Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

do not add noalias in return position #106371

Merged
merged 1 commit into from
Jan 3, 2023
Merged

do not add noalias in return position #106371

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
6 changes: 4 additions & 2 deletions compiler/rustc_ty_utils/src/abi.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -273,9 +273,11 @@ fn adjust_for_rust_scalar<'tcx>(
| PointerKind::UniqueBorrowed
| PointerKind::UniqueBorrowedPinned => false,
PointerKind::UniqueOwned => noalias_for_box,
PointerKind::Frozen => !is_return,
PointerKind::Frozen => true,
};
if no_alias {
// 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);
}

Expand Down
2 changes: 1 addition & 1 deletion src/test/codegen/function-arguments.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -145,7 +145,7 @@ pub fn raw_struct(_: *const S) {

// `Box` can get deallocated during execution of the function, so it should
// not get `dereferenceable`.
// CHECK: noalias noundef nonnull align 4 {{i32\*|ptr}} @_box({{i32\*|ptr}} noalias noundef nonnull align 4 %x)
// CHECK: noundef nonnull align 4 {{i32\*|ptr}} @_box({{i32\*|ptr}} noalias noundef nonnull align 4 %x)
#[no_mangle]
pub fn _box(x: Box<i32>) -> Box<i32> {
x
Expand Down