bjoernager/rust
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Do not create move paths that do not need dropping.

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This commit is contained in:
Camille GILLOT 2023-09-30 21:42:49 +00:00
parent f038882fc0
commit c9c0c0cbca
5 changed files with 64 additions and 60 deletions
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17
compiler/rustc_mir_transform/src/elaborate_drops.rs
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@ -54,7 +54,10 @@ impl<'tcx> MirPass<'tcx> for ElaborateDrops {
let def_id = body.source.def_id();
let param_env = tcx.param_env_reveal_all_normalized(def_id);
let move_data = MoveData::gather_moves(&body, tcx, param_env, |_| true);
// For types that do not need dropping, the behaviour is trivial. So we only need to track
// init/uninit for types that do need dropping.
let move_data =
MoveData::gather_moves(&body, tcx, param_env, |ty| ty.needs_drop(tcx, param_env));
let elaborate_patch = {
let env = MoveDataParamEnv { move_data, param_env };
@ -338,6 +341,18 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
continue;
};
// This place does not need dropping. It is not have an associated move-path, so the
// match below will conservatively keep an unconditional drop. As that drop is useless,
// just remove it here and now.
if !place
.ty(&self.body.local_decls, self.tcx)
.ty
.needs_drop(self.tcx, self.env.param_env)
{
self.patch.patch_terminator(bb, TerminatorKind::Goto { target });
continue;
}
let path = self.move_data().rev_lookup.find(place.as_ref());
match path {
LookupResult::Exact(path) => {