pangen2.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

		} else
			fprintf(tb, ";");
	} else
		fprintf(tb, ";");
	fprintf(tb, "\n\t\t");

	if (multi_undo)
	{	fprintf(tb, "ungrab_ints(trpt->bup.ovals, %d);\n\t\t",
			multi_undo);
		multi_undo = 0;
	}
	if (didcase)
	{	fprintf(tb, "goto R999;\n");
		bupcase = casenr;
	}

	if (!e->merge && !e->merge_start)
		new_case(e, casenr, bupcase, Pid);

gotit:
	j = a;
	if (e->merge_start)
		j = e->merge_start;
	else if (e->merge)
		j = e->merge;
haveit:
	fprintf(tt, "%ssettr(%d,%d,%d,%d,%d,\"", fromcache?"/* c */ ":"",
		e->Seqno, mark, j, casenr, bupcase);

	return (fromcache)?0:casenr;
}

static void
put_el(Element *e, int Tt0, int Tt1)
{	int a, casenr, Global_ref;
	Element *g = ZE;

	if (e->n->ntyp == GOTO)
	{	g = get_lab(e->n, 1);
		g = huntele(g, e->status, -1);
		cross_dsteps(e->n, g->n);
		a = g->seqno;
	} else if (e->nxt)
	{	g = huntele(e->nxt, e->status, -1);
		a = g->seqno;
	} else
		a = 0;
	if (g
	&&  (g->status&CHECK2	/* entering remotely ref'd state */
	||   e->status&CHECK2))	/* leaving  remotely ref'd state */
		e->status |= I_GLOB;

	/* don't remove dead edges in here, to preserve structure of fsm */
	if (e->merge_start || e->merge)
		goto non_generic;

	/*** avoid duplicate or redundant cases in pan.m ***/
	switch (e->n->ntyp) {
	case ELSE:
		casenr = 2; /* standard else */
		putskip(e->seqno);
		goto generic_case;
		/* break; */
	case '.':
	case GOTO:
	case BREAK:
		putskip(e->seqno); 
		casenr = 1; /* standard goto */
generic_case:	fprintf(tt, "\ttrans[%d][%d]\t= ", Pid, e->seqno);
		fprintf(tt, "settr(%d,%d,%d,%d,0,\"",
			e->Seqno, e->status&ATOM, a, casenr);
		break;
#ifndef PRINTF
	case PRINT:
		goto non_generic;
	case PRINTM:
		goto non_generic;
#endif
	case 'c':
		if (e->n->lft->ntyp == CONST
		&&  e->n->lft->val == 1)	/* skip or true */
		{	casenr = 1;
			putskip(e->seqno);
			goto generic_case;
		}
		goto non_generic;

	default:
non_generic:
		casenr = case_cache(e, a);
		if (casenr < 0) return;	/* unreachable state */
		break;
	}
	/* tailend of settr(...); */
	Global_ref = (e->status&I_GLOB)?1:has_global(e->n);
	comment(tt, e->n, e->seqno);
	fprintf(tt, "\", %d, ", Global_ref);
	if (Tt0 != 2)
	{	fprintf(tt, "%d, %d);", Tt0, Tt1);
	} else
	{	Tpe(e->n);	/* sets EPT */
		fprintf(tt, "%d, %d);", EPT[0], EPT[1]);
	}
	if ((e->merge_start && e->merge_start != a)
	||  (e->merge && e->merge != a))
	{	fprintf(tt, " /* m: %d -> %d,%d */\n",
			a, e->merge_start, e->merge);
		fprintf(tt, "	reached%d[%d] = 1;",
			Pid, a); /* Sheinman's example */
	}
	fprintf(tt, "\n");

	if (casenr > 2)
		tr_map(casenr, e);
	put_escp(e);
}

static void
nested_unless(Element *e, Element *g)
{	struct SeqList *y = e->esc, *z = g->esc;

	for ( ; y && z; y = y->nxt, z = z->nxt)
		if (z->this != y->this)
			break;
	if (!y && !z)
		return;

	if (g->n->ntyp != GOTO
	&&  g->n->ntyp != '.'
	&&  e->sub->nxt)
	{	printf("error: (%s:%d) saw 'unless' on a guard:\n",
			(e->n)?e->n->fn->name:"-",
			(e->n)?e->n->ln:0);
		printf("=====>instead of\n");
		printf("	do (or if)\n");
		printf("	:: ...\n");
		printf("	:: stmnt1 unless stmnt2\n");
		printf("	od (of fi)\n");
		printf("=====>use\n");
		printf("	do (or if)\n");
		printf("	:: ...\n");
		printf("	:: stmnt1\n");
		printf("	od (or fi) unless stmnt2\n");
		printf("=====>or rewrite\n");
	}
}

static void
put_seq(Sequence *s, int Tt0, int Tt1)
{	SeqList *h;
	Element *e, *g;
	int a, deadlink;

	if (0) printf("put_seq %d\n", s->frst->seqno);

	for (e = s->frst; e; e = e->nxt)
	{
		if (0) printf("	step %d\n", e->seqno);
		if (e->status & DONE)
		{
			if (0) printf("		done before\n");
			goto checklast;
		}
		e->status |= DONE;

		if (e->n->ln)
			putsrc(e);

		if (e->n->ntyp == UNLESS)
		{
			if (0) printf("		an unless\n");
			put_seq(e->sub->this, Tt0, Tt1);
		} else if (e->sub)
		{
			if (0) printf("		has sub\n");
			fprintf(tt, "\tT = trans[%d][%d] = ",
				Pid, e->seqno);
			fprintf(tt, "settr(%d,%d,0,0,0,\"",
				e->Seqno, e->status&ATOM);
			comment(tt, e->n, e->seqno);
			if (e->status&CHECK2)
				e->status |= I_GLOB;
			fprintf(tt, "\", %d, %d, %d);",
				(e->status&I_GLOB)?1:0, Tt0, Tt1);
			blurb(tt, e);
			for (h = e->sub; h; h = h->nxt)
			{	putskip(h->this->frst->seqno);
				g = huntstart(h->this->frst);
				if (g->esc)
					nested_unless(e, g);
				a = g->seqno;

				if (g->n->ntyp == 'c'
				&&  g->n->lft->ntyp == CONST
				&&  g->n->lft->val == 0		/* 0 or false */
				&& !g->esc)
				{	fprintf(tt, "#if 0\n\t/* dead link: */\n");
					deadlink = 1;
					if (verbose&32)
					printf("spin: line %3d  %s, Warning: condition is always false\n",
						g->n->ln, g->n->fn?g->n->fn->name:"");
				} else
					deadlink = 0;
				if (0) printf("			settr %d %d\n", a, 0);
				if (h->nxt)
					fprintf(tt, "\tT = T->nxt\t= ");
				else
					fprintf(tt, "\t    T->nxt\t= ");
				fprintf(tt, "settr(%d,%d,%d,0,0,\"",
					e->Seqno, e->status&ATOM, a);
				comment(tt, e->n, e->seqno);
				if (g->status&CHECK2)
					h->this->frst->status |= I_GLOB;
				fprintf(tt, "\", %d, %d, %d);",
					(h->this->frst->status&I_GLOB)?1:0,
					Tt0, Tt1);
				blurb(tt, e);
				if (deadlink)
					fprintf(tt, "#endif\n");
			}
			for (h = e->sub; h; h = h->nxt)
				put_seq(h->this, Tt0, Tt1);
		} else
		{
			if (0) printf("		[non]atomic %d\n", e->n->ntyp);
			if (e->n->ntyp == ATOMIC
			||  e->n->ntyp == D_STEP
			||  e->n->ntyp == NON_ATOMIC)
				put_sub(e, Tt0, Tt1);
			else 
			{
				if (0) printf("			put_el %d\n", e->seqno);
				put_el(e, Tt0, Tt1);
			}
		}
checklast:	if (e == s->last)
			break;
	}
	if (0) printf("put_seq done\n");
}

static void
patch_atomic(Sequence *s)	/* catch goto's that break the chain */
{	Element *f, *g;
	SeqList *h;

	for (f = s->frst; f ; f = f->nxt)
	{
		if (f->n && f->n->ntyp == GOTO)
		{	g = get_lab(f->n,1);
			cross_dsteps(f->n, g->n);
			if ((f->status & (ATOM|L_ATOM))
			&& !(g->status & (ATOM|L_ATOM)))
			{	f->status &= ~ATOM;
				f->status |= L_ATOM;
			}
			/* bridge atomics */
			if ((f->status & L_ATOM)
			&&  (g->status & (ATOM|L_ATOM)))
			{	f->status &= ~L_ATOM;
				f->status |= ATOM;
			}
		} else
		for (h = f->sub; h; h = h->nxt)
			patch_atomic(h->this);
		if (f == s->extent)
			break;
	}
}

static void
mark_seq(Sequence *s)
{	Element *f;
	SeqList *h;

	for (f = s->frst; f; f = f->nxt)
	{	f->status |= I_GLOB;

		if (f->n->ntyp == ATOMIC
		||  f->n->ntyp == NON_ATOMIC
		||  f->n->ntyp == D_STEP)
			mark_seq(f->n->sl->this);

		for (h = f->sub; h; h = h->nxt)
			mark_seq(h->this);
		if (f == s->last)
			return;
	}
}

static Element *
find_target(Element *e)
{	Element *f;

	if (!e) return e;

	if (t_cyc++ > 32)
	{	fatal("cycle of goto jumps", (char *) 0);
	}
	switch (e->n->ntyp) {
	case  GOTO:
		f = get_lab(e->n,1);
		cross_dsteps(e->n, f->n);
		f = find_target(f);
		break;
	case BREAK:
		if (e->nxt)
		f = find_target(huntele(e->nxt, e->status, -1));
		/* else fall through */
	default:
		f = e;
		break;
	}
	return f;
}

Element *
target(Element *e)
{
	if (!e) return e;
	lineno = e->n->ln;
	Fname  = e->n->fn;
	t_cyc = 0;
	return find_target(e);
}

static int
scan_seq(Sequence *s)
{	Element *f, *g;
	SeqList *h;

	for (f = s->frst; f; f = f->nxt)
	{	if ((f->status&CHECK2)
		||  has_global(f->n))
			return 1;
		if (f->n->ntyp == GOTO)	/* may reach other atomic */
		{	g = target(f);
			if (g
			&& !(f->status & L_ATOM)
			&& !(g->status & (ATOM|L_ATOM)))
			{	fprintf(tt, "	/* goto mark-down, ");
				fprintf(tt, "line %d - %d */\n",
					f->n->ln, (g->n)?g->n->ln:0);
				return 1; /* assume worst case */
		}	}
		for (h = f->sub; h; h = h->nxt)
			if (scan_seq(h->this))
				return 1;
		if (f == s->last)
			break;
	}
	return 0;
}

static int
glob_args(Lextok *n)
{	int result = 0;
	Lextok *v;

	for (v = n->rgt; v; v = v->rgt)
	{	if (v->lft->ntyp == CONST)
			continue;
		if (v->lft->ntyp == EVAL)
			result += has_global(v->lft->lft);
		else
			result += has_global(v->lft);
	}
	return result;
}

int
has_global(Lextok *n)
{	Lextok *v; extern int runsafe;

	if (!n) return 0;
	if (AllGlobal) return 1;	/* global provided clause */

	switch (n->ntyp) {
	case ATOMIC:
	case D_STEP:
	case NON_ATOMIC:
		return scan_seq(n->sl->this);

	case '.':
	case BREAK:
	case GOTO:
	case CONST:
		return 0;

	case   ELSE: return n->val; /* true if combined with chan refs */

	case    's': return glob_args(n)!=0 || ((n->sym->xu&(XS|XX)) != XS);
	case    'r': return glob_args(n)!=0 || ((n->sym->xu&(XR|XX)) != XR);
	case    'R': return glob_args(n)!=0 || (((n->sym->xu)&(XR|XS|XX)) != (XR|XS));
	case NEMPTY: return ((n->sym->xu&(XR|XX)) != XR);
	case  NFULL: return ((n->sym->xu&(XS|XX)) != XS);
	case   FULL: return ((n->sym->xu&(XR|XX)) != XR);
	case  EMPTY: return ((n->sym->xu&(XS|XX)) != XS);
	case  LEN:   return (((n->sym->xu)&(XR|XS|XX)) != (XR|XS));

	case   NAME:
		if (n->sym->context
		|| (n->sym->hidden&64)
		||  strcmp(n->sym->name, "_pid") == 0
		||  strcmp(n->sym->name, "_") == 0)
			return 0;
		return 1;

	case RUN: return 1-runsafe;

	case C_CODE: case C_EXPR:
		return glob_inline(n->sym->name);

	case ENABLED: case PC_VAL: case NONPROGRESS:
	case 'p': case 'q':
	case TIMEOUT:
		return 1;

	/* 	@ was 1 (global) since 2.8.5
		in 3.0 it is considered local and
		conditionally safe, provided:
			II is the youngest process
			and nrprocs < MAXPROCS
	*/
	case '@': return 0;

	case '!': case UMIN: case '~': case ASSERT:
		return has_global(n->lft);

	case '/': case '*': case '-': case '+':
	case '%': case LT:  case GT: case '&': case '^':
	case '|': case LE:  case GE:  case NE: case '?':
	case EQ:  case OR:  case AND: case LSHIFT:
	case RSHIFT: case 'c': case ASGN:
		return has_global(n->lft) || has_global(n->rgt);

	case PRINT:
		for (v = n->lft; v; v = v->rgt)
			if (has_global(v->lft)) return 1;
		return 0;
	case PRINTM:
		return has_global(n->lft);
	}
	return 0;
}

static void
Bailout(FILE *fd, char *str)
{
	if (!GenCode)
		fprintf(fd, "continue%s", str);
	else if (IsGuard)
		fprintf(fd, "%s%s", NextLab[Level], str);
	else
		fprintf(fd, "Uerror(\"block in step seq\")%s", str);
}

#define cat0(x)   	putstmnt(fd,now->lft,m); fprintf(fd, x); \
			putstmnt(fd,now->rgt,m)
#define cat1(x)		fprintf(fd,"("); cat0(x); fprintf(fd,")")
#define cat2(x,y)  	fprintf(fd,x); putstmnt(fd,y,m)
#define cat3(x,y,z)	fprintf(fd,x); putstmnt(fd,y,m); fprintf(fd,z)

void
putstmnt(FILE *fd, Lextok *now, int m)
{	Lextok *v;
	int i, j;

	if (!now) { fprintf(fd, "0"); return; }
	lineno = now->ln;
	Fname  = now->fn;

	switch (now->ntyp) {
	case CONST:	fprintf(fd, "%d", now->val); break;
	case '!':	cat3(" !(", now->lft, ")"); break;
	case UMIN:	cat3(" -(", now->lft, ")"); break;
	case '~':	cat3(" ~(", now->lft, ")"); break;

	case '/':	cat1("/");  break;
	case '*':	cat1("*");  break;
	case '-':	cat1("-");  break;
	case '+':	cat1("+");  break;
	case '%':	cat1("%%"); break;
	case '&':	cat1("&");  break;
	case '^':	cat1("^");  break;
	case '|':	cat1("|");  break;
	case LT:	cat1("<");  break;
	case GT:	cat1(">");  break;
	case LE:	cat1("<="); break;
	case GE:	cat1(">="); break;
	case NE:	cat1("!="); break;
	case EQ:	cat1("=="); break;
	case OR:	cat1("||"); break;
	case AND:	cat1("&&"); break;
	case LSHIFT:	cat1("<<"); break;
	case RSHIFT:	cat1(">>"); break;

	case TIMEOUT:
		if (separate == 2)
			fprintf(fd, "((tau)&1)");
		else
			fprintf(fd, "((trpt->tau)&1)");
		if (GenCode)
		 printf("spin: line %3d, warning: 'timeout' in d_step sequence\n",
			lineno);
		/* is okay as a guard */
		break;

	case RUN:
		if (claimproc
		&&  strcmp(now->sym->name, claimproc) == 0)