[llvm-dev] Making loop guards part of canonical loop structure

[Krzysztof Parzyszek via llvm-dev]

I don't really care that much about that particular case.  We generate hardware loops somewhat late in codegen, so this is long past IR-level loop transformations.  It's just a case where having guarded loops would make things easier to analyze, regardless of how the loop code may have been reorganized in the meantime.

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Krzysztof Parzyszek  kparzysz at quicinc.com   LLVM compiler development

-----Original Message-----
From: Philip Reames <listmail at philipreames.com> 
Sent: Thursday, May 30, 2019 4:57 PM
To: Krzysztof Parzyszek <kparzysz at quicinc.com>; Finkel, Hal J. <hfinkel at anl.gov>; Kit Barton <kit.barton at gmail.com>; llvm-dev at lists.llvm.org
Subject: [EXT] Re: [llvm-dev] Making loop guards part of canonical loop structure

Seems like a case which should be handled by loop rotation.  If you find a reproducer for it, that's where I'd start looking rather than anything specific to guarded loops. 

Philip

On 5/30/19 1:44 PM, Krzysztof Parzyszek wrote:
> I don't remember the details of the particular case where we encountered this, but I think the loop started with the condition check and ended with an unconditional branch back to the beginning.
>