Bug 41215 – JIT property access should mark internal references to GC'd objects

• Status: RESOLVED
• Resolution: INVALID
• Component: JavaScriptCore

[Nathan Lawrence]

Created attachment 59771 [details]
Patch

The JIT code contains a number of direct references to GC'd objects.  When we have movable objects, these references will need to be updated.

[WebKit Review Bot]

Attachment 59771 [details] did not pass style-queue:

Failed to run "['WebKitTools/Scripts/check-webkit-style', '--no-squash']" exit_code: 1
JavaScriptCore/bytecode/StructureStubInfo.h:38:  Code inside a namespace should not be indented.  [whitespace/indent] [4]
JavaScriptCore/bytecode/Instruction.h:84:  _stubRoutine is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:84:  _base is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:84:  _chain is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:84:  _count is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Total errors found: 5 in 10 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Early Warning System Bot]

Attachment 59771 [details] did not build on qt:
Build output: http://webkit-commit-queue.appspot.com/results/3276777

[WebKit Review Bot]

Attachment 59771 [details] did not build on gtk:
Build output: http://webkit-commit-queue.appspot.com/results/3303756

[Nathan Lawrence]

Created attachment 59775 [details]
Patch

This should fix the compilation problems on 32 bit.

[WebKit Review Bot]

Attachment 59775 [details] did not pass style-queue:

Failed to run "['WebKitTools/Scripts/check-webkit-style', '--no-squash']" exit_code: 1
JavaScriptCore/bytecode/StructureStubInfo.h:38:  Code inside a namespace should not be indented.  [whitespace/indent] [4]
JavaScriptCore/bytecode/Instruction.h:84:  _stubRoutine is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:84:  _base is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:84:  _chain is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:84:  _count is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Total errors found: 5 in 11 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Nathan Lawrence]

Created attachment 60146 [details]
Patch (now with asserts!)

Per Gavin's suggestion, there are now ASSERT_JIT_OFFSETS for the constants used in patching the generated code.  Currently the constants only exist for X86_64 with JSValue64 and X86 with JSValue32_64.

[Nathan Lawrence]

Created attachment 60149 [details]
Patch

[WebKit Review Bot]

Attachment 60149 [details] did not pass style-queue:

Failed to run "['WebKitTools/Scripts/check-webkit-style', '--no-squash']" exit_code: 1
JavaScriptCore/bytecode/StructureStubInfo.h:38:  Code inside a namespace should not be indented.  [whitespace/indent] [4]
JavaScriptCore/jit/JITMarkObjects.cpp:40:  Alphabetical sorting problem.  [build/include_order] [4]
JavaScriptCore/bytecode/Instruction.h:84:  _stubRoutine is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:84:  _base is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:84:  _chain is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:84:  _count is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Total errors found: 6 in 19 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Oliver Hunt]

Comment on attachment 60149 [details]
Patch

The various count members should only be included in builds that have ENABLE(MOVABLE_GC_OBJECTS), otherwise it increases the size of the struct.

[Nathan Lawrence]

Created attachment 62958 [details]
Patch

Adds preprocessor conditionals around more added code + also marks the loads into the prototype object.

[WebKit Review Bot]

Attachment 62958 [details] did not pass style-queue:

Failed to run "['WebKitTools/Scripts/check-webkit-style']" exit_code: 1
JavaScriptCore/jit/JITMarkObjects.cpp:35:  Alphabetical sorting problem.  [build/include_order] [4]
JavaScriptCore/jit/JITMarkObjects.cpp:65:  Missing space before ( in switch(  [whitespace/parens] [5]
JavaScriptCore/bytecode/Instruction.h:80:  _stubRoutine is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _base is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _proto is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _propertyType is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _stubRoutine is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _base is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _chain is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _count is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _propertyType is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Total errors found: 11 in 19 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Nathan Lawrence]

Created attachment 62963 [details]
Patch

should be #define ENABLE_MOVABLE_GC_OBJECTS 0

[WebKit Review Bot]

Attachment 62963 [details] did not pass style-queue:

Failed to run "['WebKitTools/Scripts/check-webkit-style']" exit_code: 1
JavaScriptCore/jit/JITMarkObjects.cpp:35:  Alphabetical sorting problem.  [build/include_order] [4]
JavaScriptCore/jit/JITMarkObjects.cpp:65:  Missing space before ( in switch(  [whitespace/parens] [5]
JavaScriptCore/bytecode/Instruction.h:80:  _stubRoutine is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _base is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _proto is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _propertyType is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _stubRoutine is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _base is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _chain is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _count is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _propertyType is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Total errors found: 11 in 19 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Oliver Hunt]

Comment on attachment 62963 [details]
Patch

r=me, but there's some cruft in the changelog that you should remove

[Nathan Lawrence]

Created attachment 63236 [details]
Patch (minus ChangeLog cruft)

[WebKit Review Bot]

Attachment 63236 [details] did not pass style-queue:

Failed to run "['WebKitTools/Scripts/check-webkit-style']" exit_code: 1
JavaScriptCore/jit/JITPropertyAccess.cpp:577:  One line control clauses should not use braces.  [whitespace/braces] [4]
JavaScriptCore/jit/JITMarkObjects.cpp:35:  Alphabetical sorting problem.  [build/include_order] [4]
JavaScriptCore/jit/JITMarkObjects.cpp:66:  Missing space before ( in switch(  [whitespace/parens] [5]
JavaScriptCore/bytecode/Instruction.h:80:  _stubRoutine is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _base is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _proto is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _propertyType is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _stubRoutine is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _base is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _chain is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _count is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _propertyType is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Total errors found: 12 in 19 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[WebKit Review Bot]

Attachment 63236 [details] did not build on win:
Build output: http://queues.webkit.org/results/3578831

[Oliver Hunt]

Comment on attachment 63236 [details]
Patch (minus ChangeLog cruft)

r=me

[WebKit Commit Bot]

Comment on attachment 63236 [details]
Patch (minus ChangeLog cruft)

Rejecting patch 63236 from commit-queue.

Failed to run "[u'/Users/eseidel/Projects/CommitQueue/WebKitTools/Scripts/svn-apply', u'--reviewer', u'Oliver Hunt', u'--force']" exit_code: 1
Last 500 characters of output:
ed at 1071 (offset 28 lines).
Hunk #11 succeeded at 1089 (offset 30 lines).
Hunk #12 FAILED at 1110.
4 out of 12 hunks FAILED -- saving rejects to file JavaScriptCore/jit/JITPropertyAccess.cpp.rej
patching file JavaScriptCore/jit/JITStubs.cpp
Hunk #1 FAILED at 934.
Hunk #2 FAILED at 954.
Hunk #3 FAILED at 1569.
3 out of 3 hunks FAILED -- saving rejects to file JavaScriptCore/jit/JITStubs.cpp.rej
patching file JavaScriptCore/wtf/Platform.h
Hunk #1 succeeded at 1073 with fuzz 2 (offset 12 lines).

Full output: http://queues.webkit.org/results/3642303

[Nathan Lawrence]

Created attachment 63508 [details]
patch (up to date)

[WebKit Review Bot]

Attachment 63508 [details] did not pass style-queue:

Failed to run "['WebKitTools/Scripts/check-webkit-style']" exit_code: 1
JavaScriptCore/jit/JITPropertyAccess.cpp:580:  One line control clauses should not use braces.  [whitespace/braces] [4]
JavaScriptCore/jit/JITMarkObjects.cpp:35:  Alphabetical sorting problem.  [build/include_order] [4]
JavaScriptCore/jit/JITMarkObjects.cpp:66:  Missing space before ( in switch(  [whitespace/parens] [5]
JavaScriptCore/bytecode/Instruction.h:80:  _stubRoutine is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _base is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _proto is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _propertyType is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _stubRoutine is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _base is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _chain is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _count is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _propertyType is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Total errors found: 12 in 19 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[WebKit Review Bot]

Attachment 63508 [details] did not build on win:
Build output: http://queues.webkit.org/results/3601744

[Eric Seidel (no email)]

Comment on attachment 63236 [details]
Patch (minus ChangeLog cruft)

Cleared Oliver Hunt's review+ from obsolete attachment 63236 [details] so that this bug does not appear in http://webkit.org/pending-commit.

[Oliver Hunt]

Comment on attachment 63508 [details]
patch (up to date)

This basically looks fine, but you should remove the change from platform.h that turns the movable logic on.

[Nathan Lawrence]

Created attachment 63642 [details]
patch

[WebKit Review Bot]

Attachment 63642 [details] did not pass style-queue:

Failed to run "['WebKitTools/Scripts/check-webkit-style']" exit_code: 1
JavaScriptCore/jit/JITPropertyAccess.cpp:580:  One line control clauses should not use braces.  [whitespace/braces] [4]
JavaScriptCore/jit/JITMarkObjects.cpp:35:  Alphabetical sorting problem.  [build/include_order] [4]
JavaScriptCore/jit/JITMarkObjects.cpp:66:  Missing space before ( in switch(  [whitespace/parens] [5]
JavaScriptCore/bytecode/Instruction.h:80:  _stubRoutine is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _base is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _proto is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _propertyType is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _stubRoutine is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _base is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _chain is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _count is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _propertyType is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Total errors found: 12 in 18 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Nathan Lawrence]

Created attachment 63643 [details]
patch

fixed some of the style issues

[WebKit Review Bot]

Attachment 63643 [details] did not pass style-queue:

Failed to run "['WebKitTools/Scripts/check-webkit-style']" exit_code: 1
JavaScriptCore/bytecode/Instruction.h:80:  _stubRoutine is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _base is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _proto is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _propertyType is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _stubRoutine is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _base is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _chain is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _count is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _propertyType is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Total errors found: 9 in 18 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Nathan Lawrence]

Created attachment 63655 [details]
patch (up to date)

[WebKit Review Bot]

Attachment 63655 [details] did not pass style-queue:

Failed to run "['WebKitTools/Scripts/check-webkit-style']" exit_code: 1
JavaScriptCore/bytecode/Instruction.h:80:  _stubRoutine is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _base is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _proto is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _propertyType is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _stubRoutine is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _base is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _chain is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _count is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _propertyType is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Total errors found: 9 in 18 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Early Warning System Bot]

Attachment 63655 [details] did not build on qt:
Build output: http://queues.webkit.org/results/3595889

[Nathan Lawrence]

Created attachment 63662 [details]
patch

This should fix the QT build errors.

[WebKit Review Bot]

Attachment 63662 [details] did not pass style-queue:

Failed to run "['WebKitTools/Scripts/check-webkit-style']" exit_code: 1
JavaScriptCore/bytecode/Instruction.h:80:  _stubRoutine is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _base is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _proto is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _propertyType is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _stubRoutine is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _base is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _chain is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _count is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _propertyType is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Total errors found: 9 in 19 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[WebKit Review Bot]

Attachment 63662 [details] did not build on win:
Build output: http://queues.webkit.org/results/3626497

[Nathan Lawrence]

Created attachment 63754 [details]
patch (with vcproj)

[Geoffrey Garen]

Comment on attachment 63662 [details]
patch

I think this is the kind of patch that would benefit from some line-by-line explanation in the ChangeLog.

+        compileGetDirectOffset(protoObject, regT1, regT1, regT2, cachedOffset);
+        move(regT2, regT0);

I think it's layering violation to require the JIT to know which temporary registers to use, because some temporaries on some platforms change the size of the instruction. That's very subtle, and likely to go wrong in the future. I'd prefer having compileGetDirectOffset use a MacroAssembler API that guarantees a constant size for its instructions.

[Nathan Lawrence]

Created attachment 63764 [details]
patch

[WebKit Review Bot]

Attachment 63764 [details] did not pass style-queue:

Failed to run "['WebKitTools/Scripts/check-webkit-style']" exit_code: 1
JavaScriptCore/bytecode/Instruction.h:80:  _stubRoutine is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _base is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _proto is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:80:  _propertyType is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _stubRoutine is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _base is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _chain is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _count is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/bytecode/Instruction.h:95:  _propertyType is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Total errors found: 9 in 22 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Geoffrey Garen]

Comment on attachment 63764 [details]
patch

r=me

[Eric Seidel (no email)]

Comment on attachment 63764 [details]
patch

Clearing flags on attachment: 63764

Committed r64938: <http://trac.webkit.org/changeset/64938>

[Eric Seidel (no email)]

All reviewed patches have been landed.  Closing bug.

[Geoffrey Garen]

Rolled out in bug 43685.

[Filip Pizlo]

This isn't necessary anymore.  We have a twofold story for this:

1) The GC can pin objects.

2) The JITs tell the GC what objects the JIT code references, and in what manner (strong, weak, ephemeral).

[Filip Pizlo]

Meant to be resolved/invalid.