mirror of
https://github.com/golang/go
synced 2024-11-12 08:40:21 -07:00
38 lines
719 B
Go
38 lines
719 B
Go
|
// run
|
||
|
|
|
||
|
|
// Copyright 2012 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 4448: 64-bit indices that are statically known
|
||
|
|
// to be bounded make 5g and 8g generate a dangling branch.
|
||
|
|
|
||
|
|
package main
|
||
|
|
|
||
|
|
const b26 uint64 = 0x022fdd63cc95386d
|
||
|
|
|
||
|
|
var bitPos [64]int
|
||
|
|
|
||
|
|
func init() {
|
||
|
|
for p := uint(0); p < 64; p++ {
|
||
|
|
bitPos[b26<<p>>58] = int(p)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
func MinPos(w uint64) int {
|
||
|
|
if w == 0 {
|
||
|
|
panic("bit: MinPos(0) undefined")
|
||
|
|
}
|
||
|
|
return bitPos[((w&-w)*b26)>>58]
|
||
|
|
}
|
||
|
|
|
||
|
|
func main() {
|
||
|
|
const one = uint64(1)
|
||
|
|
for i := 0; i < 64; i++ {
|
||
|
|
if MinPos(1<<uint(i)) != i {
|
||
|
|
println("i =", i)
|
||
|
|
panic("MinPos(1<<uint(i)) != i")
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|