From: Peter Maydell <peter.maydell@linaro.org>
To: Richard Henderson <richard.henderson@linaro.org>
Cc: "Alex Bennée" <alex.bennee@linaro.org>,
"QEMU Developers" <qemu-devel@nongnu.org>,
"Aurelien Jarno" <aurelien@aurel32.net>
Subject: Re: [PATCH v1 5/7] fpu/softfloat: avoid undefined behaviour when normalising empty sigs
Date: Fri, 27 Mar 2020 22:33:02 +0000 [thread overview]
Message-ID: <CAFEAcA9f4VtrWfmHGL=1WMMwGNHPV8Jc0XBQgPRyFCi5Lu1+KA@mail.gmail.com> (raw)
In-Reply-To: <91caa195-fe72-d533-1da2-4bbdeccb4e38@linaro.org>
On Fri, 27 Mar 2020 at 22:27, Richard Henderson
<richard.henderson@linaro.org> wrote:
> I wonder if I have the energy to petition the committee to drop, for C202? all
> of the "undefined" nonsense that only applies to sign-magnitute and
> ones-compliment computers, which haven't been seen since the 70's...
There was certainly a proposal to do that (I think from a Google
engineer) for C++, I forget whether the equivalent C change has
also been proposed.
> > That said, is it valid for this function to be called with a zero
> > aSig value ? I think all these normalizeFloat*Subnormal() functions
> > assume non-zero sig input, and the only callsite where it's not clearly
> > obvious that this is obvious that the sig input is non-zero is the call to
> > normalizeFloatx80Subnormal() from addFloatx80Sigs(). So perhaps we
> > just need to check and fix that callsite ??
>
> You're right -- addFloatx80Sigs is the only use out of 26 that doesn't have a
> preceding check for 0.
Mmm. My vote is for fixing addFloatx80Sigs -- now we just need
to figure out what the desired behaviour is.
thanks
-- PMM
next prev parent reply other threads:[~2020-03-27 22:34 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-27 9:49 [PATCH for 5.0 v1 0/7] A selection of sanitiser fixes Alex Bennée
2020-03-27 9:49 ` [PATCH v1 1/7] elf-ops: bail out if we have no function symbols Alex Bennée
2020-03-27 10:53 ` Philippe Mathieu-Daudé
2020-03-27 11:10 ` Philippe Mathieu-Daudé
2020-03-27 11:45 ` Peter Maydell
2020-03-27 22:09 ` Richard Henderson
2020-03-27 9:49 ` [PATCH v1 2/7] linux-user: protect fcntl64 with an #ifdef Alex Bennée
2020-03-27 10:40 ` Laurent Vivier
2020-03-27 22:10 ` Richard Henderson
2020-03-27 9:49 ` [PATCH v1 3/7] tests/tcg: remove extraneous pasting macros Alex Bennée
2020-03-27 10:54 ` Philippe Mathieu-Daudé
2020-03-27 22:11 ` Richard Henderson
2020-03-27 9:49 ` [PATCH v1 4/7] linux-user: more debug for init_guest_space Alex Bennée
2020-03-27 10:50 ` Laurent Vivier
2020-03-27 9:49 ` [PATCH v1 5/7] fpu/softfloat: avoid undefined behaviour when normalising empty sigs Alex Bennée
2020-03-27 10:09 ` Peter Maydell
2020-03-27 22:27 ` Richard Henderson
2020-03-27 22:33 ` Peter Maydell [this message]
2020-03-27 10:13 ` Aleksandar Markovic
2020-03-27 10:31 ` Alex Bennée
2020-03-27 9:49 ` [PATCH v1 6/7] target/xtensa: add FIXME for translation memory leak Alex Bennée
2020-03-27 9:49 ` [PATCH v1 7/7] gdbstub: fix compiler complaining Alex Bennée
2020-03-27 10:56 ` Philippe Mathieu-Daudé
2020-03-27 10:53 ` [PATCH for 5.0 v1 0/7] A selection of sanitiser fixes no-reply
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