Previously, we were just running ObjCARCContract when codegening. This is out of
character with the rest of the LLVM passes in Swift, namely that after these
have run, an IR pass no longer contains any compiler intrinsics. This can be
seen by SwiftARCContract running in the -O pipeline.
This commit harmonizes the behavior here.
For testing purposes, I added a flag that disables the running of
ObjCARCContract for testing purposes.
rdar://34824507
We need this because that global state includes tables like llvm[.compiler].used
which would otherwise be sorely missed.
This fixes an issue of the clang importer that would cause us to fail whenever
we imported a function (say it is marked as static inline) that performs an
objective-c method call and we optimize the code. The optimizer would not see
the objective-c selector global variable (which is marked private) as being
"used by unkown i.e the objc runtime" and would rightly assume it could
propagate the value of the global variable's initializer value as a constant to
loads of the global variable.
Now we call the ClangCodeGenerators translation unit finalization code which
will emit these tables and other module flags. We need to take care that we
merge those datastrutures with datastructures that we emit from swift's IRGen.
rdar://21115194
Swift SVN r29176