6g: new interface rules (code got simpler!)

R=ken
OCL=28374
CL=28378

src/cmd/gc/dcl.c

@@ -129,7 +129,6 @@ updatetype(Type *n, Type *t)
 	n->sym = s;
 	n->local = local;
 	n->siggen = 0;
-	n->methptr = 0;
 	n->printed = 0;
 	n->method = nil;
 	n->vargen = 0;
@@ -293,7 +292,7 @@ addmethod(Node *n, Type *t, int local)
 	if(pa == T)
 		goto bad;
 
-	f = dclmethod(pa);
+	f = methtype(pa);
 	if(f == T)
 		goto bad;
 

src/cmd/gc/go.h

@@ -137,7 +137,6 @@ struct	Type
 	uchar	chan;
 	uchar	recur;		// to detect loops
 	uchar	trecur;		// to detect loops
-	uchar	methptr;	// 1=direct 2=pointer
 	uchar	printed;
 	uchar	embedded;	// TFIELD embedded type
 	uchar	siggen;
@@ -725,9 +724,7 @@ int	isinter(Type*);
 int	isnilinter(Type*);
 int	isddd(Type*);
 Type*	maptype(Type*, Type*);
-Type*	dclmethod(Type*);
 Type*	methtype(Type*);
-int	methconv(Type*);
 Sym*	signame(Type*);
 int	eqtype(Type*, Type*, int);
 int	eqtypenoname(Type*, Type*);
@@ -787,10 +784,8 @@ int	lookdot0(Sym*, Type*, Type**);
 Type*	lookdot1(Sym*, Type*, Type*);
 int	adddot1(Sym*, Type*, int, Type**);
 Node*	adddot(Node*);
-void	expand0(Type*);
-void	expand1(Type*, int);
 void	expandmeth(Sym*, Type*);
-void	genptrtramp(Sym*, Sym*, Type*, Type*, Sym*, Type*);
+void	genwrapper(Type*, Type*, Sym*);
 
 /*
  *	dcl.c

src/cmd/gc/obj.c

@@ -140,6 +140,12 @@ ieeedtod(uint64 *ieee, double native)
 	*ieee = ((uint64)h << 32) | l;
 }
 
+static int
+sigcmp(Sig *a, Sig *b)
+{
+	return strcmp(a->name, b->name);
+}
+
 /*
  * Add DATA for signature s.
  *	progt - type in program
@@ -165,13 +171,6 @@ ieeedtod(uint64 *ieee, double native)
  *		} meth[1];			// one or more - last name is nil
  *	};
  */
-
-static int
-sigcmp(Sig *a, Sig *b)
-{
-	return strcmp(a->name, b->name);
-}
-
 void
 dumpsigt(Type *progt, Type *ifacet, Type *rcvrt, Type *methodt, Sym *s)
 {
@@ -180,12 +179,16 @@ dumpsigt(Type *progt, Type *ifacet, Type *rcvrt, Type *methodt, Sym *s)
 	Sig *a, *b;
 	char buf[NSYMB];
 	Type *this;
-	Iter savet;
 	Prog *oldlist;
 	Sym *method;
 	uint32 sighash;
 	int ot;
 
+	if(debug['r']) {
+		print("dumpsigt progt=%T ifacet=%T rcvrt=%T methodt=%T s=%S\n",
+			progt, ifacet, rcvrt, methodt, s);
+	}
+
 	a = nil;
 	o = 0;
 	oldlist = nil;
@@ -201,6 +204,16 @@ dumpsigt(Type *progt, Type *ifacet, Type *rcvrt, Type *methodt, Sym *s)
 		if(method == nil)
 			continue;
 
+		// get receiver type for this particular method.
+		this = getthisx(f->type)->type->type;
+		if(f->embedded != 2 && isptr[this->etype] && !isptr[progt->etype]) {
+			// pointer receiver method but value method set.
+			// ignore.
+			if(debug['r'])
+				print("ignore %T for %T\n", f, progt);
+			continue;
+		}
+
 		b = mal(sizeof(*b));
 		b->link = a;
 		a = b;
@@ -216,31 +229,19 @@ dumpsigt(Type *progt, Type *ifacet, Type *rcvrt, Type *methodt, Sym *s)
 
 		if(!a->sym->siggen) {
 			a->sym->siggen = 1;
-			// TODO(rsc): This test is still not quite right.
 
-			this = structfirst(&savet, getthis(f->type))->type;
-			if(isptr[this->etype] != isptr[ifacet->etype]) {
+			if(!eqtype(this, ifacet, 0)) {
 				if(oldlist == nil)
 					oldlist = pc;
 
-				// indirect vs direct mismatch
-				Sym *oldname, *newname;
-				Type *oldthis, *newthis;
-
-				newthis = ifacet;
-				if(isptr[newthis->etype])
-					oldthis = ifacet->type;
-				else
-					oldthis = ptrto(ifacet);
-				newname = a->sym;
-				oldname = methodsym(method, oldthis);
-				genptrtramp(method, oldname, oldthis, f->type, newname, newthis);
-			} else
-			if(f->embedded) {
-				// TODO(rsc): only works for pointer receivers
-				if(oldlist == nil)
-					oldlist = pc;
+				// It would be okay to call genwrapper here always,
+				// but we can generate more efficient code
+				// using genembedtramp if all that is necessary
+				// is a pointer adjustment and a JMP.
+				if(f->embedded && isptr[ifacet->etype])
 					genembedtramp(ifacet, a);
+				else
+					genwrapper(ifacet, f, a->sym);
 			}
 		}
 		o++;
@@ -449,23 +450,17 @@ dumpsignatures(void)
 		rcvrt = t;
 
 		// if there's a pointer, methods are on base.
-		if(isptr[methodt->etype] && methodt->type->sym != S) {
-			methodt = methodt->type;
+		methodt = methtype(progt);
+		if(methodt == T) {
+			// if that failed, go back to progt,
+			// assuming we're writing out a signature
+			// for a type with no methods
+			methodt = progt;
+		} else {
 			expandmeth(methodt->sym, methodt);
-
-			// if methodt had a name, we don't want to see
-			// it in the method names that go into the sigt.
-			// e.g., if
-			//	type item *rat
-			// then item needs its own sigt distinct from *rat,
-			// but it needs to have all of *rat's methods, using
-			// the *rat (not item) in the method names.
-			if(rcvrt->sym != S)
-				rcvrt = ptrto(methodt);
 		}
 
-		// and if ifacet is too wide, the methods
-		// will see a pointer anyway.
+		// if ifacet is too wide, the methods will see a pointer.
 		if(ifacet->width > 8) {
 			ifacet = ptrto(progt);
 			rcvrt = ptrto(progt);
@@ -473,7 +468,7 @@ dumpsignatures(void)
 
 		// don't emit non-trivial signatures for types defined outside this file.
 		// non-trivial signatures might also drag in generated trampolines,
-		// and ar can't handle duplicates of the trampolines.
+		// and ar can't handle duplicate functions.
 		// only pay attention to types with symbols, because
 		// the ... structs and maybe other internal structs
 		// don't get marked as local.

src/cmd/gc/subr.c

@@ -1495,7 +1495,7 @@ isddd(Type *t)
  * return type to hang methods off (r).
  */
 Type*
-dclmethod(Type *t)
+methtype(Type *t)
 {
 	int ptr;
 
@@ -1517,15 +1517,6 @@ dclmethod(Type *t)
 	if(t->sym == S)
 		return T;
 
-	// check that all method receivers are consistent
-	if(t->methptr != 0 && t->methptr != (1<<ptr)) {
-		if(t->methptr != 3) {
-			t->methptr = 3;
-			yyerror("methods on both %T and *%T", t, t);
-		}
-	}
-	t->methptr |= 1<<ptr;
-
 	// check types
 	if(!issimple[t->etype])
 	switch(t->etype) {
@@ -1543,50 +1534,6 @@ dclmethod(Type *t)
 	return t;
 }
 
-/*
- * this is dclmethod() without side effects.
- */
-Type*
-methtype(Type *t)
-{
-	if(t == T)
-		return T;
-	if(isptr[t->etype]) {
-		if(t->sym != S)
-			return T;
-		t = t->type;
-	}
-	if(t == T || t->etype == TINTER || t->sym == S)
-		return T;
-	return t;
-}
-
-/*
- * given type t in a method call, returns op
- * to convert t into appropriate receiver.
- * returns OADDR if t==x and method takes *x
- * returns OIND if t==*x and method takes x
- */
-int
-methconv(Type *t)
-{
-	Type *m;
-
-	m = methtype(t);
-	if(m == T)
-		return 0;
-	if(m->methptr&2) {
-		// want pointer
-		if(t == m)
-			return OADDR;
-		return 0;
-	}
-	// want non-pointer
-	if(t != m)
-		return OIND;
-	return 0;
-}
-
 int
 iscomposite(Type *t)
 {
@@ -2604,19 +2551,22 @@ struct	Symlink
 {
 	Type*		field;
 	uchar		good;
+	uchar		followptr;
 	Symlink*	link;
 };
 static	Symlink*	slist;
 
-void
-expand0(Type *t)
+static void
+expand0(Type *t, int followptr)
 {
 	Type *f, *u;
 	Symlink *sl;
 
 	u = t;
-	if(isptr[u->etype])
+	if(isptr[u->etype]) {
+		followptr = 1;
 		u = u->type;
+	}
 
 	u = methtype(t);
 	if(u != T) {
@@ -2629,13 +2579,14 @@ expand0(Type *t)
 			sl = mal(sizeof(*sl));
 			sl->field = f;
 			sl->link = slist;
+			sl->followptr = followptr;
 			slist = sl;
 		}
 	}
 }
 
-void
-expand1(Type *t, int d)
+static void
+expand1(Type *t, int d, int followptr)
 {
 	Type *f, *u;
 
@@ -2646,11 +2597,13 @@ expand1(Type *t, int d)
 	t->trecur = 1;
 
 	if(d != nelem(dotlist)-1)
-		expand0(t);
+		expand0(t, followptr);
 
 	u = t;
-	if(isptr[u->etype])
+	if(isptr[u->etype]) {
+		followptr = 1;
 		u = u->type;
+	}
 	if(u->etype != TSTRUCT && u->etype != TINTER)
 		goto out;
 
@@ -2659,7 +2612,7 @@ expand1(Type *t, int d)
 			continue;
 		if(f->sym == S)
 			continue;
-		expand1(f->type, d-1);
+		expand1(f->type, d-1, followptr);
 	}
 
 out:
@@ -2682,7 +2635,7 @@ expandmeth(Sym *s, Type *t)
 
 	// generate all reachable methods
 	slist = nil;
-	expand1(t, nelem(dotlist)-1);
+	expand1(t, nelem(dotlist)-1, 0);
 
 	// check each method to be uniquely reachable
 	for(sl=slist; sl!=nil; sl=sl->link) {
@@ -2704,7 +2657,8 @@ expandmeth(Sym *s, Type *t)
 			f = typ(TFIELD);
 			*f = *sl->field;
 			f->embedded = 1;	// needs a trampoline
-
+			if(sl->followptr)
+				f->embedded = 2;
 			f->down = t->method;
 			t->method = f;
 
@@ -2742,43 +2696,46 @@ structargs(Type **tl, int mustname)
 }
 
 /*
- * Generate a trampoline to convert
- * from an indirect receiver to a direct receiver
- * or vice versa.
+ * Generate a wrapper function to convert from
+ * a receiver of type T to a receiver of type U.
+ * That is,
+ *
+ *	func (t T) M() {
+ *		...
+ *	}
+ *
+ * already exists; this function generates
+ *
+ *	func (u U) M() {
+ *		u.M()
+ *	}
  *
- *	method - short name of method (Len)
- *	oldname - old mangled method name (x·y·Len)
- *	oldthis - old this type (y)
- *	oldtype - type of method being called;
- *		only in and out params are known okay,
- *		receiver might be != oldthis.
- *	newnam [sic] - new mangled method name (x·*y·Len)
- *	newthis - new this type (*y)
+ * where the types T and U are such that u.M() is valid
+ * and calls the T.M method.
+ * The resulting function is for use in method tables.
+ *
+ *	rcvrtype - U
+ *	method - M func (t T)(), a TFIELD type struct
+ *	newnam - the eventual mangled name of this function
  */
 void
-genptrtramp(Sym *method, Sym *oldname, Type *oldthis, Type *oldtype, Sym *newnam, Type *newthis)
+genwrapper(Type *rcvrtype, Type *method, Sym *newnam)
 {
-	Node *fn, *args, *l, *in, *call, *out, *this, *rcvr, *meth;
+	Node *this, *in, *out, *fn, *args, *call;
+	Node *l;
 	Iter savel;
 
 	if(debug['r']) {
-		print("\ngenptrtramp method=%S oldname=%S oldthis=%T\n",
-			method, oldname, oldthis);
-		print("\toldtype=%T newnam=%S newthis=%T\n",
-			oldtype, newnam, newthis);
+		print("genwrapper rcvrtype=%T method=%T newnam=%S\n",
+			rcvrtype, method, newnam);
 	}
 
 	dclcontext = PEXTERN;
 	markdcl();
 
-	this = nametodcl(newname(lookup(".this")), newthis);
-	in = structargs(getinarg(oldtype), 1);
-	out = structargs(getoutarg(oldtype), 0);
-
-	// fix up oldtype
-	markdcl();
-	oldtype = functype(nametodcl(newname(lookup(".this")), oldthis), in, out);
-	popdcl();
+	this = nametodcl(newname(lookup(".this")), rcvrtype);
+	in = structargs(getinarg(method->type), 1);
+	out = structargs(getoutarg(method->type), 0);
 
 	fn = nod(ODCLFUNC, N, N);
 	fn->nname = newname(newnam);
@@ -2791,19 +2748,10 @@ genptrtramp(Sym *method, Sym *oldname, Type *oldthis, Type *oldtype, Sym *newnam
 		args = list(args, l->left);
 	args = rev(args);
 
-	// method to call
-	if(isptr[oldthis->etype])
-		rcvr = nod(OADDR, this->left, N);
-	else
-		rcvr = nod(OIND, this->left, N);
-	gettype(rcvr, N);
-	meth = nod(ODOTMETH, rcvr, newname(oldname));
-	meth->xoffset = BADWIDTH;	// TODO(rsc): necessary?
-	meth->type = oldtype;
-
-	call = nod(OCALL, meth, args);
+	// generate call
+	call = nod(OCALL, adddot(nod(ODOT, this->left, newname(method->sym))), args);
 	fn->nbody = call;
-	if(oldtype->outtuple > 0)
+	if(method->type->outtuple > 0)
 		fn->nbody = nod(ORETURN, call, N);
 
 	if(debug['r'])
@@ -2850,11 +2798,13 @@ ifacecheck(Type *dst, Type *src, int lineno, int explicit)
 }
 
 Type*
-ifacelookdot(Sym *s, Type *t)
+ifacelookdot(Sym *s, Type *t, int *followptr)
 {
-	int c, d;
+	int i, c, d;
 	Type *m;
 
+	*followptr = 0;
+
 	if(t == T)
 		return T;
 
@@ -2864,9 +2814,16 @@ ifacelookdot(Sym *s, Type *t)
 			yyerror("%T.%S is ambiguous", t, s);
 			return T;
 		}
-		if(c == 1)
+		if(c == 1) {
+			for(i=0; i<d; i++) {
+				if(isptr[dotlist[i].field->type->etype]) {
+					*followptr = 1;
+					break;
+				}
+			}
 			return m;
 		}
+	}
 	return T;
 }
 
@@ -2875,23 +2832,11 @@ ifacelookdot(Sym *s, Type *t)
 int
 ifaceokT2I(Type *t0, Type *iface, Type **m)
 {
-	Type *t, *im, *tm;
-	int imhash;
+	Type *t, *im, *tm, *rcvr;
+	int imhash, followptr;
 
 	t = methtype(t0);
 
-	// stopgap: check for
-	// non-pointer type in T2I, methods want pointers.
-	// supposed to do something better eventually
-	// but this will catch errors while we decide the
-	// details of the "better" solution.
-	// only warn if iface is not interface{}.
-	if(t == t0 && t->methptr == 2 && iface->type != T) {
-		yyerror("probably wanted *%T not %T", t, t);
-		*m = iface->type;
-		return 0;
-	}
-
 	// if this is too slow,
 	// could sort these first
 	// and then do one loop.
@@ -2905,11 +2850,20 @@ ifaceokT2I(Type *t0, Type *iface, Type **m)
 
 	for(im=iface->type; im; im=im->down) {
 		imhash = typehash(im, 0, 0);
-		tm = ifacelookdot(im->sym, t);
+		tm = ifacelookdot(im->sym, t, &followptr);
 		if(tm == T || typehash(tm, 0, 0) != imhash) {
 			*m = im;
 			return 0;
 		}
+		// if pointer receiver in method,
+		// the method does not exist for value types.
+		rcvr = getthisx(tm->type)->type->type;
+		if(isptr[rcvr->etype] && !isptr[t0->etype] && !followptr) {
+			if(debug['r'])
+				yyerror("interface pointer mismatch");
+			*m = im;
+			return 0;
+		}
 	}
 	return 1;
 }

src/cmd/gc/walk.c

@@ -1590,8 +1590,7 @@ lookdot1(Sym *s, Type *t, Type *f)
 int
 lookdot(Node *n, Type *t)
 {
-	Type *f1, *f2, *tt;
-	int op;
+	Type *f1, *f2, *tt, *rcvr;
 	Sym *s;
 
 	s = n->right->sym;
@@ -1618,18 +1617,19 @@ lookdot(Node *n, Type *t)
 
 	if(f2 != T) {
 		tt = n->left->type;
-		if((op = methconv(tt)) != 0) {
-			switch(op) {
-			case OADDR:
+		rcvr = getthisx(f2->type)->type->type;
+		if(!eqtype(rcvr, tt, 0)) {
+			if(rcvr->etype == tptr && eqtype(rcvr->type, tt, 0)) {
 				walktype(n->left, Elv);
 				addrescapes(n->left);
 				n->left = nod(OADDR, n->left, N);
 				n->left->type = ptrto(tt);
-				break;
-			case OIND:
+			} else if(tt->etype == tptr && eqtype(tt->type, rcvr, 0)) {
 				n->left = nod(OIND, n->left, N);
 				n->left->type = tt->type;
-				break;
+			} else {
+				// method is attached to wrong type?
+				fatal("method mismatch: %T for %T", rcvr, tt);
 			}
 		}
 		n->right = methodname(n->right, n->left->type);