[llvm-bugs] [Bug 40496] a pass error, this pass never consider data overflow

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=40496

Richard Smith <richard-llvm at metafoo.co.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |INVALID
             Status|NEW                         |RESOLVED

--- Comment #1 from Richard Smith <richard-llvm at metafoo.co.uk> ---
This example has undefined behaviour due to signed overflow. In a correct
program, it is not possible for adding an unsigned char to a positive integer
to produce a negative integer, so the optimisation is correct.

If you want to write nonstandard code that assumes that signed overflow wraps
around, you can use -fwrapv to define this otherwise-undefined behaviour as
wrapping.

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