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https://github.com/golang/go
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a0f57c3fd0
x = map[string(byteslice)] is already optimized by the compiler to avoid a
string allocation. This CL generalizes this optimization to:
x = map[T1{ ... Tn{..., string(byteslice), ...} ... }]
where T1 to Tn is a nesting of struct and array literals.
Found in a hot code path that used a struct of strings made from []byte
slices to make a map lookup.
There are no uses of the more generalized optimization in the standard library.
Passes toolstash -cmp.
MapStringConversion/32/simple 21.9ns ± 2% 21.9ns ± 3% ~ (p=0.995 n=17+20)
MapStringConversion/32/struct 28.8ns ± 3% 22.0ns ± 2% -23.80% (p=0.000 n=20+20)
MapStringConversion/32/array 28.5ns ± 2% 21.9ns ± 2% -23.14% (p=0.000 n=19+16)
MapStringConversion/64/simple 21.0ns ± 2% 21.1ns ± 3% ~ (p=0.072 n=19+18)
MapStringConversion/64/struct 72.4ns ± 3% 21.3ns ± 2% -70.53% (p=0.000 n=20+20)
MapStringConversion/64/array 72.8ns ± 1% 21.0ns ± 2% -71.13% (p=0.000 n=17+19)
name old allocs/op new allocs/op delta
MapStringConversion/32/simple 0.00 0.00 ~ (all equal)
MapStringConversion/32/struct 0.00 0.00 ~ (all equal)
MapStringConversion/32/array 0.00 0.00 ~ (all equal)
MapStringConversion/64/simple 0.00 0.00 ~ (all equal)
MapStringConversion/64/struct 1.00 ± 0% 0.00 -100.00% (p=0.000 n=20+20)
MapStringConversion/64/array 1.00 ± 0% 0.00 -100.00% (p=0.000 n=20+20)
Change-Id: I483b4d84d8d74b1025b62c954da9a365e79b7a3a
Reviewed-on: https://go-review.googlesource.com/c/116275
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
125 lines
2.8 KiB
Go
125 lines
2.8 KiB
Go
// asmcheck
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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 codegen
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// This file contains code generation tests related to the handling of
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// map types.
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// ------------------- //
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// Access Const //
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// ------------------- //
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// Direct use of constants in fast map access calls (Issue #19015).
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func AccessInt1(m map[int]int) int {
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// amd64:"MOVQ\t[$]5"
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return m[5]
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}
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func AccessInt2(m map[int]int) bool {
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// amd64:"MOVQ\t[$]5"
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_, ok := m[5]
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return ok
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}
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func AccessString1(m map[string]int) int {
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// amd64:`.*"abc"`
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return m["abc"]
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}
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func AccessString2(m map[string]int) bool {
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// amd64:`.*"abc"`
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_, ok := m["abc"]
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return ok
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}
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// ------------------- //
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// String Conversion //
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// ------------------- //
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func LookupStringConversionSimple(m map[string]int, bytes []byte) int {
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// amd64:-`.*runtime\.slicebytetostring\(`
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return m[string(bytes)]
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}
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func LookupStringConversionStructLit(m map[struct{ string }]int, bytes []byte) int {
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// amd64:-`.*runtime\.slicebytetostring\(`
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return m[struct{ string }{string(bytes)}]
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}
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func LookupStringConversionArrayLit(m map[[2]string]int, bytes []byte) int {
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// amd64:-`.*runtime\.slicebytetostring\(`
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return m[[2]string{string(bytes), string(bytes)}]
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}
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func LookupStringConversionNestedLit(m map[[1]struct{ s [1]string }]int, bytes []byte) int {
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// amd64:-`.*runtime\.slicebytetostring\(`
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return m[[1]struct{ s [1]string }{struct{ s [1]string }{s: [1]string{string(bytes)}}}]
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}
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func LookupStringConversionKeyedArrayLit(m map[[2]string]int, bytes []byte) int {
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// amd64:-`.*runtime\.slicebytetostring\(`
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return m[[2]string{0: string(bytes)}]
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}
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// ------------------- //
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// Map Clear //
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// ------------------- //
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// Optimization of map clear idiom (Issue #20138).
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func MapClearReflexive(m map[int]int) {
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// amd64:`.*runtime\.mapclear`
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// amd64:-`.*runtime\.mapiterinit`
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for k := range m {
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delete(m, k)
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}
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}
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func MapClearIndirect(m map[int]int) {
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s := struct{ m map[int]int }{m: m}
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// amd64:`.*runtime\.mapclear`
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// amd64:-`.*runtime\.mapiterinit`
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for k := range s.m {
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delete(s.m, k)
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}
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}
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func MapClearPointer(m map[*byte]int) {
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// amd64:`.*runtime\.mapclear`
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// amd64:-`.*runtime\.mapiterinit`
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for k := range m {
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delete(m, k)
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}
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}
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func MapClearNotReflexive(m map[float64]int) {
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// amd64:`.*runtime\.mapiterinit`
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// amd64:-`.*runtime\.mapclear`
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for k := range m {
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delete(m, k)
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}
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}
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func MapClearInterface(m map[interface{}]int) {
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// amd64:`.*runtime\.mapiterinit`
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// amd64:-`.*runtime\.mapclear`
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for k := range m {
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delete(m, k)
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}
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}
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func MapClearSideEffect(m map[int]int) int {
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k := 0
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// amd64:`.*runtime\.mapiterinit`
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// amd64:-`.*runtime\.mapclear`
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for k = range m {
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delete(m, k)
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}
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return k
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}
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