cmd/compile,runtime: make selectnbrecv return two values

The only different between selectnbrecv and selectnbrecv2 is the later
set the input pointer value by second return value from chanrecv.

So by making selectnbrecv return two values from chanrecv, we can get
rid of selectnbrecv2, the compiler can now call only selectnbrecv and
generate simpler code.

Change-Id: Ifaf6cf1314c4f47b06ed9606b1578319be808507
Reviewed-on: https://go-review.googlesource.com/c/go/+/292890
Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

src/cmd/compile/internal/typecheck/builtin.go

@@ -316,7 +316,7 @@ func runtimeTypes() []*types.Type {
 	typs[92] = newSig(params(typs[1], typs[3]), nil)
 	typs[93] = newSig(params(typs[1], typs[3], typs[15], typs[3], typs[15]), params(typs[15]))
 	typs[94] = newSig(params(typs[87], typs[3]), params(typs[6]))
-	typs[95] = newSig(params(typs[3], typs[84]), params(typs[6]))
+	typs[95] = newSig(params(typs[3], typs[84]), params(typs[6], typs[6]))
 	typs[96] = types.NewPtr(typs[6])
 	typs[97] = newSig(params(typs[3], typs[96], typs[84]), params(typs[6]))
 	typs[98] = newSig(params(typs[63]), nil)

src/cmd/compile/internal/typecheck/builtin/runtime.go

@@ -166,7 +166,7 @@ func typedmemclr(typ *byte, dst *any)
 func typedslicecopy(typ *byte, dstPtr *any, dstLen int, srcPtr *any, srcLen int) int
 
 func selectnbsend(hchan chan<- any, elem *any) bool
-func selectnbrecv(elem *any, hchan <-chan any) bool
+func selectnbrecv(elem *any, hchan <-chan any) (bool, bool)
 func selectnbrecv2(elem *any, received *bool, hchan <-chan any) bool
 
 func selectsetpc(pc *uintptr)

src/cmd/compile/internal/walk/select.go

@@ -106,7 +106,7 @@ func walkSelectCases(cases []*ir.CommClause) []ir.Node {
 		ir.SetPos(n)
 		r := ir.NewIfStmt(base.Pos, nil, nil, nil)
 		*r.PtrInit() = cas.Init()
-		var call ir.Node
+		var cond ir.Node
 		switch n.Op() {
 		default:
 			base.Fatalf("select %v", n.Op())
@@ -115,7 +115,7 @@ func walkSelectCases(cases []*ir.CommClause) []ir.Node {
 			// if selectnbsend(c, v) { body } else { default body }
 			n := n.(*ir.SendStmt)
 			ch := n.Chan
-			call = mkcall1(chanfn("selectnbsend", 2, ch.Type()), types.Types[types.TBOOL], r.PtrInit(), ch, n.Value)
+			cond = mkcall1(chanfn("selectnbsend", 2, ch.Type()), types.Types[types.TBOOL], r.PtrInit(), ch, n.Value)
 
 		case ir.OSELRECV2:
 			n := n.(*ir.AssignListStmt)
@@ -125,18 +125,14 @@ func walkSelectCases(cases []*ir.CommClause) []ir.Node {
 			if ir.IsBlank(elem) {
 				elem = typecheck.NodNil()
 			}
-			if ir.IsBlank(n.Lhs[1]) {
+			cond = typecheck.Temp(types.Types[types.TBOOL])
-				// if selectnbrecv(&v, c) { body } else { default body }
+			fn := chanfn("selectnbrecv", 2, ch.Type())
-				call = mkcall1(chanfn("selectnbrecv", 2, ch.Type()), types.Types[types.TBOOL], r.PtrInit(), elem, ch)
+			call := mkcall1(fn, fn.Type().Results(), r.PtrInit(), elem, ch)
-			} else {
+			as := ir.NewAssignListStmt(r.Pos(), ir.OAS2, []ir.Node{cond, n.Lhs[1]}, []ir.Node{call})
-				// TODO(cuonglm): make this use selectnbrecv()
+			r.PtrInit().Append(typecheck.Stmt(as))
-				// if selectnbrecv2(&v, &received, c) { body } else { default body }
-				receivedp := typecheck.Expr(typecheck.NodAddr(n.Lhs[1]))
-				call = mkcall1(chanfn("selectnbrecv2", 2, ch.Type()), types.Types[types.TBOOL], r.PtrInit(), elem, receivedp, ch)
-			}
 		}
 
-		r.Cond = typecheck.Expr(call)
+		r.Cond = typecheck.Expr(cond)
 		r.Body = cas.Body
 		r.Else = append(dflt.Init(), dflt.Body...)
 		return []ir.Node{r, ir.NewBranchStmt(base.Pos, ir.OBREAK, nil)}

src/runtime/chan.go

@@ -687,28 +687,6 @@ func selectnbsend(c *hchan, elem unsafe.Pointer) (selected bool) {
 	return chansend(c, elem, false, getcallerpc())
 }
 
-// compiler implements
-//
-//	select {
-//	case v = <-c:
-//		... foo
-//	default:
-//		... bar
-//	}
-//
-// as
-//
-//	if selectnbrecv(&v, c) {
-//		... foo
-//	} else {
-//		... bar
-//	}
-//
-func selectnbrecv(elem unsafe.Pointer, c *hchan) (selected bool) {
-	selected, _ = chanrecv(c, elem, false)
-	return
-}
-
 // compiler implements
 //
 //	select {
@@ -720,16 +698,14 @@ func selectnbrecv(elem unsafe.Pointer, c *hchan) (selected bool) {
 //
 // as
 //
-//	if c != nil && selectnbrecv2(&v, &ok, c) {
+//	if selected, ok = selectnbrecv(&v, c); selected {
 //		... foo
 //	} else {
 //		... bar
 //	}
 //
-func selectnbrecv2(elem unsafe.Pointer, received *bool, c *hchan) (selected bool) {
+func selectnbrecv(elem unsafe.Pointer, c *hchan) (selected, received bool) {
-	// TODO(khr): just return 2 values from this function, now that it is in Go.
+	return chanrecv(c, elem, false)
-	selected, *received = chanrecv(c, elem, false)
-	return
 }
 
 //go:linkname reflect_chansend reflect.chansend