[llvm-bugs] [Bug 41875] Incorrect code is generated for rotation of 32-bit value to 32-bits

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=41875

Sanjay Patel <spatel+llvm at rotateright.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |INVALID
                 CC|                            |spatel+llvm at rotateright.com
             Status|NEW                         |RESOLVED

--- Comment #1 from Sanjay Patel <spatel+llvm at rotateright.com> ---
The function invokes undefined behavior, so anything is possible.

You can test for that by adding a 'main' wrapper and:

$ clang -fsanitize=undefined 41875.c 
$ ./a.out 
41875.c:9:14: runtime error: shift exponent 32 is too large for 32-bit type
'uint32_t' (aka 'unsigned int')

For safe code and likely better code optimization, you may want to use the
clang builtins for bitwise rotation:
https://clang.llvm.org/docs/LanguageExtensions.html#builtin-functions

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