MIPS: Add NaN handling to floating point operators in simulators.

MIPS: Add NaN handling to floating point operators in simulators.

Committed: https://crrev.com/06c6591d0f83b34da6dabd93a96f09aefabb35bb
Cr-Commit-Position: refs/heads/master@{#39584}

[balazs.kilvady, 2016-07-26 17:31:16]

balazs.kilvady@imgtec.com changed reviewers:
+ akos.palfi@imgtec.com, ilija.pavlovic@imgtec.com,
ivica.bogosavljevic@imgtec.com, marija.antic@imgtec.com, miran.karic@imgtec.com

[balazs.kilvady, 2016-07-26 17:40:09]

I started to add the quietNaN behavior to simulator by this documentation part:

6.3.1.5 Quiet Non-Number (QNaN)
...
QNaN operands do not cause arithmetic operations to signal an exception. When a
floating point result is to be delivered, a QNaN operand causes an arithmetic
operation to supply a QNaN result. When possible, this QNaN result is one of the
operand QNaN values. QNaNs do have effects similar to SNaNs on operations that
do not deliver a floating point result—specifically, comparisons. (For more
information, see the detailed description of the floating point compare
instruction, C.cond.fmt.)

When certain invalid operations not involving QNaN operands are performed but do
not trap (because the trap is not enabled), a new QNaN value is created. (as
result)

[balazs.kilvady, 2016-08-29 15:36:52]

PTAL

[balazs.kilvady, 2016-09-16 18:04:08]

ping

[ivica.bogosavljevic, 2016-09-19 08:41:18]

https://codereview.chromium.org/2184843002/diff/140001/src/mips/simulator-mip...
File src/mips/simulator-mips.cc (right):

https://codereview.chromium.org/2184843002/diff/140001/src/mips/simulator-mip...
src/mips/simulator-mips.cc:2380: return resBits & Double::kSignMask ? -qNaN :
qNaN;
There is a more portable way of doing this:

use std::signbit to inspect the sign of double value

and use std::copysign to create positive or negative NaN

(according to the C++ spec, this is the only portable way to manipulate NaN)

[balazs.kilvady, 2016-09-20 08:28:39]

https://codereview.chromium.org/2184843002/diff/140001/src/mips/simulator-mip...
File src/mips/simulator-mips.cc (right):

https://codereview.chromium.org/2184843002/diff/140001/src/mips/simulator-mip...
src/mips/simulator-mips.cc:2380: return resBits & Double::kSignMask ? -qNaN :
qNaN;
On 2016/09/19 08:41:18, ivica.bogosavljevic wrote:
> There is a more portable way of doing this:
> 
> use std::signbit to inspect the sign of double value
> 
> and use std::copysign to create positive or negative NaN
> 
> (according to the C++ spec, this is the only portable way to manipulate NaN)

Thanks for pointing it out. Done.

[balazs.kilvady, 2016-09-20 10:50:21]

The CQ bit was checked by balazs.kilvady@imgtec.com to run a CQ dry run

[commit-bot: I haz the power, 2016-09-20 10:50:25]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-09-20 11:21:33]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-09-20 11:21:34]

Dry run: This issue passed the CQ dry run.

[ivica.bogosavljevic, 2016-09-21 07:21:40]

lgtm, but you need Akosz' approval, mine doesn't work

[balazs.kilvady, 2016-09-21 09:32:28]

The CQ bit was checked by balazs.kilvady@imgtec.com

[commit-bot: I haz the power, 2016-09-21 09:32:38]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-09-21 09:35:18]

Committed patchset #9 (id:160001)

[commit-bot: I haz the power, 2016-09-21 09:36:16]

Description was changed from

==========
MIPS: Add NaN handling to floating point operators in simulators.
==========

to

==========
MIPS: Add NaN handling to floating point operators in simulators.

Committed: https://crrev.com/06c6591d0f83b34da6dabd93a96f09aefabb35bb
Cr-Commit-Position: refs/heads/master@{#39584}
==========

[commit-bot: I haz the power, 2016-09-21 09:36:17]

Patchset 9 (id:??) landed as
https://crrev.com/06c6591d0f83b34da6dabd93a96f09aefabb35bb
Cr-Commit-Position: refs/heads/master@{#39584}