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

#include "gc.h"

void
cgen(Node *n, int result, Node *nn)
{
	Node *l, *r, nod;
	int lg, rg, xg, yg, g, o;
	long v;
	Prog *p1;

	if(n == Z || n->type == T)
		return;
	if(typesuv[n->type->etype]) {
		sugen(n, result, nn, n->type->width);
		return;
	}
	if(debug['g']) {
		if(result == D_TREE)
			prtree(nn, "result");
		else
			print("result = %R\n", result);
		prtree(n, "cgen");
	}
	l = n->left;
	r = n->right;
	o = n->op;
	if(n->addable >= INDEXED) {
		if(result == D_NONE) {
			if(nn == Z)
				switch(o) {
				default:
					nullwarn(Z, Z);
					break;
				case OINDEX:
					nullwarn(l, r);
					break;
				}
			return;
		}
		gmove(n->type, nn->type, D_TREE, n, result, nn);
		return;
	}

	v = 0; /* set */
	switch(o) {
	default:
		diag(n, "unknown op in cgen: %O", o);
		break;

	case OAS:
		if(l->op == OBIT)
			goto bitas;
		/*
		 * recursive use of result
		 */
		if(result == D_NONE)
		if(l->addable > INDEXED)
		if(l->complex < FNX) {
			cgen(r, D_TREE, l);
			break;
		}

		/*
		 * function calls on both sides
		 */
		if(l->complex >= FNX && r->complex >= FNX) {
			cgen(r, D_TOS, r);
			v = argoff;
			lg = regaddr(result);
			lcgen(l, lg, Z);
			lg |= I_INDIR;
			adjsp(v - argoff);
			gmove(r->type, l->type, D_TOS, r, lg, l);
			if(result != D_NONE)
				gmove(l->type, nn->type, lg, l, result, nn);
			regfree(lg);
			break;
		}

		rg = D_TREE;
		lg = D_TREE;
		if(r->complex >= l->complex) {
			/*
			 * right side before left
			 */
			if(result != D_NONE) {
				rg = regalloc(n->type, result);
				cgen(r, rg, n);
			} else
			if(r->complex >= FNX || r->addable < INDEXED) {
				rg = regalloc(r->type, result);
				cgen(r, rg, r);
			}
			if(l->addable < INDEXED) {
				lg = regaddr(lg);
				lcgen(l, lg, Z);
				lg |= I_INDIR;
			}
		} else {
			/*
			 * left before right
			 */
			if(l->complex >= FNX || l->addable < INDEXED) {
				lg = regaddr(lg);
				lcgen(l, lg, Z);
				lg |= I_INDIR;
			}
			if(result != D_NONE) {
				rg = regalloc(n->type, result);
				cgen(r, rg, n);
			} else
			if(r->addable < INDEXED) {
				rg = regalloc(r->type, result);
				cgen(r, rg, r);
			}
		}
		if(result != D_NONE) {
			gmove(n->type, l->type, rg, r, lg, l);
			gmove(n->type, nn->type, rg, r, result, nn);
		} else
			gmove(r->type, l->type, rg, r, lg, l);
		regfree(lg);
		regfree(rg);
		break;

	bitas:
		n = l->left;
		rg = regalloc(tfield, result);
		if(l->complex >= r->complex) {
			lg = regaddr(D_NONE);
			lcgen(n, lg, Z);
			lg |= I_INDIR;
			cgen(r, rg, r);
		} else {
			cgen(r, rg, r);
			lg = regaddr(D_NONE);
			lcgen(n, lg, Z);
			lg |= I_INDIR;
		}
		g = regalloc(n->type, D_NONE);
		gmove(l->type, l->type, lg, l, g, l);
		bitstore(l, rg, lg, g, result, nn);
		break;

	case OBIT:
		if(result == D_NONE) {
			nullwarn(l, Z);
			break;
		}
		g = bitload(n, D_NONE, D_NONE, result, nn);
		gopcode(OAS, nn->type, g, n, result, nn);
		regfree(g);
		break;

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

	case OASLDIV:
	case OASLMOD:
	case OASDIV:
	case OASMOD:
		if(l->op == OBIT)
			goto asbitop;
		if(typefd[n->type->etype])
			goto asbinop;
		rg = D_TREE;
		if(l->complex >= FNX || r->complex >= FNX) {
			rg = D_TOS;
			cgen(r, rg, r);
			v = argoff;
		} else
		if(r->addable < INDEXED) {
			rg = regalloc(n->type, D_NONE);
			cgen(r, rg, r);
		}
		lg = D_TREE;
		if(!simplv(l)) {
			lg = regaddr(D_NONE);
			lcgen(l, lg, Z);	/* destroys register optimization */
			lg |= I_INDIR;
		}
		g = regpair(result);
		gmove(l->type, n->type, lg, l, g, n);
		if(rg == D_TOS)
			adjsp(v - argoff);
		gopcode(o, n->type, rg, r, g, n);
		if(o == OASLMOD || o == OASMOD)
			gmove(n->type, l->type, g+1, n, lg, l);
		else
			gmove(n->type, l->type, g, n, lg, l);
		if(result != D_NONE)
		if(o == OASLMOD || o == OASMOD)
			gmove(n->type, nn->type, g+1, n, result, nn);
		else
			gmove(n->type, nn->type, g, n, result, nn);
		regfree(g);
		regfree(g+1);
		regfree(lg);
		regfree(rg);
		break;

	case OASXOR:
	case OASAND:
	case OASOR:
		if(l->op == OBIT)
			goto asbitop;
		if(l->complex >= FNX ||
		   l->addable < INDEXED ||
		   result != D_NONE ||
		   typefd[n->type->etype])
			goto asbinop;
		rg = D_TREE;
		if(r->op != OCONST) {
			rg = regalloc(n->type, D_NONE);
			cgen(r, rg, r);
		}
		gopcode(o, l->type, rg, r, D_TREE, l);
		regfree(rg);
		break;

	case OASADD:
	case OASSUB:
		if(l->op == OBIT ||
		   l->complex >= FNX ||
		   l->addable < INDEXED ||
		   result != D_NONE ||
		   typefd[n->type->etype])
			goto asbinop;
		v = vconst(r);
		if(v > 0 && v <= 8) {
			gopcode(o, n->type, D_TREE, r, D_TREE, l);
			break;
		}
		rg = regalloc(n->type, D_NONE);
		cgen(r, rg, r);
		gopcode(o, n->type, rg, r, D_TREE, l);
		regfree(rg);
		break;

	case OASLSHR:
	case OASASHR:
	case OASASHL:
		if(l->op == OBIT ||
		   l->complex >= FNX ||
		   l->addable < INDEXED ||
		   result != D_NONE ||
		   typefd[n->type->etype])
			goto asbinop;
		rg = D_TREE;
		v = vconst(r);
		if(v <= 0 || v > 8) {
			rg = regalloc(n->type, D_NONE);
			cgen(r, rg, r);
		}
		lg = regalloc(n->type, D_NONE);
		cgen(l, lg, l);
		gopcode(o, n->type, rg, r, lg, l);
		gmove(n->type, n->type, lg, l, D_TREE, l);
		regfree(lg);
		regfree(rg);
		break;

	case OASLMUL:
	case OASMUL:
	asbinop:
		if(l->op == OBIT)
			goto asbitop;
		rg = D_TREE;
		if(l->complex >= FNX || r->complex >= FNX) {
			rg = D_TOS;
			cgen(r, rg, r);
			v = argoff;
		} else
		if(r->addable < INDEXED) {
			rg = regalloc(n->type, D_NONE);
			cgen(r, rg, r);
		} else {
			if(o == OASLSHR || o == OASASHR || o == OASASHL) {
				v = vconst(r);
				if(v <= 0 || v > 8) {
					rg = regalloc(n->type, D_NONE);
					cgen(r, rg, r);
				}
			}
		}
		lg = D_TREE;
		if(!simplv(l)) {
			lg = regaddr(D_NONE);
			lcgen(l, lg, Z);	/* destroys register optimization */
			lg |= I_INDIR;
		}
		g = regalloc(n->type, result);
		gmove(l->type, n->type, lg, l, g, n);
		if(rg == D_TOS)
			adjsp(v - argoff);
		if(o == OASXOR)
			if(rg == D_TREE) {
				rg = regalloc(n->type, D_NONE);
				cgen(r, rg, r);
			}
		if(o == OASXOR || o == OASLSHR || o == OASASHR || o == OASASHL)
			if(rg == D_TOS) {
				rg = regalloc(n->type, D_NONE);
				gmove(n->type, n->type, D_TOS, n, rg, n);
			}
		gopcode(o, n->type, rg, r, g, n);
		gmove(n->type, l->type, g, n, lg, l);
		if(result != D_NONE)
			gmove(n->type, nn->type, g, n, result, nn);
		regfree(g);
		regfree(lg);
		regfree(rg);
		break;

	asbitop:
		rg = regaddr(D_NONE);
		lg = regalloc(tfield, D_NONE);
		if(l->complex >= r->complex) {
			g = bitload(l, lg, rg, result, nn);
			xg = regalloc(r->type, D_NONE);
			cgen(r, xg, nn);
		} else {
			xg = regalloc(r->type, D_NONE);
			cgen(r, xg, nn);
			g = bitload(l, lg, rg, result, nn);
		}

		if(!typefd[n->type->etype]) {
			if(o == OASLDIV || o == OASDIV) {
				yg = regpair(result);
				gmove(tfield, n->type, g, l, yg, n);
				gopcode(o, n->type, xg, r, yg, n);
				gmove(n->type, tfield, yg, n, g, l);
				regfree(yg);
				regfree(yg+1);

				regfree(xg);
				bitstore(l, g, rg, lg, D_NONE, nn);
				break;
			}
			if(o == OASLMOD || o == OASMOD) {
				yg = regpair(result);
				gmove(tfield, n->type, g, l, yg, n);
				gopcode(o, n->type, xg, r, yg, n);
				gmove(n->type, tfield, yg+1, n, g, l);
				regfree(yg);
				regfree(yg+1);

				regfree(xg);
				bitstore(l, g, rg, lg, D_NONE, nn);
				break;
			}
		}

		yg = regalloc(n->type, result);
		gmove(tfield, n->type, g, l, yg, n);
		gopcode(o, n->type, xg, r, yg, n);
		gmove(n->type, tfield, yg, n, g, l);
		regfree(yg);

		regfree(xg);
		bitstore(l, g, rg, lg, D_NONE, nn);
		break;

	case OCAST:
		if(result == D_NONE) {
			nullwarn(l, Z);
			break;
		}
		lg = result;
		if(l->complex >= FNX)
			lg = regret(l->type);
		lg = eval(l, lg);
		if(nocast(l->type, n->type)) {
			gmove(n->type, nn->type, lg, l, result, nn);
			regfree(lg);
			break;
		}
		if(nocast(n->type, nn->type)) {
			gmove(l->type, n->type, lg, l, result, nn);
			regfree(lg);
			break;
		}
		rg = regalloc(n->type, result);
		gmove(l->type, n->type, lg, l, rg, n);
		gmove(n->type, nn->type, rg, n, result, nn);
		regfree(rg);
		regfree(lg);
		break;

	case OCOND:
		doinc(l, PRE);
		boolgen(l, 1, D_NONE, Z, l);
		p1 = p;

		inargs++;
		doinc(r->left, PRE);
		cgen(r->left, result, nn);
		doinc(r->left, POST);
		gbranch(OGOTO);
		patch(p1, pc);
		p1 = p;

		doinc(r->right, PRE);
		cgen(r->right, result, nn);
		doinc(r->right, POST);
		patch(p1, pc);
		inargs--;
		break;

	case OIND:
		if(result == D_NONE) {
			nullwarn(l, Z);
			break;
		}
		lg = nodalloc(types[TIND], result, &nod);
		nod.lineno = n->lineno;
		if(l->op == OADD) {
			if(l->left->op == OCONST) {
				nod.xoffset += l->left->vconst;
				l = l->right;
			} else
			if(l->right->op == OCONST) {
				nod.xoffset += l->right->vconst;
				l = l->left;
			}
		}
		cgen(l, lg, l);
		gmove(n->type, nn->type, D_TREE, &nod, result, nn);
		regfree(lg);
		break;

	case OFUNC:
		v = argoff;
		inargs++;
		gargs(r);
		lg = D_TREE;
		if(l->addable < INDEXED) {
			lg = regaddr(result);
			lcgen(l, lg, Z);
			lg |= I_INDIR;
		}
		inargs--;
		doinc(r, POST);
		doinc(l, POST);
		gopcode(OFUNC, types[TCHAR], D_NONE, Z, lg, l);
		regfree(lg);
		if(inargs)
			adjsp(v - argoff);
		if(result != D_NONE) {
			lg = regret(n->type);
			gmove(n->type, nn->type, lg, n, result, nn);
		}
		break;

	case OLDIV:
	case OLMOD:
	case ODIV:
	case OMOD:
		if(result == D_NONE) {
			nullwarn(l, r);
			break;
		}
		if(typefd[n->type->etype])
			goto binop;
		if(r->addable >= INDEXED && r->complex < FNX) {
			lg = regpair(result);
			cgen(l, lg, l);
			rg = D_TREE;
		} else {
			cgen(r, D_TOS, r);
			v = argoff;
			lg = regpair(result);
			cgen(l, lg, l);
			adjsp(v - argoff);
			rg = D_TOS;
		}
		gopcode(o, n->type, rg, r, lg, l);
		if(o == OMOD || o == OLMOD)
			gmove(l->type, nn->type, lg+1, l, result, nn);
		else
			gmove(l->type, nn->type, lg, l, result, nn);
		regfree(lg);
		regfree(lg+1);
		break;

	case OMUL:
	case OLMUL:
		if(l->op == OCONST)
			if(mulcon(r, l, result, nn))
				break;
		if(r->op == OCONST)
			if(mulcon(l, r, result, nn))
				break;
		if(debug['M'])
			print("%L multiply\n", n->lineno);
		goto binop;

	case OAND:
		if(r->op == OCONST)
		if(typeil[n->type->etype])
		if(l->op == OCAST) {
			if(typec[l->left->type->etype])
			if(!(r->vconst & ~0xff)) {
				l = l->left;
				goto binop;
			}
			if(typeh[l->left->type->etype])
			if(!(r->vconst & ~0xffff)) {
				l = l->left;
				goto binop;
			}
		}
		goto binop;

	case OADD:
		if(result == D_TOS)
		if(r->addable >= INDEXED)
		if(l->op == OCONST)
		if(typeil[l->type->etype]) {
			v = l->vconst;
			if(v > -32768 && v < 32768) {
				rg = regaddr(D_NONE);
				gmove(r->type, r->type, D_TREE, r, rg, r);
				gopcode(OADDR, types[TSHORT], D_NONE, Z, rg, r);
				p->to.offset = v;
				p->to.type |= I_INDIR;
				regfree(rg);
				break;
			}
		}

	case OSUB:
		if(result == D_TOS)
		if(l->addable >= INDEXED)
		if(r->op == OCONST)
		if(typeil[r->type->etype]) {
			v = r->vconst;
			if(v > -32768 && v < 32768) {
				if(n->op == OSUB)
					v = -v;
				lg = regaddr(D_NONE);
				gmove(l->type, l->type, D_TREE, l, lg, l);
				gopcode(OADDR, types[TSHORT], D_NONE, Z, lg, l);
				p->to.offset = v;
				p->to.type |= I_INDIR;
				regfree(lg);
				break;
			}
		}
		goto binop;

	case OOR:
	case OXOR:
	binop:
		if(result == D_NONE) {
			nullwarn(l, r);
			break;
		}
		if(l->complex >= FNX && r->complex >= FNX) {
			cgen(r, D_TOS, r);
			v = argoff;
			lg = regalloc(l->type, result);
			cgen(l, lg, l);
			adjsp(v - argoff);
			if(o == OXOR) {
				rg = regalloc(r->type, D_NONE);
				gmove(r->type, r->type, D_TOS, r, rg, r);
				gopcode(o, n->type, rg, r, lg, l);
				regfree(rg);
			} else
				gopcode(o, n->type, D_TOS, r, lg, l);
			gmove(n->type, nn->type, lg, l, result, nn);
			regfree(lg);
			break;
		}
		if(l->complex >= r->complex) {
			if(l->op == OADDR && (o == OADD || o == OSUB))
				lg = regaddr(result);
			else
				lg = regalloc(l->type, result);
			cgen(l, lg, l);
			rg = eval(r, D_NONE);
		} else {
			rg = regalloc(r->type, D_NONE);
			cgen(r, rg, r);
			lg = regalloc(l->type, result);
			cgen(l, lg, l);
		}
		if(o == OXOR) {
			if(rg == D_TREE) {
				rg = regalloc(r->type, D_NONE);
				cgen(r, rg, r);
			}
			if(rg == D_TOS) {
				rg = regalloc(r->type, D_NONE);
				gmove(r->type, r->type, D_TOS, r, rg, r);
			}
		}
		gopcode(o, n->type, rg, r, lg, l);
		gmove(n->type, nn->type, lg, l, result, nn);
		regfree(lg);
		regfree(rg);
		break;

	case OASHL:
		if(r->op == OCONST)
			if(shlcon(l, r, result, nn))
				break;
	case OLSHR:
	case OASHR:
		if(result == D_NONE) {
			nullwarn(l, r);
			break;
		}

		if(l->complex >= FNX && r->complex >= FNX) {
			cgen(r, D_TOS, r);
			v = argoff;
			lg = regalloc(l->type, result);
			cgen(l, lg, l);
			adjsp(v - argoff);
			rg = regalloc(r->type, D_NONE);
			gopcode(OAS, r->type, D_TOS, r, rg, r);
			gopcode(n->op, n->type, rg, r, lg, l);
			gmove(n->type, nn->type, lg, l, result, nn);
			regfree(lg);
			regfree(rg);
			break;
		}
		if(l->complex >= r->complex) {
			lg = regalloc(l->type, result);
			cgen(l, lg, l);
			v = vconst(r);
			if(v <= 0 || v > 8) {
				rg = regalloc(r->type, D_NONE);
				cgen(r, rg, r);
			} else
				rg = eval(r, D_NONE);
		} else {
			rg = regalloc(r->type, D_NONE);
			cgen(r, rg, r);
			lg = regalloc(l->type, result);
			cgen(l, lg, l);
		}
		gopcode(o, n->type, rg, r, lg, l);
		gmove(n->type, nn->type, lg, l, result, nn);
		regfree(lg);
		regfree(rg);
		break;

	case ONEG:
	case OCOM:
		if(result == D_NONE) {
			nullwarn(l, Z);
			break;
		}
		lg = regalloc(l->type, result);
		cgen(l, lg, l);
		gopcode(o, l->type, D_NONE, Z, lg, l);
		gmove(n->type, nn->type, lg, l, result, nn);
		regfree(lg);
		break;

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

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