VM: Reland Inline instance object hash code into object header on 64bit.

VM: Reland Inline instance object hash code into object header on 64bit.

Inline instance object hash code into object header on 64 bit.

64 bit objects have 32 bits of free space in the header word.
This is used for the hash code in string objects. We take it
for the default hash code on all objects that don't override
the hashCode getter.

This is both faster and a memory reduction. Eg it makes the
MegaHashCode part of the Megamorphic benchmark 6 times faster.

This is a reland of https://codereview.chromium.org/2954453002/
which fixes an issue that made script snapshots generated on
64 bit platforms incompatible with 32 bit VMs.

BUG=
R=vegorov@google.com

Committed: https://github.com/dart-lang/sdk/commit/955a4b6e711fc66a906b5e3d96c96d637ff45833

[erikcorry, 2017-06-30 15:23:49]

Description was changed from

==========
VM: Reland Inline instance object hash code into object header on 64bit.

Inline instance object hash code into object header on 64 bit.

64 bit objects have 32 bits of free space in the header word.
This is used for the hash code in string objects. We take it
for the default hash code on all objects that don't override
the hashCode getter.

This is both faster and a memory reduction. Eg it makes the
MegaHashCode part of the Megamorphic benchmark 6 times faster.

This is a reland of https://codereview.chromium.org/2954453002/
which fixes an issue that made script snapshots generated on
64 bit platforms incompatible with 32 bit VMs.

BUG=
==========

to

==========
VM: Reland Inline instance object hash code into object header on 64bit.

Inline instance object hash code into object header on 64 bit.

64 bit objects have 32 bits of free space in the header word.
This is used for the hash code in string objects. We take it
for the default hash code on all objects that don't override
the hashCode getter.

This is both faster and a memory reduction. Eg it makes the
MegaHashCode part of the Megamorphic benchmark 6 times faster.

This is a reland of https://codereview.chromium.org/2954453002/
which fixes an issue that made script snapshots generated on
64 bit platforms incompatible with 32 bit VMs.

BUG=
==========

[erikcorry, 2017-06-30 15:23:49]

erikcorry@google.com changed reviewers:
+ vegorov@google.com

[erikcorry, 2017-06-30 15:23:57]

PTAL

[Vyacheslav Egorov (Google), 2017-06-30 16:47:26]

lgtm

https://codereview.chromium.org/2965723002/diff/20001/runtime/vm/intrinsifier.cc
File runtime/vm/intrinsifier.cc (right):

https://codereview.chromium.org/2965723002/diff/20001/runtime/vm/intrinsifier...
runtime/vm/intrinsifier.cc:231: #if !defined(HASH_IN_OBJECT_HEADER)
I think it is just okay to have an empty intrinsic on these platforms. Does
having empty intrinsic break anything?

[erikcorry, 2017-06-30 20:00:09]

https://codereview.chromium.org/2965723002/diff/20001/runtime/vm/intrinsifier.cc
File runtime/vm/intrinsifier.cc (right):

https://codereview.chromium.org/2965723002/diff/20001/runtime/vm/intrinsifier...
runtime/vm/intrinsifier.cc:231: #if !defined(HASH_IN_OBJECT_HEADER)
On 2017/06/30 16:47:26, Vyacheslav Egorov (Google) wrote:
> I think it is just okay to have an empty intrinsic on these platforms. Does
> having empty intrinsic break anything?

I assumed it would break things.  The implementation on 32 bit is a native,
whereas on 64 bit it's intrinsified.

I guess you can't fall through from an intrinsified version to a native version.

[erikcorry, 2017-07-03 07:26:52]

Description was changed from

==========
VM: Reland Inline instance object hash code into object header on 64bit.

Inline instance object hash code into object header on 64 bit.

64 bit objects have 32 bits of free space in the header word.
This is used for the hash code in string objects. We take it
for the default hash code on all objects that don't override
the hashCode getter.

This is both faster and a memory reduction. Eg it makes the
MegaHashCode part of the Megamorphic benchmark 6 times faster.

This is a reland of https://codereview.chromium.org/2954453002/
which fixes an issue that made script snapshots generated on
64 bit platforms incompatible with 32 bit VMs.

BUG=
==========

to

==========
VM: Reland Inline instance object hash code into object header on 64bit.

Inline instance object hash code into object header on 64 bit.

64 bit objects have 32 bits of free space in the header word.
This is used for the hash code in string objects. We take it
for the default hash code on all objects that don't override
the hashCode getter.

This is both faster and a memory reduction. Eg it makes the
MegaHashCode part of the Megamorphic benchmark 6 times faster.

This is a reland of https://codereview.chromium.org/2954453002/
which fixes an issue that made script snapshots generated on
64 bit platforms incompatible with 32 bit VMs.

BUG=
R=vegorov@google.com

Committed:
https://github.com/dart-lang/sdk/commit/955a4b6e711fc66a906b5e3d96c96d637ff45833
==========

[erikcorry, 2017-07-03 07:26:53]

Committed patchset #2 (id:20001) manually as
955a4b6e711fc66a906b5e3d96c96d637ff45833 (presubmit successful).