Analysis of Speedup Gain of Undefined Behavior Optimizations in OpenBSD.

The ISO C Standard added the undefined behavior notion as a mean to portability. State-of-the-art compilers such as GCC and Clang/LLVM use it to issue aggressive optimizations that break the the intention of the progammer. We argue that the performance impact of undefined behavior (UB) optimizations in operating systems, such as OpenBSD, is low. Furthermore they introduce unobservable and undocumented effects that have great impact of program robustness and security. To test our hypothesis we take the compiler implementation used in OpenBSD, i.e.Clang/LLVM, and disable all undefined behavior optimizations.Then we compare the performance of the system on multiple hardware architectures with the above mentioned optimizations turned on and off...

https://tildegit.org/lucic71/dissertation/src/branch/master/TSW/tsw.pdf

#system #optimizations