[NFC][flang][OpenMP] Split `DataSharing` and `Clause` processors (#81973)

This started as an experiment to reduce the compilation time of
iterating over `Lower/OpenMP.cpp` a bit since it is too slow at the
moment. Trying to do that, I split the `DataSharingProcessor`,
`ReductionProcessor`, and `ClauseProcessor` into their own files and
extracted some shared code into a util file. All of these new `.h/.cpp`
files as well as `OpenMP.cpp` are now under a `Lower/OpenMP/` directory.

This resulted is a slightly better organization of the OpenMP lowering
code and hence opening this NFC.

As for the compilation time, this unfortunately does not affect it much
(it shaves off a few seconds of `OpenMP.cpp` compilation) since from
what I learned the bottleneck is in `DirectivesCommon.h` and
`PFTBuilder.h` which both consume a lot of time in template
instantiation it seems.

1 files changed, 5 insertions, 1 deletions

diff --git a/flang/lib/Lower/CMakeLists.txt b/flang/lib/Lower/CMakeLists.txt
index b13d415..5577a60 100644
--- a/flang/lib/Lower/CMakeLists.txt
+++ b/flang/lib/Lower/CMakeLists.txt
@@ -24,7 +24,11 @@ add_flang_library(FortranLower
   LoweringOptions.cpp
   Mangler.cpp
   OpenACC.cpp
-  OpenMP.cpp
+  OpenMP/ClauseProcessor.cpp
+  OpenMP/DataSharingProcessor.cpp
+  OpenMP/OpenMP.cpp
+  OpenMP/ReductionProcessor.cpp
+  OpenMP/Utils.cpp
   PFTBuilder.cpp
   Runtime.cpp
   SymbolMap.cpp