reg.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

		if(s == v->sym)
		if(n == v->name)
		if(o == v->offset)
			goto out;
		v++;
	}
	if(s)
		if(s->name[0] == '.')
			goto none;
	if(nvar >= NVAR) {
		if(debug['w'] > 1 && s)
			warn(Z, "variable not optimized: %s", s->name);
		goto none;
	}
	i = nvar;
	nvar++;
	v = &var[i];
	v->sym = s;
	v->offset = o;
	v->etype = et;
	v->name = n;
	if(debug['R'])
		print("bit=%2d et=%2d %D\n", i, et, a);
out:
	bit = blsh(i);
	if(n == D_EXTERN || n == D_STATIC)
		for(z=0; z<BITS; z++)
			externs.b[z] |= bit.b[z];
	if(n == D_PARAM)
		for(z=0; z<BITS; z++)
			params.b[z] |= bit.b[z];
	if(v->etype != et || !typechlpfd[et])	/* funny punning */
		for(z=0; z<BITS; z++)
			addrs.b[z] |= bit.b[z];
	if(t == D_CONST) {
		if(s == S) {
			for(z=0; z<BITS; z++)
				consts.b[z] |= bit.b[z];
			return bit;
		}
		if(et != TARRAY)
			for(z=0; z<BITS; z++)
				addrs.b[z] |= bit.b[z];
		for(z=0; z<BITS; z++)
			params.b[z] |= bit.b[z];
		return bit;
	}
	if(t == D_OREG)
		return bit;

none:
	return zbits;
}

void
prop(Reg *r, Bits ref, Bits cal)
{
	Reg *r1, *r2;
	int z;

	for(r1 = r; r1 != R; r1 = r1->p1) {
		for(z=0; z<BITS; z++) {
			ref.b[z] |= r1->refahead.b[z];
			if(ref.b[z] != r1->refahead.b[z]) {
				r1->refahead.b[z] = ref.b[z];
				change++;
			}
			cal.b[z] |= r1->calahead.b[z];
			if(cal.b[z] != r1->calahead.b[z]) {
				r1->calahead.b[z] = cal.b[z];
				change++;
			}
		}
		switch(r1->prog->as) {
		case ABL:
			for(z=0; z<BITS; z++) {
				cal.b[z] |= ref.b[z] | externs.b[z];
				ref.b[z] = 0;
			}
			break;

		case ATEXT:
			for(z=0; z<BITS; z++) {
				cal.b[z] = 0;
				ref.b[z] = 0;
			}
			break;

		case ARET:
			for(z=0; z<BITS; z++) {
				cal.b[z] = externs.b[z];
				ref.b[z] = 0;
			}
		}
		for(z=0; z<BITS; z++) {
			ref.b[z] = (ref.b[z] & ~r1->set.b[z]) |
				r1->use1.b[z] | r1->use2.b[z];
			cal.b[z] &= ~(r1->set.b[z] | r1->use1.b[z] | r1->use2.b[z]);
			r1->refbehind.b[z] = ref.b[z];
			r1->calbehind.b[z] = cal.b[z];
		}
		if(r1->active)
			break;
		r1->active = 1;
	}
	for(; r != r1; r = r->p1)
		for(r2 = r->p2; r2 != R; r2 = r2->p2link)
			prop(r2, r->refbehind, r->calbehind);
}

/*
 * find looping structure
 *
 * 1) find reverse postordering
 * 2) find approximate dominators,
 *	the actual dominators if the flow graph is reducible
 *	otherwise, dominators plus some other non-dominators.
 *	See Matthew S. Hecht and Jeffrey D. Ullman,
 *	"Analysis of a Simple Algorithm for Global Data Flow Problems",
 *	Conf.  Record of ACM Symp. on Principles of Prog. Langs, Boston, Massachusetts,
 *	Oct. 1-3, 1973, pp.  207-217.
 * 3) find all nodes with a predecessor dominated by the current node.
 *	such a node is a loop head.
 *	recursively, all preds with a greater rpo number are in the loop
 */
long
postorder(Reg *r, Reg **rpo2r, long n)
{
	Reg *r1;

	r->rpo = 1;
	r1 = r->s1;
	if(r1 && !r1->rpo)
		n = postorder(r1, rpo2r, n);
	r1 = r->s2;
	if(r1 && !r1->rpo)
		n = postorder(r1, rpo2r, n);
	rpo2r[n] = r;
	n++;
	return n;
}

long
rpolca(long *idom, long rpo1, long rpo2)
{
	long t;

	if(rpo1 == -1)
		return rpo2;
	while(rpo1 != rpo2){
		if(rpo1 > rpo2){
			t = rpo2;
			rpo2 = rpo1;
			rpo1 = t;
		}
		while(rpo1 < rpo2){
			t = idom[rpo2];
			if(t >= rpo2)
				fatal(Z, "bad idom");
			rpo2 = t;
		}
	}
	return rpo1;
}

int
doms(long *idom, long r, long s)
{
	while(s > r)
		s = idom[s];
	return s == r;
}

int
loophead(long *idom, Reg *r)
{
	long src;

	src = r->rpo;
	if(r->p1 != R && doms(idom, src, r->p1->rpo))
		return 1;
	for(r = r->p2; r != R; r = r->p2link)
		if(doms(idom, src, r->rpo))
			return 1;
	return 0;
}

void
loopmark(Reg **rpo2r, long head, Reg *r)
{
	if(r->rpo < head || r->active == head)
		return;
	r->active = head;
	r->loop += LOOP;
	if(r->p1 != R)
		loopmark(rpo2r, head, r->p1);
	for(r = r->p2; r != R; r = r->p2link)
		loopmark(rpo2r, head, r);
}

void
loopit(Reg *r, long nr)
{
	Reg *r1;
	long i, d, me;

	if(nr > maxnr) {
		rpo2r = alloc(nr * sizeof(Reg*));
		idom = alloc(nr * sizeof(long));
		maxnr = nr;
	}

	d = postorder(r, rpo2r, 0);
	if(d > nr)
		fatal(Z, "too many reg nodes");
	nr = d;
	for(i = 0; i < nr / 2; i++){
		r1 = rpo2r[i];
		rpo2r[i] = rpo2r[nr - 1 - i];
		rpo2r[nr - 1 - i] = r1;
	}
	for(i = 0; i < nr; i++)
		rpo2r[i]->rpo = i;

	idom[0] = 0;
	for(i = 0; i < nr; i++){
		r1 = rpo2r[i];
		me = r1->rpo;
		d = -1;
		if(r1->p1 != R && r1->p1->rpo < me)
			d = r1->p1->rpo;
		for(r1 = r1->p2; r1 != nil; r1 = r1->p2link)
			if(r1->rpo < me)
				d = rpolca(idom, d, r1->rpo);
		idom[i] = d;
	}

	for(i = 0; i < nr; i++){
		r1 = rpo2r[i];
		r1->loop++;
		if(r1->p2 != R && loophead(idom, r1))
			loopmark(rpo2r, i, r1);
	}
}

void
synch(Reg *r, Bits dif)
{
	Reg *r1;
	int z;

	for(r1 = r; r1 != R; r1 = r1->s1) {
		for(z=0; z<BITS; z++) {
			dif.b[z] = (dif.b[z] &
				~(~r1->refbehind.b[z] & r1->refahead.b[z])) |
					r1->set.b[z] | r1->regdiff.b[z];
			if(dif.b[z] != r1->regdiff.b[z]) {
				r1->regdiff.b[z] = dif.b[z];
				change++;
			}
		}
		if(r1->active)
			break;
		r1->active = 1;
		for(z=0; z<BITS; z++)
			dif.b[z] &= ~(~r1->calbehind.b[z] & r1->calahead.b[z]);
		if(r1->s2 != R)
			synch(r1->s2, dif);
	}
}

ulong
allreg(ulong b, Rgn *r)
{
	Var *v;
	int i;

	v = var + r->varno;
	r->regno = 0;
	switch(v->etype) {

	default:
		diag(Z, "unknown etype %d/%d", bitno(b), v->etype);
		break;

	case TCHAR:
	case TUCHAR:
	case TSHORT:
	case TUSHORT:
	case TINT:
	case TUINT:
	case TLONG:
	case TULONG:
	case TIND:
	case TARRAY:
		i = BtoR(~b);
		if(i && r->cost >= 0) {
			r->regno = i;
			return RtoB(i);
		}
		break;

	case TVLONG:
	case TDOUBLE:
	case TFLOAT:
		i = BtoF(~b);
		if(i && r->cost >= 0) {
			r->regno = i+NREG;
			return FtoB(i);
		}
		break;
	}
	return 0;
}

void
paint1(Reg *r, int bn)
{
	Reg *r1;
	Prog *p;
	int z;
	ulong bb;

	z = bn/32;
	bb = 1L<<(bn%32);
	if(r->act.b[z] & bb)
		return;
	for(;;) {
		if(!(r->refbehind.b[z] & bb))
			break;
		r1 = r->p1;
		if(r1 == R)
			break;
		if(!(r1->refahead.b[z] & bb))
			break;
		if(r1->act.b[z] & bb)
			break;
		r = r1;
	}

	if(LOAD(r) & ~(r->set.b[z] & ~(r->use1.b[z]|r->use2.b[z])) & bb) {
		change -= CLOAD * r->loop;
		if(debug['R'] && debug['v'])
			print("%ld%P\tld %B $%d\n", r->loop,
				r->prog, blsh(bn), change);
	}
	for(;;) {
		r->act.b[z] |= bb;
		p = r->prog;

		if(r->use1.b[z] & bb) {
			change += CREF * r->loop;
			if(debug['R'] && debug['v'])
				print("%ld%P\tu1 %B $%d\n", r->loop,
					p, blsh(bn), change);
		}

		if((r->use2.b[z]|r->set.b[z]) & bb) {
			change += CREF * r->loop;
			if(debug['R'] && debug['v'])
				print("%ld%P\tu2 %B $%d\n", r->loop,
					p, blsh(bn), change);
		}

		if(STORE(r) & r->regdiff.b[z] & bb) {
			change -= CLOAD * r->loop;
			if(debug['R'] && debug['v'])
				print("%ld%P\tst %B $%d\n", r->loop,
					p, blsh(bn), change);
		}

		if(r->refbehind.b[z] & bb)
			for(r1 = r->p2; r1 != R; r1 = r1->p2link)
				if(r1->refahead.b[z] & bb)
					paint1(r1, bn);

		if(!(r->refahead.b[z] & bb))
			break;
		r1 = r->s2;
		if(r1 != R)
			if(r1->refbehind.b[z] & bb)
				paint1(r1, bn);
		r = r->s1;
		if(r == R)
			break;
		if(r->act.b[z] & bb)
			break;
		if(!(r->refbehind.b[z] & bb))
			break;
	}
}

ulong
paint2(Reg *r, int bn)
{
	Reg *r1;
	int z;
	ulong bb, vreg;

	z = bn/32;
	bb = 1L << (bn%32);
	vreg = regbits;
	if(!(r->act.b[z] & bb))
		return vreg;
	for(;;) {
		if(!(r->refbehind.b[z] & bb))
			break;
		r1 = r->p1;
		if(r1 == R)
			break;
		if(!(r1->refahead.b[z] & bb))
			break;
		if(!(r1->act.b[z] & bb))
			break;
		r = r1;
	}
	for(;;) {
		r->act.b[z] &= ~bb;

		vreg |= r->regu;

		if(r->refbehind.b[z] & bb)
			for(r1 = r->p2; r1 != R; r1 = r1->p2link)
				if(r1->refahead.b[z] & bb)
					vreg |= paint2(r1, bn);

		if(!(r->refahead.b[z] & bb))
			break;
		r1 = r->s2;
		if(r1 != R)
			if(r1->refbehind.b[z] & bb)
				vreg |= paint2(r1, bn);
		r = r->s1;
		if(r == R)
			break;
		if(!(r->act.b[z] & bb))
			break;
		if(!(r->refbehind.b[z] & bb))
			break;
	}
	return vreg;
}

void
paint3(Reg *r, int bn, long rb, int rn)
{
	Reg *r1;
	Prog *p;
	int z;
	ulong bb;

	z = bn/32;
	bb = 1L << (bn%32);
	if(r->act.b[z] & bb)
		return;
	for(;;) {
		if(!(r->refbehind.b[z] & bb))
			break;
		r1 = r->p1;
		if(r1 == R)
			break;
		if(!(r1->refahead.b[z] & bb))
			break;
		if(r1->act.b[z] & bb)
			break;
		r = r1;
	}

	if(LOAD(r) & ~(r->set.b[z] & ~(r->use1.b[z]|r->use2.b[z])) & bb)
		addmove(r, bn, rn, 0);
	for(;;) {
		r->act.b[z] |= bb;
		p = r->prog;

		if(r->use1.b[z] & bb) {
			if(debug['R'])
				print("%P", p);
			addreg(&p->from, rn);
			if(debug['R'])
				print("\t.c%P\n", p);
		}
		if((r->use2.b[z]|r->set.b[z]) & bb) {
			if(debug['R'])
				print("%P", p);
			addreg(&p->to, rn);
			if(debug['R'])
				print("\t.c%P\n", p);
		}

		if(STORE(r) & r->regdiff.b[z] & bb)
			addmove(r, bn, rn, 1);
		r->regu |= rb;

		if(r->refbehind.b[z] & bb)
			for(r1 = r->p2; r1 != R; r1 = r1->p2link)
				if(r1->refahead.b[z] & bb)
					paint3(r1, bn, rb, rn);

		if(!(r->refahead.b[z] & bb))
			break;
		r1 = r->s2;
		if(r1 != R)
			if(r1->refbehind.b[z] & bb)
				paint3(r1, bn, rb, rn);
		r = r->s1;
		if(r == R)
			break;
		if(r->act.b[z] & bb)
			break;
		if(!(r->refbehind.b[z] & bb))
			break;
	}
}

void
addreg(Adr *a, int rn)
{

	a->sym = 0;
	a->name = D_NONE;
	a->type = D_REG;
	a->reg = rn;
	if(rn >= NREG) {
		a->type = D_FREG;
		a->reg = rn-NREG;
	}
}

/*
 *	bit	reg
 *	0	R0
 *	1	R1
 *	...	...
 *	10	R10
 */
long
RtoB(int r)
{

	if(r < 2 || r >= REGTMP)
		return 0;
	return 1L << r;
}

int
BtoR(long b)
{
	b &= 0x07fcL;
	if(b == 0)
		return 0;
	return bitno(b);
}

/*
 *	bit	reg
 *	18	F2
 *	19	F3
 *	...	...
 *	23	F7
 */
long
FtoB(int f)
{

	if(f < 2 || f > NFREG-1)
		return 0;
	return 1L << (f + 16);
}

int
BtoF(long b)
{

	b &= 0xfc0000L;
	if(b == 0)
		return 0;
	return bitno(b) - 16;
}