLONG:
	case BVLONG|BLONG|BINT:
	case BVLONG|BLONG|BSIGNED:
	case BVLONG|BLONG|BINT|BSIGNED:
		return types[TVLONG];

	case BVLONG|BLONG|BUNSIGNED:
	case BVLONG|BLONG|BINT|BUNSIGNED:
		return types[TUVLONG];

	case BFLOAT:
		return types[TFLOAT];

	case BDOUBLE:
	case BDOUBLE|BLONG:
	case BFLOAT|BLONG:
		return types[TDOUBLE];

	case BVOID:
		return types[TVOID];
	}

	diag(Z, "illegal combination of types %Q", b);
	return types[TINT];
}

int
stcompat(Node *n, Type *t1, Type *t2, long ttab[])
{
	int i;
	ulong b;

	i = 0;
	if(t2 != T)
		i = t2->etype;
	b = 1L << i;
	i = 0;
	if(t1 != T)
		i = t1->etype;
	if(b & ttab[i]) {
		if(ttab == tasign)
			if(b == BSTRUCT || b == BUNION)
				if(!sametype(t1, t2))
					return 1;
		if(n->op != OCAST)
		 	if(b == BIND && i == TIND)
				if(!sametype(t1, t2))
					return 1;
		return 0;
	}
	return 1;
}

int
tcompat(Node *n, Type *t1, Type *t2, long ttab[])
{

	if(stcompat(n, t1, t2, ttab)) {
		if(t1 == T)
			diag(n, "incompatible type: \"%T\" for op \"%O\"",
				t2, n->op);
		else
			diag(n, "incompatible types: \"%T\" and \"%T\" for op \"%O\"",
				t1, t2, n->op);
		return 1;
	}
	return 0;
}

void
makedot(Node *n, Type *t, long o)
{
	Node *n1, *n2;

	if(t->nbits) {
		n1 = new(OXXX, Z, Z);
		*n1 = *n;
		n->op = OBIT;
		n->left = n1;
		n->right = Z;
		n->type = t;
		n->addable = n1->left->addable;
		n = n1;
	}
	n->addable = n->left->addable;
	if(n->addable == 0) {
		n1 = new1(OCONST, Z, Z);
		n1->vconst = o;
		n1->type = types[TLONG];
		n->right = n1;
		n->type = t;
		return;
	}
	n->left->type = t;
	if(o == 0) {
		*n = *n->left;
		return;
	}
	n->type = t;
	n1 = new1(OCONST, Z, Z);
	n1->vconst = o;
	t = typ(TIND, t);
	t->width = types[TIND]->width;
	n1->type = t;

	n2 = new1(OADDR, n->left, Z);
	n2->type = t;

	n1 = new1(OADD, n1, n2);
	n1->type = t;

	n->op = OIND;
	n->left = n1;
	n->right = Z;
}

Type*
dotsearch(Sym *s, Type *t, Node *n, long *off)
{
	Type *t1, *xt, *rt;

	xt = T;

	/*
	 * look it up by name
	 */
	for(t1 = t; t1 != T; t1 = t1->down)
		if(t1->sym == s) {
			if(xt != T)
				goto ambig;
			xt = t1;
		}

	/*
	 * look it up by type
	 */
	if(s->class == CTYPEDEF || s->class == CTYPESTR)
		for(t1 = t; t1 != T; t1 = t1->down)
			if(t1->sym == S && typesu[t1->etype])
				if(sametype(s->type, t1)) {
					if(xt != T)
						goto ambig;
					xt = t1;
				}
	if(xt != T) {
		*off = xt->offset;
		return xt;
	}

	/*
	 * look it up in unnamed substructures
	 */
	for(t1 = t; t1 != T; t1 = t1->down)
		if(t1->sym == S && typesu[t1->etype]){
			rt = dotsearch(s, t1->link, n, off);
			if(rt != T) {
				if(xt != T)
					goto ambig;
				xt = rt;
				*off += t1->offset;
			}
		}
	return xt;

ambig:
	diag(n, "ambiguous structure element: %s", s->name);
	return xt;
}

long
dotoffset(Type *st, Type *lt, Node *n)
{
	Type *t;
	Sym *g;
	long o, o1;

	o = -1;
	/*
	 * first try matching at the top level
	 * for matching tag names
	 */
	g = st->tag;
	if(g != S)
		for(t=lt->link; t!=T; t=t->down)
			if(t->sym == S)
				if(g == t->tag) {
					if(o >= 0)
						goto ambig;
					o = t->offset;
				}
	if(o >= 0)
		return o;

	/*
	 * second try matching at the top level
	 * for similar types
	 */
	for(t=lt->link; t!=T; t=t->down)
		if(t->sym == S)
			if(sametype(st, t)) {
				if(o >= 0)
					goto ambig;
				o = t->offset;
			}
	if(o >= 0)
		return o;

	/*
	 * last try matching sub-levels
	 */
	for(t=lt->link; t!=T; t=t->down)
		if(t->sym == S)
		if(typesu[t->etype]) {
			o1 = dotoffset(st, t, n);
			if(o1 >= 0) {
				if(o >= 0)
					goto ambig;
				o = o1 + t->offset;
			}
		}
	return o;

ambig:
	diag(n, "ambiguous unnamed structure element");
	return o;
}

/*
 * look into tree for floating point constant expressions
 */
int
allfloat(Node *n, int flag)
{

	if(n != Z) {
		if(n->type->etype != TDOUBLE)
			return 1;
		switch(n->op) {
		case OCONST:
			if(flag)
				n->type = types[TFLOAT];
			return 1;
		case OADD:	/* no need to get more exotic than this */
		case OSUB:
		case OMUL:
		case ODIV:
			if(!allfloat(n->right, flag))
				break;
		case OCAST:
			if(!allfloat(n->left, flag))
				break;
			if(flag)
				n->type = types[TFLOAT];
			return 1;
		}
	}
	return 0;
}

void
constas(Node *n, Type *il, Type *ir)
{
	Type *l, *r;

	l = il;
	r = ir;

	if(l == T)
		return;
	if(l->garb & GCONSTNT) {
		warn(n, "assignment to a constant type (%T)", il);
		return;
	}
	if(r == T)
		return;
	for(;;) {
		if(l->etype != TIND || r->etype != TIND)
			break;
		l = l->link;
		r = r->link;
		if(l == T || r == T)
			break;
		if(r->garb & GCONSTNT)
			if(!(l->garb & GCONSTNT)) {
				warn(n, "assignment of a constant pointer type (%T)", ir);
				break;
			}
	}
}

void
typeext1(Type *st, Node *l)
{
	if(st->etype == TFLOAT && allfloat(l, 0))
		allfloat(l, 1);
}

void
typeext(Type *st, Node *l)
{
	Type *lt;
	Node *n1, *n2;
	long o;

	lt = l->type;
	if(lt == T)
		return;
	if(st->etype == TIND && vconst(l) == 0) {
		l->type = st;
		l->vconst = 0;
		return;
	}
	typeext1(st, l);

	/*
	 * extension of C
	 * if assign of struct containing unnamed sub-struct
	 * to type of sub-struct, insert the DOT.
	 * if assign of *struct containing unnamed substruct
	 * to type of *sub-struct, insert the add-offset
	 */
	if(typesu[st->etype] && typesu[lt->etype]) {
		o = dotoffset(st, lt, l);
		if(o >= 0) {
			n1 = new1(OXXX, Z, Z);
			*n1 = *l;
			l->op = ODOT;
			l->left = n1;
			l->right = Z;
			makedot(l, st, o);
		}
		return;
	}
	if(st->etype == TIND && typesu[st->link->etype])
	if(lt->etype == TIND && typesu[lt->link->etype]) {
		o = dotoffset(st->link, lt->link, l);
		if(o >= 0) {
			l->type = st;
			if(o == 0)
				return;
			n1 = new1(OXXX, Z, Z);
			*n1 = *l;
			n2 = new1(OCONST, Z, Z);
			n2->vconst = o;
			n2->type = st;
			l->op = OADD;
			l->left = n1;
			l->right = n2;
		}
		return;
	}
}

/*
 * a cast that generates no code
 * (same size move)
 */
int
nocast(Type *t1, Type *t2)
{
	int i, b;

	if(t1->nbits)
		return 0;
	i = 0;
	if(t2 != T)
		i = t2->etype;
	b = 1<<i;
	i = 0;
	if(t1 != T)
		i = t1->etype;
	if(b & ncast[i])
		return 1;
	return 0;
}

/*
 * a cast that has a noop semantic
 * (small to large, convert)
 */
int
nilcast(Type *t1, Type *t2)
{
	int et1, et2;

	if(t1 == T)
		return 0;
	if(t1->nbits)
		return 0;
	if(t2 == T)
		return 0;
	et1 = t1->etype;
	et2 = t2->etype;
	if(et1 == et2)
		return 1;
	if(typefd[et1] && typefd[et2]) {
		if(ewidth[et1] < ewidth[et2])
			return 1;
		return 0;
	}
	if(typechlp[et1] && typechlp[et2]) {
		if(ewidth[et1] < ewidth[et2])
			return 1;
		return 0;
	}
	return 0;
}

/*
 * "the usual arithmetic conversions are performed"
 */
void
arith(Node *n, int f)
{
	Type *t1, *t2;
	int i, j, k;
	Node *n1;
	long w;

	t1 = n->left->type;
	if(n->right == Z)
		t2 = t1;
	else
		t2 = n->right->type;
	i = TXXX;
	if(t1 != T)
		i = t1->etype;
	j = TXXX;
	if(t2 != T)
		j = t2->etype;
	k = tab[i][j];