cmd/gc: use a register to checknil constants.

Fixes issue 7346.

LGTM=rsc
R=rsc, iant, khr
CC=golang-codereviews
https://codereview.appspot.com/69050044

1 files changed, 14 insertions, 0 deletions

diff --git a/test/fixedbugs/issue7346.go b/test/fixedbugs/issue7346.go
new file mode 100644
index 000000000..dd5ea222f
--- /dev/null
+++ b/test/fixedbugs/issue7346.go
@@ -0,0 +1,14 @@
+// compile
+
+// Copyright 2014 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 7346 : internal error "doasm" error due to checknil
+// of a nil literal.
+
+package main
+
+func main() {
+	_ = *(*int)(nil)
+}