[llvm-dev] Loop Opt WG Meeting Minutes for July 17, 2019

Bardia Mahjour via llvm-dev llvm-dev at lists.llvm.org
Wed Jul 17 10:26:12 PDT 2019

Hi all,

Apparently some people had trouble joining today. I also had trouble using
the attendee ID provided by webex. I've canceled the meeting series and
will be scheduling a new one with an updated link. Please remember to
update your calendars with the new invite.

My apologies to those who couldn't join today, and to everyone for the

Today's Meeting Minutes:

Wed, July 17th, 2019:
- Data Dependence Graph Presentation
     - Minimal vs full graph: Start with the full graph implementation and
       leave optimizations until later when we have more imperical evidence
       where the bottlenecks are in this implementation.
     - Trade-offs of the current proposal discussed with no objections to
       overall design from the audience at this time. More feedback is
     - The approximate sequence of patches to be posted for review will
       1. DDG (basic),
       2. DDG (with simplification)
       3. DDG (with root node and pi-blocks)
       4. Control Dependence Graph (CDG)
       5. Program Dependence Graph (PDG)

- Status Updates:
     - Directed Graph  (https://reviews.llvm.org/D64088)
        - Patch is approved and ready to land.
        - First patch of DDG to be posted soon.
     - Loop Cache Cost Analysis (https://reviews.llvm.org/D63459)
        - Ready and awaiting approval.
     - Loop Guard API (https://reviews.llvm.org/D63885)
        - Need to clarify comments from Philip to agree on the strength of
          definition of a loop guard
     - Impact of Loop Rotation on existing passes
        - Min unable to join today, will send a follow up email and/or
          next meeting.
     - Bugzilla bugs update
        - Ran out of time. Postponed to next meeting.

Tentative Agenda for next meeting (July 31 @ 11:00 am EST):
- Status Updates
    - Impact of Loop Rotation on existing passes (Min-Yih)
    - Bugzilla bugs update (Vivek)
    - Loop Cache Cost Analysis (https://reviews.llvm.org/D63459) (Ettore)
    - Loop Guard API (https://reviews.llvm.org/D63885) (Whitney)
    - Data Dependence Graph (Bardia)

- Delinearization (Gary Elsesser)
- Loop vs Function pass (Jamie Schmeiser)
- Loop Guard API (Whitney)

Bardia Mahjour
Compiler Optimizations
IBM Toronto Software Lab
bmahjour at ca.ibm.com (905) 413-2336
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