Remove on_all_drop_children_bits.

As drop elaboration only tracks places that need dropping, is has become
equivalent to `on_all_children_bits`.

Author: cjgillot

Diff for: compiler/rustc_mir_dataflow/src/drop_flag_effects.rs

@@ -75,29 +75,6 @@ pub fn on_all_children_bits<'tcx, F>(
     on_all_children_bits(tcx, body, move_data, move_path_index, &mut each_child);
 }
 
-pub fn on_all_drop_children_bits<'tcx, F>(
-    tcx: TyCtxt<'tcx>,
-    body: &Body<'tcx>,
-    ctxt: &MoveDataParamEnv<'tcx>,
-    path: MovePathIndex,
-    mut each_child: F,
-) where
-    F: FnMut(MovePathIndex),
-{
-    on_all_children_bits(tcx, body, &ctxt.move_data, path, |child| {
-        let place = &ctxt.move_data.move_paths[path].place;
-        let ty = place.ty(body, tcx).ty;
-        debug!("on_all_drop_children_bits({:?}, {:?} : {:?})", path, place, ty);
-
-        let erased_ty = tcx.erase_regions(ty);
-        if erased_ty.needs_drop(tcx, ctxt.param_env) {
-            each_child(child);
-        } else {
-            debug!("on_all_drop_children_bits - skipping")
-        }
-    })
-}
-
 pub fn drop_flag_effects_for_function_entry<'tcx, F>(
     tcx: TyCtxt<'tcx>,
     body: &Body<'tcx>,

Diff for: compiler/rustc_mir_dataflow/src/impls/initialized.rs

@@ -10,7 +10,7 @@ use crate::framework::SwitchIntEdgeEffects;
 use crate::move_paths::{HasMoveData, InitIndex, InitKind, LookupResult, MoveData, MovePathIndex};
 use crate::on_lookup_result_bits;
 use crate::MoveDataParamEnv;
-use crate::{drop_flag_effects, on_all_children_bits, on_all_drop_children_bits};
+use crate::{drop_flag_effects, on_all_children_bits};
 use crate::{lattice, AnalysisDomain, GenKill, GenKillAnalysis, MaybeReachable};
 
 /// `MaybeInitializedPlaces` tracks all places that might be
@@ -72,7 +72,7 @@ impl<'a, 'tcx> MaybeInitializedPlaces<'a, 'tcx> {
     ) -> bool {
         if let LookupResult::Exact(path) = self.move_data().rev_lookup.find(place.as_ref()) {
             let mut maybe_live = false;
-            on_all_drop_children_bits(self.tcx, self.body, self.mdpe, path, |child| {
+            on_all_children_bits(self.tcx, self.body, self.move_data(), path, |child| {
                 maybe_live |= state.contains(child);
             });
             !maybe_live

Diff for: compiler/rustc_mir_dataflow/src/lib.rs

@@ -23,8 +23,7 @@ use rustc_span::symbol::{sym, Symbol};
 
 pub use self::drop_flag_effects::{
     drop_flag_effects_for_function_entry, drop_flag_effects_for_location,
-    move_path_children_matching, on_all_children_bits, on_all_drop_children_bits,
-    on_lookup_result_bits,
+    move_path_children_matching, on_all_children_bits, on_lookup_result_bits,
 };
 pub use self::framework::{
     fmt, graphviz, lattice, visit_results, Analysis, AnalysisDomain, AnalysisResults, Backward,

Diff for: compiler/rustc_mir_transform/src/elaborate_drops.rs

@@ -9,9 +9,9 @@ use rustc_mir_dataflow::elaborate_drops::{elaborate_drop, DropFlagState, Unwind}
 use rustc_mir_dataflow::elaborate_drops::{DropElaborator, DropFlagMode, DropStyle};
 use rustc_mir_dataflow::impls::{MaybeInitializedPlaces, MaybeUninitializedPlaces};
 use rustc_mir_dataflow::move_paths::{LookupResult, MoveData, MovePathIndex};
+use rustc_mir_dataflow::on_all_children_bits;
 use rustc_mir_dataflow::on_lookup_result_bits;
 use rustc_mir_dataflow::MoveDataParamEnv;
-use rustc_mir_dataflow::{on_all_children_bits, on_all_drop_children_bits};
 use rustc_mir_dataflow::{Analysis, ResultsCursor};
 use rustc_span::Span;
 use rustc_target::abi::{FieldIdx, VariantIdx};
@@ -172,13 +172,19 @@ impl<'a, 'tcx> DropElaborator<'a, 'tcx> for Elaborator<'a, '_, 'tcx> {
                 let mut some_live = false;
                 let mut some_dead = false;
                 let mut children_count = 0;
-                on_all_drop_children_bits(self.tcx(), self.body(), self.ctxt.env, path, |child| {
-                    let (live, dead) = self.ctxt.init_data.maybe_live_dead(child);
-                    debug!("elaborate_drop: state({:?}) = {:?}", child, (live, dead));
-                    some_live |= live;
-                    some_dead |= dead;
-                    children_count += 1;
-                });
+                on_all_children_bits(
+                    self.tcx(),
+                    self.body(),
+                    self.ctxt.move_data(),
+                    path,
+                    |child| {
+                        let (live, dead) = self.ctxt.init_data.maybe_live_dead(child);
+                        debug!("elaborate_drop: state({:?}) = {:?}", child, (live, dead));
+                        some_live |= live;
+                        some_dead |= dead;
+                        children_count += 1;
+                    },
+                );
                 ((some_live, some_dead), children_count != 1)
             }
         };
@@ -298,7 +304,7 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
             match path {
                 LookupResult::Exact(path) => {
                     self.init_data.seek_before(self.body.terminator_loc(bb));
-                    on_all_drop_children_bits(self.tcx, self.body, self.env, path, |child| {
+                    on_all_children_bits(self.tcx, self.body, self.move_data(), path, |child| {
                         let (maybe_live, maybe_dead) = self.init_data.maybe_live_dead(child);
                         debug!(
                             "collect_drop_flags: collecting {:?} from {:?}@{:?} - {:?}",