Bdragon28 added a comment. In D79916#2279045 <https://reviews.llvm.org/D79916#2279045>, @jrtc27 wrote:
> This has significantly regressed FreeBSD's performance with the new version > of Clang. It seems Clang does not inline functions at -O1, unlike GCC, and > since FreeBSD currently compiles its kernel with -O whenever debug symbols > are enabled[1] (which, of course, is almost always true), this results in all > its `static inline` helper functions not being inlined at all, a pattern that > is common in the kernel, used for things like `get_curthread` and the atomics > implementations. > > [1] This is a dubious decision made in r140400 in 2005 to provide "truer > debugger stack traces" (well, before then there was ping-ponging between -O > and -O2 based on concerns around correctness vs performance, but amd64 is an > exception that has always used -O2 since r127180 it seems). Given that GCC > will inline at -O, at least these days, the motivation seems to no longer > exist, and compiling a kernel at anything other than -O2 (or maybe -O3) seems > like a silly thing to do, but nevertheless it's what is currently done. > > Cc: @dim @trasz This is actually SUCH a bad idea that a kernel built with -O will *not work at all* on 32 bit powerpc platforms (presumably due to allocating stack frames in the middle of assembly fragments in the memory management that are supposed to be inlined at all times.) I had to hack kern.pre.mk to rquest -O2 at all times just to get a functioning kernel. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D79916/new/ https://reviews.llvm.org/D79916 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
