[PATCH] D105545: Conditional store elimination

[Momchil Velikov via Phabricator via llvm-commits]

chill created this revision.
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This patch implements replacement of certain conditional stores with
unconditional ones (subject to constraints).

A triangle shaped part of the CFG like:

  header:
    ...
    br %cond, label %if.then, label %if.end
      
  if.then:
    store %s.new, %addr
    br label %if.end
      
  if.end:
     ...

would become

   header:
     ...
     br %cond, label %if.then, label %if.else
      
  if.then:
     br %if.end
      
  if.else:
    %s.old = load %addr
    br label %if.end
      
  if.end:
    %s = phi [%s.new, if.then], [%s.old, if.else]
    store %s, %addr

At the moment the patch considers only stores to local, non-escaping objects,
which stores are alone in the block.


https://reviews.llvm.org/D105545

Files:
  llvm/lib/Transforms/Scalar/MergedLoadStoreMotion.cpp
  llvm/test/CodeGen/AMDGPU/opt-pipeline.ll
  llvm/test/Other/opt-LTO-pipeline.ll
  llvm/test/Other/opt-O2-pipeline.ll
  llvm/test/Other/opt-O3-pipeline-enable-matrix.ll
  llvm/test/Other/opt-O3-pipeline.ll
  llvm/test/Other/opt-Os-pipeline.ll

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