Clarify comment and add Core.throw anyway

FluxML · Oct 17, 2023 · bcf996a · bcf996a
1 parent e09f407
commit bcf996a
Showing 1 changed file with 2 additions and 1 deletion.
diff --git a/src/compiler/reverse.jl b/src/compiler/reverse.jl
@@ -257,7 +257,8 @@ function adjointcfg(pr::Primal)
  branch!(rb, preds[i].id, unless = cond)
  end
  if isempty(preds) || (!isempty(branches(b)) && branches(b)[end] == IRTools.unreachable)
- # An unreachable block in the primal will also be unreachable in the adjoint
+ # If `b` is unreachable, then no context produced by the primal should end up branching to `rb`
+ push!(rb, xcall(Core, :throw, "unreachable")) # `throw` is necessary for inference not to hit the `unreachable`
  branch!(rb, 0)
  end
  end