On Mon, Jul 14, 2025 at 03:03:46PM -0700, Florian Weimer wrote: > * Segher Boessenkool: > > > -fwrapv is a great way to get slower code, too. Is there something in > > your code that does not work without this reality-distorting flag? > > It really depends on the code. In many cases, -fwrapv enables > additional optimizations. For example, it's much easier to use (in C > code) the implicit sign bit many CPUs compute for free. -fwrapv says "I want something that is not valid C code". Code that requires -fwrapv to work as intended is not valid C code (will have UB). In almost all cases -fwrapv reduces performance, even ignoring that what you started with is likely not C code at all. Segher
