Re: Math errors

[Jim Wilson <jimw@sifive.com>]

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

Jim