[x64] Use smaller code sequence when pushing SMIs

[x64] Use smaller code sequence when pushing SMIs

If exactly one byte in the upper half of the pushed 8-byte value is
set, use a smaller code sequence to push this value on the stack.
Before, we did
  movq r10,<constant>
  push r10
Now, we do
  push 0x0
  movb [rsp+<offset>],<byte>

The old sequence had 12 bytes, the new one has 7.
Pushing such values is used a lot for stack frame markers, which are
small numbers (1-17) encoded as SMIs.

Review-Url: https://codereview.chromium.org/2685213004
Cr-Commit-Position: refs/heads/master@{#43146}
Committed: https://chromium.googlesource.com/v8/v8/+/45f1bf80eaa72e05ead6c435b66e9607a6f65170

[Clemens Hammacher, 2017-02-10 20:03:14]

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

[commit-bot: I haz the power, 2017-02-10 20:03:22]

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, 2017-02-10 20:29:07]

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

[commit-bot: I haz the power, 2017-02-10 20:29:08]

Dry run: This issue passed the CQ dry run.

[Clemens Hammacher, 2017-02-12 17:44:36]

Description was changed from

==========
[x64] Use smaller code sequence when pushing SMIs

If only one byte in the smi is set (not necessarily the lowest), use a
smaller code sequence to push this value on the stack.
Before, we did
  movq r10,<constant>
  push r10
Now, we do
  push 0x0
  movb [rsp+<0-7>],<byte>

The old sequence had 12 bytes, the new one has 7.
Pushing such values is used a lot for stack frame markers, which are
small numbers encoded as SMIs.
==========

to

==========
[x64] Use smaller code sequence when pushing SMIs

If only one byte in the smi is set, but a 32-bit push is not
sufficient, use a smaller code sequence to push this value on the
stack.
Before, we did
  movq r10,<constant>
  push r10
Now, we do
  push 0x0
  movb [rsp+<0-7>],<byte>

The old sequence had 12 bytes, the new one has 7.
Pushing such values is used a lot for stack frame markers, which are
small numbers encoded as SMIs.
==========

[Clemens Hammacher, 2017-02-13 09:20:49]

Description was changed from

==========
[x64] Use smaller code sequence when pushing SMIs

If only one byte in the smi is set, but a 32-bit push is not
sufficient, use a smaller code sequence to push this value on the
stack.
Before, we did
  movq r10,<constant>
  push r10
Now, we do
  push 0x0
  movb [rsp+<0-7>],<byte>

The old sequence had 12 bytes, the new one has 7.
Pushing such values is used a lot for stack frame markers, which are
small numbers encoded as SMIs.
==========

to

==========
[x64] Use smaller code sequence when pushing SMIs

If exactly one byte in the upper half of the pushed 8-byte value is
set, use a smaller code sequence to push this value on the stack.
Before, we did
  movq r10,<constant>
  push r10
Now, we do
  push 0x0
  movb [rsp+<offset>],<byte>

The old sequence had 12 bytes, the new one has 7.
Pushing such values is used a lot for stack frame markers, which are
small numbers (1-17) encoded as SMIs.
==========

[Clemens Hammacher, 2017-02-13 09:20:49]

clemensh@chromium.org changed reviewers:
+ ahaas@chromium.org, bmeurer@chromium.org

[Clemens Hammacher, 2017-02-13 09:23:27]

perf try bots show that this reduces code size significantly on wasm.
Performance changes are within the noise, but more on the positive side.

https://00e9e64bac6e8d82a7f397a656739504eb2cd5a032bf5c8ceb-apidata.googleuser...
https://00e9e64bac8dbda97ef310c004c271925741ea021657eb4460-apidata.googleuser...

[Benedikt Meurer, 2017-02-13 09:30:50]

lgtm

[ahaas, 2017-02-13 09:36:19]

lgtm

[Clemens Hammacher, 2017-02-13 09:40:46]

The CQ bit was checked by clemensh@chromium.org

[commit-bot: I haz the power, 2017-02-13 09:40:52]

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, 2017-02-13 10:03:07]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1486978846073600, "parent_rev":
"c495421cc229738bc4dd0fdf8bb65fd45f1244b9", "commit_rev":
"45f1bf80eaa72e05ead6c435b66e9607a6f65170"}

[commit-bot: I haz the power, 2017-02-13 10:03:13]

Description was changed from

==========
[x64] Use smaller code sequence when pushing SMIs

If exactly one byte in the upper half of the pushed 8-byte value is
set, use a smaller code sequence to push this value on the stack.
Before, we did
  movq r10,<constant>
  push r10
Now, we do
  push 0x0
  movb [rsp+<offset>],<byte>

The old sequence had 12 bytes, the new one has 7.
Pushing such values is used a lot for stack frame markers, which are
small numbers (1-17) encoded as SMIs.
==========

to

==========
[x64] Use smaller code sequence when pushing SMIs

If exactly one byte in the upper half of the pushed 8-byte value is
set, use a smaller code sequence to push this value on the stack.
Before, we did
  movq r10,<constant>
  push r10
Now, we do
  push 0x0
  movb [rsp+<offset>],<byte>

The old sequence had 12 bytes, the new one has 7.
Pushing such values is used a lot for stack frame markers, which are
small numbers (1-17) encoded as SMIs.

Review-Url: https://codereview.chromium.org/2685213004
Cr-Commit-Position: refs/heads/master@{#43146}
Committed:
https://chromium.googlesource.com/v8/v8/+/45f1bf80eaa72e05ead6c435b66e9607a6f...
==========

[commit-bot: I haz the power, 2017-02-13 10:03:14]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/v8/v8/+/45f1bf80eaa72e05ead6c435b66e9607a6f...