cgen.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

				case OASLMUL:
					mulgen(n->type, r, &nod);
					break;
				case OASDIV:
					sdiv2(r->vconst, v, l, &nod);
					break;
				case OASMOD:
					smod2(r->vconst, v, l, &nod);
					break;
				}
			havev:
				gmove(&nod, &nod2);
				if(nn != Z)
					gmove(&nod, nn);
				if(hardleft)
					regfree(&nod2);
				regfree(&nod);
				goto done;
			case OASLDIV:
				c = r->vconst;
				if((c & 0x80000000) == 0)
					break;
				if(hardleft)
					reglcgen(&nod2, l, Z);
				else
					nod2 = *l;
				regalloc(&nod1, l, nn);
				cgen(&nod2, &nod1);
				regalloc(&nod, l, nn);
				zeroregm(&nod);
				gins(ACMPL, &nod1, nodconst(c));
				gins(ASBBL, nodconst(-1), &nod);
				regfree(&nod1);
				goto havev;
			}
		}

		if(o == OASMUL) {
/* should favour AX */
			regalloc(&nod, l, nn);
			if(r->complex >= FNX) {
				regalloc(&nod1, r, Z);
				cgen(r, &nod1);
				r = &nod1;
			}
			if(hardleft)
				reglcgen(&nod2, l, Z);
			else
				nod2 = *l;
			cgen(&nod2, &nod);
			if(r->addable < INDEXED) {
				if(r->complex < FNX) {
					regalloc(&nod1, r, Z);
					cgen(r, &nod1);
				}
				gopcode(OASMUL, n->type, &nod1, &nod);
				regfree(&nod1);
			}
			else
				gopcode(OASMUL, n->type, r, &nod);
			if(r == &nod1)
				regfree(r);
			gmove(&nod, &nod2);
			if(nn != Z)
				gmove(&nod, nn);
			regfree(&nod);
			if(hardleft)
				regfree(&nod2);
			goto done;
		}

		/*
		 * get nod to be D_AX
		 * get nod1 to be D_DX
		 */
		if(nodreg(&nod, nn, D_AX)) {
			regsalloc(&nod2, n);
			gmove(&nod, &nod2);
			v = reg[D_AX];
			reg[D_AX] = 0;

			if(isreg(l, D_AX)) {
				nod3 = *n;
				nod3.left = &nod2;
				cgen(&nod3, nn);
			} else
			if(isreg(r, D_AX)) {
				nod3 = *n;
				nod3.right = &nod2;
				cgen(&nod3, nn);
			} else
				cgen(n, nn);

			gmove(&nod2, &nod);
			reg[D_AX] = v;
			break;
		}
		if(nodreg(&nod1, nn, D_DX)) {
			regsalloc(&nod2, n);
			gmove(&nod1, &nod2);
			v = reg[D_DX];
			reg[D_DX] = 0;

			if(isreg(l, D_DX)) {
				nod3 = *n;
				nod3.left = &nod2;
				cgen(&nod3, nn);
			} else
			if(isreg(r, D_DX)) {
				nod3 = *n;
				nod3.right = &nod2;
				cgen(&nod3, nn);
			} else
				cgen(n, nn);

			gmove(&nod2, &nod1);
			reg[D_DX] = v;
			break;
		}
		reg[D_AX]++;
		reg[D_DX]++;

		if(l->complex >= r->complex) {
			if(hardleft)
				reglcgen(&nod2, l, Z);
			else
				nod2 = *l;
			cgen(&nod2, &nod);
			if(r->op == OCONST) {
				switch(o) {
				case OASDIV:
					sdivgen(&nod2, r, &nod, &nod1);
					goto divdone;
				case OASLDIV:
					udivgen(&nod2, r, &nod, &nod1);
				divdone:
					gmove(&nod1, &nod2);
					if(nn != Z)
						gmove(&nod1, nn);
					goto freelxaxdx;
				}
			}
			if(o == OASDIV || o == OASMOD)
				gins(ACDQ, Z, Z);
			if(o == OASLDIV || o == OASLMOD)
				zeroregm(&nod1);
			if(r->addable < INDEXED || r->op == OCONST ||
			   !typeil[r->type->etype]) {
				regalloc(&nod3, r, Z);
				cgen(r, &nod3);
				gopcode(o, l->type, &nod3, Z);
				regfree(&nod3);
			} else
				gopcode(o, n->type, r, Z);
		} else {
			regalloc(&nod3, r, Z);
			cgen(r, &nod3);
			if(hardleft)
				reglcgen(&nod2, l, Z);
			else
				nod2 = *l;
			cgen(&nod2, &nod);
			if(o == OASDIV || o == OASMOD)
				gins(ACDQ, Z, Z);
			if(o == OASLDIV || o == OASLMOD)
				zeroregm(&nod1);
			gopcode(o, l->type, &nod3, Z);
			regfree(&nod3);
		}
		if(o == OASMOD || o == OASLMOD) {
			gmove(&nod1, &nod2);
			if(nn != Z)
				gmove(&nod1, nn);
		} else {
			gmove(&nod, &nod2);
			if(nn != Z)
				gmove(&nod, nn);
		}
	freelxaxdx:
		if(hardleft)
			regfree(&nod2);
		regfree(&nod);
		regfree(&nod1);
		break;

	fop:
		if(l->complex >= r->complex) {
			cgen(l, &fregnode0);
			if(r->addable < INDEXED) {
				cgen(r, &fregnode0);
				fgopcode(o, &fregnode0, &fregnode1, 1, 0);
			} else
				fgopcode(o, r, &fregnode0, 0, 0);
		} else {
			cgen(r, &fregnode0);
			if(l->addable < INDEXED) {
				cgen(l, &fregnode0);
				fgopcode(o, &fregnode0, &fregnode1, 1, 1);
			} else
				fgopcode(o, l, &fregnode0, 0, 1);
		}
		gmove(&fregnode0, nn);
		break;

	asfop:
		if(l->complex >= r->complex) {
			if(hardleft)
				reglcgen(&nod, l, Z);
			else
				nod = *l;
			cgen(r, &fregnode0);
		} else {
			cgen(r, &fregnode0);
			if(hardleft)
				reglcgen(&nod, l, Z);
			else
				nod = *l;
		}
		if(!typefd[l->type->etype]) {
			gmove(&nod, &fregnode0);
			fgopcode(o, &fregnode0, &fregnode1, 1, 1);
		} else
			fgopcode(o, &nod, &fregnode0, 0, 1);
		if(nn != Z)
			gins(AFMOVD, &fregnode0, &fregnode0);
		gmove(&fregnode0, &nod);
		if(nn != Z)
			gmove(&fregnode0, nn);
		if(hardleft)
			regfree(&nod);
		break;

	asbitop:
		regalloc(&nod4, n, nn);
		if(l->complex >= r->complex) {
			bitload(l, &nod, &nod1, &nod2, &nod4);
			regalloc(&nod3, r, Z);
			cgen(r, &nod3);
		} else {
			regalloc(&nod3, r, Z);
			cgen(r, &nod3);
			bitload(l, &nod, &nod1, &nod2, &nod4);
		}
		gmove(&nod, &nod4);

		if(typefd[nod3.type->etype])
			fgopcode(o, &fregnode0, &fregnode1, 1, 1);
		else {
			Node onod;

			/* incredible grot ... */
			onod = nod3;
			onod.op = o;
			onod.complex = 2;
			onod.addable = 0;
			onod.type = tfield;
			onod.left = &nod4;
			onod.right = &nod3;
			cgen(&onod, Z);
		}
		regfree(&nod3);
		gmove(&nod4, &nod);
		regfree(&nod4);
		bitstore(l, &nod, &nod1, &nod2, nn);
		break;

	case OADDR:
		if(nn == Z) {
			nullwarn(l, Z);
			break;
		}
		lcgen(l, nn);
		break;

	case OFUNC:
		if(l->complex >= FNX) {
			if(l->op != OIND)
				diag(n, "bad function call");

			regret(&nod, l->left);
			cgen(l->left, &nod);
			regsalloc(&nod1, l->left);
			gmove(&nod, &nod1);
			regfree(&nod);

			nod = *n;
			nod.left = &nod2;
			nod2 = *l;
			nod2.left = &nod1;
			nod2.complex = 1;
			cgen(&nod, nn);

			return;
		}
		gargs(r, &nod, &nod1);
		if(l->addable < INDEXED) {
			reglcgen(&nod, l, nn);
			nod.op = OREGISTER;
			gopcode(OFUNC, n->type, Z, &nod);
			regfree(&nod);
		} else
			gopcode(OFUNC, n->type, Z, l);
		if(REGARG>=0 && reg[REGARG])
			reg[REGARG]--;
		if(nn != Z) {
			regret(&nod, n);
			gmove(&nod, nn);
			regfree(&nod);
		} else
		if(typefd[n->type->etype])
			gins(AFMOVDP, &fregnode0, &fregnode0);
		break;

	case OIND:
		if(nn == Z) {
			nullwarn(l, Z);
			break;
		}
		regialloc(&nod, n, nn);
		r = l;
		while(r->op == OADD)
			r = r->right;
		if(sconst(r)) {
			v = r->vconst;
			r->vconst = 0;
			cgen(l, &nod);
			nod.xoffset += v;
			r->vconst = v;
		} else
			cgen(l, &nod);
		regind(&nod, n);
		gmove(&nod, nn);
		regfree(&nod);
		break;

	case OEQ:
	case ONE:
	case OLE:
	case OLT:
	case OGE:
	case OGT:
	case OLO:
	case OLS:
	case OHI:
	case OHS:
		if(nn == Z) {
			nullwarn(l, r);
			break;
		}
		boolgen(n, 1, nn);
		break;

	case OANDAND:
	case OOROR:
		boolgen(n, 1, nn);
		if(nn == Z)
			patch(p, pc);
		break;

	case ONOT:
		if(nn == Z) {
			nullwarn(l, Z);
			break;
		}
		boolgen(n, 1, nn);
		break;

	case OCOMMA:
		cgen(l, Z);
		cgen(r, nn);
		break;

	case OCAST:
		if(nn == Z) {
			nullwarn(l, Z);
			break;
		}
		/*
		 * convert from types l->n->nn
		 */
		if(nocast(l->type, n->type) && nocast(n->type, nn->type)) {
			/* both null, gen l->nn */
			cgen(l, nn);
			break;
		}
		if(typev[l->type->etype]) {
			cgen64(n, nn);
			break;
		}
		regalloc(&nod, l, nn);
		cgen(l, &nod);
		regalloc(&nod1, n, &nod);
		gmove(&nod, &nod1);
		gmove(&nod1, nn);
		regfree(&nod1);
		regfree(&nod);
		break;

	case ODOT:
		sugen(l, nodrat, l->type->width);
		if(nn == Z)
			break;
		warn(n, "non-interruptable temporary");
		nod = *nodrat;
		if(!r || r->op != OCONST) {
			diag(n, "DOT and no offset");
			break;
		}
		nod.xoffset += (long)r->vconst;
		nod.type = n->type;
		cgen(&nod, nn);
		break;

	case OCOND:
		bcgen(l, 1);
		p1 = p;
		cgen(r->left, nn);
		gbranch(OGOTO);
		patch(p1, pc);
		p1 = p;
		cgen(r->right, nn);
		patch(p1, pc);
		break;

	case OPOSTINC:
	case OPOSTDEC:
		v = 1;
		if(l->type->etype == TIND)
			v = l->type->link->width;
		if(o == OPOSTDEC)
			v = -v;
		if(l->op == OBIT)
			goto bitinc;
		if(nn == Z)
			goto pre;

		if(hardleft)
			reglcgen(&nod, l, Z);
		else
			nod = *l;

		if(typefd[n->type->etype])
			goto fltinc;
		gmove(&nod, nn);
		gopcode(OADD, n->type, nodconst(v), &nod);
		if(hardleft)
			regfree(&nod);
		break;

	case OPREINC:
	case OPREDEC:
		v = 1;
		if(l->type->etype == TIND)
			v = l->type->link->width;
		if(o == OPREDEC)
			v = -v;
		if(l->op == OBIT)
			goto bitinc;

	pre:
		if(hardleft)
			reglcgen(&nod, l, Z);
		else
			nod = *l;
		if(typefd[n->type->etype])
			goto fltinc;
		gopcode(OADD, n->type, nodconst(v), &nod);
		if(nn != Z)
			gmove(&nod, nn);
		if(hardleft)
			regfree(&nod);
		break;

	fltinc:
		gmove(&nod, &fregnode0);
		if(nn != Z && (o == OPOSTINC || o == OPOSTDEC))
			gins(AFMOVD, &fregnode0, &fregnode0);
		gins(AFLD1, Z, Z);
		if(v < 0)
			fgopcode(OSUB, &fregnode0, &fregnode1, 1, 0);
		else
			fgopcode(OADD, &fregnode0, &fregnode1, 1, 0);
		if(nn != Z && (o == OPREINC || o == OPREDEC))
			gins(AFMOVD, &fregnode0, &fregnode0);
		gmove(&fregnode0, &nod);
		if(hardleft)
			regfree(&nod);
		break;

	bitinc:
		if(nn != Z && (o == OPOSTINC || o == OPOSTDEC)) {
			bitload(l, &nod, &nod1, &nod2, Z);
			gmove(&nod, nn);
			gopcode(OADD, tfield, nodconst(v), &nod);
			bitstore(l, &nod, &nod1, &nod2, Z);
			break;
		}
		bitload(l, &nod, &nod1, &nod2, nn);
		gopcode(OADD, tfield, nodconst(v), &nod);
		bitstore(l, &nod, &nod1, &nod2, nn);
		break;
	}
done:
	cursafe = curs;
}

void
reglcgen(Node *t, Node *n, Node *nn)
{
	Node *r;
	long v;

	regialloc(t, n, nn);
	if(n->op == OIND) {
		r = n->left;
		while(r->op == OADD)
			r = r->right;
		if(sconst(r)) {
			v = r->vconst;
			r->vconst = 0;
			lcgen(n, t);
			t->xoffset += v;
			r->vconst = v;
			regind(t, n);
			return;
		}
	}
	lcgen(n, t);
	regind(t, n);
}

void
lcgen(Node *n, Node *nn)
{
	Prog *p1;
	Node nod;

	if(debug['g']) {
		prtree(nn, "lcgen lhs");
		prtree(n, "lcgen");
	}
	if(n == Z || n->type == T)
		return;
	if(nn == Z) {
		nn = &nod;
		regalloc(&nod, n, Z);
	}
	switch(n->op) {
	default:
		if(n->addable < INDEXED) {
			diag(n, "unknown op in lcgen: %O", n->op);
			break;
		}
		gopcode(OADDR, n->type, n, nn);
		break;

	case OCOMMA:
		cgen(n->left, n->left);
		lcgen(n->right, nn);
		break;

	case OIND:
		cgen(n->left, nn);
		break;

	case OCOND:
		bcgen(n->left, 1);
		p1 = p;
		lcgen(n->right->left, nn);
		gbranch(OGOTO);
		patch(p1, pc);
		p1 = p;
		lcgen(n->right->right, nn);
		patch(p1, pc);
		break;
	}
}

void
bcgen(Node *n, int true)
{

	if(n->type == T)
		gbranch(OGOTO);
	else
		boolgen(n, true, Z);
}

void
boolgen(Node *n, int true, Node *nn)
{
	int o;
	Prog *p1, *p2;
	Node *l, *r, nod, nod1;
	long curs;

	if(debug['g']) {
		prtree(nn, "boolgen lhs");
		prtree(n, "boolgen");
	}
	curs = cursafe;
	l = n->left;
	r = n->right;
	switch(n->op) {

	default:
		if(typev[n->type->etype]) {
			testv(n, true);
			goto com;
		}
		o = ONE;
		if(true)
			o = OEQ;
		if(typefd[n->type->etype]) {