| // 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") |
| } |
| } |
| } |
