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https://github.com/golang/go
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38 lines
719 B
Go
38 lines
719 B
Go
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// run
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// Copyright 2012 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Issue 4448: 64-bit indices that are statically known
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// to be bounded make 5g and 8g generate a dangling branch.
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package main
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const b26 uint64 = 0x022fdd63cc95386d
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var bitPos [64]int
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func init() {
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for p := uint(0); p < 64; p++ {
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bitPos[b26<<p>>58] = int(p)
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}
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}
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func MinPos(w uint64) int {
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if w == 0 {
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panic("bit: MinPos(0) undefined")
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}
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return bitPos[((w&-w)*b26)>>58]
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}
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func main() {
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const one = uint64(1)
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for i := 0; i < 64; i++ {
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if MinPos(1<<uint(i)) != i {
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println("i =", i)
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panic("MinPos(1<<uint(i)) != i")
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}
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}
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}
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