[PATCH] D102834: [SLPVectorizer] Implement initial memory versioning.

[Florian Hahn via Phabricator via llvm-commits]

fhahn updated this revision to Diff 365819.
fhahn added a comment.

Some major restructuring of the code for the basic block handling and removed some restrictions. The code now keeps track of the first and last instruction that uses a tracked object and only duplicates the instructions in between. The blocks are split in a way that allows us to roll back the changes to the original CFG. The runtime checks are now only generated if profitable. This has the drawback that we have to estimate the cost a bit differently. But it has the advantage that we only need to change the function if we vectorize.

The compile-time impact looks reasonable, worst geomean change is +0.09 for NewPM-ReleaseLTO-g http://llvm-compile-time-tracker.com/compare.php?from=7c61447052351b722c4d5aa4254cca9054a0be79&to=831b8bc299ef904a9980e59f59eab936d93bc9e1&stat=instructions .

We probably also can add additional heuristics to avoid attempting versioning in a few more cases.

The patch still needs additional comments, but I think the overall structure should be a good start now.

In D102834#2919138 <https://reviews.llvm.org/D102834#2919138>, @SjoerdMeijer wrote:

> Sorry for the late reply, but just wanted to confirm this: yes, that `@f_alias` in `../AArch64/loadi8.ll` is a reproducer from x264.

Great thanks. The code in the test should be transformed now. If you point me to the C code, I can check if it is transformed as expected now.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D102834/new/

https://reviews.llvm.org/D102834

Files:
  llvm/include/llvm/Transforms/Vectorize/SLPVectorizer.h
  llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
  llvm/test/Transforms/SLPVectorizer/AArch64/loadi8.ll
  llvm/test/Transforms/SLPVectorizer/AArch64/memory-runtime-checks-in-loops.ll
  llvm/test/Transforms/SLPVectorizer/AArch64/memory-runtime-checks.ll
  llvm/test/Transforms/SLPVectorizer/X86/memory-runtime-checks.ll

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