gc, runtime: replace closed(c) with x, ok := <-c

R=ken2, ken3
CC=golang-dev
https://golang.org/cl/4259064

src/cmd/gc/builtin.c.boot

@@ -66,15 +66,17 @@ char *runtimeimport =
 	"func \"\".mapiter2 (hiter *any) (key any, val any)\n"
 	"func \"\".makechan (elem *uint8, hint int64) chan any\n"
 	"func \"\".chanrecv1 (hchan <-chan any) any\n"
-	"func \"\".chanrecv3 (hchan <-chan any) (elem any, closed bool)\n"
+	"func \"\".chanrecv2 (hchan <-chan any) (elem any, received bool)\n"
 	"func \"\".chansend1 (hchan chan<- any, elem any)\n"
 	"func \"\".closechan (hchan any)\n"
 	"func \"\".closedchan (hchan any) bool\n"
 	"func \"\".selectnbsend (hchan chan<- any, elem any) bool\n"
 	"func \"\".selectnbrecv (elem *any, hchan <-chan any) bool\n"
+	"func \"\".selectnbrecv2 (elem *any, received *bool, hchan <-chan any) bool\n"
 	"func \"\".newselect (size int) *uint8\n"
 	"func \"\".selectsend (sel *uint8, hchan chan<- any, elem any) bool\n"
 	"func \"\".selectrecv (sel *uint8, hchan <-chan any, elem *any) bool\n"
+	"func \"\".selectrecv2 (sel *uint8, hchan <-chan any, elem *any, received *bool) bool\n"
 	"func \"\".selectdefault (sel *uint8) bool\n"
 	"func \"\".selectgo (sel *uint8)\n"
 	"func \"\".block ()\n"

src/cmd/gc/go.h

@@ -356,12 +356,11 @@ enum
 	OARRAY,
 	OARRAYBYTESTR, OARRAYRUNESTR,
 	OSTRARRAYBYTE, OSTRARRAYRUNE,
-	OAS, OAS2, OAS2MAPW, OAS2FUNC, OAS2RECVCLOSED, OAS2MAPR, OAS2DOTTYPE, OASOP,
+	OAS, OAS2, OAS2MAPW, OAS2FUNC, OAS2RECV, OAS2MAPR, OAS2DOTTYPE, OASOP,
 	OBAD,
 	OCALL, OCALLFUNC, OCALLMETH, OCALLINTER,
 	OCAP,
 	OCLOSE,
-	OCLOSED,
 	OCLOSURE,
 	OCMPIFACE, OCMPSTR,
 	OCOMPLIT, OMAPLIT, OSTRUCTLIT, OARRAYLIT,
@@ -389,6 +388,7 @@ enum
 	ORECV,
 	ORUNESTR,
 	OSELRECV,
+	OSELRECV2,
 	OIOTA,
 	OREAL, OIMAG, OCOMPLEX,
 

src/cmd/gc/go.y

@@ -461,23 +461,32 @@ case:
 		}
 		break;
 	}
-|	LCASE expr '=' expr ':'
+|	LCASE expr_or_type_list '=' expr ':'
 	{
+		Node *n;
+
 		// will be converted to OCASE
 		// right will point to next case
 		// done in casebody()
 		poptodcl();
 		$$ = nod(OXCASE, N, N);
-		$$->list = list1(nod(OAS, $2, $4));
+		if($2->next == nil)
+			n = nod(OAS, $2->n, $4);
+		else {
+			n = nod(OAS2, N, N);
+			n->list = $2;
+			n->rlist = list1($4);
+		}
+		$$->list = list1(n);
 	}
-|	LCASE name LCOLAS expr ':'
+|	LCASE expr_or_type_list LCOLAS expr ':'
 	{
 		// will be converted to OCASE
 		// right will point to next case
 		// done in casebody()
 		poptodcl();
 		$$ = nod(OXCASE, N, N);
-		$$->list = list1(colas(list1($2), list1($4)));
+		$$->list = list1(colas($2, list1($4)));
 	}
 |	LDEFAULT ':'
 	{

src/cmd/gc/lex.c

@@ -1555,7 +1555,6 @@ static	struct
 	"append",		LNAME,		Txxx,		OAPPEND,
 	"cap",		LNAME,		Txxx,		OCAP,
 	"close",	LNAME,		Txxx,		OCLOSE,
-	"closed",	LNAME,		Txxx,		OCLOSED,
 	"complex",	LNAME,		Txxx,		OCOMPLEX,
 	"copy",		LNAME,		Txxx,		OCOPY,
 	"imag",		LNAME,		Txxx,		OIMAG,

src/cmd/gc/print.c

@@ -52,7 +52,6 @@ exprfmt(Fmt *f, Node *n, int prec)
 	case OARRAYBYTESTR:
 	case OCAP:
 	case OCLOSE:
-	case OCLOSED:
 	case OCOPY:
 	case OLEN:
 	case OMAKE:
@@ -405,7 +404,6 @@ exprfmt(Fmt *f, Node *n, int prec)
 	case OAPPEND:
 	case OCAP:
 	case OCLOSE:
-	case OCLOSED:
 	case OLEN:
 	case OCOPY:
 	case OMAKE:

src/cmd/gc/range.c

@@ -203,8 +203,8 @@ walkrange(Node *n)
 		hb = nod(OXXX, N, N);
 		tempname(hb, types[TBOOL]);
 
-		n->ntest = nod(ONOT, hb, N);
-		a = nod(OAS2RECVCLOSED, N, N);
+		n->ntest = hb;
+		a = nod(OAS2RECV, N, N);
 		a->typecheck = 1;
 		a->list = list(list1(hv1), hb);
 		a->rlist = list1(nod(ORECV, ha, N));

src/cmd/gc/runtime.go

@@ -92,17 +92,19 @@ func mapiter2(hiter *any) (key any, val any)
 // *byte is really *runtime.Type
 func makechan(elem *byte, hint int64) (hchan chan any)
 func chanrecv1(hchan <-chan any) (elem any)
-func chanrecv3(hchan <-chan any) (elem any, closed bool)
+func chanrecv2(hchan <-chan any) (elem any, received bool)
 func chansend1(hchan chan<- any, elem any)
 func closechan(hchan any)
 func closedchan(hchan any) bool
 
 func selectnbsend(hchan chan<- any, elem any) bool
 func selectnbrecv(elem *any, hchan <-chan any) bool
+func selectnbrecv2(elem *any, received *bool, hchan <-chan any) bool
 
 func newselect(size int) (sel *byte)
 func selectsend(sel *byte, hchan chan<- any, elem any) (selected bool)
 func selectrecv(sel *byte, hchan <-chan any, elem *any) (selected bool)
+func selectrecv2(sel *byte, hchan <-chan any, elem *any, received *bool) (selected bool)
 func selectdefault(sel *byte) (selected bool)
 func selectgo(sel *byte)
 func block()

src/cmd/gc/select.c

@@ -58,6 +58,18 @@ typecheckselect(Node *sel)
 				n->op = OSELRECV;
 				break;
 
+			case OAS2RECV:
+				// convert x, ok = <-c into OSELRECV(x, <-c) with ntest=ok
+				if(n->right->op != ORECV) {
+					yyerror("select assignment must have receive on right hand side");
+					break;
+				}
+				n->op = OSELRECV2;
+				n->left = n->list->n;
+				n->ntest = n->list->next->n;
+				n->right = n->rlist->n;
+				break;
+
 			case ORECV:
 				// convert <-c into OSELRECV(N, <-c)
 				n = nod(OSELRECV, N, n);
@@ -122,6 +134,18 @@ walkselect(Node *sel)
 					typecheck(&n, Etop);
 				}
 				break;
+			
+			case OSELRECV2:
+				r = n->right;
+				ch = cheapexpr(r->left, &l);
+				r->left = ch;
+				
+				a = nod(OAS2, N, N);
+				a->list = n->list;
+				a->rlist = n->rlist;
+				n = a;
+				typecheck(&n, Etop);
+				break;
 			}
 
 			// if ch == nil { block() }; n;
@@ -146,6 +170,7 @@ walkselect(Node *sel)
 			continue;
 		switch(n->op) {
 		case OSELRECV:
+		case OSELRECV2:
 			ch = n->right->left;
 
 			// If we can use the address of the target without
@@ -154,6 +179,28 @@ walkselect(Node *sel)
 			// Also introduce a temporary for := variables that escape,
 			// so that we can delay the heap allocation until the case
 			// is selected.
+			if(n->op == OSELRECV2) {
+				if(n->ntest == N || isblank(n->ntest))
+					n->ntest = nodnil();
+				else if(n->ntest->op == ONAME &&
+						(!n->colas || (n->ntest->class&PHEAP) == 0) &&
+						convertop(types[TBOOL], n->ntest->type, nil) == OCONVNOP) {
+					n->ntest = nod(OADDR, n->ntest, N);
+					n->ntest->etype = 1;  // pointer does not escape
+					typecheck(&n->ntest, Erv);
+				} else {
+					tmp = nod(OXXX, N, N);
+					tempname(tmp, types[TBOOL]);
+					a = nod(OADDR, tmp, N);
+					a->etype = 1;  // pointer does not escape
+					typecheck(&a, Erv);
+					r = nod(OAS, n->ntest, tmp);
+					typecheck(&r, Etop);
+					cas->nbody = concat(list1(r), cas->nbody);
+					n->ntest = a;
+				}
+			}
+
 			if(n->left == N || isblank(n->left))
 				n->left = nodnil();
 			else if(n->left->op == ONAME &&
@@ -171,10 +218,12 @@ walkselect(Node *sel)
 				r = nod(OAS, n->left, tmp);
 				typecheck(&r, Etop);
 				cas->nbody = concat(list1(r), cas->nbody);
-				cas->nbody = concat(n->ninit, cas->nbody);
-				n->ninit = nil;
 				n->left = a;
 			}
+			
+			cas->nbody = concat(n->ninit, cas->nbody);
+			n->ninit = nil;
+			break;
 		}
 	}
 
@@ -212,6 +261,16 @@ walkselect(Node *sel)
 				mkcall1(chanfn("selectnbrecv", 2, ch->type),
 					types[TBOOL], &r->ninit, n->left, ch));
 			break;
+
+		case OSELRECV2:
+			// if c != nil && selectnbrecv2(&v, c) { body } else { default body }
+			r = nod(OIF, N, N);
+			r->ninit = cas->ninit;
+			ch = cheapexpr(n->right->left, &r->ninit);
+			r->ntest = nod(OANDAND, nod(ONE, ch, nodnil()),
+				mkcall1(chanfn("selectnbrecv2", 2, ch->type),
+					types[TBOOL], &r->ninit, n->left, n->ntest, ch));
+			break;
 		}
 		typecheck(&r->ntest, Erv);
 		r->nbody = cas->nbody;
@@ -254,11 +313,18 @@ walkselect(Node *sel)
 				r->ntest = mkcall1(chanfn("selectsend", 2, n->left->type), types[TBOOL],
 					&init, var, n->left, n->right);
 				break;
+
 			case OSELRECV:
 				// selectrecv(sel *byte, hchan *chan any, elem *any) (selected bool);
 				r->ntest = mkcall1(chanfn("selectrecv", 2, n->right->left->type), types[TBOOL],
 					&init, var, n->right->left, n->left);
 				break;
+
+			case OSELRECV2:
+				// selectrecv2(sel *byte, hchan *chan any, elem *any, received *bool) (selected bool);
+				r->ntest = mkcall1(chanfn("selectrecv2", 2, n->right->left->type), types[TBOOL],
+					&init, var, n->right->left, n->left, n->ntest);
+				break;
 			}
 		}
 		r->nbody = concat(r->nbody, cas->nbody);

src/cmd/gc/sinit.c

@@ -94,7 +94,7 @@ init1(Node *n, NodeList **out)
 		case OAS2FUNC:
 		case OAS2MAPR:
 		case OAS2DOTTYPE:
-		case OAS2RECVCLOSED:
+		case OAS2RECV:
 			if(n->defn->initorder)
 				break;
 			n->defn->initorder = 1;

src/cmd/gc/subr.c

@@ -834,7 +834,6 @@ goopnames[] =
 	[OCALL]	= "function call",
 	[OCAP]		= "cap",
 	[OCASE]		= "case",
-	[OCLOSED]	= "closed",
 	[OCLOSE]	= "close",
 	[OCOMPLEX]	= "complex",
 	[OCOM]		= "^",
@@ -1669,6 +1668,9 @@ isselect(Node *n)
 	if(s == n->sym)
 		return 1;
 	s = pkglookup("selectrecv", runtimepkg);
+	if(s == n->sym)
+		return 1;
+	s = pkglookup("selectrecv2", runtimepkg);
 	if(s == n->sym)
 		return 1;
 	s = pkglookup("selectdefault", runtimepkg);

src/cmd/gc/typecheck.c

@@ -921,7 +921,6 @@ reswitch:
 		n->type = t;
 		goto ret;
 
-	case OCLOSED:
 	case OCLOSE:
 		if(onearg(n, "%#O", n->op) < 0)
 			goto error;
@@ -934,11 +933,7 @@ reswitch:
 			yyerror("invalid operation: %#N (non-chan type %T)", n, t);
 			goto error;
 		}
-		if(n->op == OCLOSED) {
-			n->type = types[TBOOL];
-			ok |= Erv;
-		} else
-			ok |= Etop;
+		ok |= Etop;
 		goto ret;
 
 	case OAPPEND:
@@ -2377,8 +2372,9 @@ typecheckas2(Node *n)
 			n->op = OAS2MAPR;
 			goto common;
 		case ORECV:
-			yyerror("cannot use multiple-value assignment for non-blocking receive; use select");
-			goto out;
+			n->op = OAS2RECV;
+			n->right = n->rlist->n;
+			goto common;
 		case ODOTTYPE:
 			n->op = OAS2DOTTYPE;
 			r->op = ODOTTYPE2;

src/cmd/gc/walk.c

@@ -403,12 +403,11 @@ walkstmt(Node **np)
 	case OAS:
 	case OAS2:
 	case OAS2DOTTYPE:
-	case OAS2RECVCLOSED:
+	case OAS2RECV:
 	case OAS2FUNC:
 	case OAS2MAPW:
 	case OAS2MAPR:
 	case OCLOSE:
-	case OCLOSED:
 	case OCOPY:
 	case OCALLMETH:
 	case OCALLINTER:
@@ -822,14 +821,13 @@ walkexpr(Node **np, NodeList **init)
 		n = liststmt(concat(concat(list1(r), ll), lpost));
 		goto ret;
 
-	case OAS2RECVCLOSED:
-		// a = <-c; b = closed(c) but atomic
+	case OAS2RECV:
 		*init = concat(*init, n->ninit);
 		n->ninit = nil;
 		r = n->rlist->n;
 		walkexprlistsafe(n->list, init);
 		walkexpr(&r->left, init);
-		fn = chanfn("chanrecv3", 2, r->left->type);
+		fn = chanfn("chanrecv2", 2, r->left->type);
 		r = mkcall1(fn, getoutargx(fn->type), init, r->left);
 		n->rlist->n = r;
 		n->op = OAS2FUNC;
@@ -1309,13 +1307,6 @@ walkexpr(Node **np, NodeList **init)
 		n = mkcall1(fn, T, init, n->left);
 		goto ret;
 
-	case OCLOSED:
-		// cannot use chanfn - closechan takes any, not chan any
-		fn = syslook("closedchan", 1);
-		argtype(fn, n->left->type);
-		n = mkcall1(fn, n->type, init, n->left);
-		goto ret;
-
 	case OMAKECHAN:
 		n = mkcall1(chanfn("makechan", 1, n->type), n->type, init,
 			typename(n->type->type),

src/pkg/runtime/chan.c

@@ -7,12 +7,6 @@
 
 static	int32	debug	= 0;
 
-enum
-{
-	Wclosed		= 0x0001,	// writer has closed
-	Rclosed		= 0x0002,	// reader has seen close
-};
-
 typedef	struct	Link	Link;
 typedef	struct	WaitQ	WaitQ;
 typedef	struct	SudoG	SudoG;
@@ -40,7 +34,7 @@ struct	Hchan
 	uint32	qcount;			// total data in the q
 	uint32	dataqsiz;		// size of the circular q
 	uint16	elemsize;
-	uint16	closed;			// Wclosed Rclosed errorcount
+	bool	closed;
 	uint8	elemalign;
 	Alg*	elemalg;		// interface for element type
 	Link*	senddataq;		// pointer for sender
@@ -57,15 +51,26 @@ struct	Link
 	byte	elem[8];		// asynch queue data element (+ more)
 };
 
+enum
+{
+	// Scase.kind
+	CaseRecv,
+	CaseSend,
+	CaseDefault,
+};
+
 struct	Scase
 {
 	Hchan*	chan;			// chan
 	byte*	pc;			// return pc
-	uint16	send;			// 0-recv 1-send 2-default
+	uint16	kind;
 	uint16	so;			// vararg of selected bool
 	union {
-		byte	elem[8];	// element (send)
-		byte*	elemp;		// pointer to element (recv)
+		byte	elem[2*sizeof(void*)];	// element (send)
+		struct {
+			byte*	elemp;		// pointer to element (recv)
+			bool*	receivedp;	// pointer to received bool (recv2)
+		} recv;
 	} u;
 };
 
@@ -183,7 +188,7 @@ runtime·chansend(Hchan *c, byte *ep, bool *pres)
 
 	runtime·lock(c);
 loop:
-	if(c->closed & Wclosed)
+	if(c->closed)
 		goto closed;
 
 	if(c->dataqsiz > 0)
@@ -228,7 +233,7 @@ loop:
 	return;
 
 asynch:
-	if(c->closed & Wclosed)
+	if(c->closed)
 		goto closed;
 
 	if(c->qcount >= c->dataqsiz) {
@@ -269,7 +274,7 @@ closed:
 }
 
 void
-runtime·chanrecv(Hchan* c, byte *ep, bool *pres, bool *closed)
+runtime·chanrecv(Hchan* c, byte *ep, bool *selected, bool *received)
 {
 	SudoG *sg;
 	G *gp;
@@ -284,14 +289,12 @@ runtime·chanrecv(Hchan* c, byte *ep, bool *pres, bool *closed)
 		runtime·printf("chanrecv: chan=%p\n", c);
 
 	runtime·lock(c);
-	if(closed != nil)
-		*closed = false;
 
 loop:
 	if(c->dataqsiz > 0)
 		goto asynch;
 
-	if(c->closed & Wclosed)
+	if(c->closed)
 		goto closed;
 
 	sg = dequeue(&c->sendq, c);
@@ -305,14 +308,16 @@ loop:
 		runtime·unlock(c);
 		runtime·ready(gp);
 
-		if(pres != nil)
-			*pres = true;
+		if(selected != nil)
+			*selected = true;
+		if(received != nil)
+			*received = true;
 		return;
 	}
 
-	if(pres != nil) {
+	if(selected != nil) {
 		runtime·unlock(c);
-		*pres = false;
+		*selected = false;
 		return;
 	}
 
@@ -331,18 +336,20 @@ loop:
 	if(ep != nil)
 		c->elemalg->copy(c->elemsize, ep, sg->elem);
 	c->elemalg->copy(c->elemsize, sg->elem, nil);
+	if(received != nil)
+		*received = true;
 	freesg(c, sg);
 	runtime·unlock(c);
 	return;
 
 asynch:
 	if(c->qcount <= 0) {
-		if(c->closed & Wclosed)
+		if(c->closed)
 			goto closed;
 
-		if(pres != nil) {
+		if(selected != nil) {
 			runtime·unlock(c);
-			*pres = false;
+			*selected = false;
 			return;
 		}
 		sg = allocsg(c);
@@ -365,24 +372,22 @@ asynch:
 		freesg(c, sg);
 		runtime·unlock(c);
 		runtime·ready(gp);
-		if(pres != nil)
-			*pres = true;
-		return;
-	}
+	} else
+		runtime·unlock(c);
 
-	runtime·unlock(c);
-	if(pres != nil)
-		*pres = true;
+	if(selected != nil)
+		*selected = true;
+	if(received != nil)
+		*received = true;
 	return;
 
 closed:
-	if(closed != nil)
-		*closed = true;
 	if(ep != nil)
 		c->elemalg->copy(c->elemsize, ep, nil);
-	c->closed |= Rclosed;
-	if(pres != nil)
-		*pres = true;
+	if(selected != nil)
+		*selected = true;
+	if(received != nil)
+		*received = false;
 	runtime·unlock(c);
 }
 
@@ -416,16 +421,16 @@ runtime·chanrecv1(Hchan* c, ...)
 	runtime·chanrecv(c, ae, nil, nil);
 }
 
-// chanrecv3(hchan *chan any) (elem any, closed bool);
+// chanrecv2(hchan *chan any) (elem any, received bool);
 #pragma textflag 7
 void
-runtime·chanrecv3(Hchan* c, ...)
+runtime·chanrecv2(Hchan* c, ...)
 {
 	int32 o;
 	byte *ae, *ac;
 	
 	if(c == nil)
-		runtime·panicstring("range over nil channel");
+		runtime·panicstring("receive from nil channel");
 
 	o = runtime·rnd(sizeof(c), Structrnd);
 	ae = (byte*)&c + o;
@@ -490,9 +495,35 @@ runtime·selectnbsend(Hchan *c, ...)
 //
 #pragma textflag 7
 void
-runtime·selectnbrecv(byte *v, Hchan *c, bool ok)
+runtime·selectnbrecv(byte *v, Hchan *c, bool selected)
 {
-	runtime·chanrecv(c, v, &ok, nil);
+	runtime·chanrecv(c, v, &selected, nil);
+}	
+
+// func selectnbrecv2(elem *any, ok *bool, c chan any) bool
+//
+// compiler implements
+//
+//	select {
+//	case v = <-c:
+//		... foo
+//	default:
+//		... bar
+//	}
+//
+// as
+//
+//	if c != nil && selectnbrecv(&v, c) {
+//		... foo
+//	} else {
+//		... bar
+//	}
+//
+#pragma textflag 7
+void
+runtime·selectnbrecv2(byte *v, bool *received, Hchan *c, bool selected)
+{
+	runtime·chanrecv(c, v, &selected, received);
 }	
 
 static void newselect(int32, Select**);
@@ -556,22 +587,22 @@ runtime·selectsend(Select *sel, Hchan *c, ...)
 	eo = runtime·rnd(sizeof(sel), sizeof(c));
 	eo = runtime·rnd(eo+sizeof(c), c->elemsize);
 	cas->so = runtime·rnd(eo+c->elemsize, Structrnd);
-	cas->send = 1;
+	cas->kind = CaseSend;
 
 	ae = (byte*)&sel + eo;
 	c->elemalg->copy(c->elemsize, cas->u.elem, ae);
 
 	if(debug)
-		runtime·printf("selectsend s=%p pc=%p chan=%p so=%d send=%d\n",
-			sel, cas->pc, cas->chan, cas->so, cas->send);
+		runtime·printf("selectsend s=%p pc=%p chan=%p so=%d\n",
+			sel, cas->pc, cas->chan, cas->so);
 }
 
 // selectrecv(sel *byte, hchan *chan any, elem *any) (selected bool);
 #pragma textflag 7
 void
-runtime·selectrecv(Select *sel, Hchan *c, ...)
+runtime·selectrecv(Select *sel, Hchan *c, void *elem, bool selected)
 {
-	int32 i, eo;
+	int32 i;
 	Scase *cas;
 
 	// nil cases do not compete
@@ -587,30 +618,60 @@ runtime·selectrecv(Select *sel, Hchan *c, ...)
 	cas->pc = runtime·getcallerpc(&sel);
 	cas->chan = c;
 
-	eo = runtime·rnd(sizeof(sel), sizeof(c));
-	eo = runtime·rnd(eo+sizeof(c), sizeof(byte*));
-	cas->so = runtime·rnd(eo+sizeof(byte*), Structrnd);
-	cas->send = 0;
-	cas->u.elemp = *(byte**)((byte*)&sel + eo);
+	cas->so = (byte*)&selected - (byte*)&sel;
+	cas->kind = CaseRecv;
+	cas->u.recv.elemp = elem;
+	cas->u.recv.receivedp = nil;
+
+	if(debug)
+		runtime·printf("selectrecv s=%p pc=%p chan=%p so=%d\n",
+			sel, cas->pc, cas->chan, cas->so);
+}
+
+// selectrecv2(sel *byte, hchan *chan any, elem *any, received *bool) (selected bool);
+#pragma textflag 7
+void
+runtime·selectrecv2(Select *sel, Hchan *c, void *elem, bool *received, bool selected)
+{
+	int32 i;
+	Scase *cas;
+
+	// nil cases do not compete
+	if(c == nil)
+		return;
+
+	i = sel->ncase;
+	if(i >= sel->tcase)
+		runtime·throw("selectrecv: too many cases");
+	sel->ncase = i+1;
+	cas = runtime·mal(sizeof *cas);
+	sel->scase[i] = cas;
+	cas->pc = runtime·getcallerpc(&sel);
+	cas->chan = c;
+
+	cas->so = (byte*)&selected - (byte*)&sel;
+	cas->kind = CaseRecv;
+	cas->u.recv.elemp = elem;
+	cas->u.recv.receivedp = received;
 
 	if(debug)
-		runtime·printf("selectrecv s=%p pc=%p chan=%p so=%d send=%d\n",
-			sel, cas->pc, cas->chan, cas->so, cas->send);
+		runtime·printf("selectrecv2 s=%p pc=%p chan=%p so=%d elem=%p recv=%p\n",
+			sel, cas->pc, cas->chan, cas->so, cas->u.recv.elemp, cas->u.recv.receivedp);
 }
 
 
-static void selectdefault(Select*, void*);
+static void selectdefault(Select*, void*, int32);
 
 // selectdefault(sel *byte) (selected bool);
 #pragma textflag 7
 void
-runtime·selectdefault(Select *sel, ...)
+runtime·selectdefault(Select *sel, bool selected)
 {
-	selectdefault(sel, runtime·getcallerpc(&sel));
+	selectdefault(sel, runtime·getcallerpc(&sel), (byte*)&selected - (byte*)&sel);
 }
 
 static void
-selectdefault(Select *sel, void *callerpc)
+selectdefault(Select *sel, void *callerpc, int32 so)
 {
 	int32 i;
 	Scase *cas;
@@ -624,13 +685,12 @@ selectdefault(Select *sel, void *callerpc)
 	cas->pc = callerpc;
 	cas->chan = nil;
 
-	cas->so = runtime·rnd(sizeof(sel), Structrnd);
-	cas->send = 2;
-	cas->u.elemp = nil;
+	cas->so = so;
+	cas->kind = CaseDefault;
 
 	if(debug)
-		runtime·printf("selectdefault s=%p pc=%p so=%d send=%d\n",
-			sel, cas->pc, cas->so, cas->send);
+		runtime·printf("selectdefault s=%p pc=%p so=%d\n",
+			sel, cas->pc, cas->so);
 }
 
 static void
@@ -747,8 +807,8 @@ loop:
 		cas = sel->scase[o];
 		c = cas->chan;
 
-		switch(cas->send) {
-		case 0:	// recv
+		switch(cas->kind) {
+		case CaseRecv:
 			if(c->dataqsiz > 0) {
 				if(c->qcount > 0)
 					goto asyncrecv;
@@ -757,12 +817,12 @@ loop:
 				if(sg != nil)
 					goto syncrecv;
 			}
-			if(c->closed & Wclosed)
+			if(c->closed)
 				goto rclose;
 			break;
 
-		case 1:	// send
-			if(c->closed & Wclosed)
+		case CaseSend:
+			if(c->closed)
 				goto sclose;
 			if(c->dataqsiz > 0) {
 				if(c->qcount < c->dataqsiz)
@@ -774,7 +834,7 @@ loop:
 			}
 			break;
 
-		case 2:	// default
+		case CaseDefault:
 			dfl = cas;
 			break;
 		}
@@ -794,12 +854,12 @@ loop:
 		sg = allocsg(c);
 		sg->offset = o;
 
-		switch(cas->send) {
-		case 0:	// recv
+		switch(cas->kind) {
+		case CaseRecv:
 			enqueue(&c->recvq, sg);
 			break;
 		
-		case 1:	// send
+		case CaseSend:
 			if(c->dataqsiz == 0)
 				c->elemalg->copy(c->elemsize, sg->elem, cas->u.elem);
 			enqueue(&c->sendq, sg);
@@ -821,7 +881,7 @@ loop:
 		if(sg == nil || i != sg->offset) {
 			cas = sel->scase[i];
 			c = cas->chan;
-			if(cas->send)
+			if(cas->kind == CaseSend)
 				dequeueg(&c->sendq, c);
 			else
 				dequeueg(&c->recvq, c);
@@ -841,12 +901,14 @@ loop:
 	}
 
 	if(debug)
-		runtime·printf("wait-return: sel=%p c=%p cas=%p send=%d o=%d\n",
-			sel, c, cas, cas->send, o);
-
-	if(!cas->send) {
-		if(cas->u.elemp != nil)
-			c->elemalg->copy(c->elemsize, cas->u.elemp, sg->elem);
+		runtime·printf("wait-return: sel=%p c=%p cas=%p kind=%d o=%d\n",
+			sel, c, cas, cas->kind, o);
+
+	if(cas->kind == CaseRecv) {
+		if(cas->u.recv.receivedp != nil)
+			*cas->u.recv.receivedp = true;
+		if(cas->u.recv.elemp != nil)
+			c->elemalg->copy(c->elemsize, cas->u.recv.elemp, sg->elem);
 		c->elemalg->copy(c->elemsize, sg->elem, nil);
 	}
 
@@ -855,8 +917,10 @@ loop:
 
 asyncrecv:
 	// can receive from buffer
-	if(cas->u.elemp != nil)
-		c->elemalg->copy(c->elemsize, cas->u.elemp, c->recvdataq->elem);
+	if(cas->u.recv.receivedp != nil)
+		*cas->u.recv.receivedp = true;
+	if(cas->u.recv.elemp != nil)
+		c->elemalg->copy(c->elemsize, cas->u.recv.elemp, c->recvdataq->elem);
 	c->elemalg->copy(c->elemsize, c->recvdataq->elem, nil);
 	c->recvdataq = c->recvdataq->link;
 	c->qcount--;
@@ -886,8 +950,10 @@ syncrecv:
 	// can receive from sleeping sender (sg)
 	if(debug)
 		runtime·printf("syncrecv: sel=%p c=%p o=%d\n", sel, c, o);
-	if(cas->u.elemp != nil)
-		c->elemalg->copy(c->elemsize, cas->u.elemp, sg->elem);
+	if(cas->u.recv.receivedp != nil)
+		*cas->u.recv.receivedp = true;
+	if(cas->u.recv.elemp != nil)
+		c->elemalg->copy(c->elemsize, cas->u.recv.elemp, sg->elem);
 	c->elemalg->copy(c->elemsize, sg->elem, nil);
 	gp = sg->g;
 	gp->param = sg;
@@ -896,16 +962,17 @@ syncrecv:
 
 rclose:
 	// read at end of closed channel
-	if(cas->u.elemp != nil)
-		c->elemalg->copy(c->elemsize, cas->u.elemp, nil);
-	c->closed |= Rclosed;
+	if(cas->u.recv.receivedp != nil)
+		*cas->u.recv.receivedp = false;
+	if(cas->u.recv.elemp != nil)
+		c->elemalg->copy(c->elemsize, cas->u.recv.elemp, nil);
 	goto retc;
 
 syncsend:
 	// can send to sleeping receiver (sg)
 	if(debug)
 		runtime·printf("syncsend: sel=%p c=%p o=%d\n", sel, c, o);
-	if(c->closed & Wclosed)
+	if(c->closed)
 		goto sclose;
 	c->elemalg->copy(c->elemsize, sg->elem, cas->u.elem);
 	gp = sg->g;
@@ -916,7 +983,6 @@ retc:
 	selunlock(sel);
 
 	// return to pc corresponding to chosen case
-	
 	pc = cas->pc;
 	as = (byte*)selp + cas->so;
 	freesel(sel);
@@ -941,12 +1007,12 @@ runtime·closechan(Hchan *c)
 		runtime·gosched();
 
 	runtime·lock(c);
-	if(c->closed & Wclosed) {
+	if(c->closed) {
 		runtime·unlock(c);
 		runtime·panicstring("close of closed channel");
 	}
 
-	c->closed |= Wclosed;
+	c->closed = true;
 
 	// release all readers
 	for(;;) {
@@ -979,12 +1045,6 @@ runtime·chanclose(Hchan *c)
 	runtime·closechan(c);
 }
 
-bool
-runtime·chanclosed(Hchan *c)
-{
-	return (c->closed & Rclosed) != 0;
-}
-
 int32
 runtime·chanlen(Hchan *c)
 {
@@ -997,15 +1057,6 @@ runtime·chancap(Hchan *c)
 	return c->dataqsiz;
 }
 
-
-// closedchan(sel *byte) bool;
-void
-runtime·closedchan(Hchan *c, bool closed)
-{
-	closed = runtime·chanclosed(c);
-	FLUSH(&closed);
-}
-
 static SudoG*
 dequeue(WaitQ *q, Hchan *c)
 {

src/pkg/runtime/reflect.goc

@@ -70,22 +70,18 @@ func makechan(typ *byte, size uint32) (ch *byte) {
 	ch = (byte*)runtime·makechan_c(t->elem, size);
 }
 
-func chansend(ch *byte, val *byte, pres *bool) {
-	runtime·chansend((Hchan*)ch, val, pres);
+func chansend(ch *byte, val *byte, selected *bool) {
+	runtime·chansend((Hchan*)ch, val, selected);
 }
 
-func chanrecv(ch *byte, val *byte, pres *bool) {
-	runtime·chanrecv((Hchan*)ch, val, pres, nil);
+func chanrecv(ch *byte, val *byte, selected *bool, received *bool) {
+	runtime·chanrecv((Hchan*)ch, val, selected, received);
 }
 
 func chanclose(ch *byte) {
 	runtime·chanclose((Hchan*)ch);
 }
 
-func chanclosed(ch *byte) (r bool) {
-	r = runtime·chanclosed((Hchan*)ch);
-}
-
 func chanlen(ch *byte) (r int32) {
 	r = runtime·chanlen((Hchan*)ch);
 }

src/pkg/runtime/runtime.h

@@ -585,7 +585,6 @@ Hchan*	runtime·makechan_c(Type*, int64);
 void	runtime·chansend(Hchan*, void*, bool*);
 void	runtime·chanrecv(Hchan*, void*, bool*, bool*);
 void	runtime·chanclose(Hchan*);
-bool	runtime·chanclosed(Hchan*);
 int32	runtime·chanlen(Hchan*);
 int32	runtime·chancap(Hchan*);