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eff27e858b
Ensure constant shift amounts are in the range [0-31]. When shift amounts are out of range, bad things happen. Shift amounts out of range occur when lowering 64-bit shifts (we take an in-range shift s in [0-63] and calculate s-32 and 32-s, both of which might be out of [0-31]). The constant shift operations themselves still work, but their shift amounts get copied unmolested to operations like ORshiftLL which use only the low 5 bits. That changes an operation like <<100 which unconditionally produces 0, to <<4, which doesn't. Fixes #48476 Change-Id: I87363ef2b4ceaf3b2e316426064626efdfbb8ee3 Reviewed-on: https://go-review.googlesource.com/c/go/+/350969 Trust: Keith Randall <khr@golang.org> Run-TryBot: Keith Randall <khr@golang.org> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Cherry Mui <cherryyz@google.com>
22 lines
402 B
Go
22 lines
402 B
Go
// run
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// Copyright 2021 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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//go:noinline
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func f(x uint64) uint64 {
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s := "\x04"
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c := s[0]
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return x << c << 4
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}
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func main() {
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if want, got := uint64(1<<8), f(1); 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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