[PATCH] D144225: [InstCombine] Add constant combines for `(urem/srem (shl X, Y), (shl X, Z))`

[Noah Goldstein via Phabricator via llvm-commits]

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Forked from D142901 <https://reviews.llvm.org/D142901> to deduce more `nsw`/`nuw` flag for the output
`shl`.

We can handle the following cases + some `nsw`/`nuw` flags:

The rationale for doing this all in `InstCombine` rather than handling
the constant `shl` cases in `InstSimplify` is we often create a new
instruction because we are able to deduce more `nsw`/`nuw` flags than
the original instruction had.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D144225

Files:
  llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
  llvm/test/Transforms/InstCombine/rem-mul-shl.ll

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