Move non-common files from FortranCommon to FortranSupport (analogous to
LLVMSupport) such that
* declarations and definitions that are only used by the Flang compiler,
but not by the runtime, are moved to FortranSupport
* declarations and definitions that are used by both ("common"), the
compiler and the runtime, remain in FortranCommon
* generic STL-like/ADT/utility classes and algorithms remain in
FortranCommon
This allows a for cleaner separation between compiler and runtime
components, which are compiled differently. For instance, runtime
sources must not use STL's `<optional>` which causes problems with CUDA
support. Instead, the surrogate header `flang/Common/optional.h` must be
used. This PR fixes this for `fast-int-sel.h`.
Declarations in include/Runtime are also used by both, but are
header-only. `ISO_Fortran_binding_wrapper.h`, a header used by compiler
and runtime, is also moved into FortranCommon.
Certain functions in glibc have "nonnull" attributes on pointer
parameters (even in cases where passing a null pointer should be handled
correctly). There are a few cases of such calls in flang: memcmp and
memcpy with the length parameter set to 0.
Avoid passing a null pointer to these functions, since the conflict with
the nonnull attribute could cause an undefined behavior.
This was detected by the undefined behavior sanitizer.
These functions will be used as part of the HLFIR lowering for
forall/where. The contents of the API were requested by @jeanPerier.
The API is designed around that use case, assuming that the caller knows
through some side channel what size to allocate for boxes returned from
the pop() function.
Differential Revision: https://reviews.llvm.org/D150050
