[llvm-bugs] [Bug 20750] Good codegen for bitwise rotate requires code that is technically undefined behavior

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Sat Nov 10 21:10:42 PST 2018


Trass3r <trass3r at gmail.com> changed:

           What    |Removed                     |Added
             Status|NEW                         |RESOLVED
                 CC|                            |trass3r at gmail.com
         Resolution|---                         |DUPLICATE

--- Comment #11 from Trass3r <trass3r at gmail.com> ---
Your code is still UB if rot is >= 32.

Fix it to v >> (rot & 31) | v << (-rot & 31) and you also get a rot
For more complex cases when the code gets inlined see:

*** This bug has been marked as a duplicate of bug 37417 ***

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