Changes to create an application snapshot which can be layered on top

Changes to create an application snapshot which can be layered on top
after an isolate is created and initialized.

Added an option --use_script_snapshot which creates a snapshot of the specified script in an isolate, shuts that down and restarts on a new isolate and loads the script from the snapshot buffer and executes it.
Committed: https://code.google.com/p/dart/source/detail?r=2609

[siva, 2011-12-16 21:44:41]

synched up to tot and added option --use_script_snapshot to be able to test the
script snapshot feature on the command line with any application

[Ivan Posva, 2011-12-19 21:32:42]

Please at least fix the Dart_CreateScriptSnapshot API and the flag handling in
the binary. The logic in the snapshot readers and writers can be addressed in a
different change.

Otherwise LGTM.

-Ivan

http://codereview.chromium.org/8970004/diff/2011/bin/main.cc
File bin/main.cc (right):

http://codereview.chromium.org/8970004/diff/2011/bin/main.cc#newcode76
bin/main.cc:76: { "--use_script_snapshot", ProcessSnapshotOption },
What about compile-all? In general we should figure out if we can pull these
kind of testing flags out of the production binary.

http://codereview.chromium.org/8970004/diff/2011/bin/main.cc#newcode328
bin/main.cc:328: // Save the script snapshot as we are about to shutdown
isolate.
shutdown the isolate.

http://codereview.chromium.org/8970004/diff/2011/vm/dart_api_impl.cc
File vm/dart_api_impl.cc (right):

http://codereview.chromium.org/8970004/diff/2011/vm/dart_api_impl.cc#newcode639
vm/dart_api_impl.cc:639: DART_EXPORT Dart_Handle
Dart_CreateScriptSnapshot(Dart_Handle library,
As I mentioned in person already, I think passing the library here is confusing
as the isolate should already know which library refers is the root library (aka
script).

http://codereview.chromium.org/8970004/diff/2011/vm/raw_object_snapshot.cc
File vm/raw_object_snapshot.cc (right):

http://codereview.chromium.org/8970004/diff/2011/vm/raw_object_snapshot.cc#ne...
vm/raw_object_snapshot.cc:33: (kind == Snapshot::kScript &&
!RawObject::IsCreatedFromSnapshot(tags))) {
I am wondering if there is a way to simplify the logic here. The snapshot writer
should be able to communicate in the tags which way to branch here is my
expectation.

[siva, 2011-12-19 23:50:00]

Addressed review comments.

http://codereview.chromium.org/8970004/diff/2011/bin/main.cc
File bin/main.cc (right):

http://codereview.chromium.org/8970004/diff/2011/bin/main.cc#newcode76
bin/main.cc:76: { "--use_script_snapshot", ProcessSnapshotOption },
Added --compile_all to this list.
As discussed off-line we could potentially move these testing flags out of the
production binary and into the binary run_vm_tests. 

On 2011/12/19 21:32:42, Ivan Posva wrote:
> What about compile-all? In general we should figure out if we can pull these
> kind of testing flags out of the production binary.

http://codereview.chromium.org/8970004/diff/2011/bin/main.cc#newcode328
bin/main.cc:328: // Save the script snapshot as we are about to shutdown
isolate.
On 2011/12/19 21:32:42, Ivan Posva wrote:
> shutdown the isolate.

Done.

http://codereview.chromium.org/8970004/diff/2011/vm/dart_api_impl.cc
File vm/dart_api_impl.cc (right):

http://codereview.chromium.org/8970004/diff/2011/vm/dart_api_impl.cc#newcode639
vm/dart_api_impl.cc:639: DART_EXPORT Dart_Handle
Dart_CreateScriptSnapshot(Dart_Handle library,
On 2011/12/19 21:32:42, Ivan Posva wrote:
> As I mentioned in person already, I think passing the library here is
confusing
> as the isolate should already know which library refers is the root library
(aka
> script).

Done.

http://codereview.chromium.org/8970004/diff/2011/vm/raw_object_snapshot.cc
File vm/raw_object_snapshot.cc (right):

http://codereview.chromium.org/8970004/diff/2011/vm/raw_object_snapshot.cc#ne...
vm/raw_object_snapshot.cc:33: (kind == Snapshot::kScript &&
!RawObject::IsCreatedFromSnapshot(tags))) {
I would have to think about how this can be done by using information purely
from the writer. Let me do this in another CL.

On 2011/12/19 21:32:42, Ivan Posva wrote:
> I am wondering if there is a way to simplify the logic here. The snapshot
writer
> should be able to communicate in the tags which way to branch here is my
> expectation.