On Mon, Sep 14, 2015 at 9:35 AM, Sedat Dilek <sedat.di...@gmail.com> wrote: > On Mon, Sep 14, 2015 at 9:12 AM, Peter Zijlstra <pet...@infradead.org> wrote: >> On Sun, Sep 13, 2015 at 04:33:39AM +0200, Sedat Dilek wrote: >>> > It looks like an inline-optimization bug in CLANG when the compiler's >>> > optimization-level is higher than -O2. >> >>> > [1] >>> > http://lists.linuxfoundation.org/pipermail/llvmlinux/2015-September/001355.html >>> >>> After some discussion on #llvm it turned out to be a known issue in >>> LLVMLinux! >>> >>> Unfortunately, an existing patch [1] got archived which is still >>> required to build x86_64 correctly. >> >>> [1] >>> http://git.linuxfoundation.org/?p=llvmlinux.git;a=blob_plain;f=arch/x86_64/patches/ARCHIVE/0029-Fix-ARCH_HWEIGHT-for-compilation-with-clang.patch;hb=HEAD >> >> As long as LLVM cannot do things like that and requires full function >> calls I cannot see it being a sensible compiler to use from a >> performance POV. >> >> There's a fairly large difference between an inline POPCNT instruction >> and a full out-of-line function call. >> >> /me goes back to ignoring LLVM for the time being. > > [ CC llvmlinux ML ] > > Hi Peter, > > Clear words and a clear statement! > ( Men want clear statements see [1]. ) > > The issue was reported as LLVM PR #9457 [1] and the bug-history [2] says... > > Reported: 2011-03-11 07:27 CST by PaX Team > > ...so it is a known and old issue. > > Cannot say if "ignoring" is really helpful or not :-). > Sanjoy Das (a LLVM/Clang developer) joined the vital discussion in the > thread (see [3])... > > "[llvmlinux] [PATCH] x86/hweight: LLVMLinux: Fix __arch_hweight{32, > 64}() for compilation with clang" > > Beyond "fixing" or implementing missing (GCC) features on the > LLVM-Clang-side... > People there have some discussion and ideas on a "workaround" or fix > it on the Linux-kernel-side. > > Ignoring does not help - ignorance is a hard (hardest?) punishment for men. > > I invite you to join the discussion at LLVMLinux... > As I know... "YES, you can." Linux x86/x86_64 (assembler) Kung-Fu. > ( I admit I have not these skillz. ) > > Regards, > - Sedat - > > [1] https://llvm.org/bugs/show_bug.cgi?id=9457 > [2] https://llvm.org/bugs/show_activity.cgi?id=9457 > [3] [1] > http://lists.linuxfoundation.org/pipermail/llvmlinux/2015-September/001369.html
For the sake of completeness... Jan-Simon pointed to CLANG PR #24487 in [2]... "Bug 24487 -clang fails to compile linux "ALTERNATIVE" (integrated-as)" If someone is really interested in helping - join the discussion on llvmlinux ML. - Sedat - [1] https://llvm.org/bugs/show_bug.cgi?id=24487 [2] http://lists.linuxfoundation.org/pipermail/llvmlinux/2015-September/001359.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
