[PATCH] D12286: [LV] Never widen an induction variable.

[James Molloy via llvm-commits]

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There's no need to widen canonical induction variables. It's just as efficient to create a *new*, wide, induction variable.

Consider, if we widen an indvar, then we'll have to truncate it before its uses anyway (1 trunc). If we create a new indvar instead, we'll have to truncate that instead (1 trunc) [besides which IndVars should go and clean up our mess after us anyway on principle].

This lets us remove a ton of special-casing code.

Repository:
  rL LLVM

http://reviews.llvm.org/D12286

Files:
  lib/Transforms/Vectorize/LoopVectorize.cpp
  test/Transforms/LoopVectorize/induction.ll

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