[Libre-soc-dev] [RFC] horizontal SVP64 vectors

Jacob Lifshay programmerjake at gmail.com
Thu Jul 8 20:08:59 BST 2021

On Thu, Jul 8, 2021, 12:03 Luke Kenneth Casson Leighton <lkcl at lkcl.net>

> ok don't use integer predication.  CR predication, which reads one CR
> Field per element, is ok.  Int predicates on the other hand, get
> quickly out of hand: one instruction in a loop could modify the source
> predicate integer used by instructions further down.

> even CR-based predication is pretty dicey, i mean, fine as long as
> there's no horizontal interaction i.e. all CR bits in all CR elements
> are completely independent, but the moment a horizontal CR instruction
> is encountered, spangg all bets are off.

Well, we're going to have to deal with instructions modifying the int/cr
predicate part-way through anyway, nothing specific to horizontal loops...


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