[turbofan] Implemented the ChangeFloat64ToInt64 TurboFan operator.

[turbofan] Implemented the ChangeFloat64ToInt64 TurboFan operator.

The ChangeFloat64ToInt64 operator changes the representation of a
float64 input value to int64 if the input value can be represented
exactly on int64. Otherwise the result is currently undefined.

R=titzer@chromium.org

Committed: https://crrev.com/ed570fac4479dd6392e3333c2fe4442d431ea646
Cr-Commit-Position: refs/heads/master@{#32102}

[titzer, 2015-11-18 16:50:30]

On 2015/11/18 13:27:48, ahaas wrote:

lgtm

[ahaas, 2015-11-19 08:25:27]

The CQ bit was checked by ahaas@chromium.org

[commit-bot: I haz the power, 2015-11-19 08:25:33]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1455983002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1455983002/1

[commit-bot: I haz the power, 2015-11-19 08:26:44]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-19 08:27:39]

Patchset 1 (id:??) landed as
https://crrev.com/ed570fac4479dd6392e3333c2fe4442d431ea646
Cr-Commit-Position: refs/heads/master@{#32102}

[Benedikt Meurer, 2015-11-19 11:28:18]

bmeurer@chromium.org changed reviewers:
+ bmeurer@chromium.org

[Benedikt Meurer, 2015-11-19 11:28:18]

I think we shouldn't use "Change" as name for operators that do not preserve the
exact value. For the other direction we used "Round"; if it's not rounding,
maybe we can rename this one to "Convert" then?

[titzer, 2015-11-19 13:16:13]

On 2015/11/19 11:28:18, Benedikt Meurer wrote:
> I think we shouldn't use "Change" as name for operators that do not preserve
the
> exact value. For the other direction we used "Round"; if it's not rounding,
> maybe we can rename this one to "Convert" then?

On second thought, it should probably be called "Truncate", since that's what it
does. It's meant to reflect the hardware instruction underlying it; it's
undefined behavior what it does for values of the the int64 range.

[ahaas, 2015-11-19 13:20:47]

I will rename the operator in a separate CL to TruncateFloat64ToInt64.