| // Copyright 2018 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. |
| |
| // +build !go1.9 |
| |
| package ssa |
| |
| const deBruijn64 = 0x03f79d71b4ca8b09 |
| |
| var deBruijn64tab = [64]byte{ |
| 0, 1, 56, 2, 57, 49, 28, 3, 61, 58, 42, 50, 38, 29, 17, 4, |
| 62, 47, 59, 36, 45, 43, 51, 22, 53, 39, 33, 30, 24, 18, 12, 5, |
| 63, 55, 48, 27, 60, 41, 37, 16, 46, 35, 44, 21, 52, 32, 23, 11, |
| 54, 26, 40, 15, 34, 20, 31, 10, 25, 14, 19, 9, 13, 8, 7, 6, |
| } |
| |
| // TrailingZeros64 returns the number of trailing zero bits in x; the result is 64 for x == 0. |
| func TrailingZeros64(x uint64) int { |
| if x == 0 { |
| return 64 |
| } |
| return int(deBruijn64tab[(x&-x)*deBruijn64>>(64-6)]) |
| } |
