Implement verification of context separation.

Implement verification of context separation.

This adds the --verify-context-separation flag which can be used to
verify that no code object keeps more than one context alive. It uses
the same definition of connectivity as the full GC does. At the moment
we only verify optimized code, but should extend it to other kinds of
code later.

R=verwaest@chromium.org

[Toon Verwaest, 2012-07-13 09:02:04]

LGTM with comments.

https://chromiumcodereview.appspot.com/10694157/diff/1/src/flag-definitions.h
File src/flag-definitions.h (right):

https://chromiumcodereview.appspot.com/10694157/diff/1/src/flag-definitions.h...
src/flag-definitions.h:545: "verify that code objects keep at most one context
alive after GC")
Is it one context, or one global context?

https://chromiumcodereview.appspot.com/10694157/diff/1/src/mark-compact.cc
File src/mark-compact.cc (right):

https://chromiumcodereview.appspot.com/10694157/diff/1/src/mark-compact.cc#ne...
src/mark-compact.cc:305: EnableCodeFlushing(was_code_flushing_enabled);
Please move the surrounding code into VerifyContextSeparation and add a comment
explaining the main idea; why code flushing needs to be disabled; why we need to
verify that the mark bits are clean etc.

https://chromiumcodereview.appspot.com/10694157/diff/1/src/mark-compact.cc#ne...
src/mark-compact.cc:1669: ASSERT(context->IsGlobalContext());
Can this happen?

[Michael Starzinger, 2012-09-21 13:46:05]

Code review spring cleaning. This was superseded.

https://codereview.chromium.org/10830049