From: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
To: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [Bug 1759264] Re: fpu/softfloat: round_to_int_and_pack refactor broke TriCore ftoi insns
Date: Wed, 11 Apr 2018 12:46:50 -0000 [thread overview]
Message-ID: <a8872e48-4dea-9394-3974-eb067df252d7@mail.uni-paderborn.de> (raw)
In-Reply-To: 87woxe3t2t.fsf@linaro.org
On 04/11/2018 01:01 PM, Alex Bennée wrote:
> Bastian Koppelmann <kbastian@mail.uni-paderborn.de> writes:
>
>> On 04/10/2018 10:07 PM, Alex Bennée wrote:
>>> Yeah it looks like it was missed, the round_to_uint code does it.
>>>
>>> Do you have a test case I can verify?
>>>
>>
>> For the NaN input 0xffffffff the expected result for the flags is that
>> flag_invalid is raised.
>>
>> I can provide you with some TriCore asm, but it is a bit of pain to get
>> the gnu assembler to build, since the public version is a decade old.
>
> I'll trust you if you send me a static binary for this particular
> verification ;-)
I set up a github repo with working binutils and the corresponding
testcase:
https://github.com/bkoppelmann/tricore-fpu
The one caveat is, that we cannot produce any binaries with the TriCore
ISA > 1.3.
In this testcase the last ftoi instruction is supposed to raise the
invalid flag and return 0 since the input was NaN. We did that by only
checking for NaN if any flag was raised after ftoi, then do the NaN
check, and if positive, return 0.
Cheers,
Bastian
--
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https://bugs.launchpad.net/bugs/1759264
Title:
fpu/softfloat: round_to_int_and_pack refactor broke TriCore ftoi insns
Status in QEMU:
New
Bug description:
After the refactor from ab52f973a504f8de0c5df64631ba4caea70a7d9e the
bahaviour of int32_to_float32() was altered.
helper_ftoi() in target/tricore/fpu_helper.c relied on
int32_to_float32 to raise the invalid flag if the input was NaN to
properly return 0. Likewise if the input is infinity.
The obvious fix for softfloat would be to raise this flag in round_to_int_and_pack(). However,
I'm not sure if this breaks other targets and I have no easy way to test it.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1759264/+subscriptions
next prev parent reply other threads:[~2018-04-11 13:02 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-27 13:00 [Qemu-devel] [Bug 1759264] [NEW] fpu/softfloat: round_to_int_and_pack refactor broke TriCore ftoi insns Bastian Koppelmann
2018-04-10 20:07 ` [Qemu-devel] [Bug 1759264] " Alex Bennée
2018-04-11 9:23 ` Bastian Koppelmann
2018-04-11 11:01 ` Alex Bennée
2018-04-11 11:16 ` Bastian Koppelmann
2018-04-11 12:46 ` Bastian Koppelmann [this message]
2018-04-12 13:41 ` Alex Bennée
2018-04-13 14:09 ` Bastian Koppelmann
2018-04-16 16:20 ` Bastian Koppelmann
2018-04-26 5:10 ` Thomas Huth
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