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585c9e8412
Allow shifts by signed amounts. Panic if the shift amount is negative. TODO: We end up doing two compares per shift, see Ian's comment https://github.com/golang/go/issues/19113#issuecomment-443241799 that we could do it with a single comparison in the normal case. The prove pass mostly handles this code well. For instance, it removes the <0 check for cases like this: if s >= 0 { _ = x << s } _ = x << len(a) This case isn't handled well yet: _ = x << (y & 0xf) I'll do followon CLs for unhandled cases as needed. Update #19113 R=go1.13 Change-Id: I839a5933d94b54ab04deb9dd5149f32c51c90fa1 Reviewed-on: https://go-review.googlesource.com/c/158719 Run-TryBot: Keith Randall <khr@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
15 lines
312 B
Go
15 lines
312 B
Go
// compile
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// Copyright 2009 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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func main() {
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var s int = 0
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var x int = 0
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x = x << s // as of 1.13, these are ok
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x = x >> s // as of 1.13, these are ok
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}
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