[llvm-dev] Questions on LLVM vectorization diagnostics
Dangeti Tharun kumar via llvm-dev
llvm-dev at lists.llvm.org
Thu Jun 23 08:20:05 PDT 2016
Dear LLVM Community,
I am D Tharun Kumar, masters student at Indian Institute of Technology
Hyderabad, working in a team to improve current vectorizer in LLVM. As an
initial study, we are studying various benchmarks to analyze and compare
vectorizing capabilities of LLVM, GCC and ICC. We found that vectorization
remarks given by LLVM are vague and brief, comparatively GCC and ICC are
giving detailed diagnostics.
- I am interested to know why the LLVM diagnostics are brief and not
intuitive (making them less helpful)?
- In our analysis we never seen llvm trying to vectorize outer loops. Is
this well known? Is outer loop vectorization implemented in LLVM as in GCC?
(http://dl.acm.org/citation.cfm?id=1454119) If not, is someone working
- On the TSVC benchmark suite, out of a total of 151 loops, LLVM, GCC
and ICC vectorized 70, 82 and 112 loops respectively. Is the cause for lag
of LLVM the inability of LLVM’s vectorizer, or are there any (enabling)
optimization passes running before GCC’s vectorizer that are helping GCC
- Loop peeling to enhance vectorization is present in GCC and ICC, but,
the LLVM remarks don’t say anything about alignment. Does LLVM has this
functionality and the vectorizer doesn’t remark about it, or it doesn’t it
have the functionality at all?
Finally, we appreciate suggestions and directions for improving the
vectorization framework of LLVM.
I would also like to know if anyone worked or is working on improving
Dangeti Tharun kumar
M.TECH Computer Science
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