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Date: Thu, 5 Apr 2018 00:45:03 -0400
From: "Emilio G. Cota" <cota@braap.org>
Message-ID: <20180405044503.GA10986@flamenco>
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Subject: Re: [Qemu-devel] [PULL 16/20] target/arm: Use vector infrastructure
 for aa64 compares
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To: Richard Henderson <richard.henderson@linaro.org>
Cc: qemu-devel@nongnu.org, peter.maydell@linaro.org, Alex =?utf-8?B?QmVubu+/vWU=?= <alex.bennee@linaro.org>

On Thu, Apr 05, 2018 at 10:54:46 +1000, Richard Henderson wrote:
> On 04/05/2018 10:07 AM, Richard Henderson wrote:
> > On 04/05/2018 02:49 AM, Emilio G. Cota wrote:
> >> 1. grab this binary:
> >>   http://cs.columbia.edu/~cota/qemu/nbench-aarch64
> >> 2. run it on a PowerPC host with:
> >>   $ aarch64-linux-user/qemu-aarch64 nbench-aarch64 -V
> >>
> >> Note: the "-V" (or "-v") flag is important! Without it, there's no segfault.
> > 
> > How quickly?  I did not see one up until it exited for lack of NNET.DAT.
> > 
> > I will note that I am using gcc 7.2 on gcc112 (/opt/cfarm/gcc-latest/bin/gcc).
> > 
> > Are you using gcc 4.8.5, and is commit 74912f6dad in your tree?
> > That commit might have made a difference...
> 
> Bah.  I confirm that it doesn't, and that the test still fails.
> 
> Since qemu does work on the same host when built with gcc 7.2, I can only blame
> this failure on a compiler bug wrt gcc 4.8 on ppc64.

Thanks! I confirm it as well that it works with the more recent gcc.

> I have not tracked down exactly what's going wrong, and probably won't unless
> someone feels that it's worthwhile.  This only begs the question of whether we
> should blacklist this compiler entirely.  Certainly it's old enough that it's
> probably not worth fixing.

Agreed.

Thanks,

		Emilio