[MLIR][CF] Avoid collapsing blocks which participate in cycles (#160783) Previously, collapseBranch did not return failure for successor blocks which were part of a cycle. mlir-opt --canonicalize would run indefinitely for any N-block cycle which is kicked off with an unconditional jump. The simplifyPassThroughBr transform would continue alternating which block was targeted in ^bb0, resulting in an infinite loop. collapseBranch will not result in any useful transformation on blocks which participate in cycles, since the block is aliased by a different block. To avoid this, we can check for cycles in collapseBranch and abort when one is detected. Simplification of the cycle is left for other transforms. Fixes #159743.
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.