[PATCH] D135017: [LV] Move exit cond simplification to separate transform.

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: Ayal, reames, gilr.
Herald added subscribers: rogfer01, javed.absar, bollu, hiraditya.
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This sets the stage for D133017 <https://reviews.llvm.org/D133017> by moving out the code that performs
VPlan based simplifications to a separate transform that takes the
chosen VF & UF as arguments.

The main advantage is that this transform runs before any changes to
the CFG are being made. This allows using SCEV without worrying about
making queries while the IR is in an incomplete state.

Note that this patch switches the reasoning to use SCEV, but still only
simplifies loops with constant trip counts. Using SCEV here is needed to
access the backedge taken count, because the trip count IR value has not
been created yet.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D135017

Files:
  llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
  llvm/lib/Transforms/Vectorize/VPlan.cpp
  llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
  llvm/lib/Transforms/Vectorize/VPlanTransforms.h
  llvm/test/Transforms/LoopVectorize/lcssa-crashes.ll

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