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The recently added rule only works before decomposing slices. Add a rule that works after decomposing slices. The reason we need the latter is because although the length may be a constant, it can be hidden inside a slice that is not constant (its pointer or capacity might be changing). By applying this optimization after decomposing slices, we can find more cases where it applies. Fixes #56440 Change-Id: I0094e59eee3065ab4d210defdda8227a6e897420 Reviewed-on: https://go-review.googlesource.com/c/go/+/446277 Run-TryBot: Keith Randall <khr@golang.org> Reviewed-by: Cherry Mui <cherryyz@google.com> TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Keith Randall <khr@google.com>
35 lines
689 B
Go
35 lines
689 B
Go
// asmcheck
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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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// Check to make sure that we recognize when the length of an append
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// is constant. We check this by making sure that the constant length
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// is folded into a load offset.
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package p
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func f(x []int) int {
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s := make([]int, 3)
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s = append(s, 4, 5)
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// amd64:`MOVQ\t40\(.*\),`
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return x[len(s)]
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}
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func g(x []int, p *bool) int {
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s := make([]int, 3)
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for {
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s = s[:3]
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if cap(s) < 5 {
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s = make([]int, 3, 5)
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}
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s = append(s, 4, 5)
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if *p {
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// amd64:`MOVQ\t40\(.*\),`
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return x[len(s)]
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}
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}
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return 0
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}
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