cmd/gc: eliminate dead code in switch statements
Ordinary switch statements are rewritten
into a sequence of if statements.
Staticly dead cases were not being eliminated
because the rewrite introduced a temporary,
which hid the fact that the case was a constant.
Stop doing that.
This eliminates dead code in the standard library at:
runtime/cgocall.go:219
runtime/cgocall.go:269
debug/gosym/pclntab.go:175
debug/macho/file.go:208
math/big/nat.go:635
math/big/nat.go:850
math/big/nat.go:1058
cmd/pprof/internal/commands/commands.go:86
net/sock_bsd.go:19
cmd/go/build.go:2657
cmd/go/env.go:90
Fixes #9608.
Change-Id: Ic23a05dfbb1ad91d5f62a6506b35a13e51b33e38
Reviewed-on: https://go-review.googlesource.com/3980
Reviewed-by: Keith Randall <khr@golang.org>
diff --git a/test/fixedbugs/issue9608.go b/test/fixedbugs/issue9608.go
new file mode 100644
index 0000000..92592d7
--- /dev/null
+++ b/test/fixedbugs/issue9608.go
@@ -0,0 +1,14 @@
+// rundir
+
+// Copyright 2015 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 9608: dead code elimination in switch statements.
+
+// This has to be done as a package rather than as a file,
+// because run.go runs files with 'go run', which passes the
+// -complete flag to compiler, causing it to complain about
+// the intentionally unimplemented function fail.
+
+package ignored
