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624e197c71
A Go user made a well-documented request for a slightly lower threshold. I tested against a selection of other people's benchmarks, and saw a tiny benefit (possibly noise) at equally tiny cost, and no unpleasant surprises observed in benchmarking. I.e., might help, doesn't hurt, low risk, request was delivered on a silver platter. It did, however, change the behavior of one test because now bytes.Buffer.Grow is eligible for inlining. Updates #19348. Change-Id: I85e3088a4911290872b8c6bda9601b5354c48695 Reviewed-on: https://go-review.googlesource.com/c/151977 Run-TryBot: David Chase <drchase@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Keith Randall <khr@golang.org>
58 lines
2.6 KiB
Go
58 lines
2.6 KiB
Go
// +build !gcflags_noopt
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// errorcheck -0 -m
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// Copyright 2018 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 foo
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import "bytes"
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// In order to get desired results, we need a combination of
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// both escape analysis and inlining.
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func bufferNotEscape() string {
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// b itself does not escape, only its buf field will be
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// copied during String() call, but object "handle" itself
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// can be stack-allocated.
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var b bytes.Buffer
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b.WriteString("123") // ERROR "bufferNotEscape b does not escape$"
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b.Write([]byte{'4'}) // ERROR "bufferNotEscape \[\]byte literal does not escape$" "bufferNotEscape b does not escape$"
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return b.String() // ERROR "bufferNotEscape b does not escape$" "inlining call to bytes.\(\*Buffer\).String$" "string\(bytes.b.buf\[bytes.b.off:\]\) escapes to heap$"
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}
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func bufferNoEscape2(xs []string) int { // ERROR "bufferNoEscape2 xs does not escape$"
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b := bytes.NewBuffer(make([]byte, 0, 64)) // ERROR "bufferNoEscape2 &bytes.Buffer literal does not escape$" "bufferNoEscape2 make\(\[\]byte, 0, 64\) does not escape$" "inlining call to bytes.NewBuffer$"
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for _, x := range xs {
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b.WriteString(x)
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}
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return b.Len() // ERROR "inlining call to bytes.\(\*Buffer\).Len$"
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}
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func bufferNoEscape3(xs []string) string { // ERROR "bufferNoEscape3 xs does not escape$"
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b := bytes.NewBuffer(make([]byte, 0, 64)) // ERROR "bufferNoEscape3 &bytes.Buffer literal does not escape$" "bufferNoEscape3 make\(\[\]byte, 0, 64\) does not escape$" "inlining call to bytes.NewBuffer$"
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for _, x := range xs {
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b.WriteString(x)
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b.WriteByte(',')
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}
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return b.String() // ERROR "inlining call to bytes.\(\*Buffer\).String$" "string\(bytes.b.buf\[bytes.b.off:\]\) escapes to heap$"
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}
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func bufferNoEscape4() []byte {
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var b bytes.Buffer
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b.Grow(64) // ERROR "bufferNoEscape4 b does not escape$" "bufferNoEscape4 ignoring self-assignment in bytes.b.buf = bytes.b.buf\[:bytes.m·3\]$" "inlining call to bytes.\(\*Buffer\).Grow$"
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useBuffer(&b) // ERROR "bufferNoEscape4 &b does not escape$"
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return b.Bytes() // ERROR "bufferNoEscape4 b does not escape$" "inlining call to bytes.\(\*Buffer\).Bytes$"
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}
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func bufferNoEscape5() { // ERROR "can inline bufferNoEscape5$"
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b := bytes.NewBuffer(make([]byte, 0, 128)) // ERROR "bufferNoEscape5 &bytes.Buffer literal does not escape$" "bufferNoEscape5 make\(\[\]byte, 0, 128\) does not escape$" "inlining call to bytes.NewBuffer$"
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useBuffer(b)
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}
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//go:noinline
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func useBuffer(b *bytes.Buffer) { // ERROR "useBuffer b does not escape$"
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b.WriteString("1234")
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}
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