Re: GCC 8.0.0 Status Report (2018-01-15), Trunk in Regression and Documentation fixes only mode

[Vincent Lefevre <vincent+gcc@vinc17.org>]

On 2018-02-06 10:49:48 +0100, Matthias Klose wrote:
> I have seen some issues with mpfr 4.0.0 on 32bit platforms, however
> not in GCC itself yet. These are all fixed in 4.0.1 rc2, so maybe
> document 4.0.1 instead of 4.0.0 once it is released.

The issues were also present on 64-bit platforms and were due to
a bug in mpfr_div_ui, which has always been present, since 1999.
With MPFR 4.0.0, they are also visible with mpfr_div just because
mpfr_div now uses mpfr_div_ui in some simple cases. I don't think
that GCC could be affected because AFAIK, a failure can only occur
when the input and output precisions are different, or is this
possible with GCC?

Now, I've just found a "regression" when comparing Sipe results with
MPFR results, but it is the Sipe result with SIPE_FLOAT equal to 1
(float) or 2 (double) that is incorrect, 3 (long double) being OK.
Bug triggered with -O2 -march=native on an Intel Xeon E5-2609 v3
machine. At least from 4.9 to 8.0.1 20180124 [trunk revision 257009]
are affected. I'll try to find a simple test case for a bug report.
I suspect that the regression comes from the fact this is a new
machine + the use (as in the past) of -march=native.

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Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
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