Add CodeView S_LABEL32 symbols for jump table targets (for Windows debugging) (#146121) This PR provides more information to debuggers and analysis tools on Windows. It adds `S_LABEL32` symbols for each target BB of each jump table. This allows debuggers to insert symbolic labels when disassembling code. `S_LABEL32` symbol records indicate that a location is definitely code, and can optionally associate a string label with the code location. BBs generated for jump tables may or may not have string labels, so it is acceptable for the "name" field within `S_LABEL32` symbols to be an empty string. More importantly, this PR allows Windows analysis tools, such as those that generate hot-patches for the Windows kernel, to use these labels to distinguish code basic blocks from data blocks. Microsoft's analysis tools (similar to Bolt) rely on being able to identify all code blocks, so that the tools can traverse all instructions and verify that important requirements for hot-patching are met. This PR has no effect on code generation. It only affects the CodeView symbols that are emitted into OBJ files, which the linker then repackages into PDB files.
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.