[llvm-dev] Loop Opt WG Meeting Minutes for Sep 25, 2019

[Bardia Mahjour via llvm-dev]

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Wed, Sep 25, 2019:
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Presentation from Marc Moreno Maza about his work on delinearization.
  - Slides attached.

- Issues with the DomTreeUpdater (Kit):
  - The direction going forward is to use the updater (instead of manual
    changes to the tree).
  - Other people have run into nasty bugs with it (in edge cases). Reviews
    are available for patches to the uses of DomTreeUpdater.
  - No documentation on how to (how not to) use the updater other than
    the comments in the source.
  - The updater uses a heuristic to decide to rebuild the entire tree
    instead of updating it.
	- Kit to work with Nicole to investigate if more obvious bugs are
      exposed by turning off the heuristic.

- Status Updates
  - Data Dependence Graph (Bardia)
    - https://reviews.llvm.org/D65350 - Done.
    - https://reviews.llvm.org/D67970 - Ready for Review

----------------------------
Tentative Agenda for Oct 9th
----------------------------

Introducing Concept of Perfect Loop Nest in LLVM (Ettore)

- Status Updates
  - DomTreeUpdater investigation (Kit)
  - Data Dependence Graph (Bardia)
    - https://reviews.llvm.org/D67970
  - Follow up on multi-dimensional array indexing RFC (Siddharth)
  - Impact of Loop Rotation on existing passes (Min-Yih)
  - Bugzilla bugs update (Vivek)
  - Others?
(See attached file:
On_the_delinearization_of_array_references_in_for_loop_nests.pdf)

Bardia Mahjour
Compiler Optimizations
IBM Toronto Software Lab
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