Merge from rustc

3 files changed, 29 insertions, 6 deletions

diff --git a/compiler/rustc_mir_transform/src/check_packed_ref.rs b/compiler/rustc_mir_transform/src/check_packed_ref.rs
index f5f1c1010e1..b9bc89fcf8f 100644
--- a/compiler/rustc_mir_transform/src/check_packed_ref.rs
+++ b/compiler/rustc_mir_transform/src/check_packed_ref.rs
@@ -56,8 +56,11 @@ impl<'tcx> Visitor<'tcx> for PackedRefChecker<'_, 'tcx> {
                         "reference to packed field is unaligned"
                     )
                     .note(
-                        "fields of packed structs are not properly aligned, and creating \
-                        a misaligned reference is undefined behavior (even if that \
+                        "packed structs are only aligned by one byte, and many modern architectures \
+                        penalize unaligned field accesses"
+                    )
+                    .note(
+                        "creating a misaligned reference is undefined behavior (even if that \
                         reference is never dereferenced)",
                     ).help(
                         "copy the field contents to a local variable, or replace the \
diff --git a/compiler/rustc_mir_transform/src/lib.rs b/compiler/rustc_mir_transform/src/lib.rs
index 25d7db0ee60..8d9a22ea30d 100644
--- a/compiler/rustc_mir_transform/src/lib.rs
+++ b/compiler/rustc_mir_transform/src/lib.rs
@@ -616,13 +616,10 @@ fn promoted_mir(tcx: TyCtxt<'_>, def: LocalDefId) -> &IndexVec<Promoted, Body<'_
         return tcx.arena.alloc(IndexVec::new());
     }
 
-    let tainted_by_errors = tcx.mir_borrowck(def).tainted_by_errors;
+    tcx.ensure_with_value().mir_borrowck(def);
     let mut promoted = tcx.mir_promoted(def).1.steal();
 
     for body in &mut promoted {
-        if let Some(error_reported) = tainted_by_errors {
-            body.tainted_by_errors = Some(error_reported);
-        }
         run_analysis_to_runtime_passes(tcx, body);
     }
 
diff --git a/compiler/rustc_mir_transform/src/lower_intrinsics.rs b/compiler/rustc_mir_transform/src/lower_intrinsics.rs
index 62b727674c5..69ba4840146 100644
--- a/compiler/rustc_mir_transform/src/lower_intrinsics.rs
+++ b/compiler/rustc_mir_transform/src/lower_intrinsics.rs
@@ -179,6 +179,29 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
                             }
                         }
                     }
+                    sym::write_via_move => {
+                        let target = target.unwrap();
+                        let Ok([ptr, val]) = <[_; 2]>::try_from(std::mem::take(args)) else {
+                            span_bug!(
+                                terminator.source_info.span,
+                                "Wrong number of arguments for write_via_move intrinsic",
+                            );
+                        };
+                        let derefed_place =
+                            if let Some(place) = ptr.place() && let Some(local) = place.as_local() {
+                                tcx.mk_place_deref(local.into())
+                            } else {
+                                span_bug!(terminator.source_info.span, "Only passing a local is supported");
+                            };
+                        block.statements.push(Statement {
+                            source_info: terminator.source_info,
+                            kind: StatementKind::Assign(Box::new((
+                                derefed_place,
+                                Rvalue::Use(val),
+                            ))),
+                        });
+                        terminator.kind = TerminatorKind::Goto { target };
+                    }
                     sym::discriminant_value => {
                         if let (Some(target), Some(arg)) = (*target, args[0].place()) {
                             let arg = tcx.mk_place_deref(arg);