Add --check-code-pointer flag for debug builds

Add --check-code-pointer flag for debug builds

- Introduce --check-code-pointer which is false by default.
- Sort DECLARE / DEFINE flag macros in assembler*.cc

Fixes #25361

R=rmacnak@google.com

Committed: https://github.com/dart-lang/sdk/commit/768e4ddee703c80b362644c4518db2077a057368

[Cutch, 2016-01-11 18:32:38]

Description was changed from

==========
Add --check-code-pointer flag for debug builds

BUG=
==========

to

==========
Add --check-code-pointer flag for debug builds

Fixes #25361
==========

[Cutch, 2016-01-11 18:32:39]

johnmccutchan@google.com changed reviewers:
+ rmacnak@google.com

[Cutch, 2016-01-11 18:33:41]

Description was changed from

==========
Add --check-code-pointer flag for debug builds

Fixes #25361
==========

to

==========
Add --check-code-pointer flag for debug builds

- Introduce --check-code-pointer which is false by default.
- Sort DECLARE / DEFINE flag macros in assembler*.cc

Fixes #25361
==========

[rmacnak, 2016-01-11 21:19:34]

lgtm. 

cc Florian. I think we can restore this check to be enabled by default if we
move the pool pointer load to the end of the frame building sequence.

[Cutch, 2016-01-11 21:20:17]

Description was changed from

==========
Add --check-code-pointer flag for debug builds

- Introduce --check-code-pointer which is false by default.
- Sort DECLARE / DEFINE flag macros in assembler*.cc

Fixes #25361
==========

to

==========
Add --check-code-pointer flag for debug builds

- Introduce --check-code-pointer which is false by default.
- Sort DECLARE / DEFINE flag macros in assembler*.cc

Fixes #25361

R=rmacnak@google.com

Committed:
https://github.com/dart-lang/sdk/commit/768e4ddee703c80b362644c4518db2077a057368
==========

[Cutch, 2016-01-11 21:20:18]

Committed patchset #1 (id:1) manually as
768e4ddee703c80b362644c4518db2077a057368 (presubmit successful).

[Florian Schneider, 2016-01-12 11:31:23]

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

[Florian Schneider, 2016-01-12 11:31:23]

I'd like to keep the assertion on by default. I think Ryan is right: We can just
insert
 the code pointer check in EnterDartFrame, so we can still have the assertion.

https://codereview.chromium.org/1574993003/diff/1/runtime/vm/assembler_x64.cc
File runtime/vm/assembler_x64.cc (right):

https://codereview.chromium.org/1574993003/diff/1/runtime/vm/assembler_x64.cc...
runtime/vm/assembler_x64.cc:3352: pushq(PP);
Would it work to do CheckCodePointer here instead, after the Dart frame is
built? (and remove it from LoadPoolPointer)