ff6db94c18
Now that SSA values can be derefs and they have special rules, we have to be a bit more careful about our LCSSA phis. In particular, we need to clean up in case LCSSA ended up creating a phi node for a deref. This fixes validation issues with some Vulkan CTS tests with the new deref instructions. Reviewed-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>