Adds a new backend to power the GISel Combiners using the InstructionSelector's match tables.
This does not depend on any of the data structures created for the current combiner and is intended to replace it entirely.
See the RFC for more details: https://discourse.llvm.org/t/rfc-matchtable-based-globalisel-combiners/71457/6
Note: this would replace D141135.
Reviewed By: aemerson, arsenm
Differential Revision: https://reviews.llvm.org/D153757
Makes `InstructionSelector.h`/`InstructionSelectorImpl.h` generic so the match tables can also be used for the combiner.
Some notes:
- Coverage was made an optional parameter of `executeMatchTable`, combines won't use it for now.
- `GIPFP_` -> `GICXXPred_` so it's more generic. Those are just C++ predicates and aren't PatFrag-specific.
- Pass the MatcherState directly to testMIPredicate_MI, the combiner will need it.
Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D153755
Accidentally copy-pasted them into the .cpp while refactoring the file in D151432
Those functions are currently only used in the .cpp so it didn't cause an issue, but it causes an undefined reference if another file attempts to use them.
This patch splits the GlobalISelEmitter.cpp file, which imports DAG ISel patterns for GISel, into separate "GISelMatchTable.h/cpp" files.
The main motive is readability & maintainability. GlobalISelEmitter.cpp was about 6400 lines of mixed code, some bits implementing the match table codegen, some others dedicated to importing DAG patterns.
Now it's down to 2700 + a 2150 header + 2000 impl.
It's a tiny bit more lines overall but that's to be expected - moving
inline definitions to out-of-line, adding comments in the .cpp, etc. all of that takes additional space, but I think the tradeoff is worth it.
I did as little unrelated code changes as possible, I would say the biggest change is the introduction of the `gi` namespace used to prevent name conflicts/ODR violations with type common names such as `Matcher`.
It was previously not an issue because all of the code was in an anonymous namespace.
This moves all of the "match table" code out of the file, so predicates,
rules, and actions are all separated now. I believe this helps separating concerns, now `GlobalISelEmitter.cpp` is more focused on importing DAG patterns into GI, instead of also containing the whole match table internals as well.
Note: the new files have a "GISel" prefix to make them distinct from the other "GI" files in the same folder, which are for the combiner.
Reviewed By: aemerson
Differential Revision: https://reviews.llvm.org/D151432
