[PATCH] D15118: [InstCombine] Make MatchBSwap also match bit reversals

[James Molloy via llvm-commits]

jmolloy created this revision.
jmolloy added reviewers: majnemer, hfinkel.
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MatchBSwap has most of the functionality to match bit reversals already. If we switch it from looking at bytes to individual bits and remove a few early exits, we can extend the main recursive function to match any sequence of ORs, ANDs and shifts that assemble a value from different parts of another, base value. Once we have this bit->bit mapping, we can very simply detect if it is appropriate for a bswap or bitreverse.

Repository:
  rL LLVM

http://reviews.llvm.org/D15118

Files:
  lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
  lib/Transforms/InstCombine/InstCombineInternal.h
  test/Transforms/InstCombine/bitreverse-recognize.ll

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