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42fd1306ce
We're using sort.SliceStable, so no need to keep track of indexes as well. Use a more robust test for whether a node is a call. Add a test that we're actually reordering comparisons. This test fails without the alg.go changes in this CL because eqstring uses OCALLFUNC instead of OCALL for its data comparisons. Update #8606 Change-Id: Ieeec33434c72e3aa328deb11cc415cfda05632e2 Reviewed-on: https://go-review.googlesource.com/c/go/+/237921 Run-TryBot: Keith Randall <khr@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Matthew Dempsky <mdempsky@google.com>
63 lines
1.6 KiB
Go
63 lines
1.6 KiB
Go
// run
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// Copyright 2020 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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// This is an optimization check. We want to make sure that we compare
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// string lengths, and other scalar fields, before checking string
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// contents. There's no way to verify this in the language, and
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// codegen tests in test/codegen can't really detect ordering
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// optimizations like this. Instead, we generate invalid strings with
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// bad backing store pointers but nonzero length, so we can check that
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// the backing store never gets compared.
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//
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// We use two different bad strings so that pointer comparisons of
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// backing store pointers fail.
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package main
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import (
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"fmt"
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"reflect"
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"unsafe"
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)
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func bad1() string {
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s := "foo"
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(*reflect.StringHeader)(unsafe.Pointer(&s)).Data = 1 // write bad value to data ptr
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return s
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}
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func bad2() string {
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s := "foo"
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(*reflect.StringHeader)(unsafe.Pointer(&s)).Data = 2 // write bad value to data ptr
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return s
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}
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type SI struct {
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s string
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i int
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}
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type SS struct {
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s string
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t string
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}
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func main() {
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for _, test := range []struct {
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a, b interface{}
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}{
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{SI{s: bad1(), i: 1}, SI{s: bad2(), i: 2}},
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{SS{s: bad1(), t: "a"}, SS{s: bad2(), t: "aa"}},
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{SS{s: "a", t: bad1()}, SS{s: "b", t: bad2()}},
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// This one would panic because the length of both strings match, and we check
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// the body of the bad strings before the body of the good strings.
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//{SS{s: bad1(), t: "a"}, SS{s: bad2(), t: "b"}},
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} {
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if test.a == test.b {
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panic(fmt.Sprintf("values %#v and %#v should not be equal", test.a, test.b))
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}
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}
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}
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