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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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Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal  due to a kernel NULL pointer dereference) Baoquan He <bhe@redhat.com> - 2015-09-09 04:40 +0200
  Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal due  to a kernel NULL pointer dereference) Sedat Dilek <sedat.dilek@gmail.com> - 2015-09-09 05:00 +0200
    Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal due  to a kernel NULL pointer dereference) Sedat Dilek <sedat.dilek@gmail.com> - 2015-09-09 05:20 +0200
    Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal  due to a kernel NULL pointer dereference) Baoquan He <bhe@redhat.com> - 2015-09-09 05:30 +0200
      Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal due  to a kernel NULL pointer dereference) Sedat Dilek <sedat.dilek@gmail.com> - 2015-09-09 05:50 +0200
        Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal  due to a kernel NULL pointer dereference) Peter Zijlstra <peterz@infradead.org> - 2015-09-09 15:00 +0200
          Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal due  to a kernel NULL pointer dereference) Sedat Dilek <sedat.dilek@gmail.com> - 2015-09-12 23:30 +0200
            Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal  due to a kernel NULL pointer dereference) Peter Zijlstra <peterz@infradead.org> - 2015-09-14 09:20 +0200
              Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal due  to a kernel NULL pointer dereference) Sedat Dilek <sedat.dilek@gmail.com> - 2015-09-14 09:40 +0200
                Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal due  to a kernel NULL pointer dereference) Sedat Dilek <sedat.dilek@gmail.com> - 2015-09-14 10:00 +0200
                Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal  due to a kernel NULL pointer dereference) Peter Zijlstra <peterz@infradead.org> - 2015-09-14 11:00 +0200
                Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal  due to a kernel NULL pointer dereference) Ingo Molnar <mingo@kernel.org> - 2015-09-14 11:40 +0200
                Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal  due to a kernel NULL pointer dereference) Ingo Molnar <mingo@kernel.org> - 2015-09-14 12:00 +0200
                Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal due  to a kernel NULL pointer dereference) Sedat Dilek <sedat.dilek@gmail.com> - 2015-09-14 12:30 +0200
                Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal  due to a kernel NULL pointer dereference) Ingo Molnar <mingo@kernel.org> - 2015-09-14 14:50 +0200
                Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal due  to a kernel NULL pointer dereference) Sedat Dilek <sedat.dilek@gmail.com> - 2015-09-14 12:00 +0200
              Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal due  to a kernel NULL pointer dereference) Sedat Dilek <sedat.dilek@gmail.com> - 2015-09-14 09:50 +0200
                Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal due  to a kernel NULL pointer dereference) Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-09-14 20:00 +0200
                Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal  due to a kernel NULL pointer dereference) Christoph Lameter <cl@linux.com> - 2015-09-14 20:30 +0200
                Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal due  to a kernel NULL pointer dereference) Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-09-14 20:40 +0200
                Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal  due to a kernel NULL pointer dereference) Ingo Molnar <mingo@kernel.org> - 2015-09-15 08:20 +0200

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