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This isn't really a bug, but it's a pretty awesome thing to have. Many modern crypto hash and encryption algorithms make use of rotl and rotr (circular shift) operations. MurmurHash3 is one example. In C/C++ compilers, the expression:
(x >> r) | (x << (32 - r))
is recognized and is compiled to a single x86 ROR/ROL instruction. While CIL has no opcode for rotation, it has a distinct signature which the JIT should be able to recognize:
Rotate left is pretty similar, with the shr.un / shl flipped.
X86, ARM, PowerPC, and Itanium all have a rotate instruction, but SPARC does not.
Thanks for the feedback. Right now this sort of optimization is left for LLVM to do.