Hello!

This is probably a newbie question. But I noticed that this code that stacks takes 56 seconds the first time I run it:

for(_ <- 1..10_000, do: Nx.broadcast(0, {1024}))
|> Nx.stack()

while stacking in BinaryBackend then transferring to EXLA only takes 0.4 seconds:

zero = Nx.tensor([0], backend: Nx.BinaryBackend)
for(_ <- 1..10_000, do: Nx.broadcast(zero, {1024}))
|> Nx.stack()
|> Nx.backend_transfer(EXLA.Backend)

The first version also takes an additional minute whenever the length of the list changes. Why is that? I noticed the current function was stuck on EXLA.NIF.mlir_compile/7. Is there a new version of stack being compiled for each input list size?