// compile

// 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.

// Make sure VARDEF can be a top-level statement.

package p

func f() {
	var s string
	var as []string
	switch false && (s+"a"+as[0]+s+as[0]+s == "") {
	}

// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Triggers a bug in writebarrier, which inserts one
// between (first block) OpAddr x and (second block) a VarDef x,
// which are then in the wrong order and unable to be
// properly scheduled.

package q

var S interface{}

func F(n int) {
	fun := func(x int) int {
		S = 1
		return n
	}

					//
					// If we have:
					//
					//   NilCheck p
					//   VarDef x
					//   x = *p
					//
					// We can't rewrite that to
					//
					//   VarDef x
					//   NilCheck p
					//   x = *p
					//
					// Particularly, even though *p faults on p==nil, we still
					// have to do the explicit nil check before the VarDef.
					// See issue #32288.
				}

	&& clobber(move)
	=> (Move {t} [n] dst1 src1 mem)
(Zero {t} [n] dst1 vardef:(VarDef {x} move:(Move {t} [n] dst2 _ mem)))
	&& move.Uses == 1 && vardef.Uses == 1
	&& isSamePtr(dst1, dst2)
	&& clobber(move, vardef)
	=> (Zero {t} [n] dst1 (VarDef {x} mem))
(Move {t} [n] dst1 src1 vardef:(VarDef {x} move:(Move {t} [n] dst2 _ mem)))
	&& move.Uses == 1 && vardef.Uses == 1
	&& isSamePtr(dst1, dst2) && disjoint(src1, n, dst2, n)

// variable lifetime ranges within a linearized program representation
// where each IR instruction has a slot or index. Example:
//
//          b1:
//  0        VarDef abc
//  1        memset(abc,0)
//  2        VarDef xyz
//  3        memset(xyz,0)
//  4        abc.f1 = 2
//  5        xyz.f3 = 9
//  6        if q goto B4
//  7 B3:    z = xyz.x
//  8        goto B5
//  9 B4:    z = abc.x

// this used to have a spurious "live at entry to f12: ~r0".

func f12() *int {
	if b {
		select {}
	} else {
		return nil
	}
}

// incorrectly placed VARDEF annotations can cause missing liveness annotations.
// this used to be missing the fact that s is live during the call to g13 (because it is
// needed for the call to h13).

func f13() {
	s := g14()

			continue
		}
		// replace with OpCopy
		v.SetArgs1(v.MemoryArg())
		v.Aux = nil
		v.AuxInt = 0
		v.Op = OpCopy
	}
}

// elimUnreadAutos deletes stores (and associated bookkeeping ops VarDef and VarKill)
// to autos that are never read from.
func elimUnreadAutos(f *Func) {
	// Loop over all ops that affect autos taking note of which
	// autos we need and also stores that we might be able to
	// eliminate.

// this used to have a spurious "live at entry to f12: ~r0".

func f12() *int {
	if b {
		select {}
	} else {
		return nil
	}
}

// incorrectly placed VARDEF annotations can cause missing liveness annotations.
// this used to be missing the fact that s is live during the call to g13 (because it is
// needed for the call to h13).

func f13() {
	s := g14()

	for _, b := range f.Blocks {
		for _, v := range b.Values {
			if n, ok := v.Aux.(*ir.Name); ok {
				switch n.Class {
				case ir.PPARAMOUT:
					if n.IsOutputParamInRegisters() && v.Op == ssa.OpVarDef {
						// ignore VarDef, look for "real" uses.
						// TODO: maybe do this for PAUTO as well?
						continue
					}
					fallthrough
				case ir.PPARAM, ir.PAUTO:
					n.SetUsed(true)
				}
			}
		}
	}

	}
	// match: (Zero {t} [s] dst1 vardef:(VarDef (Zero {t} [s] dst2 _)))
	// cond: isSamePtr(dst1, dst2)
	// result: vardef
	for {
		s := auxIntToInt64(v.AuxInt)
		t := auxToType(v.Aux)
		dst1 := v_0
		vardef := v_1
		if vardef.Op != OpVarDef {
			break
		}
		vardef_0 := vardef.Args[0]
		if vardef_0.Op != OpZero || auxIntToInt64(vardef_0.AuxInt) != s || auxToType(vardef_0.Aux) != t {