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  • Glasgow Haskell CompilerGlasgow Haskell Compiler
  • GHCGHC
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  • #7337
Closed
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Issue created Oct 16, 2012 by bos@trac-bos

GHC does not generate great code for bit-level rotation

I'm working on some hashing functions at the moment, and I notice that GHC generates an or and a pair of shifts for a rotate. The LLVM back end is smart enough to recover the code's intent via strength reduction and emit a single rot instruction, but the regular code generator emits three instructions.

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Version 7.6.1
Type FeatureRequest
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler
Test case
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