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https://github.com/golang/go
synced 2024-11-27 05:01:19 -07:00
755b36aa53
The sub-word shifts need to sign-extend before shifting, to avoid bringing in data from higher in the argument. Fixes #23812 Change-Id: I0a95a0b49c48f3b40b85765bb4a9bb492be0cd73 Reviewed-on: https://go-review.googlesource.com/93716 Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Cherry Zhang <cherryyz@google.com>
35 lines
585 B
Go
35 lines
585 B
Go
// run
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// Copyright 2018 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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package main
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import "fmt"
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func main() {
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want := int32(0x3edae8)
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got := foo(1)
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if want != got {
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panic(fmt.Sprintf("want %x, got %x", want, got))
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}
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}
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func foo(a int32) int32 {
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return shr1(int32(shr2(int64(0x14ff6e2207db5d1f), int(a))), 4)
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}
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func shr1(n int32, m int) int32 { return n >> uint(m) }
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func shr2(n int64, m int) int64 {
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if m < 0 {
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m = -m
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}
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if m >= 64 {
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return n
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}
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return n >> uint(m)
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}
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