Fix bug with captured parameters and optimized try-catch.

Fix captured parameters and optimized try-catch.

The stack slots of captured parameters must be skipped when
generating sync code in optimized try-catch. Since those parameters
are initially copied into the context, their values are not recorded
in the environment.

Store-to-load forwarding may though use the original initial value
from the stack and therefore it must not be overwritten by try-sync
code that predeeds every call inside optimized try-blocks.

R=srdjan@google.com

Committed: https://code.google.com/p/dart/source/detail?r=41099

[Florian Schneider, 2014-10-14 12:39:08]

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

[Florian Schneider, 2014-10-14 12:39:09]

I adapted Mathias repro for a regression test here. I could not repro it without
using async since it's hard to create the exact set of live variables needed to
trigger the bug. 

@Mathias: Please try if this fixes the problem with optimized async closures. If
it does, we can remove the TODO in your CL.

[srdjan, 2014-10-14 13:45:09]

lgtm

https://codereview.chromium.org/653073002/diff/1/runtime/vm/flow_graph_compil...
File runtime/vm/flow_graph_compiler.cc (right):

https://codereview.chromium.org/653073002/diff/1/runtime/vm/flow_graph_compil...
runtime/vm/flow_graph_compiler.cc:414: // Don't sync captured parameters. They
are not the environment.
s/not the environment/ not in the environment/   ; also below.

https://codereview.chromium.org/653073002/diff/1/tests/language/vm/optimized_...
File tests/language/vm/optimized_await_regress_test.dart (right):

https://codereview.chromium.org/653073002/diff/1/tests/language/vm/optimized_...
tests/language/vm/optimized_await_regress_test.dart:6: 
Maybe add a brief description why the test is needed.

[Florian Schneider, 2014-10-14 14:44:01]

https://codereview.chromium.org/653073002/diff/1/runtime/vm/flow_graph_compil...
File runtime/vm/flow_graph_compiler.cc (right):

https://codereview.chromium.org/653073002/diff/1/runtime/vm/flow_graph_compil...
runtime/vm/flow_graph_compiler.cc:414: // Don't sync captured parameters. They
are not the environment.
On 2014/10/14 13:45:09, srdjan wrote:
> s/not the environment/ not in the environment/   ; also below.

Done.

https://codereview.chromium.org/653073002/diff/1/tests/language/vm/optimized_...
File tests/language/vm/optimized_await_regress_test.dart (right):

https://codereview.chromium.org/653073002/diff/1/tests/language/vm/optimized_...
tests/language/vm/optimized_await_regress_test.dart:6: 
On 2014/10/14 13:45:09, srdjan wrote:
> Maybe add a brief description why the test is needed.

Done.

[Florian Schneider, 2014-10-14 14:48:40]

Committed patchset #2 (id:20001) manually as r41099 (presubmit successful).