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Editing: stack.go

// asmcheck

// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package codegen

import "runtime"

// This file contains code generation tests related to the use of the
// stack.

// Check that stack stores are optimized away.

// 386:"TEXT\t.*, [$]0-"
// amd64:"TEXT\t.*, [$]0-"
// arm:"TEXT\t.*, [$]-4-"
// arm64:"TEXT\t.*, [$]0-"
// mips:"TEXT\t.*, [$]-4-"
// ppc64x:"TEXT\t.*, [$]0-"
// s390x:"TEXT\t.*, [$]0-"
func StackStore() int {
	var x int
	return *(&x)
}

type T struct {
	A, B, C, D int // keep exported fields
	x, y, z    int // reset unexported fields
}

// Check that large structs are cleared directly (issue #24416).

// 386:"TEXT\t.*, [$]0-"
// amd64:"TEXT\t.*, [$]0-"
// arm:"TEXT\t.*, [$]0-" (spills return address)
// arm64:"TEXT\t.*, [$]0-"
// mips:"TEXT\t.*, [$]-4-"
// ppc64x:"TEXT\t.*, [$]0-"
// s390x:"TEXT\t.*, [$]0-"
func ZeroLargeStruct(x *T) {
	t := T{}
	*x = t
}

// Check that structs are partially initialised directly (issue #24386).

// Notes:
// - 386 fails due to spilling a register
// amd64:"TEXT\t.*, [$]0-"
// arm:"TEXT\t.*, [$]0-" (spills return address)
// arm64:"TEXT\t.*, [$]0-"
// ppc64x:"TEXT\t.*, [$]0-"
// s390x:"TEXT\t.*, [$]0-"
// Note: that 386 currently has to spill a register.
func KeepWanted(t *T) {
	*t = T{A: t.A, B: t.B, C: t.C, D: t.D}
}

// Check that small array operations avoid using the stack (issue #15925).

// Notes:
// - 386 fails due to spilling a register
// - arm & mips fail due to softfloat calls
// amd64:"TEXT\t.*, [$]0-"
// arm64:"TEXT\t.*, [$]0-"
// ppc64x:"TEXT\t.*, [$]0-"
// s390x:"TEXT\t.*, [$]0-"
func ArrayAdd64(a, b [4]float64) [4]float64 {
	return [4]float64{a[0] + b[0], a[1] + b[1], a[2] + b[2], a[3] + b[3]}
}

// Check that small array initialization avoids using the stack.

// Check that assembly output has matching offset and base register
// (issue #21064).

func check_asmout(b [2]int) int {
	runtime.GC() // use some frame
	// amd64:`.*b\+24$SP$`
	// arm:`.*b\+4$FP$`
	return b[1]
}

// Check that simple functions get promoted to nosplit, even when
// they might panic in various ways. See issue 31219.
// amd64:"TEXT\t.*NOSPLIT.*"
func MightPanic(a []int, i, j, k, s int) {
	_ = a[i]     // panicIndex
	_ = a[i:j]   // panicSlice
	_ = a[i:j:k] // also panicSlice
	_ = i << s   // panicShift
	_ = i / j    // panicDivide
}

// Put a defer in a loop, so second defer is not open-coded
func Defer() {
	for i := 0; i < 2; i++ {
		defer func() {}()
	}
	// amd64:`CALL\truntime\.deferprocStack`
	defer func() {}()
}

BATAL