[PATCH] D93617: [LoopVectorize] Take argument's size into consideration when computing leader's demanded bits

[Nikita Popov via Phabricator via llvm-commits]

nikic added a comment.

This causes a number of test failures:

  Failed Tests (4):
    LLVM :: Transforms/LoopVectorize/AArch64/deterministic-type-shrinkage.ll
    LLVM :: Transforms/LoopVectorize/AArch64/loop-vectorization-factors.ll
    LLVM :: Transforms/LoopVectorize/ARM/tail-folding-reduces-vf.ll
    LLVM :: Transforms/LoopVectorize/demanded-bits-of-pointer-instruction.ll

Last one is an assertion failure because you assume non-pointer types, the others are presumably optimization regressions. What you are effectively doing here is to disable the truncation optimization completely for any case where the instruction chain contains an argument or a constant somewhere. Especially the latter case is probably very common. So while this change does fix the miscompile, it effectively disables the optimization entirely, which is probably not desired.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D93617/new/

https://reviews.llvm.org/D93617