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mentioned_items: avoid adding str/slice unsizing casts

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This commit is contained in:
Ralf Jung 2024-03-20 11:16:11 +01:00
parent 682991d2c7
commit feeffaeff9
1 changed files with 16 additions and 9 deletions
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19
compiler/rustc_mir_transform/src/mentioned_items.rs
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@ -1,6 +1,6 @@
use rustc_middle::mir::visit::Visitor;
use rustc_middle::mir::{self, Location, MentionedItem, MirPass};
use rustc_middle::ty::{adjustment::PointerCoercion, TyCtxt};
use rustc_middle::ty::{self, adjustment::PointerCoercion, TyCtxt};
use rustc_session::Session;
use rustc_span::source_map::Spanned;
@ -76,15 +76,22 @@ impl<'tcx> Visitor<'tcx> for MentionedItemsVisitor<'_, 'tcx> {
)
| mir::Rvalue::Cast(mir::CastKind::DynStar, ref operand, target_ty) => {
// This isn't monomorphized yet so we can't tell what the actual types are -- just
// add everything.
// add everything that may involve a vtable.
let source_ty = operand.ty(self.body, self.tcx);
let may_involve_vtable = match (
source_ty.builtin_deref(true).map(|t| t.ty.kind()),
target_ty.builtin_deref(true).map(|t| t.ty.kind()),
) {
(Some(ty::Array(..)), Some(ty::Str | ty::Slice(..))) => false, // &str/&[T] unsizing
_ => true,
};
if may_involve_vtable {
self.mentioned_items.push(Spanned {
node: MentionedItem::UnsizeCast {
source_ty: operand.ty(self.body, self.tcx),
target_ty,
},
node: MentionedItem::UnsizeCast { source_ty, target_ty },
span: span(),
});
}
}
// Similarly, record closures that are turned into function pointers.
mir::Rvalue::Cast(
mir::CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(_)),