rustc_mir: add a pass for splitting locals into their fields (aka SROA).

Author: eddyb

src/librustc_mir/transform/mod.rs

@@ -45,6 +45,7 @@ pub mod generator;
 pub mod inline;
 pub mod lower_128bit;
 pub mod uniform_array_move_out;
+pub mod split_local_fields;
 
 pub(crate) fn provide(providers: &mut Providers) {
     self::qualify_consts::provide(providers);
@@ -265,6 +266,7 @@ fn optimized_mir<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> &'tcx
 
         instcombine::InstCombine,
         deaggregator::Deaggregator,
+        split_local_fields::SplitLocalFields,
         copy_prop::CopyPropagation,
         remove_noop_landing_pads::RemoveNoopLandingPads,
         simplify::SimplifyCfg::new("final"),