[llvm-dev] Redundant copies

Sjoerd Meijer via llvm-dev llvm-dev at lists.llvm.org
Mon Mar 16 05:28:23 PDT 2020

Yep, exactly that. We see quite a lot of them, most of them get cleaned up, but not always...

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

  %14:gpr = COPY %0

Kind regards,
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