Propose a 2025H2 goal for emitting retags in codegen #350
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rrbutani
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Jul 18, 2025
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| Miri has a unique role for the Rust community as the only tool that can find violations of Rust's evolving aliasing models. However, Miri is significantly slower than native execution, and it does not support finding aliasing violations triggered by foreign function calls. Lack of FFI support has prevented developers from finding aliasing bugs in real-world libraries—including one maintained by the Rust project ([`flate2-rs`](https://github.com/rust-lang/flate2-rs/issues/392))! We need a new approach for finding these bugs in the large-scale, multi-language projects where Rust is being adopted. | ||
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| We could provide both better performance and support for multilanguage applications by inserting native run-time checks into shared formats like LLVM IR. These checks could be implemented in several different ways, possibly as [an extension to Valgrind](https://github.com/pnkfelix/krabcake) or [a new LLVM sanitizer](https://borrowsanitizer.com/). However, we can fully prototype any of these approaches, we need a way to take the type information that Miri uses to find aliasing violations and lower it into Rust's codegen backends, where it can be used to determine where and how to insert these run-time checks. |
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| We could provide both better performance and support for multilanguage applications by inserting native run-time checks into shared formats like LLVM IR. These checks could be implemented in several different ways, possibly as [an extension to Valgrind](https://github.com/pnkfelix/krabcake) or [a new LLVM sanitizer](https://borrowsanitizer.com/). However, we can fully prototype any of these approaches, we need a way to take the type information that Miri uses to find aliasing violations and lower it into Rust's codegen backends, where it can be used to determine where and how to insert these run-time checks. | |
| We could provide both better performance and support for multilanguage applications by inserting native run-time checks into shared formats like LLVM IR. These checks could be implemented in several different ways, possibly as [an extension to Valgrind](https://github.com/pnkfelix/krabcake) or [a new LLVM sanitizer](https://borrowsanitizer.com/). However, before we can fully prototype any of these approaches, we need a way to take the type information that Miri uses to find aliasing violations and lower it into Rust's codegen backends, where it can be used to determine where and how to insert these run-time checks. |
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Retagintrinsics are necessary for finding aliasing bugs. We can support new types of bug-finding tools by providing a way to lower retags from MIR into codegen backends.Rendered