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c12b185a6e
Currently rvalue m[k] is transformed during walk into:
tmp1 := *mapaccess(m, k)
tmp2 := append(tmp1, ...)
*mapassign(m, k) = tmp2
However, this is suboptimal, as we could instead produce just:
tmp := mapassign(m, k)
*tmp := append(*tmp, ...)
Optimization is possible only if during Order it may tell that m[k] is
exactly the same at left and right part of assignment. It doesn't work:
1) m[f(k)] = append(m[f(k)], ...)
2) sink, m[k] = sink, append(m[k]...)
3) m[k] = append(..., m[k],...)
Benchmark:
name old time/op new time/op delta
MapAppendAssign/Int32/256-8 33.5ns ± 3% 22.4ns ±10% -33.24% (p=0.000 n=16+18)
MapAppendAssign/Int32/65536-8 68.2ns ± 6% 48.5ns ±29% -28.90% (p=0.000 n=20+20)
MapAppendAssign/Int64/256-8 34.3ns ± 4% 23.3ns ± 5% -32.23% (p=0.000 n=17+18)
MapAppendAssign/Int64/65536-8 65.9ns ± 7% 61.2ns ±19% -7.06% (p=0.002 n=18+20)
MapAppendAssign/Str/256-8 116ns ±12% 79ns ±16% -31.70% (p=0.000 n=20+19)
MapAppendAssign/Str/65536-8 134ns ±15% 111ns ±45% -16.95% (p=0.000 n=19+20)
name old alloc/op new alloc/op delta
MapAppendAssign/Int32/256-8 47.0B ± 0% 46.0B ± 0% -2.13% (p=0.000 n=19+18)
MapAppendAssign/Int32/65536-8 27.0B ± 0% 20.7B ±30% -23.33% (p=0.000 n=20+20)
MapAppendAssign/Int64/256-8 47.0B ± 0% 46.0B ± 0% -2.13% (p=0.000 n=20+17)
MapAppendAssign/Int64/65536-8 27.0B ± 0% 27.0B ± 0% ~ (all equal)
MapAppendAssign/Str/256-8 94.0B ± 0% 78.0B ± 0% -17.02% (p=0.000 n=20+16)
MapAppendAssign/Str/65536-8 54.0B ± 0% 54.0B ± 0% ~ (all equal)
Fixes #24364
Updates #5147
Change-Id: Id257d052b75b9a445b4885dc571bf06ce6f6b409
Reviewed-on: https://go-review.googlesource.com/100838
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
117 lines
2 KiB
Go
117 lines
2 KiB
Go
// run
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// Copyright 2017 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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// Test to make sure RHS is evaluated before map insert is started.
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// The RHS panics in all of these cases.
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package main
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import "fmt"
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func main() {
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for i, f := range []func(map[int]int){
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f0, f1, f2, f3, f4, f5, f6, f7, f8,
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} {
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m := map[int]int{}
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func() { // wrapper to scope the defer.
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defer func() {
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recover()
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}()
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f(m) // Will panic. Shouldn't modify m.
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fmt.Printf("RHS didn't panic, case f%d\n", i)
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}()
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if len(m) != 0 {
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fmt.Printf("map insert happened, case f%d\n", i)
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}
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}
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// Append slice.
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for i, f := range []func(map[int][]int){
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fa0, fa1, fa2, fa3,
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} {
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m := map[int][]int{}
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func() { // wrapper to scope the defer.
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defer func() {
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recover()
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}()
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f(m) // Will panic. Shouldn't modify m.
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fmt.Printf("RHS didn't panic, case fa%d\n", i)
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}()
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if len(m) != 0 {
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fmt.Printf("map insert happened, case fa%d\n", i)
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}
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}
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}
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func f0(m map[int]int) {
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var p *int
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m[0] = *p
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}
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func f1(m map[int]int) {
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var p *int
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m[0] += *p
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}
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func f2(m map[int]int) {
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var p *int
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sink, m[0] = sink, *p
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}
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func f3(m map[int]int) {
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var p *chan int
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m[0], sink = <-(*p)
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}
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func f4(m map[int]int) {
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var p *interface{}
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m[0], sink = (*p).(int)
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}
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func f5(m map[int]int) {
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var p *map[int]int
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m[0], sink = (*p)[0]
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}
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func f6(m map[int]int) {
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var z int
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m[0] /= z
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}
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func f7(m map[int]int) {
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var a []int
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m[0] = a[0]
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}
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func f8(m map[int]int) {
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var z int
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m[0] %= z
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}
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func fa0(m map[int][]int) {
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var p *int
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m[0] = append(m[0], *p)
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}
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func fa1(m map[int][]int) {
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var p *int
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sink, m[0] = !sink, append(m[0], *p)
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}
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func fa2(m map[int][]int) {
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var p *int
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m[0], _ = append(m[0], 0), *p
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}
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func fa3(m map[int][]int) {
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// OSLICE has similar in-place-reassignment
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// optimizations as OAPPEND, but we need to make sure
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// to *not* optimize them, because we can't guarantee
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// the slice indices are within bounds.
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m[0] = m[0][:1]
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}
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var sink bool
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