[mlir][Interfaces][NFC] Simplify and align `RegionSuccessor` design / API (#174945)
Simplify the design of `RegionSuccessor`. There is no need to store the
`Operation *` pointer when branching out of the region branch op (to the
parent). There is no API to even access the `Operation *` pointer.
Add a new helper function `RegionSuccessor::parent` to construct a
region successor that points to the parent. This aligns the
`RegionSuccessor` design and API with `RegionBranchPoint`:
* Both classes now have a `parent()` helper function.
`ClassName::parent()` can be used in documentation to precisely describe
the source/target of a region branch.
* Both classes now use `nullptr` internally to represent "parent".
This API change also protects against incorrect API usage: users can no
longer pass an incorrect parent op. If a region successor is not a
region of the region branch op, it *must* branch out of region branch op
itself ("parent"). However, the previous API allowed passing other
operations. There was one such API violation in a [test
case](https://github.com/llvm/llvm-project/pull/174945/files#diff-d5717e4a8d7344b2ff77762b8fa480bcfec0eeee97a86195c787d791a6217e13L71).
Also clean up the documentation to use the correct terminology (such as
"successor operands", "successor inputs") consistently.
Note: This PR effectively rolls back some changes from #161575. That PR
introduced `llvm::PointerUnion<Region *, Operation *>
successor{nullptr};`. It is unclear from the commit message why that
change was made.
Note for LLVM integration: You may have to slightly modify
`getSuccessorRegion` implementations: Replace
`RegionSuccessor(getOperation(), getOperation()->getResults())` with
`RegionSuccessor::parent(getResults())`.
Welcome to the LLVM project!
This repository contains the source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and run-time environments.
The LLVM project has multiple components. The core of the project is itself called “LLVM”. This contains all of the tools, libraries, and header files needed to process intermediate representations and convert them into object files. Tools include an assembler, disassembler, bitcode analyzer, and bitcode optimizer.
C-like languages use the Clang frontend. This component compiles C, C++, Objective-C, and Objective-C++ code into LLVM bitcode -- and from there into object files, using LLVM.
Other components include: the libc++ C++ standard library, the LLD linker, and more.
Consult the Getting Started with LLVM page for information on building and running LLVM.
For information on how to contribute to the LLVM project, please take a look at the Contributing to LLVM guide.
Join the LLVM Discourse forums, Discord chat, LLVM Office Hours or Regular sync-ups.
The LLVM project has adopted a code of conduct for participants to all modes of communication within the project.