Changes in this CR add part of the, Swift based, Autodiff specific
closure specialization optimization pass. The pass does not modify any
code nor does it even exist in any of the optimization pipelines. The
rationale for pushing this partially complete optimization pass upstream
is to keep up with the breaking changes in the underlying Swift based
compiler infrastructure.
Provide APIs needed by lifetime dependence diagnostics, namely LifetimeDependenceConvention.
Reorganize the APIs so it's easy to find related functionality which
API is responsible for which functionality.
Remove the originalFunctionConvention complexity. It is no longer
needed for lifetime dependence inference, and generally should be
avoided in SIL.
Add some placeholder FIXMEs because this not a good PR in which to
change existing functionality.
In the C++ sources it is slightly more convenient to dump to stderr than
to print to stdout, but it is rather more unsightly to print to stderr
from the Swift sources. Switch to stdout. Also allows the dump
functions to be marked debug only.
Introduce two modes of bridging:
* inline mode: this is basically how it worked so far. Using full C++ interop which allows bridging functions to be inlined.
* pure mode: bridging functions are not inlined but compiled in a cpp file. This allows to reduce the C++ interop requirements to a minimum. No std/llvm/swift headers are imported.
This change requires a major refactoring of bridging sources. The implementation of bridging functions go to two separate files: SILBridgingImpl.h and OptimizerBridgingImpl.h.
Depending on the mode, those files are either included in the corresponding header files (inline mode), or included in the c++ file (pure mode).
The mode can be selected with the BRIDGING_MODE cmake variable. By default it is set to the inline mode (= existing behavior). The pure mode is only selected in certain configurations to work around C++ interop issues:
* In debug builds, to workaround a problem with LLDB's `po` command (rdar://115770255).
* On windows to workaround a build problem.
