transmutability: remove NFA intermediate representation #139990
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Prior to this commit, the transmutability analysis used an intermediate NFA representation of type layout. We then determinized this representation into a DFA, upon which we ran the core transmutability analysis. Unfortunately, determinizing NFAs is expensive. In this commit, we avoid NFAs entirely by observing that Rust `union`s are the only source of nondeterminism and that it is comparatively cheap to compute the DFA union of DFAs. We also implement Graphviz DOT debug formatting of DFAs. Fixes rust-lang/project-safe-transmute#23 Fixes rust-lang/project-safe-transmute#24
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Thanks. r? tmiasko @bors r+ rollup |
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transmutability: remove NFA intermediate representation Prior to this commit, the transmutability analysis used an intermediate NFA representation of type layout. We then determinized this representation into a DFA, upon which we ran the core transmutability analysis. Unfortunately, determinizing NFAs is expensive. In this commit, we avoid NFAs entirely by observing that Rust `union`s are the only source of nondeterminism and that it is comparatively cheap to compute the DFA union of DFAs. We also implement Graphviz DOT debug formatting of DFAs. Fixes rust-lang/project-safe-transmute#23 Fixes rust-lang/project-safe-transmute#24 r? `@compiler-errors`
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…enton Rollup of 3 pull requests Successful merges: - rust-lang#139990 (transmutability: remove NFA intermediate representation) - rust-lang#140044 (rustc-dev-guide subtree update) - rust-lang#140051 (Switch exploit mitigations to mdbook footnotes) r? `@ghost` `@rustbot` modify labels: rollup
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…enton Rollup of 5 pull requests Successful merges: - rust-lang#137953 (simd intrinsics with mask: accept unsigned integer masks, and fix some of the errors) - rust-lang#139990 (transmutability: remove NFA intermediate representation) - rust-lang#140044 (rustc-dev-guide subtree update) - rust-lang#140051 (Switch exploit mitigations to mdbook footnotes) - rust-lang#140054 (docs: fix typo change from inconstants to invariants) r? `@ghost` `@rustbot` modify labels: rollup
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…enton Rollup of 5 pull requests Successful merges: - rust-lang#137953 (simd intrinsics with mask: accept unsigned integer masks, and fix some of the errors) - rust-lang#139990 (transmutability: remove NFA intermediate representation) - rust-lang#140044 (rustc-dev-guide subtree update) - rust-lang#140051 (Switch exploit mitigations to mdbook footnotes) - rust-lang#140054 (docs: fix typo change from inconstants to invariants) r? `@ghost` `@rustbot` modify labels: rollup
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…enton Rollup of 5 pull requests Successful merges: - rust-lang#137953 (simd intrinsics with mask: accept unsigned integer masks, and fix some of the errors) - rust-lang#139990 (transmutability: remove NFA intermediate representation) - rust-lang#140044 (rustc-dev-guide subtree update) - rust-lang#140051 (Switch exploit mitigations to mdbook footnotes) - rust-lang#140054 (docs: fix typo change from inconstants to invariants) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of rust-lang#139990 - jswrenn:no-nfas, r=tmiasko transmutability: remove NFA intermediate representation Prior to this commit, the transmutability analysis used an intermediate NFA representation of type layout. We then determinized this representation into a DFA, upon which we ran the core transmutability analysis. Unfortunately, determinizing NFAs is expensive. In this commit, we avoid NFAs entirely by observing that Rust `union`s are the only source of nondeterminism and that it is comparatively cheap to compute the DFA union of DFAs. We also implement Graphviz DOT debug formatting of DFAs. Fixes rust-lang/project-safe-transmute#23 Fixes rust-lang/project-safe-transmute#24 r? ``@compiler-errors``
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Prior to this commit, the transmutability analysis used an intermediate NFA representation of type layout. We then determinized this representation into a DFA, upon which we ran the core transmutability analysis. Unfortunately, determinizing NFAs is expensive. In this commit, we avoid NFAs entirely by observing that Rust
unions are the only source of nondeterminism and that it is comparatively cheap to compute the DFA union of DFAs.We also implement Graphviz DOT debug formatting of DFAs.
Fixes rust-lang/project-safe-transmute#23
Fixes rust-lang/project-safe-transmute#24
r? @compiler-errors