[llvm-dev] Redundant copies

Roger Ferrer Ibáñez via llvm-dev llvm-dev at lists.llvm.org
Mon Mar 23 06:52:51 PDT 2020

Hi Sam,

just a short question: I was taking a look at the RDA pass and it doesn't
currently handle RegMasks. Is in your backlog to add support for those?

I am asking because I found myself analyzing across call instructions. Not
taking the regmasks into account leads to inexact results and needs extra
care. So I wondered if this was already in your phabricator backlog. I made
a first implementation downstream but before I continue with it I wanted to
make sure I'm not stepping on your toes :)

Thank you very much,

Missatge de Sjoerd Meijer <Sjoerd.Meijer at arm.com> del dia dl., 16 de març
2020 a les 13:28:

> Yep, exactly that. We see quite a lot of them, most of them get cleaned
> up, but not always...
> Cheers.
> ------------------------------
> *From:* Roger Ferrer Ibáñez <rofirrim at gmail.com>
> *Sent:* 16 March 2020 08:53
> *To:* Sjoerd Meijer <Sjoerd.Meijer at arm.com>
> *Cc:* LLVM-Dev <llvm-dev at lists.llvm.org>; Sam Parker <Sam.Parker at arm.com>
> *Subject:* Re: [llvm-dev] Redundant copies
> At this point however it doesn't (obviously) look like one (it still using
> different vregs) which suggests it might require a bit more of work to
> discover something that will ultimately lead to a redundant copy. I will
> investigate this option as well.
> I correct myself here: in the MIR dumps (for this example) right after
> copy coalescing the copy is redundant even at vregs
>   %14:gpr = COPY %0
>   BEQ %6, $x0, %bb.3
>   PseudoBR %bb.1
> bb.1.for.body.preheader:
>   %14:gpr = COPY %0
> Kind regards,

Roger Ferrer Ibáñez
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