cmd/compile: stop constructing sudog type

The compiler doesn't care about the runtime's sudog type. Stop
constructing it.

Change-Id: If1885fe30b2e215a08d17662eab5ea6d81fe58ab
Reviewed-on: https://go-review.googlesource.com/20797
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

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

@@ -317,24 +317,10 @@ out:
 	lineno = lno
 }
 
-// Keep in sync with src/runtime/runtime2.go and src/runtime/select.go.
+// Keep in sync with src/runtime/select.go.
 func selecttype(size int32) *Type {
-	// TODO(dvyukov): it's possible to generate SudoG and Scase only once
+	// TODO(dvyukov): it's possible to generate Scase only once
 	// and then cache; and also cache Select per size.
-	sudog := Nod(OTSTRUCT, nil, nil)
-
-	sudog.List.Append(Nod(ODCLFIELD, newname(Lookup("g")), typenod(Ptrto(Types[TUINT8]))))
-	sudog.List.Append(Nod(ODCLFIELD, newname(Lookup("selectdone")), typenod(Ptrto(Types[TUINT8]))))
-	sudog.List.Append(Nod(ODCLFIELD, newname(Lookup("next")), typenod(Ptrto(Types[TUINT8]))))
-	sudog.List.Append(Nod(ODCLFIELD, newname(Lookup("prev")), typenod(Ptrto(Types[TUINT8]))))
-	sudog.List.Append(Nod(ODCLFIELD, newname(Lookup("elem")), typenod(Ptrto(Types[TUINT8]))))
-	sudog.List.Append(Nod(ODCLFIELD, newname(Lookup("releasetime")), typenod(Types[TUINT64])))
-	sudog.List.Append(Nod(ODCLFIELD, newname(Lookup("ticket")), typenod(Types[TUINT32])))
-	sudog.List.Append(Nod(ODCLFIELD, newname(Lookup("waitlink")), typenod(Ptrto(Types[TUINT8]))))
-	sudog.List.Append(Nod(ODCLFIELD, newname(Lookup("c")), typenod(Ptrto(Types[TUINT8]))))
-	typecheck(&sudog, Etype)
-	sudog.Type.Noalg = true
-	sudog.Type.Local = true
 
 	scase := Nod(OTSTRUCT, nil, nil)
 	scase.List.Append(Nod(ODCLFIELD, newname(Lookup("elem")), typenod(Ptrto(Types[TUINT8]))))

src/runtime/runtime2.go

@@ -210,9 +210,6 @@ type gobuf struct {
 	bp   uintptr // for GOEXPERIMENT=framepointer
 }
 
-// Known to compiler.
-// Changes here must also be made in src/cmd/compile/internal/gc/select.go's
-// selecttype.
 type sudog struct {
 	// The following fields are protected by the hchan.lock of the
 	// channel this sudog is blocking on. shrinkstack depends on