span.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	"l.h"

void
span(void)
{
	Prog *p, *q;
	long v, c, idat;
	int m, n, again;

	xdefine("etext", STEXT, 0L);
	idat = INITDAT;
	for(p = firstp; p != P; p = p->link) {
		if(p->as == ATEXT)
			curtext = p;
		n = 0;
		if(p->to.type == D_BRANCH)
			if(p->pcond == P)
				p->pcond = p;
		if((q = p->pcond) != P)
			if(q->back != 2)
				n = 1;
		p->back = n;
		if(p->as == AADJSP) {
			p->to.type = D_SP;
			v = -p->from.offset;
			p->from.offset = v;
			p->as = AADDL;
			if(v < 0) {
				p->as = ASUBL;
				v = -v;
				p->from.offset = v;
			}
			if(v == 0)
				p->as = ANOP;
		}
	}
	n = 0;

start:
	if(debug['v'])
		Bprint(&bso, "%5.2f span\n", cputime());
	Bflush(&bso);
	c = INITTEXT;
	for(p = firstp; p != P; p = p->link) {
		if(p->as == ATEXT)
			curtext = p;
		if(p->to.type == D_BRANCH)
			if(p->back)
				p->pc = c;
		asmins(p);
		p->pc = c;
		m = andptr-and;
		p->mark = m;
		c += m;
	}

loop:
	n++;
	if(debug['v'])
		Bprint(&bso, "%5.2f span %d\n", cputime(), n);
	Bflush(&bso);
	if(n > 50) {
		print("span must be looping\n");
		errorexit();
	}
	again = 0;
	c = INITTEXT;
	for(p = firstp; p != P; p = p->link) {
		if(p->as == ATEXT)
			curtext = p;
		if(p->to.type == D_BRANCH) {
			if(p->back)
				p->pc = c;
			asmins(p);
			m = andptr-and;
			if(m != p->mark) {
				p->mark = m;
				again++;
			}
		}
		p->pc = c;
		c += p->mark;
	}
	if(again) {
		textsize = c;
		goto loop;
	}
	if(INITRND) {
		INITDAT = rnd(c, INITRND);
		if(INITDAT != idat) {
			idat = INITDAT;
			goto start;
		}
	}
	xdefine("etext", STEXT, c);
	if(debug['v'])
		Bprint(&bso, "etext = %lux\n", c);
	Bflush(&bso);
	for(p = textp; p != P; p = p->pcond)
		p->from.sym->value = p->pc;
	textsize = c - INITTEXT;
}

void
xdefine(char *p, int t, long v)
{
	Sym *s;

	s = lookup(p, 0);
	if(s->type == 0 || s->type == SXREF) {
		s->type = t;
		s->value = v;
	}
	if(s->type == STEXT && s->value == 0)
		s->value = v;
}

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

	if(t == 'f')
		s++;
	lput(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);
	}
}

void
asmsym(void)
{
	Prog *p;
	Auto *a;
	Sym *s;
	int h;

	s = lookup("etext", 0);
	if(s->type == STEXT)
		putsymb(s->name, 'T', s->value, s->version);

	for(h=0; h<NHASH; h++)
		for(s=hash[h]; s!=S; s=s->link)
			switch(s->type) {
			case SCONST:
				putsymb(s->name, 'D', s->value, s->version);
				continue;

			case SDATA:
				putsymb(s->name, 'D', s->value+INITDAT, s->version);
				continue;

			case SBSS:
				putsymb(s->name, 'B', s->value+INITDAT, s->version);
				continue;

			case SFILE:
				putsymb(s->name, 'f', s->value, s->version);
				continue;
			}

	for(p=textp; p!=P; p=p->pcond) {
		s = p->from.sym;
		if(s->type != STEXT)
			continue;

		/* 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);

		putsymb(s->name, 'T', 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
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);
}

int
oclass(Adr *a)
{
	long v;

	if(a->type >= D_INDIR || a->index != D_NONE) {
		if(a->index != D_NONE && a->scale == 0) {
			if(a->type == D_ADDR) {
				switch(a->index) {
				case D_EXTERN:
				case D_STATIC:
					return Yi32;
				case D_AUTO:
				case D_PARAM:
					return Yiauto;
				}
				return Yxxx;
			}
			return Ycol;
		}
		return Ym;
	}
	switch(a->type)
	{
	case D_AL:
		return Yal;

	case D_AX:
		return Yax;

	case D_CL:
	case D_DL:
	case D_BL:
	case D_AH:
	case D_CH:
	case D_DH:
	case D_BH:
		return Yrb;

	case D_CX:
		return Ycx;

	case D_DX:
	case D_BX:
		return Yrx;

	case D_SP:
	case D_BP:
	case D_SI:
	case D_DI:
		return Yrl;

	case D_F0+0:
		return	Yf0;

	case D_F0+1:
	case D_F0+2:
	case D_F0+3:
	case D_F0+4:
	case D_F0+5:
	case D_F0+6:
	case D_F0+7:
		return	Yrf;

	case D_NONE:
		return Ynone;

	case D_CS:	return	Ycs;
	case D_SS:	return	Yss;
	case D_DS:	return	Yds;
	case D_ES:	return	Yes;
	case D_FS:	return	Yfs;
	case D_GS:	return	Ygs;

	case D_GDTR:	return	Ygdtr;
	case D_IDTR:	return	Yidtr;
	case D_LDTR:	return	Yldtr;
	case D_MSW:	return	Ymsw;
	case D_TASK:	return	Ytask;

	case D_CR+0:	return	Ycr0;
	case D_CR+1:	return	Ycr1;
	case D_CR+2:	return	Ycr2;
	case D_CR+3:	return	Ycr3;
	case D_CR+4:	return	Ycr4;
	case D_CR+5:	return	Ycr5;
	case D_CR+6:	return	Ycr6;
	case D_CR+7:	return	Ycr7;

	case D_DR+0:	return	Ydr0;
	case D_DR+1:	return	Ydr1;
	case D_DR+2:	return	Ydr2;
	case D_DR+3:	return	Ydr3;
	case D_DR+4:	return	Ydr4;
	case D_DR+5:	return	Ydr5;
	case D_DR+6:	return	Ydr6;
	case D_DR+7:	return	Ydr7;

	case D_TR+0:	return	Ytr0;
	case D_TR+1:	return	Ytr1;
	case D_TR+2:	return	Ytr2;
	case D_TR+3:	return	Ytr3;
	case D_TR+4:	return	Ytr4;
	case D_TR+5:	return	Ytr5;
	case D_TR+6:	return	Ytr6;
	case D_TR+7:	return	Ytr7;

	case D_EXTERN:
	case D_STATIC:
	case D_AUTO:
	case D_PARAM:
		return Ym;

	case D_CONST:
	case D_ADDR:
		if(a->sym == S) {
			v = a->offset;
			if(v == 0)
				return Yi0;
			if(v == 1)
				return Yi1;
			if(v >= -128 && v <= 127)
				return Yi8;
		}
		return Yi32;

	case D_BRANCH:
		return Ybr;
	}
	return Yxxx;
}

void
asmidx(Adr *a, int base)
{
	int i;

	switch(a->index) {
	default:
		goto bad;

	case D_NONE:
		i = 4 << 3;
		goto bas;

	case D_AX:
	case D_CX:
	case D_DX:
	case D_BX:
	case D_BP:
	case D_SI:
	case D_DI:
		i = reg[a->index] << 3;
		break;
	}
	switch(a->scale) {
	default:
		goto bad;
	case 1:
		break;
	case 2:
		i |= (1<<6);
		break;
	case 4:
		i |= (2<<6);
		break;
	case 8:
		i |= (3<<6);
		break;
	}
bas:
	switch(base) {
	default:
		goto bad;
	case D_NONE:	/* must be mod=00 */
		i |= 5;
		break;
	case D_AX:
	case D_CX:
	case D_DX:
	case D_BX:
	case D_SP:
	case D_BP:
	case D_SI:
	case D_DI:
		i |= reg[base];
		break;
	}
	*andptr++ = i;
	return;
bad:
	diag("asmidx: bad address %D", a);
	*andptr++ = 0;
	return;
}

static void
put4(long v)
{
	if(dlm && curp != P && reloca != nil){
		dynreloc(reloca->sym, curp->pc + andptr - &and[0], 1);
		reloca = nil;
	}
	andptr[0] = v;
	andptr[1] = v>>8;
	andptr[2] = v>>16;
	andptr[3] = v>>24;
	andptr += 4;
}

long
vaddr(Adr *a)
{
	int t;
	long v;
	Sym *s;

	t = a->type;
	v = a->offset;
	if(t == D_ADDR)
		t = a->index;
	switch(t) {
	case D_STATIC:
	case D_EXTERN:
		s = a->sym;
		if(s != nil) {
			if(dlm && curp != P)
				reloca = a;
			switch(s->type) {
			case SUNDEF:
				ckoff(s, v);
			case STEXT:
			case SCONST:
				v += s->value;
				break;
			default:
				v += INITDAT + s->value;
			}
		}
	}
	return v;
}

void
asmand(Adr *a, int r)
{
	long v;
	int t;
	Adr aa;

	v = a->offset;
	t = a->type;
	if(a->index != D_NONE) {
		if(t >= D_INDIR) {
			t -= D_INDIR;
			if(t == D_NONE) {
				*andptr++ = (0 << 6) | (4 << 0) | (r << 3);
				asmidx(a, t);
				put4(v);
				return;
			}
			if(v == 0 && t != D_BP) {
				*andptr++ = (0 << 6) | (4 << 0) | (r << 3);
				asmidx(a, t);
				return;
			}
			if(v >= -128 && v < 128) {
				*andptr++ = (1 << 6) | (4 << 0) | (r << 3);
				asmidx(a, t);
				*andptr++ = v;
				return;
			}
			*andptr++ = (2 << 6) | (4 << 0) | (r << 3);
			asmidx(a, t);
			put4(v);
			return;
		}
		switch(t) {
		default:
			goto bad;
		case D_STATIC:
		case D_EXTERN:
			aa.type = D_NONE+D_INDIR;
			break;
		case D_AUTO:
		case D_PARAM:
			aa.type = D_SP+D_INDIR;
			break;
		}
		aa.offset = vaddr(a);
		aa.index = a->index;
		aa.scale = a->scale;
		asmand(&aa, r);
		return;
	}
	if(t >= D_AL && t <= D_F0+7) {
		if(v)
			goto bad;
		*andptr++ = (3 << 6) | (reg[t] << 0) | (r << 3);
		return;
	}
	if(t >= D_INDIR) {
		t -= D_INDIR;
		if(t == D_NONE) {
			*andptr++ = (0 << 6) | (5 << 0) | (r << 3);
			put4(v);
			return;
		}
		if(t == D_SP) {
			if(v == 0) {
				*andptr++ = (0 << 6) | (4 << 0) | (r << 3);
				asmidx(a, D_SP);
				return;
			}
			if(v >= -128 && v < 128) {
				*andptr++ = (1 << 6) | (4 << 0) | (r << 3);
				asmidx(a, D_SP);
				*andptr++ = v;
				return;
			}
			*andptr++ = (2 << 6) | (4 << 0) | (r << 3);
			asmidx(a, D_SP);
			put4(v);
			return;
		}
		if(t >= D_AX && t <= D_DI) {
			if(v == 0 && t != D_BP) {
				*andptr++ = (0 << 6) | (reg[t] << 0) | (r << 3);
				return;
			}
			if(v >= -128 && v < 128) {
				andptr[0] = (1 << 6) | (reg[t] << 0) | (r << 3);
				andptr[1] = v;
				andptr += 2;
				return;
			}
			*andptr++ = (2 << 6) | (reg[t] << 0) | (r << 3);
			put4(v);
			return;
		}
		goto bad;
	}
	switch(a->type) {
	default:
		goto bad;
	case D_STATIC:
	case D_EXTERN:
		aa.type = D_NONE+D_INDIR;
		break;
	case D_AUTO:
	case D_PARAM:
		aa.type = D_SP+D_INDIR;
		break;
	}
	aa.index = D_NONE;
	aa.scale = 1;
	aa.offset = vaddr(a);
	asmand(&aa, r);
	return;
bad:
	diag("asmand: bad address %D", a);
	return;
}

#define	E	0xff
uchar	ymovtab[] =
{
/* push */
	APUSHL,	Ycs,	Ynone,	0,	0x0e,E,0,0,
	APUSHL,	Yss,	Ynone,	0,	0x16,E,0,0,
	APUSHL,	Yds,	Ynone,	0,	0x1e,E,0,0,
	APUSHL,	Yes,	Ynone,	0,	0x06,E,0,0,
	APUSHL,	Yfs,	Ynone,	0,	0x0f,0xa0,E,0,
	APUSHL,	Ygs,	Ynone,	0,	0x0f,0xa8,E,0,

	APUSHW,	Ycs,	Ynone,	0,	Pe,0x0e,E,0,
	APUSHW,	Yss,	Ynone,	0,	Pe,0x16,E,0,
	APUSHW,	Yds,	Ynone,	0,	Pe,0x1e,E,0,
	APUSHW,	Yes,	Ynone,	0,	Pe,0x06,E,0,
	APUSHW,	Yfs,	Ynone,	0,	Pe,0x0f,0xa0,E,
	APUSHW,	Ygs,	Ynone,	0,	Pe,0x0f,0xa8,E,

/* pop */
	APOPL,	Ynone,	Yds,	0,	0x1f,E,0,0,
	APOPL,	Ynone,	Yes,	0,	0x07,E,0,0,
	APOPL,	Ynone,	Yss,	0,	0x17,E,0,0,
	APOPL,	Ynone,	Yfs,	0,	0x0f,0xa1,E,0,
	APOPL,	Ynone,	Ygs,	0,	0x0f,0xa9,E,0,