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 @@ typecheck(Node **np, int top)
 		n->type = t;
 		goto ret;
 
-	case OCLOSED:
 	case OCLOSE:
 		if(onearg(n, "%#O", n->op) < 0)
 			goto error;
@@ -934,11 +933,7 @@ typecheck(Node **np, int top)
 			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),