[SmallPtrSet] Don't leave tombstones in small mode (#96762) When erasing elements in small mode, we currently leave behind tombstones. This means that insertion into the SmallPtrSet also has to check for these, making the operation more expensive than it really should be. We don't really need the tombstones in small mode, because we can just replace with the last element in the set instead. This changes the order, but SmallPtrSet order is fundamentally unstable anyway. However, not leaving tombstones means that the erase() operation now invalidates iterators. This means that consumers that want to remove elements while iterating over the set have to use remove_if() instead. If they fail to do so, there will be an assertion failure thanks to debug epochs, so any such cases are easy to detect (and I have already fixed all cases inside llvm at least).
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.