[dev.typeparams] cmd/compile: get runtime stuff working

Remaining stuff from Dan's CL 335412 to get tests passing.

 - Removed PTRLIT case in node() that was added with the gcshape change.
   I don't think it is needed anymore.

 - Modified (*itab).init() to add an irrelevant pointer (the itab
   itself) for the '==' entry of interfaces with 'comparable'. That
   entry is not used, so we just want to avoid the error that the given
   type doesn't actually have an '==' method.

Change-Id: I9b2d4c8342c0b2048d76e003d95023f4ccd559f5
Reviewed-on: https://go-review.googlesource.com/c/go/+/336149
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>
Trust: Dan Scales <danscales@google.com>
Trust: Keith Randall <khr@golang.org>

src/cmd/compile/internal/noder/stencil.go

@@ -1394,11 +1394,6 @@ func (subst *subster) node(n ir.Node) ir.Node {
 			// TODO: need to modify m.X? I don't think any downstream passes use it.
 			m.SetType(subst.unshapifyTyp(m.Type()))
 
-		case ir.OPTRLIT:
-			m := m.(*ir.AddrExpr)
-			// Walk uses the type of the argument of ptrlit. Also could be a shape type?
-			m.X.SetType(subst.unshapifyTyp(m.X.Type()))
-
 		case ir.OMETHEXPR:
 			se := m.(*ir.SelectorExpr)
 			se.X = ir.TypeNodeAt(se.X.Pos(), subst.unshapifyTyp(se.X.Type()))

src/runtime/iface.go

@@ -214,6 +214,16 @@ imethods:
 		if ipkg == "" {
 			ipkg = inter.pkgpath.name()
 		}
+		if iname == "==" {
+			// Don't need '==' method right now (from comparable),
+			// just fill in with a random pointer for now.
+			if k == 0 {
+				fun0 = unsafe.Pointer(m)
+			} else {
+				methods[k] = unsafe.Pointer(m)
+			}
+			continue imethods
+		}
 		for ; j < nt; j++ {
 			t := &xmhdr[j]
 			tname := typ.nameOff(t.name)