| commit | a6e1700fa622f75436c3c3ead23b1eefb67e88ea | [log] [tgz] |
|---|---|---|
| author | Kunqiu Chen <camsyn@foxmail.com> | Mon Jul 14 15:45:08 2025 +0800 |
| committer | GitHub <noreply@github.com> | Mon Jul 14 15:45:08 2025 +0800 |
| tree | 83cf16981b362fdcad1150945e75e170f7eb19a1 | |
| parent | cad62df49a79df5e5136cfad280c5abc9f62c60b [diff] |
[Utils][Local] Preserve !nosanitize in combineMetadata when merging instructions (#148376) `combineMetadata` helper currently drops `!nosanitize` metadata when merging two instructions, even if both originally carried `!nosanitize`. This is problematic because `!nosanitize` is a key mechanism used by sanitizer (e.g., ASan) to suppress instrumentation. Removing it can lead to unintended sanitizer behavior. This patch adds `nosanitize` to the whitelist in combineMetadata, preserving it only if both instructions carry `!nosanitize`; otherwise, it is dropped. This patch also adds corresponding tests in a test file and regenerates it. --- ### Details **Example (see [Godbolt](https://godbolt.org/z/83P5eWczx) for details**): ```llvm %v1 = load i32, ptr %p, !nosanitize %v2 = load i32, ptr %p, !nosanitize ``` When merged via `combineMetadata(%v1, %v2, ...)`, the resulting instruction loses its `!nosanitize` metadata. Tools such as UBSan and AFL rely on `nosanitize` to prevent unwanted transformations or checks. However, the current implementation of combineMetadata mistakenly drops !nosanitize. This may lead to unintended behavior during optimization. For example, under `-fsanitize=address,undefined -O2`, IR emitted by UBSan may lose its `!nosanitize` metadata due to the incorrect metadata merging in optimization. As a result, ASan could unexpectedly instrument those instructions. > Note: due to the current UBSan handlers having relatively coarse-grained attributes, this specific case is difficult to reproduce end-to-end from source code—UBSan currently inhibits such optimizations (refer to #135135 for details). Still, I believe it's necessary to fix this now, to support future versions of UBSan that might allow such optimizations, and to support third-party tools (such as AFL-based fuzzers) that rely on the presence of !nosanitize.
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.