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perf experiment: remove noalias, readonly, dereferenceable attributes #137707

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perf experiment: remove noalias, readonly, dereferenceable attributes #137707

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18 changes: 9 additions & 9 deletions compiler/rustc_ty_utils/src/abi.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -392,13 +392,13 @@ fn adjust_for_rust_scalar<'tcx>(
// potentially self-referential types (see
// <https://github.com/rust-lang/unsafe-code-guidelines/issues/381>). If LLVM had a way
// to say "dereferenceable on entry" we could use it here.
attrs.pointee_size = match kind {
PointerKind::Box { .. }
| PointerKind::SharedRef { frozen: false }
| PointerKind::MutableRef { unpin: false } => Size::ZERO,
PointerKind::SharedRef { frozen: true }
| PointerKind::MutableRef { unpin: true } => pointee.size,
};
// attrs.pointee_size = match kind {
// PointerKind::Box { .. }
// | PointerKind::SharedRef { frozen: false }
// | PointerKind::MutableRef { unpin: false } => Size::ZERO,
// PointerKind::SharedRef { frozen: true }
// | PointerKind::MutableRef { unpin: true } => pointee.size,
// };

// The aliasing rules for `Box<T>` are still not decided, but currently we emit
// `noalias` for it. This can be turned off using an unstable flag.
Expand All @@ -424,11 +424,11 @@ fn adjust_for_rust_scalar<'tcx>(
// We can never add `noalias` in return position; that LLVM attribute has some very surprising semantics
// (see <https://github.com/rust-lang/unsafe-code-guidelines/issues/385#issuecomment-1368055745>).
if no_alias && !is_return {
attrs.set(ArgAttribute::NoAlias);
//attrs.set(ArgAttribute::NoAlias);
}

if matches!(kind, PointerKind::SharedRef { frozen: true }) && !is_return {
attrs.set(ArgAttribute::ReadOnly);
//attrs.set(ArgAttribute::ReadOnly);
}
}
}
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