remove unnecessary and ineffective caching

Author: erikdesjardins

compiler/rustc_mir/src/transform/remove_zsts.rs

@@ -1,7 +1,6 @@
 //! Removes assignments to ZST places.
 
 use crate::transform::MirPass;
-use rustc_data_structures::fx::FxHashMap;
 use rustc_middle::mir::{Body, StatementKind};
 use rustc_middle::ty::TyCtxt;
 
@@ -10,35 +9,23 @@ pub struct RemoveZsts;
 impl<'tcx> MirPass<'tcx> for RemoveZsts {
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         let param_env = tcx.param_env(body.source.def_id());
-
         let (basic_blocks, local_decls) = body.basic_blocks_and_local_decls_mut();
-
-        let mut is_zst_cache = FxHashMap::default();
-
         for block in basic_blocks.iter_mut() {
             for statement in block.statements.iter_mut() {
                 match statement.kind {
                     StatementKind::Assign(box (place, _)) => {
                         let place_ty = place.ty(local_decls, tcx).ty;
-
-                        let is_inhabited_zst = *is_zst_cache.entry(place_ty).or_insert_with(|| {
-                            if let Ok(layout) = tcx.layout_of(param_env.and(place_ty)) {
-                                if layout.is_zst() && !layout.abi.is_uninhabited() {
-                                    return true;
+                        if let Ok(layout) = tcx.layout_of(param_env.and(place_ty)) {
+                            if layout.is_zst() && !layout.abi.is_uninhabited() {
+                                if tcx.consider_optimizing(|| {
+                                    format!(
+                                        "RemoveZsts - Place: {:?} SourceInfo: {:?}",
+                                        place, statement.source_info
+                                    )
+                                }) {
+                                    statement.make_nop();
                                 }
                             }
-                            false
-                        });
-
-                        if is_inhabited_zst {
-                            if tcx.consider_optimizing(|| {
-                                format!(
-                                    "RemoveZsts - Place: {:?} SourceInfo: {:?}",
-                                    place, statement.source_info
-                                )
-                            }) {
-                                statement.make_nop();
-                            }
                         }
                     }
                     _ => {}