Messages in this thread | | | Date | Mon, 14 Sep 2015 09:12:31 +0200 | From | Peter Zijlstra <> | Subject | Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal due to a kernel NULL pointer dereference) |
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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.
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