This commit introduces a `SelectLikeOpInterface` that can be used to
handle select-like operations generically. Select operations are similar
to control flow operations, as they forward operands depending on
conditions. This is the reason why it was placed to the already existing
control flow interfaces.
This commit changes the LLVM dialect's inliner interface to properly
propagate noalias information to memory accesses that have different
underlying object. By always introducing an SSACopy intrinsic, it's
possible to understand that specific memory operations are using
unrelated pointers. Previously, the backwards slice walk did continue
beyond the boundary of the original function and failed to reason about
the "underlying objects".
This commit introduces a slicing utility that can be used to walk
arbitrary IR slices. It additionally ships logic to determine control
flow predecessors, which allows users to walk backward slices without
dealing with both `RegionBranchOpInterface` and `BranchOpInterface`.
This utility is used to improve the `noalias` propagation in the LLVM
dialect's inliner interface. Before this change, it broke down as soon
as pointer were passed through region control flow operations.
This commit changes the LLVM dialect's inliner interface to no longer be
registered at dialect initialization. Instead, it is now a promised
interface, that needs to be registered explicitly. This change is
desired to avoid pulling in a lot of dependencies into the
`MLIRLLVMDialect` library, especially considering future patches that
plan to extend it further with strong IR analysis.
