[wasm] Do not fold f32-to-f64 and f64-to-f32 conversions.

[wasm] Do not fold f32-to-f64 and f64-to-f32 conversions.

R=titzer@chromium.org

Review-Url: https://codereview.chromium.org/2669753002
Cr-Commit-Position: refs/heads/master@{#42920}
Committed: https://chromium.googlesource.com/v8/v8/+/f3ae77ffe9e862571c6cb7942123432873a3b13f

[ahaas, 2017-02-01 10:30:03]

The CQ bit was checked by ahaas@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-02-01 10:30:08]

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, 2017-02-01 10:56:13]

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

[commit-bot: I haz the power, 2017-02-01 10:56:14]

Dry run: This issue passed the CQ dry run.

[titzer, 2017-02-01 15:36:44]

https://codereview.chromium.org/2669753002/diff/1/src/compiler/machine-operat...
File src/compiler/machine-operator-reducer.cc (right):

https://codereview.chromium.org/2669753002/diff/1/src/compiler/machine-operat...
src/compiler/machine-operator-reducer.cc:612: return ReplaceFloat64(m.Value() +
m.Value());
That doesn't seem right. It would return 2x the input value.

[ahaas, 2017-02-01 16:23:56]

https://codereview.chromium.org/2669753002/diff/1/src/compiler/machine-operat...
File src/compiler/machine-operator-reducer.cc (right):

https://codereview.chromium.org/2669753002/diff/1/src/compiler/machine-operat...
src/compiler/machine-operator-reducer.cc:612: return ReplaceFloat64(m.Value() +
m.Value());
On 2017/02/01 at 15:36:44, titzer wrote:
> That doesn't seem right. It would return 2x the input value.

It is correct because m.Value() is a NaN, and therefore all the '+' does is
converting a signalling NaN into a quiet NaN. There is a patch in flight in the
spec repository which introduces proper NaN checks in spec tests, and with that
patch we can get rid of these calculations and just return the canonical NaN.
But for now we have to do these calculations to get rid of signalling NaN.

[titzer, 2017-02-01 18:00:33]

lgtm

https://codereview.chromium.org/2669753002/diff/1/src/compiler/machine-operat...
File src/compiler/machine-operator-reducer.cc (right):

https://codereview.chromium.org/2669753002/diff/1/src/compiler/machine-operat...
src/compiler/machine-operator-reducer.cc:612: return ReplaceFloat64(m.Value() +
m.Value());
On 2017/02/01 16:23:56, ahaas wrote:
> On 2017/02/01 at 15:36:44, titzer wrote:
> > That doesn't seem right. It would return 2x the input value.
> 
> It is correct because m.Value() is a NaN, and therefore all the '+' does is
> converting a signalling NaN into a quiet NaN. There is a patch in flight in
the
> spec repository which introduces proper NaN checks in spec tests, and with
that
> patch we can get rid of these calculations and just return the canonical NaN.
> But for now we have to do these calculations to get rid of signalling NaN.

Ok, make sense.

[ahaas, 2017-02-03 11:38:39]

The CQ bit was checked by ahaas@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-02-03 11:38:41]

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

[ahaas, 2017-02-03 11:39:28]

The CQ bit was unchecked by ahaas@chromium.org

[ahaas, 2017-02-03 11:39:29]

The CQ bit was checked by ahaas@chromium.org

[ahaas, 2017-02-03 11:39:30]

The patchset sent to the CQ was uploaded after l-g-t-m from titzer@chromium.org
Link to the patchset: https://codereview.chromium.org/2669753002/#ps20001
(title: "Rebase")

[commit-bot: I haz the power, 2017-02-03 11:39:32]

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, 2017-02-03 12:05:29]

CQ is committing da patch.

Bot data: {"patchset_id": 20001, "attempt_start_ts": 1486121969853910,
"parent_rev": "082bf30604a357bc318a627165b4d6f7ea097006", "commit_rev":
"f3ae77ffe9e862571c6cb7942123432873a3b13f"}

[commit-bot: I haz the power, 2017-02-03 12:05:33]

Description was changed from

==========
[wasm] Do not fold f32-to-f64 and f64-to-f32 conversions.

R=titzer@chromium.org
==========

to

==========
[wasm] Do not fold f32-to-f64 and f64-to-f32 conversions.

R=titzer@chromium.org

Review-Url: https://codereview.chromium.org/2669753002
Cr-Commit-Position: refs/heads/master@{#42920}
Committed:
https://chromium.googlesource.com/v8/v8/+/f3ae77ffe9e862571c6cb7942123432873a...
==========

[commit-bot: I haz the power, 2017-02-03 12:05:34]

Committed patchset #2 (id:20001) as
https://chromium.googlesource.com/v8/v8/+/f3ae77ffe9e862571c6cb7942123432873a...