mirror of
https://github.com/golang/go
synced 2024-11-23 06:40:05 -07:00
e283473ebb
The type of the source and destination of a memmove call isn't always accurate. It will always be a pointer (or an unsafe.Pointer), but the base type might not be accurate. This comes about because multiple copies of a pointer with different base types are coalesced into a single value. In the failing example, the IData selector of the input argument is a *[32]byte in one branch of the type switch, and a *[]byte in the other branch. During the expand_calls pass both IDatas become just copies of the input register. Those copies are deduped and an arbitrary one wins (in this case, *[]byte is the unfortunate winner). Generally an op v can rely on v.Type during rewrite rules. But relying on v.Args[i].Type is discouraged. Fixes #55122 Change-Id: I348fd9accf2058a87cd191eec01d39cda612f120 Reviewed-on: https://go-review.googlesource.com/c/go/+/431496 TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Cherry Mui <cherryyz@google.com> Run-TryBot: Keith Randall <khr@golang.org> Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com> Reviewed-by: Keith Randall <khr@google.com>
43 lines
627 B
Go
43 lines
627 B
Go
// run
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// Copyright 2022 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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for i := 0; i < 10000; i++ {
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h(i)
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sink = make([]byte, 1024) // generate some garbage
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}
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}
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func h(iter int) {
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var x [32]byte
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for i := 0; i < 32; i++ {
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x[i] = 99
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}
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g(&x)
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if x == ([32]byte{}) {
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return
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}
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for i := 0; i < 32; i++ {
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println(x[i])
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}
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panic(iter)
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}
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//go:noinline
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func g(x interface{}) {
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switch e := x.(type) {
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case *[32]byte:
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var c [32]byte
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*e = c
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case *[]byte:
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*e = nil
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}
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}
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var sink []byte
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