mirror of
https://github.com/golang/go
synced 2024-11-24 23:47:55 -07:00
4ce06f4b5c
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>
74 lines
901 B
Go
74 lines
901 B
Go
// 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.
|
|
|
|
package main
|
|
|
|
func fail() // unimplemented, to test dead code elimination
|
|
|
|
// Test dead code elimination in if statements
|
|
func init() {
|
|
if false {
|
|
fail()
|
|
}
|
|
if 0 == 1 {
|
|
fail()
|
|
}
|
|
}
|
|
|
|
// Test dead code elimination in ordinary switch statements
|
|
func init() {
|
|
const x = 0
|
|
switch x {
|
|
case 1:
|
|
fail()
|
|
}
|
|
|
|
switch 1 {
|
|
case x:
|
|
fail()
|
|
}
|
|
|
|
switch {
|
|
case false:
|
|
fail()
|
|
}
|
|
|
|
const a = "a"
|
|
switch a {
|
|
case "b":
|
|
fail()
|
|
}
|
|
|
|
const snowman = '☃'
|
|
switch snowman {
|
|
case '☀':
|
|
fail()
|
|
}
|
|
|
|
const zero = float64(0.0)
|
|
const one = float64(1.0)
|
|
switch one {
|
|
case -1.0:
|
|
fail()
|
|
case zero:
|
|
fail()
|
|
}
|
|
|
|
switch 1.0i {
|
|
case 1:
|
|
fail()
|
|
case -1i:
|
|
fail()
|
|
}
|
|
|
|
const no = false
|
|
switch no {
|
|
case true:
|
|
fail()
|
|
}
|
|
}
|
|
|
|
func main() {
|
|
}
|