[clang] Integrate LLVMABI for function call ABI lowering (#194460) This PR wires the LLVM ABI library (prototyped in https://github.com/llvm/llvm-project/pull/140112) into Clang's function call ABI lowering pipeline, behind a new `-fexperimental-abi-lowering` cc1 flag. When the flag is enabled and the active target has an LLVMABI implementation, `CodeGenTypes::arrangeLLVMFunctionInfo` constructs an `llvm::abi::FunctionInfo` from the call's argument and result types (using QualTypeMapper(https://github.com/llvm/llvm-project/pull/174634) to translate Clang QualTypes into ABI types). Asks the target's `llvm::abi::TargetInfo` to classify it, and then translates each `llvm::abi::ArgInfo` back into the ABIArgInfo consumed by the rest of CodeGen. The translation is handled by a new `convertABIArgInfo` helper covering the Direct, Extend, Indirect, and Ignore kinds, with coerce-to types lifted back into LLVM IR via a new IRTypeMapper. The integration is intentionally narrow and existing code paths are untouched. `CodeGenModule::shouldUseLLVMABILowering` only opts in for targets explicitly wired to the new library(currently only BPF).
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.