{SetOrder, 6, 100},
		{Ordered, 6, 100},
		{Ordered, 6, 101},
		{Ordered, 1, 101},

		// Undo 2 times: 1<4<7<12, 1<6<7
		{Undo, 0, 0},
		{Undo, 0, 0},
		{Ordered, 1, 6},
		{Ordered, 4, 12},
		{Ordered_Fail, 4, 6},
		{SetOrder_Fail, 6, 1},

		// Undo 2 times: 1<4<7<12
		{Undo, 0, 0},
		{Undo, 0, 0},
		{Ordered, 1, 12},
		{Ordered, 7, 12},
		{Ordered_Fail, 1, 6},
		{Ordered_Fail, 6, 7},

func (po *poset) Undo() {
	if len(po.undo) == 0 {
		panic("empty undo stack")
	}
	if debugPoset {
		defer po.CheckIntegrity()
	}

	for len(po.undo) > 0 {
		pass := po.undo[len(po.undo)-1]
		po.undo = po.undo[:len(po.undo)-1]

		switch pass.typ {
		case undoCheckpoint:
			return

		case undoSetChl:
			po.setchl(pass.idx, pass.edge)

		case undoSetChr:

}

func TestVersion3(t *testing.T) {
	undo := time.DisablePlatformSources()
	defer undo()
	_, err := time.LoadLocation("Asia/Jerusalem")
	if err != nil {
		t.Fatal(err)
	}
}

// Test that we get the correct results for times before the first
// transition time. To do this we explicitly check early dates in a
// couple of specific timezones.
func TestFirstZone(t *testing.T) {
	undo := time.DisablePlatformSources()
	defer undo()

	gp.m.newSigstack = true

	minitSignalMask()
}

// Called from dropm to undo the effect of an minit.
//
//go:nosplit
func unminit() {
	unminitSignals()
	// Don't clear procid, it is used by locking (semawake), and locking
	// must continue working after unminit.
}

// Called from exitm, but not from drop, to undo the effect of thread-owned

		exits(&emptystatus[0])
	}
	// Mask all SSE floating-point exceptions
	// when running on the 64-bit kernel.
	setfpmasks()
}

// Called from dropm to undo the effect of an minit.
func unminit() {
}

// Called from exitm, but not from drop, to undo the effect of thread-owned
// resources in minit, semacreate, or elsewhere. Do not take locks after calling this.
func mdestroy(mp *m) {
}

		if b == nil {
			// On exit from a block, this case will undo any assignments done below.
			values[work.n] = work.v
			continue
		}

		// Process phis as new defs. They come before FwdRefs in this block.
		for _, v := range b.Values {
			if v.Op != ssa.OpPhi {
				continue
			}
			n := int32(v.AuxInt)
			// Remember the old assignment so we can undo it when we exit b.

		st := stackt{ss_flags: _SS_DISABLE}
		sigaltstack(&st, nil)
	}

	minitSignals()
}

// Called from dropm to undo the effect of an minit.
//
//go:nosplit
func unminit() {
	unminitSignals()
	getg().m.procid = 0
}

// Called from exitm, but not from drop, to undo the effect of thread-owned
// resources in minit, semacreate, or elsewhere. Do not take locks after calling this.
func mdestroy(mp *m) {

	getg().m.procid = uint64(pthread_self())
}

// Called from dropm to undo the effect of an minit.
//
//go:nosplit
func unminit() {
	// iOS does not support alternate signal stack.
	// See minit.
	if !(GOOS == "ios" && GOARCH == "arm64") {
		unminitSignals()
	}
	getg().m.procid = 0
}

// Called from exitm, but not from drop, to undo the effect of thread-owned

	minitSignals()

	getg().m.procid = uint64(pthread_self())
}

// Called from dropm to undo the effect of an minit.
func unminit() {
	unminitSignals()
	getg().m.procid = 0
}

// Called from exitm, but not from drop, to undo the effect of thread-owned
// resources in minit, semacreate, or elsewhere. Do not take locks after calling this.
func mdestroy(mp *m) {
}

// type t, stored at some offset.
//
// It returns whether or not the assignment succeeded, but
// leaves any changes it made to a.steps behind, so the caller
// must undo that work by adjusting a.steps if it fails.
//
// This method along with the assign* methods represent the
// complete register-assignment algorithm for the Go ABI.