3bc2dade36
This work feeds part of PR https://github.com/llvm/llvm-project/pull/88385, and adds support for vectorising loops with uncountable early exits and outside users of loop-defined variables. When calculating the final value from an uncountable early exit we need to calculate the vector lane that triggered the exit, and hence determine the value at the point we exited. All code for calculating the last value when exiting the loop early now lives in a new vector.early.exit block, which sits between the middle.split block and the original exit block. Doing this required two fixes: 1. The vplan verifier incorrectly assumed that the block containing a definition always dominates the block of the user. That's not true if you can arrive at the use block from multiple incoming blocks. This is possible for early exit loops where both the early exit and the latch jump to the same block. 2. We were adding the new vector.early.exit to the wrong parent loop. It needs to have the same parent as the actual early exit block from the original loop. I've added a new ExtractFirstActive VPInstruction that extracts the first active lane of a vector, i.e. the lane of the vector predicate that triggered the exit. NOTE: The IR generated for dealing with live-outs from early exit loops is unoptimised, as opposed to normal loops. This inevitably leads to poor quality code, but this can be fixed up later.
The LLVM Compiler Infrastructure
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.
Getting the Source Code and Building LLVM
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.
Getting in touch
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.