[Hexagon] Use word splats for repeated HVX build-vector words (#204808) buildHvxVectorReg packs small element vectors into i32 words before using the most frequent word to initialize the HVX vector. For i8/i16 result vectors, the old lowering created SPLAT_VECTOR with the final vector type, which selected a byte or halfword splat and broadcast only the low part of the packed word. The idea is to build the splat as a vector of i32 words first, then bitcast back to the final vector type. This preserves the full packed word while keeping normal byte and halfword scalar splat lowering unchanged. The test covers packed-word i8 and i16 cases, and also checks that true i8/i16 scalar splats still lower to byte/halfword splats. After testing with the SDK simulator, it looks to me like a larger 16-byte repeated-pattern case is still miscompiled after this change. It appears to be a broader issue in this build-vector construction path, so maybe this should be addressed in a different way that could fix all cases and not only these specific ones. Please let me know what you think. I have used AI for this proposal. The bug was originally found after running llvm-reduce on a large ll that had a completely unrelated bug. Co-authored-by: L-roro <rodriguez@roofline.ai>
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.