This patch adds a few new member methods in the `PluginParseTreeAction`
frontend action base class. With these new methods, the plugin API
becomes independent of the driver internals. In particular, plugin
writers no longer require the `CompilerInstance.h` header file to access
various driver data structures (instead, they can use newly added
hooks).
This change is desirable as `CompilerInstance.h` includes various
headers from Clang (both explicitly and implicitly). Some of these
header files are generated at build time (through TableGen) and
including them creates a dependency on some of Clang's build targets.
However, plugins in Flang should not depend on Clang build targets.
Note that plugins might still work fine most of the time, even without
this change and without adding Clang build targets as dependency in
plugin's CMake definition. Indeed, these Clang build targets are often
generated early in the build process. However, that's not guaranteed and
we did notice that on occasions plugins would fail to build.
Differential Revision: https://reviews.llvm.org/D120999
Please note that the updated documentation reflects the design that we are
working towards, but haven't implemented competely yet. We took this approach
in order to provide a more holisitic and complete overview of the design.
In particular, this document assumes that Flang's frontend and compiler
driver can already generate code. This is still work-in-progress and is
being developed on the `fir-dev` branch in the F18 repository [1].
[1] https://github.com/flang-compiler/f18-llvm-project/tree/fir-dev
Differential Revision: https://reviews.llvm.org/D111573
Andrzej Warzynski