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Auto merge of #112026 - saethlin:misaligned-addrof, r=pnkfelix

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Don't check for misaligned raw pointer derefs inside Rvalue::AddressOf

From https://github.com/rust-lang/rust/pull/112026#issuecomment-1565686697:

rustc 1.70 (stable next week) added a Mir pass to add pointer alignment checks in debug mode. Adding these checks caused some crates to break, but that was expected, since they contain broken code (https://github.com/rust-lang/rust/issues/111487) for tracking that.

However, the checks added are slightly more aggressive than they should have been. Specifically, they also check the place in an `addr_of!` expression. Whether lack of alignment there is or isn't UB is unclear. This PR modifies the pass to not affect those cases.

I spot checked the crater regressions and the ones I saw were not the case that this PR is modifying. It still seems good to not land anything overaggressive though
This commit is contained in:
bors 2023-05-28 12:33:52 +00:00
commit 39c03fb652
2 changed files with 23 additions and 0 deletions
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8
compiler/rustc_mir_transform/src/check_alignment.rs
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@ -75,6 +75,14 @@ struct PointerFinder<'tcx, 'a> {
}
impl<'tcx, 'a> Visitor<'tcx> for PointerFinder<'tcx, 'a> {
fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) {
if let Rvalue::AddressOf(..) = rvalue {
// Ignore dereferences inside of an AddressOf
return;
}
self.super_rvalue(rvalue, location);
}
fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, _location: Location) {
if let PlaceContext::NonUse(_) = context {
return;