txt.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(t->op == ONAME || t->op == OINDREG || t->op == OIND) {
		switch(tt) {
		default:
			a = AMOVW;
			break;
		case TUCHAR:
			a = AMOVBZ;
			break;
		case TCHAR:
			a = AMOVB;
			break;
		case TUSHORT:
			a = AMOVHZ;
			break;
		case TSHORT:
			a = AMOVH;
			break;
		case TFLOAT:
			a = AFMOVS;
			break;
		case TVLONG:
		case TDOUBLE:
			a = AFMOVD;
			break;
		}
		if(R0ISZERO && !typefd[ft] && vconst(f) == 0) {
			gins(a, f, t);
			return;
		}
		if(ft == tt)
			regalloc(&nod, t, f);
		else
			regalloc(&nod, t, Z);
		gmove(f, &nod);
		gins(a, &nod, t);
		regfree(&nod);
		return;
	}

	/*
	 * type x type cross table
	 */
	a = AGOK;
	switch(ft) {
	case TDOUBLE:
	case TVLONG:
	case TFLOAT:
		switch(tt) {
		case TDOUBLE:
		case TVLONG:
			a = AFMOVD;
			if(ft == TFLOAT)
				a = AFMOVS;	/* AFMOVSD */
			break;
		case TFLOAT:
			a = AFRSP;
			if(ft == TFLOAT)
				a = AFMOVS;
			break;
		case TINT:
		case TUINT:
		case TLONG:
		case TULONG:
		case TIND:
		case TSHORT:
		case TUSHORT:
		case TCHAR:
		case TUCHAR:
			/* BUG: not right for unsigned long */
			regalloc(&nod, f, Z);	/* should be type float */
			regsalloc(&fxrat, f);
			gins(AFCTIWZ, f, &nod);
			gins(AFMOVD, &nod, &fxrat);
			regfree(&nod);
			fxrat.type = nodrat->type;
			fxrat.etype = nodrat->etype;
			fxrat.xoffset += 4;
			gins(AMOVW, &fxrat, t);
			gmove(t, t);
			return;
		}
		break;
	case TINT:
	case TUINT:
	case TLONG:
	case TULONG:
	case TIND:
		switch(tt) {
		case TDOUBLE:
		case TVLONG:
		case TFLOAT:
			goto fxtofl;
		case TINT:
		case TUINT:
		case TLONG:
		case TULONG:
		case TIND:
		case TSHORT:
		case TUSHORT:
		case TCHAR:
		case TUCHAR:
			a = AMOVW;
			break;
		}
		break;
	case TSHORT:
		switch(tt) {
		case TDOUBLE:
		case TVLONG:
		case TFLOAT:
			goto fxtofl;
		case TINT:
		case TUINT:
		case TLONG:
		case TULONG:
		case TIND:
			a = AMOVH;
			break;
		case TSHORT:
		case TUSHORT:
		case TCHAR:
		case TUCHAR:
			a = AMOVW;
			break;
		}
		break;
	case TUSHORT:
		switch(tt) {
		case TDOUBLE:
		case TVLONG:
		case TFLOAT:
			goto fxtofl;
		case TINT:
		case TUINT:
		case TLONG:
		case TULONG:
		case TIND:
			a = AMOVHZ;
			break;
		case TSHORT:
		case TUSHORT:
		case TCHAR:
		case TUCHAR:
			a = AMOVW;
			break;
		}
		break;
	case TCHAR:
		switch(tt) {
		case TDOUBLE:
		case TVLONG:
		case TFLOAT:
			goto fxtofl;
		case TINT:
		case TUINT:
		case TLONG:
		case TULONG:
		case TIND:
		case TSHORT:
		case TUSHORT:
			a = AMOVB;
			break;
		case TCHAR:
		case TUCHAR:
			a = AMOVW;
			break;
		}
		break;
	case TUCHAR:
		switch(tt) {
		case TDOUBLE:
		case TVLONG:
		case TFLOAT:
		fxtofl:
			/*
			 * rat[0] = 0x43300000; rat[1] = f^0x80000000;
			 * t = *(double*)rat - FREGCVI;
			 * is-unsigned(t) => if(t<0) t += 2^32;
			 * could be streamlined for int-to-float
			 */
			regalloc(&fxc0, f, Z);
			regalloc(&fxc2, f, Z);
			regsalloc(&fxrat, t);	/* should be type float */
			gins(AMOVW, nodconst(0x43300000L), &fxc0);
			gins(AMOVW, f, &fxc2);
			gins(AMOVW, &fxc0, &fxrat);
			gins(AXOR, nodconst(0x80000000L), &fxc2);
			fxc1 = fxrat;
			fxc1.type = nodrat->type;
			fxc1.etype = nodrat->etype;
			fxc1.xoffset += SZ_LONG;
			gins(AMOVW, &fxc2, &fxc1);
			regfree(&fxc2);
			regfree(&fxc0);
			regalloc(&nod, t, t);	/* should be type float */
			gins(AFMOVD, &fxrat, &nod);
			nodreg(&fxc1, t, NREG+FREGCVI);
			gins(AFSUB, &fxc1, &nod);
			a = AFMOVD;
			if(tt == TFLOAT)
				a = AFRSP;
			gins(a, &nod, t);
			regfree(&nod);
			if(ft == TULONG) {
				regalloc(&nod, t, Z);
				if(tt == TFLOAT) {
					gins(AFCMPU, t, Z);
					p->to.type = D_FREG;
					p->to.reg = FREGZERO;
					gins(ABGE, Z, Z);
					p1 = p;
					gins(AFMOVS, nodfconst(4294967296.), &nod);
					gins(AFADDS, &nod, t);
				} else {
					gins(AFCMPU, t, Z);
					p->to.type = D_FREG;
					p->to.reg = FREGZERO;
					gins(ABGE, Z, Z);
					p1 = p;
					gins(AFMOVD, nodfconst(4294967296.), &nod);
					gins(AFADD, &nod, t);
				}
				patch(p1, pc);
				regfree(&nod);
			}
			return;
		case TINT:
		case TUINT:
		case TLONG:
		case TULONG:
		case TIND:
		case TSHORT:
		case TUSHORT:
			a = AMOVBZ;
			break;
		case TCHAR:
		case TUCHAR:
			a = AMOVW;
			break;
		}
		break;
	}
	if(a == AGOK)
		diag(Z, "bad opcode in gmove %T -> %T", f->type, t->type);
	if(a == AMOVW || a == AFMOVS || a == AFMOVD)
	if(samaddr(f, t))
		return;
	gins(a, f, t);
}

void
gins(int a, Node *f, Node *t)
{

	nextpc();
	p->as = a;
	if(f != Z)
		naddr(f, &p->from);
	if(t != Z)
		naddr(t, &p->to);
	if(debug['g'])
		print("%P\n", p);
}

void
gopcode(int o, Node *f1, Node *f2, Node *t)
{
	int a, et;
	Adr ta;
	int uns;

	uns = 0;
	et = TLONG;
	if(f1 != Z && f1->type != T)
		et = f1->type->etype;
	a = AGOK;
	switch(o) {
	case OAS:
		gmove(f1, t);
		return;

	case OASADD:
	case OADD:
		a = AADD;
		if(et == TFLOAT)
			a = AFADDS;
		else
		if(et == TDOUBLE || et == TVLONG)
			a = AFADD;
		break;

	case OASSUB:
	case OSUB:
		a = ASUB;
		if(et == TFLOAT)
			a = AFSUBS;
		else
		if(et == TDOUBLE || et == TVLONG)
			a = AFSUB;
		break;

	case OASOR:
	case OOR:
		a = AOR;
		break;

	case OASAND:
	case OAND:
		a = AAND;
		if(f1->op == OCONST)
			a = AANDCC;
		break;

	case OASXOR:
	case OXOR:
		a = AXOR;
		break;

	case OASLSHR:
	case OLSHR:
		a = ASRW;
		break;

	case OASASHR:
	case OASHR:
		a = ASRAW;
		break;

	case OASASHL:
	case OASHL:
		a = ASLW;	/* BUG? */
		break;

	case OFUNC:
		a = ABL;
		break;

	case OASLMUL:
	case OLMUL:
	case OASMUL:
	case OMUL:
		if(et == TFLOAT) {
			a = AFMULS;
			break;
		} else
		if(et == TDOUBLE || et == TVLONG) {
			a = AFMUL;
			break;
		}
		a = AMULLW;
		break;

	case OASDIV:
	case ODIV:
		if(et == TFLOAT) {
			a = AFDIVS;
			break;
		} else
		if(et == TDOUBLE || et == TVLONG) {
			a = AFDIV;
			break;
		}
		a = ADIVW;
		break;

	case OASMOD:
	case OMOD:
		a = AREM;
		break;

	case OASLMOD:
	case OLMOD:
		a = AREMU;
		break;

	case OASLDIV:
	case OLDIV:
		a = ADIVWU;
		break;

	case OCOM:
		a = ANOR;
		break;

	case ONEG:
		a = ANEG;
		if(et == TFLOAT || et == TDOUBLE || et == TVLONG)
			a = AFNEG;
		break;

	case OEQ:
		a = ABEQ;
		goto cmp;

	case ONE:
		a = ABNE;
		goto cmp;

	case OLT:
		a = ABLT;
		goto cmp;

	case OLE:
		a = ABLE;
		goto cmp;

	case OGE:
		a = ABGE;
		goto cmp;

	case OGT:
		a = ABGT;
		goto cmp;

	case OLO:
		a = ABLT;
		goto cmpu;

	case OLS:
		a = ABLE;
		goto cmpu;

	case OHS:
		a = ABGE;
		goto cmpu;

	case OHI:
		a = ABGT;
		goto cmpu;

	cmpu:
		uns = 1;
	cmp:
		nextpc();
		p->as = uns? ACMPU: ACMP;
		if(et == TFLOAT)
			p->as = AFCMPU;
		else
		if(et == TDOUBLE || et == TVLONG)
			p->as = AFCMPU;
		if(f1 != Z)
			naddr(f1, &p->from);
		if(t != Z)
			naddr(t, &p->to);
		if(f1 == Z || t == Z || f2 != Z)
			diag(Z, "bad cmp in gopcode %O", o);
		if(debug['g'])
			print("%P\n", p);
		f1 = Z;
		f2 = Z;
		t = Z;
		break;
	}
	if(a == AGOK)
		diag(Z, "bad in gopcode %O", o);
	nextpc();
	p->as = a;
	if(f1 != Z)
		naddr(f1, &p->from);
	if(f2 != Z) {
		naddr(f2, &ta);
		p->reg = ta.reg;
		if(ta.type == D_CONST && ta.offset == 0) {
			if(R0ISZERO)
				p->reg = REGZERO;
			else
				diag(Z, "REGZERO in gopcode %O", o);
		}
	}
	if(t != Z)
		naddr(t, &p->to);
	if(debug['g'])
		print("%P\n", p);
}

samaddr(Node *f, Node *t)
{

	if(f->op != t->op)
		return 0;
	switch(f->op) {

	case OREGISTER:
		if(f->reg != t->reg)
			break;
		return 1;
	}
	return 0;
}

void
gbranch(int o)
{
	int a;

	a = AGOK;
	switch(o) {
	case ORETURN:
		a = ARETURN;
		break;
	case OGOTO:
		a = ABR;
		break;
	}
	nextpc();
	if(a == AGOK) {
		diag(Z, "bad in gbranch %O",  o);
		nextpc();
	}
	p->as = a;
}

void
patch(Prog *op, long pc)
{

	op->to.offset = pc;
	op->to.type = D_BRANCH;
}

void
gpseudo(int a, Sym *s, Node *n)
{

	nextpc();
	p->as = a;
	p->from.type = D_OREG;
	p->from.sym = s;
	p->reg = (profileflg ? 0 : NOPROF);
	p->from.name = D_EXTERN;
	if(s->class == CSTATIC)
		p->from.name = D_STATIC;
	naddr(n, &p->to);
	if(a == ADATA || a == AGLOBL)
		pc--;
}

int
sval(long v)
{

	if(v >= -(1<<15) && v < (1<<15))
		return 1;
	return 0;
}

int
sconst(Node *n)
{
	vlong vv;

	if(n->op == OCONST) {
		if(!typefd[n->type->etype]) {
			vv = n->vconst;
			if(vv >= -(((vlong)1)<<15) && vv < (((vlong)1)<<15))
				return 1;
		}
	}
	return 0;
}

int
uconst(Node *n)
{
	vlong vv;

	if(n->op == OCONST) {
		if(!typefd[n->type->etype]) {
			vv = n->vconst;
			if(vv >= 0 && vv < (((vlong)1)<<16))
				return 1;
		}
	}
	return 0;
}

long
exreg(Type *t)
{
	long o;

	if(typechlp[t->etype]) {
		if(exregoffset <= 3)
			return 0;
		o = exregoffset;
		exregoffset--;
		return o;
	}
	if(typefd[t->etype]) {
		if(exfregoffset <= 16)
			return 0;
		o = exfregoffset + NREG;
		exfregoffset--;
		return o;
	}
	return 0;
}

schar	ewidth[NTYPE] =
{
	-1,		/* [TXXX] */
	SZ_CHAR,	/* [TCHAR] */
	SZ_CHAR,	/* [TUCHAR] */
	SZ_SHORT,	/* [TSHORT] */
	SZ_SHORT,	/* [TUSHORT] */
	SZ_INT,		/* [TINT] */
	SZ_INT,		/* [TUINT] */
	SZ_LONG,	/* [TLONG] */
	SZ_LONG,	/* [TULONG] */
	SZ_VLONG,	/* [TVLONG] */
	SZ_VLONG,	/* [TUVLONG] */
	SZ_FLOAT,	/* [TFLOAT] */
	SZ_DOUBLE,	/* [TDOUBLE] */
	SZ_IND,		/* [TIND] */
	0,		/* [TFUNC] */
	-1,		/* [TARRAY] */
	0,		/* [TVOID] */
	-1,		/* [TSTRUCT] */
	-1,		/* [TUNION] */
	SZ_INT,		/* [TENUM] */
};
long	ncast[NTYPE] =
{
	0,				/* [TXXX] */
	BCHAR|BUCHAR,			/* [TCHAR] */
	BCHAR|BUCHAR,			/* [TUCHAR] */
	BSHORT|BUSHORT,			/* [TSHORT] */
	BSHORT|BUSHORT,			/* [TUSHORT] */
	BINT|BUINT|BLONG|BULONG|BIND,	/* [TINT] */
	BINT|BUINT|BLONG|BULONG|BIND,	/* [TUINT] */
	BINT|BUINT|BLONG|BULONG|BIND,	/* [TLONG] */
	BINT|BUINT|BLONG|BULONG|BIND,	/* [TULONG] */
	BVLONG|BUVLONG,			/* [TVLONG] */
	BVLONG|BUVLONG,			/* [TUVLONG] */
	BFLOAT,				/* [TFLOAT] */
	BDOUBLE,			/* [TDOUBLE] */
	BLONG|BULONG|BIND,		/* [TIND] */
	0,				/* [TFUNC] */
	0,				/* [TARRAY] */
	0,				/* [TVOID] */
	BSTRUCT,			/* [TSTRUCT] */
	BUNION,				/* [TUNION] */
	0,				/* [TENUM] */
};