[llvm-dev] Next steps for optimization remarks?

Brian Gesiak via llvm-dev llvm-dev at lists.llvm.org
Mon Jun 19 16:13:38 PDT 2017

Hello all,

In https://www.youtube.com/watch?v=qq0q1hfzidg, Adam Nemet (cc'ed)
describes optimization remarks and some future plans for the project. I had
a few follow-up questions:

1. As an example of future work to be done, the talk mentions expanding the
set of optimization passes that emit remarks. However, the Clang User
Manual mentions that "optimization remarks do not really make sense outside
of the major transformations (e.g.: inlining, vectorization, loop
optimizations)." [1] I am wondering: which passes exist today that are most
in need of supporting optimization remarks? Should all passes emit
optimization remarks, or are there indeed passes for which optimization
remarks "do not make sense"?

2. I tried running llvm/utils/opt-viewer/opt-viewer.py to produce an HTML
dashboard for the optimization remark YAML generated from a large C++
program. Unfortunately, the Python script does not finish, even after over
an hour of processing. It appears performance has been brought up before by
Bob Haarman (cc'ed), and some optimizations have been made since. [2] I
wonder if I'm passing in bad input (6,000+ YAML files -- too many?), or if
there's still some room to speed up the opt-viewer.py script? I tried the
C++ implementation as well, but that never completed either. [3]

Overall I'm excited to make greater use of optimization remarks, and to
contribute in any way I can. Please let me know if you have any thoughts on
my questions above!

[2] http://lists.llvm.org/pipermail/llvm-dev/2016-November/107039.html
[3] https://reviews.llvm.org/D26723

- Brian Gesiak
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