Inifinite loop in add_children!()

[johnomotani]

I have a case where I get stuck in an infinite loop here

SnoopCompile.jl/SnoopCompileCore/src/snoop_inference.jl

Lines 127 to 155 in a0a03f3

	function addchildren!(parent::InferenceTimingNode, cis, backedges, miidx, backtraces)
	handled = Set{CodeInstance}()
	for (i, ci) in pairs(cis)
	ci ∈ handled && continue
	# Follow the backedges to the root
	j = i
	be = ci
	while true
	found = false
	for k in backedges[j]
	k < j && continue # don't get caught in cycles
	be = cis[k]
	if be ∉ handled
	j = k
	found = true
	break
	end
	end
	found || break # quit when no unhandled backedge found
	end
	be ∈ handled && continue
	# bt1, bt2 = get(backtraces, Core.Compiler.get_ci_mi(be), (nothing, nothing))
	# child = InferenceTimingNode(be, make_stacktrace(bt1, bt2), parent)
	child = InferenceTimingNode(be, get(backtraces, be, nothing), parent)
	push!(handled, be)
	addchildren!(child, handled, miidx)
	end
	return parent
	end

I think what's happening is that be ∉ handled is true the first time it is tested, for k == j. That means that j never increments, and the loop never ends. I don't understand what's being done here, but if I change line 137 to

k ≤ j && continue   # don't get caught in cycles

instead of k < j, then there's no infinite loop, and the output looks reasonable. Is this a correct fix?

[timholy]

Ah yes, a method can call itself, so that's correct. Do you want to submit a PR? If you can add a test, #431 should be a model to follow.