Delta encode pc descriptors.

Delta encode pc descriptors.

328.3kB -> 160.1kB (-51.2%) for mirrors_reader_test

R=fschneider@google.com

Committed: https://code.google.com/p/dart/source/detail?r=45715

[rmacnak, 2015-05-07 17:29:21]

rmacnak@google.com changed reviewers:
+ fschneider@google.com, iposva@google.com

[Florian Schneider, 2015-05-11 11:10:56]

LGTM.

When running dart2js I see around 1% spent in DecodeInteger - called from
GetPcForDeoptId, ComputeEdgeCount in block_scheduler.cc. It may be worth
speeding up the collection of edge counters.

https://chromiumcodereview.appspot.com/1129113002/diff/80001/runtime/vm/objec...
File runtime/vm/object_test.cc (right):

https://chromiumcodereview.appspot.com/1129113002/diff/80001/runtime/vm/objec...
runtime/vm/object_test.cc:2876: builder->AddDescriptor(RawPcDescriptors::kOther,
80, 6, 150, 3);
Please add a few test cases with larger deltas is outside the range of one-byte
encoding (+63/-64)

[Ivan Posva, 2015-05-11 18:15:23]

Thanks,
-Ivan

https://codereview.chromium.org/1129113002/diff/80001/runtime/vm/code_descrip...
File runtime/vm/code_descriptors.cc (right):

https://codereview.chromium.org/1129113002/diff/80001/runtime/vm/code_descrip...
runtime/vm/code_descriptors.cc:21: try_index);
We should consider allocating the kinds sequentially so they use only 3 bits.
Then we can encode them together with the try index in the majority of cases.

[rmacnak, 2015-05-11 20:27:05]

https://chromiumcodereview.appspot.com/1129113002/diff/80001/runtime/vm/objec...
File runtime/vm/object_test.cc (right):

https://chromiumcodereview.appspot.com/1129113002/diff/80001/runtime/vm/objec...
runtime/vm/object_test.cc:2876: builder->AddDescriptor(RawPcDescriptors::kOther,
80, 6, 150, 3);
On 2015/05/11 11:10:56, Florian Schneider wrote:
> Please add a few test cases with larger deltas is outside the range of
one-byte
> encoding (+63/-64)

Done.

[rmacnak, 2015-05-11 20:27:32]

Committed patchset #6 (id:100001) manually as 45715 (presubmit successful).