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

	 * a store --
	 * put it into a register then
	 * store it.
	 */
	if(t->op == ONAME || t->op == OINDREG || t->op == OIND) {
		switch(tt) {
		default:
			a = AMOVL;
			break;
		case TUCHAR:
		case TCHAR:
			a = AMOVB;
			break;
		case TUSHORT:
		case TSHORT:
			a = AMOVW;
			break;
		case TFLOAT:
			a = AMOVS;
			break;
		case TDOUBLE:
			a = AMOVT;
			break;
		case TVLONG:
		case TUVLONG:
			a = AMOVQ;
			break;
		}
		if(!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 TFLOAT:
		switch(tt) {
		case TDOUBLE:
			a = AMOVT;
			break;
		case TFLOAT:
			a = ACVTTS;
			if(ft == TFLOAT)
				a = AMOVT;
			break;
		case TINT:
		case TUINT:
		case TLONG:
		case TULONG:
		case TUVLONG:
		case TVLONG:
		case TIND:
		case TSHORT:
		case TUSHORT:
		case TCHAR:
		case TUCHAR:
			/*warn(Z, "float to fix");	/**/
			regalloc(&nod, f, Z);	/* should be type float */
			gins(ACVTTQ, f, &nod);
			gins(AMOVT, &nod, nodrat);
			regfree(&nod);
			gins(AMOVQ, nodrat, t);
			gmove(t, t);
			if(nrathole < SZ_VLONG)
				nrathole = SZ_VLONG;
			return;
		}
		break;
	case TVLONG:
	case TUVLONG:
		switch(tt) {
		case TDOUBLE:
		case TFLOAT:
			goto fxtofl;
		case TINT:
		case TUINT:
		case TLONG:
		case TULONG:
		case TIND:
		case TSHORT:
		case TUSHORT:
		case TCHAR:
		case TUCHAR:
			a = AMOVL;
			break;
		case TVLONG:
		case TUVLONG:
			a = AMOVQ;
			break;
		}
		break;
	case TINT:
	case TUINT:
	case TULONG:
	case TLONG:
	case TIND:
		switch(tt) {
		case TDOUBLE:
		case TFLOAT:
			goto fxtofl;
		case TVLONG:
		case TUVLONG:
			if (ft == TULONG || ft == TUINT) {
				a = AMOVLU;
				break;
			}
		case TINT:
		case TUINT:
		case TLONG:
		case TULONG:
		case TIND:
		case TSHORT:
		case TUSHORT:
		case TCHAR:
		case TUCHAR:
			a = AMOVQ;
			break;
		}
		break;
	case TSHORT:
		switch(tt) {
		case TDOUBLE:
		case TFLOAT:
			goto fxtofl;
		case TINT:
		case TUINT:
		case TULONG:
		case TLONG:
		case TVLONG:
		case TUVLONG:
		case TIND:
			a = AMOVW;
			break;
		case TSHORT:
		case TUSHORT:
		case TCHAR:
		case TUCHAR:
			a = AMOVQ;
			break;
		}
		break;
	case TUSHORT:
		switch(tt) {
		case TDOUBLE:
		case TFLOAT:
			goto fxtofl;
		case TINT:
		case TUINT:
		case TLONG:
		case TULONG:
		case TVLONG:
		case TUVLONG:
		case TIND:
			a = AMOVWU;
			break;
		case TSHORT:
		case TUSHORT:
		case TCHAR:
		case TUCHAR:
			a = AMOVQ;
			break;
		}
		break;
	case TCHAR:
		switch(tt) {
		case TDOUBLE:
		case TFLOAT:
			goto fxtofl;
		case TINT:
		case TUINT:
		case TLONG:
		case TULONG:
		case TVLONG:
		case TUVLONG:
		case TIND:
		case TSHORT:
		case TUSHORT:
			a = AMOVB;
			break;
		case TCHAR:
		case TUCHAR:
			a = AMOVQ;
			break;
		}
		break;
	case TUCHAR:
		switch(tt) {
		case TDOUBLE:
		case TFLOAT:
		fxtofl:
			/*warn(Z, "fix to float");	/**/
			regalloc(&nod, t, Z);	/* should be type float */
			gins(AMOVQ, f, nodrat);
			gins(AMOVT, nodrat, &nod);
			a = ACVTQT;
			if(tt == TFLOAT)
				a = ACVTQS;
			gins(a, &nod, t);
			regfree(&nod);
			if(nrathole < SZ_VLONG)
				nrathole = SZ_VLONG;
			return;
		case TINT:
		case TUINT:
		case TLONG:
		case TULONG:
		case TVLONG:
		case TUVLONG:
		case TIND:
		case TSHORT:
		case TUSHORT:
			a = AMOVBU;
			break;
		case TCHAR:
		case TUCHAR:
			a = AMOVQ;
			break;
		}
		break;
	}
	if(a == AMOVQ || a == AMOVS || a == AMOVT)
	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;
	Node nod;

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

	case OASADD:
	case OADD:
		a = AADDL;
		if(et == TFLOAT)
			a = AADDS;
		else
		if(et == TDOUBLE)
			a = AADDT;
		else
		if(et == TVLONG || et == TUVLONG)
			a = AADDQ;
		break;

	case OASSUB:
	case OSUB:
		a = ASUBL;
		if(et == TFLOAT)
			a = ASUBS;
		else
		if(et == TDOUBLE)
			a = ASUBT;
		else
		if(et == TVLONG || et == TUVLONG)
			a = ASUBQ;
		break;

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

	case OASAND:
	case OAND:
		a = AAND;
		break;

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

	case OASLSHR:
	case OLSHR:
		a = ASRLL;
		if(et == TVLONG || et == TUVLONG)
			a = ASRLQ;
		break;

	case OASASHR:
	case OASHR:
		a = ASRAL;
		if(et == TVLONG || et == TUVLONG)
			a = ASRAQ;
		break;

	case OASASHL:
	case OASHL:
		a = ASLLL;
		if(et == TVLONG || et == TUVLONG)
			a = ASLLQ;
		break;

	case OFUNC:
		a = AJSR;
		break;

	case OASLMUL:
	case OLMUL:
	case OASMUL:
	case OMUL:
		a = AMULL;
		if(et == TFLOAT)
			a = AMULS;
		else
		if(et == TDOUBLE)
			a = AMULT;
		else
		if(et == TVLONG || et == TUVLONG)
			a = AMULQ;
		break;

	case OASDIV:
	case ODIV:
		a = ADIVL;
		if(et == TFLOAT)
			a = ADIVS;
		else
		if(et == TDOUBLE)
			a = ADIVT;
		else
		if(et == TVLONG || et == TUVLONG)
			a = ADIVQ;
		break;

	case OASMOD:
	case OMOD:
		a = AMODL;
		if(et == TVLONG || et == TUVLONG)
			a = AMODQ;
		break;

	case OASLMOD:
	case OLMOD:
		a = AMODLU;
		if(et == TVLONG || et == TUVLONG)
			a = AMODQU;
		break;

	case OASLDIV:
	case OLDIV:
		a = ADIVLU;
		if(et == TVLONG || et == TUVLONG)
			a = ADIVQU;
		break;

	case OEQ:
	case ONE:
		a = ACMPEQ;
		if(typefd[et])
			a = ACMPTEQ;
		else if (vconst(t) == 0) {
			a = (o == OEQ) ? ABEQ : ABNE;
			t = Z;
			break;
		}
		goto cmp;

	case OLT:
	case OGE:
		a = ACMPGT;
		if(typefd[et])
			a = ACMPTGT;
		else if (vconst(t) == 0) {
			a = (o == OLT) ? ABLT : ABGE;
			t = Z;
			break;
		}
		goto cmp;

	case OLE:
	case OGT:
		a = ACMPGE;
		if(typefd[et])
			a = ACMPTGE;
		else
		if(vconst(t) == 0) {
			a = (o == OLE)? ABLE: ABGT;
			t = Z;
			break;
		}
		goto cmp;

	case OLO:
	case OHS:
		a = ACMPUGT;
		goto cmp;

	case OLS:
	case OHI:
		a = ACMPUGE;
		goto cmp;

	cmp:
		nextpc();
		p->as = a;
		raddr(f1, p);
		naddr(t, &p->from);
		regalloc(&nod, t, Z);
		naddr(&nod, &p->to);
		if(debug['g'])
			print("%P\n", p);
		if(o == OEQ || o == OLT || o == OLE || o == OLO || o == OLS)
			a = typefd[et]? AFBNE: ABNE;
		else
			a = typefd[et]? AFBEQ: ABEQ;
		nextpc();
		p->as = a;
		naddr(&nod, &p->from);
		regfree(&nod);
		if(debug['g'])
			print("%P\n", p);
		return;
	}
	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)
			p->reg = REGZERO;
	}
	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 = ARET;
		break;
	case OGOTO:
		a = AJMP;
		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
sconst(Node *n)
{
	vlong vv;

	if(n->op == OCONST) {
		if(!typefd[n->type->etype]) {
			vv = n->vconst;
			if(vv >= -32766LL && vv < 32766LL)
				return 1;
		}
	}
	return 0;
}

int
sval(long v)
{
	if(v >= -32766L && v < 32766L)
		return 1;
	return 0;
}

int
bval(vlong v)
{

	if(v >= 0LL && v < 256LL)
		return 1;
	return 0;
}

int
bconst(Node *n)
{
	vlong vv;

	if(n->op == OCONST) {
		if(!typefd[n->type->etype]) {
			vv = n->vconst;
			if(vv >= 0LL && vv < 256LL)
				return 1;
		}
	}
	return 0;
}

long
exreg(Type *t)
{
	long o;

	if(typechlp[t->etype]) {
		if(exregoffset <= 12)
			return 0;
		o = exregoffset;
		exregoffset--;
		return o;
	}
	if(typefd[t->etype]) {
		if(exfregoffset <= 19)
			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] */
};