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

#include	"l.h"

short	opa[20];
short	*op;

long
entryvalue(void)
{
	char *a;
	Sym *s;

	a = INITENTRY;
	if(*a >= '0' && *a <= '9')
		return atolwhex(a);
	s = lookup(a, 0);
	if(s->type == 0)
		return INITTEXT;
	if(s->type != STEXT)
		diag("entry not text: %s", s->name);
	return s->value;
}

void
asmb(void)
{
	Prog *p;
	long v;
	int a;
	short *op1;

	if(debug['v'])
		Bprint(&bso, "%5.2f asmb\n", cputime());
	Bflush(&bso);

	seek(cout, HEADR, 0);
	pc = INITTEXT;
	curp = firstp;
	for(p = firstp; p != P; p = p->link) {
		if(p->as == ATEXT)
			curtext = p;
		if(p->pc != pc) {
			if(!debug['a'])
				print("%P\n", curp);
			diag("phase error %lux sb %lux in %s", p->pc, pc, TNAME);
			pc = p->pc;
		}
		curp = p;
		if(debug['a'])
			Bprint(&bso, "%lux:%P\n", pc, curp);
		asmins(p);
		if(cbc < sizeof(opa))
			cflush();
		for(op1 = opa; op1 < op; op1++) {
			a = *op1;
			*cbp++ = a >> 8;
			*cbp++ = a;
		}
		a = 2*(op - opa);
		pc += a;
		cbc -= a;
		if(debug['a']) {
			for(op1 = opa; op1 < op; op1++)
				if(op1 == opa)
					Bprint(&bso, "\t\t%4ux", *op1 & 0xffff);
				else
					Bprint(&bso, " %4ux", *op1 & 0xffff);
			if(op != opa)
				Bprint(&bso, "\n");
		}
	}
	cflush();
	switch(HEADTYPE) {
	case 0:	/* this is garbage */
		seek(cout, rnd(HEADR+textsize, 8192), 0);
		break;
	case 1:	/* plan9 boot data goes into text */
		seek(cout, rnd(HEADR+textsize, INITRND), 0);
		break;
	case 2:	/* plan 9 */
		seek(cout, HEADR+textsize, 0);
		break;
	case 3:	/* next boot */
		seek(cout, HEADR+rnd(textsize, INITRND), 0);
		break;
	case 4:	/* preprocess pilot */
		seek(cout, HEADR+textsize, 0);
		break;
	}

	if(debug['v'])
		Bprint(&bso, "%5.2f datblk\n", cputime());
	Bflush(&bso);

	for(v = 0; v < datsize; v += sizeof(buf)-100) {
		if(datsize-v > sizeof(buf)-100)
			datblk(v, sizeof(buf)-100);
		else
			datblk(v, datsize-v);
	}

	symsize = 0;
	spsize = 0;
	lcsize = 0;

	Bflush(&bso);

	switch(HEADTYPE) {
	default:
		seek(cout, rnd(HEADR+textsize, 8192)+datsize, 0);
		break;
	case 1:	/* plan9 boot data goes into text */
		seek(cout, rnd(HEADR+textsize, INITRND)+datsize, 0);
		break;
	case 2:	/* plan 9 */
		seek(cout, HEADR+textsize+datsize, 0);
		break;
	case 3:	/* next boot */
		seek(cout, HEADR+rnd(textsize, INITRND)+datsize, 0);
		break;
	}
	if(!debug['s']) {
		if(debug['v'])
			Bprint(&bso, "%5.2f sym\n", cputime());
		asmsym();
	}
	Bflush(&bso);
	if(!debug['s']) {
		if(debug['v'])
			Bprint(&bso, "%5.2f sp\n", cputime());
		asmsp();
	}
	Bflush(&bso);
	if(!debug['s']) {
		if(debug['v'])
			Bprint(&bso, "%5.2f pc\n", cputime());
		asmlc();
	}
	cflush();

	if(debug['v'])
		Bprint(&bso, "%5.2f headr\n", cputime());
	Bflush(&bso);
	seek(cout, 0L, 0);
	switch(HEADTYPE) {
	default:
		lput(0x160L<<16);		/* magic and sections */
		lput(0L);			/* time and date */
		lput(rnd(HEADR+textsize, 4096)+datsize);
		lput(symsize);			/* nsyms */
		lput((0x38L<<16)|7L);		/* size of optional hdr and flags */
		lput((0413<<16)|0437L);		/* magic and version */
		lput(rnd(HEADR+textsize, 4096));	/* sizes */
		lput(datsize);
		lput(bsssize);
		lput(entryvalue());		/* va of entry */
		lput(INITTEXT-HEADR);		/* va of base of text */
		lput(INITDAT);			/* va of base of data */
		lput(INITDAT+datsize);		/* va of base of bss */
		lput(~0L);			/* gp reg mask */
		lput(0L);
		lput(0L);
		lput(0L);
		lput(0L);
		lput(~0L);			/* gp value ?? */
		break;
	case 1:	/* plan9 boot data goes into text */
		lput(0407);			/* magic */
		lput(rnd(HEADR+textsize, INITRND)-HEADR+datsize);		/* sizes */
		lput(0);
		lput(bsssize);
		lput(symsize);			/* nsyms */
		lput(entryvalue());		/* va of entry */
		lput(spsize);			/* sp offsets */
		lput(lcsize);			/* line offsets */
		break;
	case 2:	/* plan 9 */
		lput(0407);			/* magic */
		lput(textsize);			/* sizes */
		lput(datsize);
		lput(bsssize);
		lput(symsize);			/* nsyms */
		lput(entryvalue());		/* va of entry */
		lput(spsize);			/* sp offsets */
		lput(lcsize);			/* line offsets */
		break;
	case 3:	/* next boot */
		/* header */
		lput(0xfeedfaceL);			/* magic */
		lput(6);				/* 68040 */
		lput(1);				/* more 68040 */
		lput(5);				/* file type 'boot' */
		lput(HEADTYPE);				/* number commands */
		lput(HEADR-7*4);			/* sizeof commands */
		lput(1);				/* no undefineds */
		/* command 1 text */
		lput(1);				/* command = 'segment' */
		lput(124);				/* command size */
		s16put("__TEXT");
			/* botch?? entryvalue() */
		lput(INITTEXT);				/* va of start */
		lput(rnd(textsize, 8192));		/* va size */
		lput(HEADR);				/* file offset */
		lput(rnd(textsize, 8192));		/* file size */
		lput(7);				/* max prot */
		lput(7);				/* init prot */
		lput(1);				/* number of sections */
		lput(0);				/* flags */
		/* text section */
		s16put("__text");
		s16put("__TEXT");
			/* botch?? entryvalue() */
		lput(INITTEXT);				/* va of start */
		lput(textsize);				/* va size */
		lput(HEADR);				/* file offset */
		lput(2);				/* align */
		lput(0);				/* reloff */
		lput(0);				/* nreloc */
		lput(0);				/* flags */
		lput(0);				/* reserved1 */
		lput(0);				/* reserved2 */
		/* command 1 data */
		lput(1);				/* command = 'segment' */
		lput(192);				/* command size */
		s16put("__DATA");
		lput(INITDAT);				/* va of start */
		lput(rnd(datsize, 8192));		/* va size */
		lput(HEADR+rnd(textsize, 8192));	/* file offset */
		lput(rnd(datsize, 8192));		/* file size */
		lput(7);				/* max prot */
		lput(7);				/* init prot */
		lput(2);				/* number of sections */
		lput(0);				/* flags */
		/* data section */
		s16put("__data");
		s16put("__DATA");
		lput(INITDAT);				/* va of start */
		lput(datsize);				/* va size */
		lput(HEADR+rnd(textsize, 8192));	/* file offset */
		lput(2);				/* align */
		lput(0);				/* reloff */
		lput(0);				/* nreloc */
		lput(0);				/* flags */
		lput(0);				/* reserved1 */
		lput(0);				/* reserved2 */
		/* bss section */
		s16put("__bss");
		s16put("__DATA");
		lput(INITDAT+datsize);			/* va of start */
		lput(bsssize);				/* va size */
		lput(0);				/* file offset */
		lput(2);				/* align */
		lput(0);				/* reloff */
		lput(0);				/* nreloc */
		lput(1);				/* flags = zero fill */
		lput(0);				/* reserved1 */
		lput(0);				/* reserved2 */
		/* command 2 symbol */
		lput(2);				/* command = 'symbol' */
		lput(24);				/* command size */
		lput(HEADR+rnd(textsize, INITRND)
			+datsize);			/* symoff */
		lput(symsize);				/* nsyms */
		lput(spsize);				/* sp offsets */
		lput(lcsize);				/* line offsets */
		break;
	}
	cflush();
}

void
asmins(Prog *p)
{
	Optab *o;
	int t, a, b;
	long v;
	Prog *q;

	op = opa + 1;
	if(special[p->from.type])
	switch(p->from.type) {

	case D_CCR:
		if(p->as != AMOVW)
			goto bad;
		a = asmea(p, &p->to);
		if((a & 0170) == 010)
			goto bad;
		opa[0] = 0x42c0 | a;		/* mov from ccr */
		return;

	case D_SR:
		if(p->as != AMOVW)
			goto bad;
		a = asmea(p, &p->to);
		if((a & 0170) == 010)
			goto bad;
		opa[0] = 0x40c0 | a;		/* mov from sr */
		return;

	case D_USP:
		if(p->as != AMOVL)
			goto bad;
		a = asmea(p, &p->to);
		if((a & 0170) == 010) {
			opa[0] = 0x4e68|(a&7);	/* mov usp An */
			return;
		}
		t = 0x800;
		goto movec1;

	case D_SFC:
		t = 0x000;
		goto movec1;

	case D_DFC:
		t = 0x001;
		goto movec1;

	case D_CACR:
		t = 0x002;
		goto movec1;

	case D_TC:
		t = 0x003;
		goto movec1;

	case D_ITT0:
		t = 0x004;
		goto movec1;

	case D_ITT1:
		t = 0x005;
		goto movec1;

	case D_DTT0:
		t = 0x006;
		goto movec1;

	case D_DTT1:
		t = 0x007;
		goto movec1;

	case D_VBR:
		t = 0x801;
		goto movec1;

	case D_CAAR:
		t = 0x802;
		goto movec1;

	case D_MSP:
		t = 0x803;
		goto movec1;

	case D_ISP:
		t = 0x804;
		goto movec1;

	case D_MMUSR:
		t = 0x805;
		goto movec1;

	case D_URP:
		t = 0x806;
		goto movec1;

	case D_SRP:
		t = 0x807;
		goto movec1;

	movec1:
		if(p->as != AMOVL)
			goto bad;
		opa[0] = 0x4e7a;			/* mov spc Dn */
		a = asmea(p, &p->to);
		b = a & 0170;
		if(b == 0 || b == 010) {
			*op++ = (a<<12) | t;
			return;
		}
		goto bad;

	case D_FPCR:
		t = 0xb000;
		goto movec3;

	case D_FPSR:
		t = 0xa800;
		goto movec3;

	case D_FPIAR:
		t = 0xa400;

	movec3:
		if(p->as != AMOVL)
			goto bad;
		op++;
		a = asmea(p, &p->to);
		opa[0] = optab[AFMOVEL].opcode0 | a;
		opa[1] = t;
		return;
	}
	if(special[p->to.type])
	switch(p->to.type) {

	case D_CCR:
		if(p->as != AMOVW)		/* botch, needs and, eor etc. */
			goto bad;
		a = asmea(p, &p->from);
		if((a & 0170) == 010)
			goto bad;
		opa[0] = 0x44c0 | a;		/* mov to ccr */
		return;

	case D_SR:
		if(p->as != AMOVW)		/* botch, needs and, eor etc. */
			goto bad;
		a = asmea(p, &p->from);
		if((a & 0170) == 010)
			goto bad;
		opa[0] = 0x46c0 | a;		/* mov to sr */
		return;

	case D_USP:
		if(p->as != AMOVL)
			goto bad;
		a = asmea(p, &p->from);
		if((a & 0170) == 010) {
			opa[0] = 0x4e60|(a&7);	/* mov An usp */
			return;
		}
		t = 0x800;
		goto movec2;

	case D_SFC:
		t = 0x000;
		goto movec2;

	case D_DFC:
		t = 0x001;
		goto movec2;

	case D_CACR:
		t = 0x002;
		goto movec2;

	case D_TC:
		t = 0x003;
		goto movec2;

	case D_ITT0:
		t = 0x004;
		goto movec2;

	case D_ITT1:
		t = 0x005;
		goto movec2;

	case D_DTT0:
		t = 0x006;
		goto movec2;

	case D_DTT1:
		t = 0x007;
		goto movec2;

	case D_VBR:
		t = 0x801;
		goto movec2;

	case D_CAAR:
		t = 0x802;
		goto movec2;

	case D_MSP:
		t = 0x803;
		goto movec2;

	case D_ISP:
		t = 0x804;
		goto movec2;

	case D_MMUSR:
		t = 0x805;
		goto movec2;

	case D_URP:
		t = 0x806;
		goto movec2;

	case D_SRP:
		t = 0x807;
		goto movec2;

	movec2:
		if(p->as != AMOVL)
			goto bad;
		opa[0] = 0x4e7b;			/* mov Dn spc */
		a = asmea(p, &p->from);
		b = a & 0170;
		if(b == 0 || b == 010) {
			*op++ = (a<<12) | t;
			return;
		}
		goto bad;

	case D_FPCR:
		t = 0x9000;
		goto movec4;

	case D_FPSR:
		t = 0x8800;
		goto movec4;

	case D_FPIAR:
		t = 0x8400;

	movec4:
		if(p->as != AMOVL)
			goto bad;
		op++;
		a = asmea(p, &p->from);
		opa[0] = optab[AFMOVEL].opcode0 | a;
		opa[1] = t;
		return;
	}

	o = &optab[p->as];
	t = o->opcode0;
	switch(o->optype) {
	case 0:		/* pseudo ops */
		if(p->as != ATEXT && p->as != ANOP) {
			if(!debug['a'])
				print("%P\n", p);
			diag("unimplemented instruction in %s", TNAME);
			return;
		}
		op = opa;
		return;

	case 1:		/* branches */
		if(p->to.type != D_BRANCH)
			goto bad;
		a = asmea(p, &p->to);
		/* hack to turn 3-word bsr into 2-word jsr */
		if(a == 0xff && p->as == ABSR &&
		   p->pcond->pc < 32768L && p->pcond->pc >= 0) {
			op = opa + 1;
			t = o->opcode1;
			*op++ = p->pcond->pc;
			break;
		}
		t |= a;
		break;

	case 2:		/* move */
		a = asmea(p, &p->from);
		b = asmea(p, &p->to);
		if((a & 0170) == 0110) { /* src quick */
			t = o->opcode1;
			if((b & 0170) != 0)
				goto bad;
			t |= a >> 7;
			t |= b << 9;
			break;
		}
		t |= a;
		t |= (b&7) << 9;
		t |= (b&070) << 3;
		break;

	case 3:		/* add */
		a = asmea(p, &p->from);
		b = asmea(p, &p->to);
		if((a & 0170) == 0110) { /* src quick */
			t = o->opcode1;
			t |= (a&01600) << 2;
			t |= b;
			break;
		}
		if((b & 0170) == 0) { /* dst Dn */
			t |= a;
			t |= (b & 7) << 9;
			break;
		}
		if((b & 0170) == 010) { /* dst An */
			if((t & 0xc0) == 0)
				goto bad;
			t = o->opcode2;
			t |= a;						
			t |= (b & 7) << 9;
			break;
		}
		if((a & 0170) == 0) { /* src Dn */
			t |= 0x100;
			t |= (a & 7) << 9;
			t |= b;
			break;
		}
		if((a & 0177) == 074) { /* src immed */
			t = o->opcode3;
			t |= b;
			break;
		}
		goto bad;

	case 4:		/* no operands */
		break;

	case 5:		/* tst */
		t |= asmea(p, &p->to);
		if((t&0170) == 010)
			goto bad;
		break;

	case 6:		/* lea */
		a = asmea(p, &p->from);
		b = asmea(p, &p->to);
		if((b & 0170) != 010)
			goto bad;
		t |= a;
		t |= (b & 7) << 9;
		break;

	case 7:		/* cmp */
		b = asmea(p, &p->to);
		a = asmea(p, &p->from);
		if((a & 0170) == 010) {	/* dst An */
			t = o->opcode1;
			if(t == 0)	/* cmpb illegal */
				goto bad;
			t |= 0xc0;
			t |= b;						
			t |= (a & 7) << 9;
			break;
		}
		if((b & 0177) == 074) { /* src immed */
			t = o->opcode2;
			t |= a;
			break;
		}
		if((a & 0170) == 0) {	/* dst Dn */
			t |= b;
			t |= (a&7) << 9;
			break;
		}
		if((b&0170) == 030 && (a&0170) == 030) { /* (A)+,(A)+ */
			t = o->opcode3;
			t |= b & 7;
			t |= (a & 7) << 9;
			break;
		}
		goto bad;

	case 8:		/* svc */
		*op++ = optab[ARTS].opcode0;
		break;

	case 9:		/* and */
		a = asmea(p, &p->from);
		b = asmea(p, &p->to);
		if((a & 0170) == 010)
			goto bad;
		if((b & 0170) == 0) { /* dst Dn */
			t |= a;
			t |= (b&7) << 9;
			break;
		}
		if((a & 0170) == 0) { /* src Dn */
			t = o->opcode1;
			t |= b;
			t |= (a&7) << 9;
			break;
		}
		if((a & 0177) == 074) { /* src immed */
			t = o->opcode2;
			t |= b;
			break;
		}
		goto bad;

	case 10:	/* eor */
		a = asmea(p, &p->from);
		b = asmea(p, &p->to);
		if((a & 0170) == 010)
			goto bad;
		if((a & 0170) == 0) { /* src Dn */
			t |= b;
			t |= (a&7) << 9;
			break;
		}
		if((a & 0177) == 074) { /* src immed */
			t = o->opcode1;
			t |= b;
			break;
		}
		goto bad;

	case 11:	/* ext */
		b = asmea(p, &p->to);
		if((b & 0170) == 0) { /* dst Dn */
			t |= b;
			break;
		}
		goto bad;

	case 12:	/* shift */
		a = asmea(p, &p->from);
		b = asmea(p, &p->to);
		if((b & 0170) == 0) { /* dst Dn */
			if((a & 0177) == 0110) { /* src quick */
				t |= (a & 01600) << 2;
				t |= b;
				break;
			}
			if((a & 0170) == 0) { /* src Dn */
				t |= 0x20;
				t |= a << 9;
				t |= b;
				break;
			}
			goto bad;
		}
		goto bad;

	case 13:	/* mul, div short */
		a = asmea(p, &p->from);
		b = asmea(p, &p->to);
		if((b & 0170) == 0) { /* dst Dn */
			if((a & 0170) == 010)
				goto bad;	
			t |= a;
			t |= b << 9;
			break;
		}
		goto bad;

	case 14:	/* mul, div long */
		*op++ = o->opcode1;
		a = asmea(p, &p->from);
		b = asmea(p, &p->to);
		if((b & 0170) == 0) { /* dst Dn */
			if((a & 0170) == 010)
				goto bad;	
			t |= a;
			opa[1] |= b << 12;
			opa[1] |= b+1;
			break;
		}
		goto bad;

	case 15:	/* dec and branch */
		if(p->to.type != D_BRANCH)
			goto bad;
		v = p->pcond->pc - p->pc - 2;
		if(v < -32768L || v >= 32768L)
			goto bad;
		*op++ = v;
		a = asmea(p, &p->from);
		if((a & 0170) != 0)
			goto bad;
		t |= a;
		break;

	case 16:	/* fmove */
		*op++ = o->opcode1;
		a = asmea(p, &p->from);
		b = asmea(p, &p->to);
		if((a & 0170) == 0100) { /* src Fn */
			if((b & 0170) == 0100) { /* both Fn */
				opa[1] |= (a&7) << 10;
				opa[1] |= (b&7) << 7;
				break;
			}
			t |= b;
			opa[1] = o->opcode2;
			opa[1] |= (a&7) << 7;
			break;
		}
		if((b & 0170) != 0100) /* dst Fn */
			goto bad;
		t |= a;
		opa[1] = o->opcode3;
		opa[1] |= (b&7) << 7;
		break;