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Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).

Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.

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Exploiting Undefined Behavior in C/C++ Programs for Optimization: A Study on the Performance Impact (web.ist.utl.pt)

submitted 19 hours ago* (last edited 17 hours ago) by HaraldvonBlauzahn@feddit.org to c/linux@lemmy.ml

3 comments fedilink hide all child comments

A thorough examination of the performance effects of using undefined behaviour in compiler optimizations.

Method:

Modifying clang to not use UB where this is possible
Run a large suite of benchmarks on different architectures, compare results for modified and unmodified clang
Do statistics on the results
Examine performance deviations
Discuss factors which could bias results.

Very good science!

Result in short:

Only on ARM and if no link-time optimization is used, a systematic small positive performance effect can be seen. For Intel and AMD CPUs, there are no systematic improvements.

Average effects are typically below 2%, which is the typical effect of system and measurement noise. Often, effects are even negative. In some cases, benchmarks show large differences, and many of these can be fixed by simple modifications to the compiler or program.

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[–] bla_bla_bla@feddit.org 3 points 12 hours ago (1 children)

C++ is probably the ugliest designed mainstream language out there

[–] mina86@lemmy.wtf 2 points 10 hours ago (1 children)

It is a product of its time. If the same research was made 30 years ago, I bet there would be a stark difference to results today. LTO wasn’t as feasible. Compilers were less capable of removing redundant checks. Branch prediction in x86 processors was still a hot new thing. And on top of it all, there was less knowledge about language development.

[–] bla_bla_bla@feddit.org 1 points 7 hours ago

Good point.