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https://github.com/golang/go
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a8a60ac2a7
Changes the compiler to recognize the slice extension pattern append(x, make([]T, y)...) and replace it with growslice and an optional memclr to avoid an allocation for make([]T, y). Memclr is not called in case growslice already allocated a new cleared backing array when T contains pointers. amd64: name old time/op new time/op delta ExtendSlice/IntSlice 103ns ± 4% 57ns ± 4% -44.55% (p=0.000 n=18+18) ExtendSlice/PointerSlice 155ns ± 3% 77ns ± 3% -49.93% (p=0.000 n=20+20) ExtendSlice/NoGrow 50.2ns ± 3% 5.2ns ± 2% -89.67% (p=0.000 n=18+18) name old alloc/op new alloc/op delta ExtendSlice/IntSlice 64.0B ± 0% 32.0B ± 0% -50.00% (p=0.000 n=20+20) ExtendSlice/PointerSlice 64.0B ± 0% 32.0B ± 0% -50.00% (p=0.000 n=20+20) ExtendSlice/NoGrow 32.0B ± 0% 0.0B -100.00% (p=0.000 n=20+20) name old allocs/op new allocs/op delta ExtendSlice/IntSlice 2.00 ± 0% 1.00 ± 0% -50.00% (p=0.000 n=20+20) ExtendSlice/PointerSlice 2.00 ± 0% 1.00 ± 0% -50.00% (p=0.000 n=20+20) ExtendSlice/NoGrow 1.00 ± 0% 0.00 -100.00% (p=0.000 n=20+20) Fixes #21266 Change-Id: Idc3077665f63cbe89762b590c5967a864fd1c07f Reviewed-on: https://go-review.googlesource.com/109517 Run-TryBot: Martin Möhrmann <moehrmann@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
64 lines
1.4 KiB
Go
64 lines
1.4 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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// slice types.
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// ------------------ //
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// Clear //
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// ------------------ //
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// Issue #5373 optimize memset idiom
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func SliceClear(s []int) []int {
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// amd64:`.*memclrNoHeapPointers`
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for i := range s {
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s[i] = 0
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}
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return s
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}
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func SliceClearPointers(s []*int) []*int {
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// amd64:`.*memclrHasPointers`
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for i := range s {
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s[i] = nil
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}
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return s
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}
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// ------------------ //
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// Extension //
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// ------------------ //
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// Issue #21266 - avoid makeslice in append(x, make([]T, y)...)
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func SliceExtensionConst(s []int) []int {
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// amd64:`.*runtime\.memclrNoHeapPointers`
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// amd64:-`.*runtime\.makeslice`
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// amd64:-`.*runtime\.panicmakeslicelen`
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return append(s, make([]int, 1<<2)...)
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}
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func SliceExtensionPointer(s []*int, l int) []*int {
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// amd64:`.*runtime\.memclrHasPointers`
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// amd64:-`.*runtime\.makeslice`
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return append(s, make([]*int, l)...)
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}
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func SliceExtensionVar(s []byte, l int) []byte {
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// amd64:`.*runtime\.memclrNoHeapPointers`
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// amd64:-`.*runtime\.makeslice`
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return append(s, make([]byte, l)...)
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}
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func SliceExtensionInt64(s []int, l64 int64) []int {
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// 386:`.*runtime\.makeslice`
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// 386:-`.*runtime\.memclr`
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return append(s, make([]int, l64)...)
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}
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