6l: do not link in objects from an archive just for init functions.

   (makes go libraries behave more like c libraries.)

R=r
DELTA=85  (67 added, 12 deleted, 6 changed)
OCL=23133
CL=23139

src/cmd/6l/go.c

@@ -489,3 +489,35 @@ definetypesigs(void)
 	if(debug['v'])
 		Bprint(&bso, "%5.2f typesigs %d\n", cputime(), n);
 }
+
+int
+isinitfunc(Sym *s)
+{
+	char *p;
+
+	p = utfrune(s->name, 0xb7);	// 0xb7 = '·'
+	if(p == nil)
+		return 0;
+	if(memcmp(p, "·Init·", 8) == 0 || memcmp(p, "·init·", 8) == 0)
+		return 1;
+	return 0;
+}
+
+void
+ignoreoptfuncs(void)
+{
+	Prog *p;
+
+	// nop out calls to optional functions
+	// that were not pulled in from libraries.
+	for(p=firstp; p != P; p=p->link) {
+		if(p->to.sym != S && p->to.sym->type == SOPT) {
+			if(p->as != ACALL)
+				diag("bad use of optional function: %P", p);
+			p->as = ANOP;
+			p->from.type = D_NONE;
+			p->to.type = D_NONE;
+		}
+	}
+}
+

src/cmd/6l/l.h

@@ -112,12 +112,14 @@ struct	Sym
 	short	version;
 	short	become;
 	short	frame;
+	ushort	file;
 	uchar	subtype;
 	uchar	dupok;
-	ushort	file;
+	uchar	reachable;
 	vlong	value;
 	int32	sig;
 	Sym*	link;
+	Prog*	text;
 };
 struct	Optab
 {
@@ -146,6 +148,7 @@ enum
 	SFILE,
 	SCONST,
 	SUNDEF,
+	SOPT,
 
 	SIMPORT,
 	SEXPORT,
@@ -381,8 +384,10 @@ void	ckoff(Sym*, int32);
 Prog*	copyp(Prog*);
 double	cputime(void);
 void	datblk(int32, int32);
+void	ignoreoptfuncs(void);
 void	definetypestrings(void);
 void definetypesigs(void);
+void	deadcode(void);
 void	diag(char*, ...);
 void	dodata(void);
 void	doinit(void);
@@ -415,6 +420,7 @@ void	main(int, char*[]);
 void	mkfwd(void);
 void*	mysbrk(uint32);
 Prog*	newdata(Sym*, int, int, int);
+Prog*	newtext(Prog*, Sym*);
 void	nuxiinit(void);
 void	objfile(char*);
 int	opsize(Prog*);
@@ -434,6 +440,7 @@ void	xdefine(char*, int, vlong);
 void	xfol(Prog*);
 void	zaddr(Biobuf*, Adr*, Sym*[]);
 void	zerosig(char*);
+int	isinitfunc(Sym*);
 
 void	machseg(char*, vlong, vlong, vlong, vlong, uint32, uint32, uint32, uint32);
 void	machsymseg(uint32, uint32);

src/cmd/6l/obj.c

@@ -368,6 +368,8 @@ main(int argc, char *argv[])
 		sprint(a, "%s/lib/lib_%s_%s.a", goroot, goarch, goos);
 		objfile(a);
 	}
+	ignoreoptfuncs();
+	// TODO(rsc): remove unused code and data
 	definetypestrings();
 	definetypesigs();
 
@@ -945,8 +947,11 @@ loop:
 		if(debug['W'])
 			print("	ANAME	%s\n", s->name);
 		h[o] = s;
-		if((v == D_EXTERN || v == D_STATIC) && s->type == 0)
+		if((v == D_EXTERN || v == D_STATIC) && s->type == 0) {
 			s->type = SXREF;
+			if(isinitfunc(s))
+				s->type = SOPT;	// optional function; don't pull in an object file just for s.
+		}
 		if(v == D_FILE) {
 			if(s->type != SFILE) {
 				histgen++;
@@ -1083,7 +1088,7 @@ loop:
 
 	case ATEXT:
 		s = p->from.sym;
-		if(ntext++ == 0 && s->type != 0 && s->type != SXREF) {
+		if(ntext++ == 0 && s->type != 0 && s->type != SXREF && s->type != SOPT) {
 			/* redefinition, so file has probably been seen before */
 			if(debug['v'])
 				Bprint(&bso, "skipping: %s: redefinition: %s", pn, s->name);
@@ -1100,26 +1105,14 @@ loop:
 			diag("%s: no TEXT symbol: %P", pn, p);
 			errorexit();
 		}
-		if(s->type != 0 && s->type != SXREF) {
+		if(s->type != 0 && s->type != SXREF && s->type != SOPT) {
 			if(p->from.scale & DUPOK) {
 				skip = 1;
 				goto casdef;
 			}
 			diag("%s: redefinition: %s\n%P", pn, s->name, p);
 		}
-		s->type = STEXT;
-		s->value = pc;
-		lastp->link = p;
-		lastp = p;
-		p->pc = pc;
-		pc++;
-		if(textp == P) {
-			textp = p;
-			etextp = p;
-			goto loop;
-		}
-		etextp->pcond = p;
-		etextp = p;
+		newtext(p, s);
 		goto loop;
 
 	case AMODE:

src/cmd/6l/pass.c

@@ -398,7 +398,8 @@ patch(void)
 			q = q->link;
 		}
 		if(q == P) {
-			diag("branch out of range in %s\n%P", TNAME, p);
+			diag("branch out of range in %s\n%P [%s]",
+				TNAME, p, p->to.sym ? p->to.sym->name : "<nil>");
 			p->to.type = D_NONE;
 		}
 		p->pcond = q;
@@ -853,6 +854,28 @@ newdata(Sym *s, int o, int w, int t)
 	return p;
 }
 
+Prog*
+newtext(Prog *p, Sym *s)
+{
+	if(p == P) {
+		p = prg();
+		p->as = ATEXT;
+		p->from.sym = s;
+	}
+	s->type = STEXT;
+	s->text = p;
+	s->value = pc;
+	lastp->link = p;
+	lastp = p;
+	p->pc = pc++;
+	if(textp == P)
+		textp = p;
+	else
+		etextp->pcond = p;
+	etextp = p;
+	return p;
+}
+
 void
 export(void)
 {