cmd/compile: fix binary import of unsafe.Pointer literals

Add a type conversion to uintptr for untyped constants
before the conversion to unsafe.Pointer.

Fixes #16317

Change-Id: Ib85feccad1019e687e7eb6135890b64b82fb87fb
Reviewed-on: https://go-review.googlesource.com/27441Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

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

@@ -807,6 +807,11 @@ func (p *importer) node() *Node {
 		typ := p.typ()
 		n := nodlit(p.value(typ))
 		if !typ.IsUntyped() {
+			if typ.IsUnsafePtr() {
+				conv := Nod(OCALL, typenod(Types[TUINTPTR]), nil)
+				conv.List.Set1(n)
+				n = conv
+			}
 			conv := Nod(OCALL, typenod(typ), nil)
 			conv.List.Set1(n)
 			n = conv

test/fixedbugs/issue16317.dir/a.go

+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+import "unsafe"
+
+func ConstUnsafePointer() unsafe.Pointer {
+	return unsafe.Pointer(uintptr(0))
+}

test/fixedbugs/issue16317.dir/b.go

+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "./a"
+
+func main() {
+	_ = a.ConstUnsafePointer()
+}

test/fixedbugs/issue16317.go

+// compiledir
+
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Issue 16317: cmd/compile: internal compiler error:
+//              unhandled OCONV INT -> TUNSAFEPTR
+
+package ignored