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Rust could pass along lots of aliasing information to LLVM via the new metadata.
http://llvm.org/docs/LangRef.html#noalias-and-alias-scope-metadata
UPDATE(@eddyb): Currently blocked on an Unsafe Code Guidelines decision, regarding the exact cases we can treat as UB, and optimize - see #16515 (comment) below, and further comments.
While LLVM can and will convert noalias attributes in function signatures into scoped !noalias metadata on instructions, when inlining, we never emit any such metadata ourselves.
Furthermore, the LLVM conversion is conservative (i.e. scoped to the entire callee) in a way that can't easily be generalized intra-function, without deciding on what to define and what to leave as UB.
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Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.Area: Code generationArea: Code generationCategory: An issue proposing an enhancement or a PR with one.Category: An issue proposing an enhancement or a PR with one.Category: An issue highlighting optimization opportunities or PRs implementing suchCategory: An issue highlighting optimization opportunities or PRs implementing suchIssue: Problems and improvements with respect to performance of generated code.Issue: Problems and improvements with respect to performance of generated code.Relevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.Working group: LLVM backend code generationWorking group: LLVM backend code generation