From: Peter Zijlstra <peterz@infradead.org>
To: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Baoquan He <bhe@redhat.com>, Denys Vlasenko <dvlasenk@redhat.com>,
Tejun Heo <tj@kernel.org>, Christoph Lameter <cl@linux.com>,
LKML <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
David Rientjes <rientjes@google.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>, Thomas Graf <tgraf@suug.ch>,
Ingo Molnar <mingo@kernel.org>,
the arch/x86 maintainers <x86@kernel.org>
Subject: Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal due to a kernel NULL pointer dereference)
Date: Mon, 14 Sep 2015 09:12:31 +0200 [thread overview]
Message-ID: <20150914071231.GM18489@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <CA+icZUU=qAJ7xqYs_k=NNG-Sj3Xv770MUNToA4JqiO3rAzUxNA@mail.gmail.com>
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.
next prev parent reply other threads:[~2015-09-14 7:12 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-06 17:45 Sedat Dilek
2015-09-07 5:58 ` Sedat Dilek
[not found] ` <CA+icZUUs3KEydWRgu_Y+YqS4TcCNp2DUw3Y+KfBzX7aPg_kzLw@mail.gmail.com>
2015-09-09 2:29 ` Baoquan He
2015-09-09 2:51 ` Sedat Dilek
2015-09-09 3:04 ` Sedat Dilek
2015-09-09 3:14 ` Sedat Dilek
2015-09-09 3:25 ` Baoquan He
2015-09-09 3:46 ` Sedat Dilek
2015-09-09 6:56 ` Sedat Dilek
2015-09-09 7:14 ` Baoquan He
2015-09-09 7:41 ` Sedat Dilek
2015-09-09 10:05 ` Sedat Dilek
2015-09-09 12:54 ` Peter Zijlstra
2015-09-12 21:22 ` Sedat Dilek
2015-09-13 2:33 ` Sedat Dilek
2015-09-14 7:12 ` Peter Zijlstra [this message]
2015-09-14 7:35 ` Sedat Dilek
2015-09-14 7:57 ` Sedat Dilek
2015-09-14 8:54 ` Peter Zijlstra
2015-09-14 9:35 ` Ingo Molnar
2015-09-14 9:55 ` Sedat Dilek
2015-09-14 9:59 ` Ingo Molnar
2015-09-14 10:22 ` Sedat Dilek
2015-09-14 12:47 ` Ingo Molnar
2015-09-14 7:49 ` Sedat Dilek
2015-09-14 17:50 ` Austin S Hemmelgarn
2015-09-14 18:27 ` Christoph Lameter
2015-09-14 18:38 ` Austin S Hemmelgarn
2015-09-15 6:11 ` Ingo Molnar
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