S390: [turbofan] Introduce TruncateTaggedToWord32 simplified operator.

S390: [turbofan] Introduce TruncateTaggedToWord32 simplified operator.

Port 0231a7efa2b5ce8108a837284e2f63dccd5dcd09

Original commit message:

    This allows us to get rid of the "push TruncateFloat64ToInt32 into Phi"
    trick that was used in the MachineOperatorReducer to combine the
    ChangeTaggedToFloat64 and TruncateFloat64ToInt32 operations. Instead of
    doing that later, we can just introduce the proper operator during the
    representation selection directly.

    Also separate the TruncateFloat64ToInt32 machine operator, which had two
    different meanings depending on a flag (either JavaScript truncation or
    C++ style round to zero). Now there's a TruncateFloat64ToWord32 which
    represents the JavaScript truncation (implemented via TruncateDoubleToI
    macro + code stub) and the RoundFloat64ToInt32, which implements the C++
    round towards zero operation (in the same style as the other WebAssembly
    driven Round* machine operators).

R=bmeurer@chromium.org, joransiu@ca.ibm.com, bjaideep@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com

BUG=
LOG=N

Committed: https://crrev.com/1decc266bad6457f7da2a8c67609a757fb85f3a3
Cr-Commit-Position: refs/heads/master@{#35802}

[john.yan, 2016-04-26 17:46:07]

PTAL

[john.yan, 2016-04-26 18:33:02]

The CQ bit was checked by jyan@ca.ibm.com to run a CQ dry run

[commit-bot: I haz the power, 2016-04-26 18:33:07]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1922183002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1922183002/1

[commit-bot: I haz the power, 2016-04-26 19:05:25]

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

[commit-bot: I haz the power, 2016-04-26 19:05:26]

Dry run: This issue passed the CQ dry run.

[JoranSiu, 2016-04-26 20:36:51]

On 2016/04/26 19:05:26, commit-bot: I haz the power wrote:
> Dry run: This issue passed the CQ dry run.

lgtm

[john.yan, 2016-04-26 21:34:54]

The CQ bit was checked by jyan@ca.ibm.com

[commit-bot: I haz the power, 2016-04-26 21:35:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1922183002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1922183002/1

[commit-bot: I haz the power, 2016-04-26 21:38:09]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-04-26 21:38:35]

Description was changed from

==========
S390: [turbofan] Introduce TruncateTaggedToWord32 simplified operator.

Port 0231a7efa2b5ce8108a837284e2f63dccd5dcd09

Original commit message:

    This allows us to get rid of the "push TruncateFloat64ToInt32 into Phi"
    trick that was used in the MachineOperatorReducer to combine the
    ChangeTaggedToFloat64 and TruncateFloat64ToInt32 operations. Instead of
    doing that later, we can just introduce the proper operator during the
    representation selection directly.

    Also separate the TruncateFloat64ToInt32 machine operator, which had two
    different meanings depending on a flag (either JavaScript truncation or
    C++ style round to zero). Now there's a TruncateFloat64ToWord32 which
    represents the JavaScript truncation (implemented via TruncateDoubleToI
    macro + code stub) and the RoundFloat64ToInt32, which implements the C++
    round towards zero operation (in the same style as the other WebAssembly
    driven Round* machine operators).

R=bmeurer@chromium.org, joransiu@ca.ibm.com, bjaideep@ca.ibm.com,
michael_dawson@ca.ibm.com, mbrandy@us.ibm.com

BUG=
LOG=N
==========

to

==========
S390: [turbofan] Introduce TruncateTaggedToWord32 simplified operator.

Port 0231a7efa2b5ce8108a837284e2f63dccd5dcd09

Original commit message:

    This allows us to get rid of the "push TruncateFloat64ToInt32 into Phi"
    trick that was used in the MachineOperatorReducer to combine the
    ChangeTaggedToFloat64 and TruncateFloat64ToInt32 operations. Instead of
    doing that later, we can just introduce the proper operator during the
    representation selection directly.

    Also separate the TruncateFloat64ToInt32 machine operator, which had two
    different meanings depending on a flag (either JavaScript truncation or
    C++ style round to zero). Now there's a TruncateFloat64ToWord32 which
    represents the JavaScript truncation (implemented via TruncateDoubleToI
    macro + code stub) and the RoundFloat64ToInt32, which implements the C++
    round towards zero operation (in the same style as the other WebAssembly
    driven Round* machine operators).

R=bmeurer@chromium.org, joransiu@ca.ibm.com, bjaideep@ca.ibm.com,
michael_dawson@ca.ibm.com, mbrandy@us.ibm.com

BUG=
LOG=N

Committed: https://crrev.com/1decc266bad6457f7da2a8c67609a757fb85f3a3
Cr-Commit-Position: refs/heads/master@{#35802}
==========

[commit-bot: I haz the power, 2016-04-26 21:38:37]

Patchset 1 (id:??) landed as
https://crrev.com/1decc266bad6457f7da2a8c67609a757fb85f3a3
Cr-Commit-Position: refs/heads/master@{#35802}