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Retag as FnEntry on drop_in_place

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This commit is contained in:
Jakob Degen 2022-11-04 00:05:15 -07:00
parent 49143814e1
commit 102040ce76
9 changed files with 192 additions and 3 deletions
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28
compiler/rustc_mir_transform/src/shim.rs
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@ -176,7 +176,33 @@ fn build_drop_shim<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, ty: Option<Ty<'tcx>>)
if ty.is_some() {
// The first argument (index 0), but add 1 for the return value.
let dropee_ptr = Place::from(Local::new(1 + 0));
let mut dropee_ptr = Place::from(Local::new(1 + 0));
if tcx.sess.opts.unstable_opts.mir_emit_retag {
// We want to treat the function argument as if it was passed by `&mut`. As such, we
// generate
// ```
// temp = &mut *arg;
// Retag(temp, FnEntry)
// ```
// It's important that we do this first, before anything that depends on `dropee_ptr`
// has been put into the body.
let reborrow = Rvalue::Ref(
tcx.lifetimes.re_erased,
BorrowKind::Mut { allow_two_phase_borrow: false },
tcx.mk_place_deref(dropee_ptr),
);
let ref_ty = reborrow.ty(body.local_decls(), tcx);
dropee_ptr = body.local_decls.push(LocalDecl::new(ref_ty, span)).into();
let new_statements = [
StatementKind::Assign(Box::new((dropee_ptr, reborrow))),
StatementKind::Retag(RetagKind::FnEntry, Box::new(dropee_ptr)),
];
for s in new_statements {
body.basic_blocks_mut()[START_BLOCK]
.statements
.push(Statement { source_info, kind: s });
}
}
let patch = {
let param_env = tcx.param_env_reveal_all_normalized(def_id);
let mut elaborator =