Eliminate 99% of allocated ExceptionHandler objects

Eliminate 99% of allocated ExceptionHandler objects

The vast majority of functions have no exception handlers, thus they can all
share a single ExceptionHandler descriptor.

This CL reduces the number of ExceptionHandler objects on the heap from
about 8400 to 16, from 132KB to less than 1KB, when running dart2js.

R=srdjan@google.com

Committed: https://code.google.com/p/dart/source/detail?r=40323

[hausner, 2014-09-15 23:33:06]

hausner@google.com changed reviewers:
+ srdjan@google.com

[hausner, 2014-09-15 23:33:17]

https://codereview.chromium.org/575663002/diff/1/runtime/vm/code_descriptors.h
File runtime/vm/code_descriptors.h (left):

https://codereview.chromium.org/575663002/diff/1/runtime/vm/code_descriptors....
runtime/vm/code_descriptors.h:77: explicit StackmapTableBuilder()
Unrelated to this CL. gcl upload complained about the explicit on a zero
parameter constructor. Interestingly, this line has been in the code sind
revision 11000 or so.

[srdjan, 2014-09-15 23:47:15]

LGTM with comments

https://codereview.chromium.org/575663002/diff/1/runtime/vm/code_descriptors.h
File runtime/vm/code_descriptors.h (left):

https://codereview.chromium.org/575663002/diff/1/runtime/vm/code_descriptors....
runtime/vm/code_descriptors.h:77: explicit StackmapTableBuilder()
On 2014/09/15 23:33:16, hausner wrote:
> Unrelated to this CL. gcl upload complained about the explicit on a zero
> parameter constructor. Interestingly, this line has been in the code sind
> revision 11000 or so.

gcl and its rules/tools get also occasionally updated, I guess.

https://codereview.chromium.org/575663002/diff/1/runtime/vm/object.cc
File runtime/vm/object.cc (right):

https://codereview.chromium.org/575663002/diff/1/runtime/vm/object.cc#newcode687
runtime/vm/object.cc:687: // and can share this cononical descriptor.
s/cononical/cananical/ ;-)

https://codereview.chromium.org/575663002/diff/1/runtime/vm/object.cc#newcode...
runtime/vm/object.cc:11010: intptr_t ExceptionHandlers::Length() const {
s/Length/num_entries/

[hausner, 2014-09-16 00:28:41]

https://codereview.chromium.org/575663002/diff/1/runtime/vm/object.cc
File runtime/vm/object.cc (right):

https://codereview.chromium.org/575663002/diff/1/runtime/vm/object.cc#newcode687
runtime/vm/object.cc:687: // and can share this cononical descriptor.
On 2014/09/15 23:47:14, srdjan wrote:
> s/cononical/cananical/ ;-)
Dro Chonoson mot dom Kontroboss, sosson of dor Strosso...

Done.

https://codereview.chromium.org/575663002/diff/1/runtime/vm/object.cc#newcode...
runtime/vm/object.cc:11010: intptr_t ExceptionHandlers::Length() const {
On 2014/09/15 23:47:15, srdjan wrote:
> s/Length/num_entries/

Done.

(But what's the point of having accessors if they have to change when the
underlying implementation changes?)

[hausner, 2014-09-16 16:27:11]

Committed patchset #4 (id:60001) manually as r40323 (presubmit successful).