new GradientTape<Gradient, BackwardFunction, TapeTensor>(false));
  AccumulatorCallState& call_state = call_state_.top();
  call_state.backward_tape = tape.get();
  auto pop_backward_tape =
      gtl::MakeCleanup([&call_state] { call_state.backward_tape = nullptr; });
  std::vector<Gradient*> forwardprop_aids;
  std::vector<int64_t> sources;
  std::unordered_set<int64_t> sources_set;

}
`

// TestGdbInfCallstack tests that gdb can unwind the callstack of cgo programs
// on arm64 platforms without endless frames of function 'crossfunc1'.
// https://golang.org/issue/37238
func TestGdbInfCallstack(t *testing.T) {
	checkGdbEnvironment(t)

	testenv.MustHaveCGO(t)
	if runtime.GOARCH != "arm64" {
		t.Skip("skipping infinite callstack test on non-arm64 arches")
	}

	t.Parallel()

	f(func() {
		runtime.deferprocat(func() { print("A") }, #defers)
	})

For this rewriting phase, we insert the explicit initialization of
#defers and then attach the #defers variable to the CallStmt
representing the defer. That variable will be propagated to the
backend and will cause the backend to compile the defer using
deferprocat instead of an ordinary deferproc.

(Move [s] dst src mem) && s > 8 && buildcfg.GOPPC64 >= 9 && logLargeCopy(v, s) =>
        (LoweredQuadMove [s] dst src mem)

// Calls
// Lowering calls
(StaticCall ...) => (CALLstatic ...)
(ClosureCall ...) => (CALLclosure ...)
(InterCall ...) => (CALLinter ...)
(TailCall ...) => (CALLtail ...)

// Miscellaneous
(GetClosurePtr ...) => (LoweredGetClosurePtr ...)

		{name: "MOVFD", argLength: 1, reg: fp11, asm: "MOVFD"},     // float32 -> float64
		{name: "MOVDF", argLength: 1, reg: fp11, asm: "MOVDF"},     // float64 -> float32

		// function calls
		{name: "CALLstatic", argLength: -1, reg: regInfo{clobbers: callerSave}, aux: "CallOff", clobberFlags: true, call: true},                                               // call static function aux.(*obj.LSym).  last arg=mem, auxint=argsize, returns mem

			//           check once we enable that again.
			p.print(n.Op, n.Op) // ++ or --
		} else {
			p.print(blank, n.Op, _Assign, blank)
			p.print(n.Rhs)
		}

	case *CallStmt:
		p.print(n.Tok, blank, n.Call)

	case *ReturnStmt:
		p.print(_Return)
		if n.Results != nil {
			p.print(blank, n.Results)
		}

	case *BranchStmt:
		p.print(n.Tok)
		if n.Label != nil {

		{name: "LoweredRound32F", argLength: 1, reg: fp11, resultInArg0: true},
		{name: "LoweredRound64F", argLength: 1, reg: fp11, resultInArg0: true},

		// Calls
		{name: "CALLstatic", argLength: -1, reg: call, aux: "CallOff", call: true},               // call static function aux.(*gc.Sym). last arg=mem, auxint=argsize, returns mem

    var dns: Dns = Dns { TODO() }

    val system: Dns = Dns.SYSTEM
  }

  @Test
  fun eventListener() {
    val eventListener =
      object : EventListener() {
        override fun callStart(call: Call) = TODO()

        override fun dnsStart(
          call: Call,
          domainName: String,
        ) = TODO()

        override fun dnsEnd(
          call: Call,

(Const32F ...) => (MOVSSconst ...)
(Const64F ...) => (MOVSDconst ...)
(ConstNil    ) => (MOVQconst [0])
(ConstBool [c]) => (MOVLconst [b2i32(c)])

// Lowering calls
(StaticCall ...) => (CALLstatic ...)
(ClosureCall ...) => (CALLclosure ...)
(InterCall ...) => (CALLinter ...)
(TailCall ...) => (CALLtail ...)

// Lowering conditional moves

	&& s > 24 && logLargeCopy(v, s) || t.Alignment()%8 != 0 =>
	(LoweredMove [t.Alignment()]
		dst
		src
		(ADDVconst <src.Type> src [s-moveSize(t.Alignment(), config)])
		mem)

// calls
(StaticCall ...) => (CALLstatic ...)
(ClosureCall ...) => (CALLclosure ...)
(InterCall ...) => (CALLinter ...)
(TailCall ...) => (CALLtail ...)

// atomic intrinsics
(AtomicLoad(8|32|64)   ...) => (LoweredAtomicLoad(8|32|64)  ...)