[llvm-dev] RFC: LoopIDs are not identifiers (and better loop-parallel metadata)

Finkel, Hal J. via llvm-dev llvm-dev at lists.llvm.org
Wed Dec 12 09:11:04 PST 2018

On 12/12/18 10:29 AM, Michael Kruse wrote:
> Am Mi., 12. Dez. 2018 um 10:10 Uhr schrieb Finkel, Hal J. <hfinkel at anl.gov>:
>>> As we have seen,
>>> there are other reasons for loops to have identical LoopIDs. With
>>> patches [3,4], llvm.loop metadata can be collapsed (unlike access
>>> groups), thus the 'distinct' is not necessary anymore. Unfortunately,
>>> there is code in LLVM (and maybe elsewhere) that depends on LoopIDs'
>>> first item, i.e. we cannot get rid of it that easily.
>> I don't think it's worth changing this first element, unless we have
>> some other reason to do so.
> Would it be worthwhile to update the metadata uniquing algorithm to
> consider shallow self-references?

What benefit would that bring?


> Michael

Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory

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