asm.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

		/* filenames first */
		for(a=p->to.autom; a; a=a->link)
			if(a->type == D_FILE)
				putsymb(a->asym->name, 'z', a->aoffset, 0);
			else
			if(a->type == D_FILE1)
				putsymb(a->asym->name, 'Z', a->aoffset, 0);

		if(s->type == STEXT)
			putsymb(s->name, 'T', s->value, s->version);
		else
			putsymb(s->name, 'L', s->value, s->version);

		/* frame, auto and param after */
		putsymb(".frame", 'm', p->to.offset+4, 0);
		for(a=p->to.autom; a; a=a->link)
			if(a->type == D_AUTO)
				putsymb(a->asym->name, 'a', -a->aoffset, 0);
			else
			if(a->type == D_PARAM)
				putsymb(a->asym->name, 'p', a->aoffset, 0);
	}
	if(debug['v'] || debug['n'])
		Bprint(&bso, "symsize = %lud\n", symsize);
	Bflush(&bso);
}

void
putsymb(char *s, int t, long v, int ver)
{
	int i, f;

	if(t == 'f')
		s++;
	LBEPUT(v);
	if(ver)
		t += 'a' - 'A';
	CPUT(t+0x80);			/* 0x80 is variable length */

	if(t == 'Z' || t == 'z') {
		CPUT(s[0]);
		for(i=1; s[i] != 0 || s[i+1] != 0; i += 2) {
			CPUT(s[i]);
			CPUT(s[i+1]);
		}
		CPUT(0);
		CPUT(0);
		i++;
	}
	else {
		for(i=0; s[i]; i++)
			CPUT(s[i]);
		CPUT(0);
	}
	symsize += 4 + 1 + i + 1;

	if(debug['n']) {
		if(t == 'z' || t == 'Z') {
			Bprint(&bso, "%c %.8lux ", t, v);
			for(i=1; s[i] != 0 || s[i+1] != 0; i+=2) {
				f = ((s[i]&0xff) << 8) | (s[i+1]&0xff);
				Bprint(&bso, "/%x", f);
			}
			Bprint(&bso, "\n");
			return;
		}
		if(ver)
			Bprint(&bso, "%c %.8lux %s<%d>\n", t, v, s, ver);
		else
			Bprint(&bso, "%c %.8lux %s\n", t, v, s);
	}
}

#define	MINLC	4
void
asmlc(void)
{
	long oldpc, oldlc;
	Prog *p;
	long v, s;

	oldpc = INITTEXT;
	oldlc = 0;
	for(p = firstp; p != P; p = p->link) {
		if(p->line == oldlc || p->as == ATEXT || p->as == ANOP) {
			if(p->as == ATEXT)
				curtext = p;
			if(debug['L'])
				Bprint(&bso, "%6lux %P\n",
					p->pc, p);
			continue;
		}
		if(debug['L'])
			Bprint(&bso, "\t\t%6ld", lcsize);
		v = (p->pc - oldpc) / MINLC;
		while(v) {
			s = 127;
			if(v < 127)
				s = v;
			CPUT(s+128);	/* 129-255 +pc */
			if(debug['L'])
				Bprint(&bso, " pc+%ld*%d(%ld)", s, MINLC, s+128);
			v -= s;
			lcsize++;
		}
		s = p->line - oldlc;
		oldlc = p->line;
		oldpc = p->pc + MINLC;
		if(s > 64 || s < -64) {
			CPUT(0);	/* 0 vv +lc */
			CPUT(s>>24);
			CPUT(s>>16);
			CPUT(s>>8);
			CPUT(s);
			if(debug['L']) {
				if(s > 0)
					Bprint(&bso, " lc+%ld(%d,%ld)\n",
						s, 0, s);
				else
					Bprint(&bso, " lc%ld(%d,%ld)\n",
						s, 0, s);
				Bprint(&bso, "%6lux %P\n",
					p->pc, p);
			}
			lcsize += 5;
			continue;
		}
		if(s > 0) {
			CPUT(0+s);	/* 1-64 +lc */
			if(debug['L']) {
				Bprint(&bso, " lc+%ld(%ld)\n", s, 0+s);
				Bprint(&bso, "%6lux %P\n",
					p->pc, p);
			}
		} else {
			CPUT(64-s);	/* 65-128 -lc */
			if(debug['L']) {
				Bprint(&bso, " lc%ld(%ld)\n", s, 64-s);
				Bprint(&bso, "%6lux %P\n",
					p->pc, p);
			}
		}
		lcsize++;
	}
	while(lcsize & 1) {
		s = 129;
		CPUT(s);
		lcsize++;
	}
	if(debug['v'] || debug['L'])
		Bprint(&bso, "lcsize = %ld\n", lcsize);
	Bflush(&bso);
}

void
datblk(long s, long n, int str)
{
	Prog *p;
	char *cast;
	long l, fl, j, d;
	int i, c;

	memset(buf.dbuf, 0, n+100);
	for(p = datap; p != P; p = p->link) {
		curp = p;
		if(str != (p->from.sym->type == SSTRING))
			continue;
		l = p->from.sym->value + p->from.offset - s;
		c = p->reg;
		i = 0;
		if(l < 0) {
			if(l+c <= 0)
				continue;
			while(l < 0) {
				l++;
				i++;
			}
		}
		if(l >= n)
			continue;
		if(p->as != AINIT && p->as != ADYNT) {
			for(j=l+(c-i)-1; j>=l; j--)
				if(buf.dbuf[j]) {
					print("%P\n", p);
					diag("multiple initialization");
					break;
				}
		}
		switch(p->to.type) {
		default:
			diag("unknown mode in initialization\n%P", p);
			break;

		case D_FCONST:
			switch(c) {
			default:
			case 4:
				fl = ieeedtof(p->to.ieee);
				cast = (char*)&fl;
				for(; i<c; i++) {
					buf.dbuf[l] = cast[fnuxi8[i+4]];
					l++;
				}
				break;
			case 8:
				cast = (char*)p->to.ieee;
				for(; i<c; i++) {
					buf.dbuf[l] = cast[fnuxi8[i]];
					l++;
				}
				break;
			}
			break;

		case D_SCONST:
			for(; i<c; i++) {
				buf.dbuf[l] = p->to.sval[i];
				l++;
			}
			break;

		case D_CONST:
			d = p->to.offset;
			if(p->to.sym) {
				switch(p->to.sym->type) {
				case STEXT:
				case SLEAF:
				case SSTRING:
					d += p->to.sym->value;
					break;
				case SDATA:
				case SBSS:
					d += p->to.sym->value + INITDAT;
					break;
				}
			}
			cast = (char*)&d;
			switch(c) {
			default:
				diag("bad nuxi %d %d\n%P", c, i, curp);
				break;
			case 1:
				for(; i<c; i++) {
					buf.dbuf[l] = cast[inuxi1[i]];
					l++;
				}
				break;
			case 2:
				for(; i<c; i++) {
					buf.dbuf[l] = cast[inuxi2[i]];
					l++;
				}
				break;
			case 4:
				for(; i<c; i++) {
					buf.dbuf[l] = cast[inuxi4[i]];
					l++;
				}
				break;
			}
			break;
		}
	}
	write(cout, buf.dbuf, n);
}

#define	OP_RRR(op,r1,r2,r3)\
	(op|(((r1)&31L)<<16)|(((r2)&31L)<<21)|(((r3)&31L)<<11))
#define	OP_IRR(op,i,r2,r3)\
	(op|((i)&0xffffL)|(((r2)&31L)<<21)|(((r3)&31L)<<16))
#define	OP_SRR(op,s,r2,r3)\
	(op|(((s)&31L)<<6)|(((r2)&31L)<<16)|(((r3)&31L)<<11))
#define	OP_FRRR(op,r1,r2,r3)\
	(op|(((r1)&31L)<<16)|(((r2)&31L)<<11)|(((r3)&31L)<<6))
#define	OP_JMP(op,i)\
		((op)|((i)&0x3ffffffL))

#define	OP(x,y)\
	(((x)<<3)|((y)<<0))
#define	SP(x,y)\
	(((x)<<29)|((y)<<26))
#define	BCOND(x,y)\
	(((x)<<19)|((y)<<16))
#define	MMU(x,y)\
	(SP(2,0)|(16<<21)|((x)<<3)|((y)<<0))
#define	FPF(x,y)\
	(SP(2,1)|(16<<21)|((x)<<3)|((y)<<0))
#define	FPD(x,y)\
	(SP(2,1)|(17<<21)|((x)<<3)|((y)<<0))
#define	FPW(x,y)\
	(SP(2,1)|(20<<21)|((x)<<3)|((y)<<0))

int vshift(int);

int
asmout(Prog *p, Optab *o, int aflag)
{
	long o1, o2, o3, o4, o5, o6, o7, v;
	Prog *ct;
	int r, a;

	o1 = 0;
	o2 = 0;
	o3 = 0;
	o4 = 0;
	o5 = 0;
	o6 = 0;
	o7 = 0;
	switch(o->type) {
	default:
		diag("unknown type %d", o->type);
		if(!debug['a'])
			prasm(p);
		break;

	case 0:		/* pseudo ops */
		if(aflag) {
			if(p->link) {
				if(p->as == ATEXT) {
					ct = curtext;
					o2 = autosize;
					curtext = p;
					autosize = p->to.offset + 4;
					o1 = asmout(p->link, oplook(p->link), aflag);
					curtext = ct;
					autosize = o2;
				} else
					o1 = asmout(p->link, oplook(p->link), aflag);
			}
			return o1;
		}
		break;

	case 1:		/* mov[v] r1,r2 ==> OR r1,r0,r2 */
		o1 = OP_RRR(oprrr(AOR), p->from.reg, REGZERO, p->to.reg);
		break;

	case 2:		/* add/sub r1,[r2],r3 */
		r = p->reg;
		if(r == NREG)
			r = p->to.reg;
		o1 = OP_RRR(oprrr(p->as), p->from.reg, r, p->to.reg);
		break;

	case 3:		/* mov $soreg, r ==> or/add $i,o,r */
		v = regoff(&p->from);
		r = p->from.reg;
		if(r == NREG)
			r = o->param;
		a = AADDU;
		if(o->a1 == C_ANDCON)
			a = AOR;
		o1 = OP_IRR(opirr(a), v, r, p->to.reg);
		break;

	case 4:		/* add $scon,[r1],r2 */
		v = regoff(&p->from);
		r = p->reg;
		if(r == NREG)
			r = p->to.reg;
		o1 = OP_IRR(opirr(p->as), v, r, p->to.reg);
		break;

	case 5:		/* syscall */
		if(aflag)
			return 0;
		o1 = oprrr(p->as);
		break;

	case 6:		/* beq r1,[r2],sbra */
		if(aflag)
			return 0;
		if(p->cond == P)
			v = -4 >> 2;
		else
			v = (p->cond->pc - pc-4) >> 2;
		if(((v << 16) >> 16) != v)
			diag("short branch too far: %d\n%P", v, p);
		o1 = OP_IRR(opirr(p->as), v, p->from.reg, p->reg);
		break;

	case 7:		/* mov r, soreg ==> sw o(r) */
		r = p->to.reg;
		if(r == NREG)
			r = o->param;
		v = regoff(&p->to);
		o1 = OP_IRR(opirr(p->as), v, r, p->from.reg);
		break;

	case 8:		/* mov soreg, r ==> lw o(r) */
		r = p->from.reg;
		if(r == NREG)
			r = o->param;
		v = regoff(&p->from);
		o1 = OP_IRR(opirr(p->as+ALAST), v, r, p->to.reg);
		break;

	case 9:		/* asl r1,[r2],r3 */
		r = p->reg;
		if(r == NREG)
			r = p->to.reg;
		o1 = OP_RRR(oprrr(p->as), r, p->from.reg, p->to.reg);
		break;

	case 10:	/* add $con,[r1],r2 ==> mov $con,t; add t,[r1],r2 */
		v = regoff(&p->from);
		r = AOR;
		if(v < 0)
			r = AADDU;
		o1 = OP_IRR(opirr(r), v, 0, REGTMP);
		r = p->reg;
		if(r == NREG)
			r = p->to.reg;
		o2 = OP_RRR(oprrr(p->as), REGTMP, r, p->to.reg);
		break;

	case 11:	/* jmp lbra */
		if(aflag)
			return 0;
		if(p->cond == P)
			v = p->pc >> 2;
		else
			v = p->cond->pc >> 2;
		o1 = OP_JMP(opirr(p->as), v);
		if(!debug['Y'] && p->link && p->cond && isnop(p->link)) {
			nop.branch.count--;
			nop.branch.outof--;
			nop.jump.outof++;
			o2 = asmout(p->cond, oplook(p->cond), 1);
			if(o2) {
				o1 += 1;
				if(debug['a'])
					Bprint(&bso, " %.8lux: %.8lux %.8lux%P\n",
						p->pc, o1, o2, p);
				LPUT(o1);
				LPUT(o2);
				return 1;
			}
		}
		break;

	case 12:	/* movbs r,r */
		v = 16;
		if(p->as == AMOVB)
			v = 24;
		o1 = OP_SRR(opirr(ASLL), v, p->from.reg, p->to.reg);
		o2 = OP_SRR(opirr(ASRA), v, p->to.reg, p->to.reg);
		break;

	case 13:	/* movbu r,r */
		if(p->as == AMOVBU)
			o1 = OP_IRR(opirr(AAND), 0xffL, p->from.reg, p->to.reg);
		else
			o1 = OP_IRR(opirr(AAND), 0xffffL, p->from.reg, p->to.reg);
		break;

	case 16:	/* sll $c,[r1],r2 */
		v = regoff(&p->from);
		r = p->reg;
		if(r == NREG)
			r = p->to.reg;

		/* OP_SRR will use only the low 5 bits of the shift value */
		if(v >= 32 && vshift(p->as))
			o1 = OP_SRR(opirr(p->as+ALAST), v-32, r, p->to.reg);
		else 
			o1 = OP_SRR(opirr(p->as), v, r, p->to.reg);
		break;

	case 18:	/* jmp [r1],0(r2) */
		if(aflag)
			return 0;
		r = p->reg;
		if(r == NREG)
			r = o->param;
		o1 = OP_RRR(oprrr(p->as), 0, p->to.reg, r);
		break;

	case 19:	/* mov $lcon,r ==> lu+or */