Code objects are exposed through JSFunction and SharedFunctionInfo.
If they are builtins, we don't have to worry about background threads
seeing partially initialized code objects. If they are optimized code
objects, we may. Background threads read the code fields with
AcquireLoad semantics. The fields are set on the main thread with
ReleaseStore semantics when appropriate.

Special care is taken when setting an optimized code object in a closure
in the interpreter entry stub. Since the MacroAssembler doesn't support
ReleaseStore semantics, this CL ensures that the optimized code object
is stored with those semantics in the feedback vector, where the
interpreter entry stub finds it.

Bug: v8:7790
Change-Id: I41ecedfe0e9d1ad5091cbe9a97f66c66ca9e07dd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2676633
Commit-Queue: Michael Stanton <mvstanton@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72869}