mirror of
https://github.com/rust-lang/rust.git
synced 2026-04-28 11:17:26 +03:00
4a7fb971c9
Attach range metadata to alignment loads from vtables ...because alignment is always nonzero[0]. This helps eliminate redundant runtime alignment checks, when a DST is a field of a struct whose remaining fields have alignment 1. Fixes #91438. --- [0]: The [reference](https://doc.rust-lang.org/reference/type-layout.html) says that alignment must be at least 1. And in practice, the alignment field for all vtables is generated here: https://github.com/rust-lang/rust/blob/772d51f887fa407216860bf8ecf3f1a32fb795b4/compiler/rustc_middle/src/ty/vtable.rs#L68-L90 and is nonzero because [`Align::bytes()`](https://github.com/rust-lang/rust/blob/772d51f887fa407216860bf8ecf3f1a32fb795b4/compiler/rustc_target/src/abi/mod.rs#L547-L549) is always nonzero.
Please read the rustc-dev-guide chapter on Backend Agnostic Codegen.