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From: Alistair Francis <alistair23@gmail.com>
Date: Tue, 14 Jan 2020 02:11:00 -0000
Message-ID: <CAKmqyKOSqsUeADkB3KDCxj67AHix7jrexDetRcG-xLbQVr3E7g@mail.gmail.com>
Subject: Re: Math errors
To: Jim Wilson <jimw@sifive.com>
Cc: Joseph Myers <joseph@codesourcery.com>, GNU C Library <libc-alpha@sourceware.org>
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On Wed, Jan 8, 2020 at 4:29 AM Jim Wilson <jimw@sifive.com> wrote:
>
> On Mon, Jan 6, 2020 at 5:33 PM Alistair Francis <alistair23@gmail.com> wrote:
> > I have the latest 5.4.x kernel, I'm not sure if that has it or not.
>
> I don't know.  I don't follow linux kernel development that closely.
> But the failures I sometimes see are test-fenv and test-fpucw which I
> don't see in your list.
>
> I only run glibc testsuite on hardware though, and I've only been
> testing rv64gc support.  I haven't tried qemu.  In the RISC-V software
> meeting this morning, Palmer mentioned that there are some known
> RISC-V qemu FP bugs, for instance fcmp doesn't set the FP reg dirty
> bit when an exception flag is set, which could cause a testcase
> failure if a context switch happens at the wrong time.  This could

I have noticed that running the tests not in parallel gives much better results

> cause tests to sometimes fail and sometimes work.  I have seen some
> RISC-V qemu FP bugs myself, for instance with NaN-boxing, where
> sometimes single float outputs aren't NaN-boxed, and sometimes
> non-NaN-boxed single float inputs don't cause failures.  This is a
> problem I noticed by accident, I don't know if that has been fixed
> yet, and I don't know if that would cause glibc testsuite failures.
> Someone will have to look at the rv32gc math failures, and keep an
> open mind that they could be glibc, qemu, gcc, linux kernel, etc

Yeah, that's what I was thinking. There are only a few math tests left
failing, so it's not too bad. Thanks for the information Jim.

Alistair

> problems.  That of course assumes you have an up-to-date ulps file as
> Joseph already mentioned.
>
> Jim