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When a defer is executed at most once in a function body, we can allocate the defer record for it on the stack instead of on the heap. This should make defers like this (which are very common) faster. This optimization applies to 363 out of the 370 static defer sites in the cmd/go binary. name old time/op new time/op delta Defer-4 52.2ns ± 5% 36.2ns ± 3% -30.70% (p=0.000 n=10+10) Fixes #6980 Update #14939 Change-Id: I697109dd7aeef9e97a9eeba2ef65ff53d3ee1004 Reviewed-on: https://go-review.googlesource.com/c/go/+/171758 Run-TryBot: Keith Randall <khr@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Austin Clements <austin@google.com>
117 lines
2.9 KiB
Go
117 lines
2.9 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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import "runtime"
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// This file contains code generation tests related to the use of the
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// stack.
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// Check that stack stores are optimized away.
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// 386:"TEXT\t.*, [$]0-"
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// amd64:"TEXT\t.*, [$]0-"
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// arm:"TEXT\t.*, [$]-4-"
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// arm64:"TEXT\t.*, [$]0-"
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// mips:"TEXT\t.*, [$]-4-"
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// ppc64:"TEXT\t.*, [$]0-"
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// ppc64le:"TEXT\t.*, [$]0-"
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// s390x:"TEXT\t.*, [$]0-"
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func StackStore() int {
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var x int
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return *(&x)
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}
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type T struct {
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A, B, C, D int // keep exported fields
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x, y, z int // reset unexported fields
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}
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// Check that large structs are cleared directly (issue #24416).
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// 386:"TEXT\t.*, [$]0-"
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// amd64:"TEXT\t.*, [$]0-"
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// arm:"TEXT\t.*, [$]0-" (spills return address)
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// arm64:"TEXT\t.*, [$]0-"
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// mips:"TEXT\t.*, [$]-4-"
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// ppc64:"TEXT\t.*, [$]0-"
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// ppc64le:"TEXT\t.*, [$]0-"
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// s390x:"TEXT\t.*, [$]0-"
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func ZeroLargeStruct(x *T) {
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t := T{}
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*x = t
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}
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// Check that structs are partially initialised directly (issue #24386).
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// Notes:
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// - 386 fails due to spilling a register
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// amd64:"TEXT\t.*, [$]0-"
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// arm:"TEXT\t.*, [$]0-" (spills return address)
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// arm64:"TEXT\t.*, [$]0-"
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// ppc64:"TEXT\t.*, [$]0-"
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// ppc64le:"TEXT\t.*, [$]0-"
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// s390x:"TEXT\t.*, [$]0-"
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// Note: that 386 currently has to spill a register.
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func KeepWanted(t *T) {
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*t = T{A: t.A, B: t.B, C: t.C, D: t.D}
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}
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// Check that small array operations avoid using the stack (issue #15925).
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// Notes:
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// - 386 fails due to spilling a register
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// - arm & mips fail due to softfloat calls
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// amd64:"TEXT\t.*, [$]0-"
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// arm64:"TEXT\t.*, [$]0-"
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// ppc64:"TEXT\t.*, [$]0-"
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// ppc64le:"TEXT\t.*, [$]0-"
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// s390x:"TEXT\t.*, [$]0-"
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func ArrayAdd64(a, b [4]float64) [4]float64 {
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return [4]float64{a[0] + b[0], a[1] + b[1], a[2] + b[2], a[3] + b[3]}
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}
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// Check that small array initialization avoids using the stack.
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// 386:"TEXT\t.*, [$]0-"
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// amd64:"TEXT\t.*, [$]0-"
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// arm:"TEXT\t.*, [$]0-" (spills return address)
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// arm64:"TEXT\t.*, [$]0-"
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// mips:"TEXT\t.*, [$]-4-"
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// ppc64:"TEXT\t.*, [$]0-"
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// ppc64le:"TEXT\t.*, [$]0-"
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// s390x:"TEXT\t.*, [$]0-"
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func ArrayInit(i, j int) [4]int {
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return [4]int{i, 0, j, 0}
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}
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// Check that assembly output has matching offset and base register
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// (issue #21064).
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func check_asmout(a, b int) int {
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runtime.GC() // use some frame
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// amd64:`.*b\+24\(SP\)`
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// arm:`.*b\+4\(FP\)`
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return b
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}
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// Check that simple functions get promoted to nosplit, even when
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// they might panic in various ways. See issue 31219.
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// amd64:"TEXT\t.*NOSPLIT.*"
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func MightPanic(a []int, i, j, k, s int) {
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_ = a[i] // panicIndex
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_ = a[i:j] // panicSlice
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_ = a[i:j:k] // also panicSlice
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_ = i << s // panicShift
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_ = i / j // panicDivide
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}
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func Defer() {
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// amd64:`CALL\truntime\.deferprocStack`
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defer func() {}()
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}
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