c10.c

unix v6 的c compiler 很老了

				reg--;
		return(reg);

	/* A1 */
	case 'A':
		p = p1;
		goto adr;

	/* A2 */
	case 'B':
		p = p2;
		goto adr;

	adr:
		c = 0;
		if (*string=='\'') {
			c = 1;
			string++;
		} else if (*string=='+') {
			c = 2;
			string++;
		}
		pname(p, c);
		goto loop;

	/* I */
	case 'M':
		if ((c = *string)=='\'')
			string++;
		else
			c = 0;
		prins(tree->op, c, instab);
		goto loop;

	/* B1 */
	case 'C':
		if ((opd&LEAF) != 0)
			p = tree;
		else
			p = p1;
		goto pbyte;

	/* BF */
	case 'P':
		p = tree;
		goto pb1;

	/* B2 */
	case 'D':
		p = p2;
	pbyte:
		if (p->type==CHAR)
			putchar('b');
	pb1:
		if (isfloat(p))
			putchar('f');
		goto loop;

	/* BE */
	case 'L':
		if (p1->type==CHAR || p2->type==CHAR)
			putchar('b');
		p = tree;
		goto pb1;

	/* F */
	case 'G':
		p = p1;
		flag = 01;
		goto subtre;

	/* S */
	case 'K':
		p = p2;
		flag = 02;
		goto subtre;

	/* H */
	case 'H':
		p = tree;
		flag = 04;

	subtre:
		ctable = regtab;
		c = *string++ - 'A';
		if (*string=='!') {
			string++;
			c =| 020;	/* force right register */
		}
		if ((c&02)!=0)
			ctable = sptab;
		if ((c&04)!=0)
			ctable = cctab;
		if ((flag&01) && ctable==regtab && (c&01)==0
		  && (tree->op==DIVIDE||tree->op==MOD
		   || tree->op==ASDIV||tree->op==ASMOD))
			ctable = cregtab;
		if ((c&01)!=0) {
			p = p->tr1;
			if(collcon(p) && ctable!=sptab) {
				if (p->op==STAR)
					p = p->tr1;
				p = p->tr1;
			}
		}
		if (table==lsptab && ctable==sptab)
			ctable = lsptab;
		if (c&010)
			r = reg1;
		else
			if (opdope[p->op]&LEAF || p->degree < 2)
				r = reg;
			else
				r = areg;
		rreg = rcexpr(p, ctable, r);
		if (ctable!=regtab && ctable!=cregtab)
			goto loop;
		if (c&010) {
			if (c&020 && rreg!=reg1)
				printf("mov%c	r%d,r%d\n",
				    isfloat(tree),rreg,reg1);
			else
				reg1 = rreg;
		} else if (rreg!=reg)
			if ((c&020)==0 && oddreg(tree, 0)==0 && (flag&04 ||
			      flag&01
			  && xdcalc(p2, nreg-rreg-1) <= (opt->tabdeg2&077)
			 ||   flag&02
			  && xdcalc(p1,nreg-rreg-1) <= (opt->tabdeg1&077))) {
				reg = rreg;
				reg1 = rreg+1;
			} else
				printf("mov%c\tr%d,r%d\n",
				    isfloat(tree), rreg, reg);
		goto loop;

	/* R */
	case 'I':
		r = reg;
		if (*string=='-') {
			string++;
			r--;
		}
		goto preg;

	/* R1 */
	case 'J':
		r = reg1;
	preg:
		if (*string=='+') {
			string++;
			r++;
		}
		if (r>nreg)
			error("Register overflow: simplify expression");
		printf("r%d", r);
		goto loop;

	case '-':		/* check -(sp) */
		if (*string=='(') {
			nstack++;
			if (table!=lsptab)
				putchar('-');
			goto loop;
		}
		break;

	case ')':		/* check (sp)+ */
		putchar(')');
		if (*string=='+')
			nstack--;
		goto loop;

	/* #1 */
	case '#':
		p = p1->tr1;
		goto nmbr;

	/* #2 */
	case '"':
		p = p2->tr1;

	nmbr:
		if(collcon(p)) {
			if (p->op==STAR) {
				printf("*");
				p = p->tr1;
			}
			if ((p = p->tr2)->op == CON) {
				if (p->value)
					psoct(p->value);
			} else if (p->op==AMPER)
				pname(p->tr1, 0);
		}
		goto loop;

	case 'T':		/* "tst R" if 1st op not in cctab */
		if (dcalc(p1, 5)>12 && !match(p1, cctab, 10))
			printf("tst	r%d\n", reg);
		goto loop;
	case 'V':	/* adc or sbc as required for longs */
		switch(tree->op) {
		case PLUS:
		case ASPLUS:
		case INCBEF:
		case INCAFT:
			printf("adc");
			break;

		case MINUS:
		case ASMINUS:
		case NEG:
		case DECBEF:
		case DECAFT:
			printf("sbc");
			break;

		default:
			while ((c = *string++)!='\n' && c!='\0');
			break;
		}
		goto loop;
	}
	putchar(c);
	goto loop;
}

/*
 * This routine just calls sreorder (below)
 * on the subtrees and then on the tree itself.
 * It returns non-zero if anything changed.
 */
reorder(treep, table, reg)
struct tnode **treep;
struct table *table;
{
	register r, r1;
	register struct tnode *p;

	p = *treep;
	if (opdope[p->op]&LEAF)
		return(0);
	r1 = 0;
	while(sreorder(&p->tr1, table, reg))
		r1++;
	if (opdope[p->op]&BINARY) 
		while(sreorder(&p->tr2, table, reg))
			r1++;
	r = 0;
	while (sreorder(treep, table, reg))
		r++;
	*treep = optim(*treep);
	return(r);
}

/*
 * Basically this routine carries out two kinds of optimization.
 * First, it observes that "x + (reg = y)" where actually
 * the = is any assignment op is better done as "reg=y; x+reg".
 * In this case rcexpr is called to do the first part and the
 * tree is modified so the name of the register
 * replaces the assignment.
 * Moreover, expressions like "reg = x+y" are best done as
 * "reg = x; reg =+ y" (so long as "reg" and "y" are not the same!).
 */
sreorder(treep, table, reg)
struct tnode **treep;
struct table *table;
{
	register struct tnode *p, *p1;

	p = *treep;
	if (opdope[p->op]&LEAF)
		return(0);
	if (p->op==PLUS)
		if (reorder(&p->tr2, table, reg))
			*treep = p = optim(p);
	p1 = p->tr1;
	if (p->op==STAR || p->op==PLUS) {
		if (reorder(&p->tr1, table, reg))
			*treep = p = optim(p);
		p1 = p->tr1;
	}
	if (p1->op==NAME) switch(p->op) {
		case ASLSH:
		case ASRSH:
		case ASSIGN:
			if (p1->class != REG || isfloat(p->tr2))
				return(0);
			if (p->op==ASSIGN) switch (p->tr2->op) {
			case TIMES:
			case DIVIDE:
				if (!ispow2(p->tr2))
					break;
				p->tr2 = pow2(p->tr2);
			case PLUS:
			case MINUS:
			case AND:
			case NAND:
			case OR:
			case EXOR:
			case LSHIFT:
			case RSHIFT:
				p1 = p->tr2->tr2;
				if (xdcalc(p1) > 12
				 || p1->op==NAME
				 &&(p1->nloc==p->tr1->nloc
				  || p1->regno==p->tr1->nloc))
					return(0);
				p1 = p->tr2;
				p->tr2 = p1->tr1;
				if (p1->tr1->op!=NAME
				 || p1->tr1->class!=REG
				 || p1->tr1->nloc!=p->tr1->nloc)
					rcexpr(p, efftab, reg);
				p->tr2 = p1->tr2;
				p->op = p1->op + ASPLUS - PLUS;
				*treep = p;
				return(1);
			}
			goto OK;

		case ASTIMES:
		case ASDIV:
			if (!ispow2(p))
				return(0);
		case ASPLUS:
		case ASMINUS:
		case ASSAND:
		case ASSNAND:
		case ASOR:
		case ASXOR:
		case DECBEF:
		case INCBEF:
		OK:
			if (table==cctab||table==cregtab)
				reg =+ 020;
			rcexpr(optim(p), efftab, ~reg);
			*treep = p1;
			return(1);
	}
	return(0);
}

/*
 * Delay handles postfix ++ and -- 
 * It observes that "x + y++" is better
 * treated as "x + y; y++".
 * If the operator is ++ or -- itself,
 * it calls rcexpr to load the operand, letting
 * the calling instance of rcexpr to do the
 * ++ using efftab.
 * Otherwise it uses sdelay to search for inc/dec
 * among the operands.
 */
delay(treep, table, reg)
struct tnode **treep;
{
	register struct tnode *p, *p1;
	register r;

	p = *treep;
	if (table!=efftab && (p->op==INCAFT||p->op==DECAFT)
	 && p->tr1->op==NAME) {
		return(1+rcexpr(p->tr1, table, reg));
	}
	p1 = 0;
	if (opdope[p->op]&BINARY)
		p1 = sdelay(&p->tr2);
	if (p1==0)
		p1 = sdelay(&p->tr1);
	if (p1) {
		r = rcexpr(optim(p), table, reg);
		*treep = p1;
		return(r+1);
	}
	return(0);
}

sdelay(ap)
struct tnode **ap;
{
	register struct tnode *p, *p1;

	p = *ap;
	if ((p->op==INCAFT||p->op==DECAFT) && p->tr1->op==NAME) {
		*ap = ncopy(p->tr1);
		return(p);
	}
	if (p->op==STAR || p->op==PLUS)
		if (p1=sdelay(&p->tr1))
			return(p1);
	if (p->op==PLUS)
		return(sdelay(&p->tr2));
	return(0);
}

/*
 * Copy a tree node for a register variable.
 * Used by sdelay because if *reg-- is turned
 * into *reg; reg-- the *reg will in turn
 * be changed to some offset class, accidentally
 * modifying the reg--.
 */
ncopy(ap)
struct tname *ap;
{
	register struct tname *p;

	p = ap;
	if (p->class!=REG)
		return(p);
	return(block(3, NAME, p->type, p->elsize, p->tr1,
	    p->offset, p->nloc));
}

/*
 * If the tree can be immediately loaded into a register,
 * produce code to do so and return success.
 */
chkleaf(atree, table, reg)
struct tnode *atree;
{
	struct tnode lbuf;
	register struct tnode *tree;

	tree = atree;
	if (tree->op!=STAR && dcalc(tree, nreg-reg) > 12)
		return(-1);
	lbuf.op = LOAD;
	lbuf.type = tree->type;
	lbuf.degree = tree->degree;
	lbuf.tr1 = tree;
	return(rcexpr(&lbuf, table, reg));
}

/*
 * Compile a function argument.
 * If the stack is currently empty, put it in (sp)
 * rather than -(sp); this will save a pop.
 * Return the number of bytes pushed,
 * for future popping.
 */
comarg(atree, flagp)
int *flagp;
{
	register struct tnode *tree;
	register retval;

	tree = atree;
	if (nstack || isfloat(tree) || tree->type==LONG) {
		rcexpr(tree, sptab, 0);
		retval = arlength(tree->type);
	} else {
		(*flagp)++;
		rcexpr(tree, lsptab, 0);
		retval = 0;
	}
	return(retval);
}