Remove saving/restoring of the context at function entry.

Remove saving/restoring of the context at function entry.

This is not needed anymore after I changed the current context
to always reside in a local variable.

Further simplifications and cleanup in the debugger.

This also fixes a bad memory retention problem with
non-capturing closures.

BUG=dartbug.com/18886
TEST=tests/language/vm/closure_memory_retention_test.dart
R=hausner@google.com

Committed: https://code.google.com/p/dart/source/detail?r=41433

[Florian Schneider, 2014-10-30 16:24:43]

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

[hausner, 2014-10-30 17:07:27]

Nice cleanup indeed.

LGTM, but I suggest that Regis look at this as well. He initially put in the
code that saves the context on entry of certain functions.

https://codereview.chromium.org/695483003/diff/20001/runtime/vm/debugger.cc
File runtime/vm/debugger.cc (right):

https://codereview.chromium.org/695483003/diff/20001/runtime/vm/debugger.cc#n...
runtime/vm/debugger.cc:475: return
reinterpret_cast<RawContext*>(GetLocalVar(var_info.index()));
This is a comment relating to your previous CL, which is already checked in:

You can use Context::RawCast(GetLocalVar(var_info.index())

https://codereview.chromium.org/695483003/diff/20001/runtime/vm/flow_graph_bu...
File runtime/vm/flow_graph_builder.cc (right):

https://codereview.chromium.org/695483003/diff/20001/runtime/vm/flow_graph_bu...
runtime/vm/flow_graph_builder.cc:3700: // allocated context but saved on entry
and restored on exit as to prevent
This comment no longer matches the code.

https://codereview.chromium.org/695483003/diff/20001/tests/language/vm/closur...
File tests/language/vm/closure_memory_retention_test.dart (right):

https://codereview.chromium.org/695483003/diff/20001/tests/language/vm/closur...
tests/language/vm/closure_memory_retention_test.dart:15: f() => [a, b];
Would be nice to add a comment that explains what is happening here (or more
precisely what should NOT happen). 

Also, I suggest adding a comment explaining that a negative test outcome is that
the program runs out of heap memory.

[siva, 2014-10-30 17:13:51]

asiva@google.com changed reviewers:
+ asiva@google.com

[siva, 2014-10-30 17:13:51]

Adding Todd to the cc list as he fixed a number of crashes in this area when
working on stack traces for the observatory.

[Florian Schneider, 2014-10-30 17:21:58]

Thanks!
@Regis, Todd: Please take a look if you would like to.

https://codereview.chromium.org/695483003/diff/20001/runtime/vm/debugger.cc
File runtime/vm/debugger.cc (right):

https://codereview.chromium.org/695483003/diff/20001/runtime/vm/debugger.cc#n...
runtime/vm/debugger.cc:475: return
reinterpret_cast<RawContext*>(GetLocalVar(var_info.index()));
On 2014/10/30 17:07:27, hausner wrote:
> This is a comment relating to your previous CL, which is already checked in:
> 
> You can use Context::RawCast(GetLocalVar(var_info.index())

Done.

https://codereview.chromium.org/695483003/diff/20001/runtime/vm/flow_graph_bu...
File runtime/vm/flow_graph_builder.cc (right):

https://codereview.chromium.org/695483003/diff/20001/runtime/vm/flow_graph_bu...
runtime/vm/flow_graph_builder.cc:3700: // allocated context but saved on entry
and restored on exit as to prevent
On 2014/10/30 17:07:27, hausner wrote:
> This comment no longer matches the code.

Done.

https://codereview.chromium.org/695483003/diff/20001/tests/language/vm/closur...
File tests/language/vm/closure_memory_retention_test.dart (right):

https://codereview.chromium.org/695483003/diff/20001/tests/language/vm/closur...
tests/language/vm/closure_memory_retention_test.dart:15: f() => [a, b];
On 2014/10/30 17:07:27, hausner wrote:
> Would be nice to add a comment that explains what is happening here (or more
> precisely what should NOT happen). 
> 
> Also, I suggest adding a comment explaining that a negative test outcome is
that
> the program runs out of heap memory.

Done.

[Florian Schneider, 2014-10-31 07:36:03]

Committed patchset #4 (id:60001) manually as r41433 (presubmit successful).