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    • Hal Finkel's avatar
      Prefer to duplicate PPC Altivec loads when expanding unaligned loads · 7d8a691b
      Hal Finkel authored
      When expanding unaligned Altivec loads, we use the decremented offset trick to
      prevent page faults. Unfortunately, if we have a sequence of consecutive
      unaligned loads, this leads to suboptimal code generation because the 'extra'
      load from the first unaligned load can be combined with the base load from the
      second (but only if the decremented offset trick is not used for the first).
      Search up and down the chain, through loads and token factors, looking for
      consecutive loads, and if one is found, don't use the offset reduction trick.
      These duplicate loads are later combined to yield the desired sequence (in the
      future, we might want a more-powerful chain search, but that will require some
      changes to allow the combiner routines to access the AA object).
      
      This should complete the initial implementation of the optimized unaligned
      Altivec load expansion. There is some refactoring that should be done, but
      that will happen when the unaligned store expansion is added.
      
      llvm-svn: 182719
      7d8a691b
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