Only load pin field once.

Author: cjgillot

compiler/rustc_mir_transform/src/coroutine.rs

@@ -133,8 +133,8 @@ struct SelfArgVisitor<'tcx> {
 }
 
 impl<'tcx> SelfArgVisitor<'tcx> {
-    fn new(tcx: TyCtxt<'tcx>, elem: ProjectionElem<Local, Ty<'tcx>>) -> Self {
-        Self { tcx, new_base: Place { local: SELF_ARG, projection: tcx.mk_place_elems(&[elem]) } }
+    fn new(tcx: TyCtxt<'tcx>, new_base: Place<'tcx>) -> Self {
+        Self { tcx, new_base }
     }
 }
 
@@ -147,16 +147,14 @@ impl<'tcx> MutVisitor<'tcx> for SelfArgVisitor<'tcx> {
         assert_ne!(*local, SELF_ARG);
     }
 
-    fn visit_place(&mut self, place: &mut Place<'tcx>, context: PlaceContext, location: Location) {
+    fn visit_place(&mut self, place: &mut Place<'tcx>, _: PlaceContext, _: Location) {
         if place.local == SELF_ARG {
             replace_base(place, self.new_base, self.tcx);
-        } else {
-            self.visit_local(&mut place.local, context, location);
+        }
 
-            for elem in place.projection.iter() {
-                if let PlaceElem::Index(local) = elem {
-                    assert_ne!(local, SELF_ARG);
-                }
+        for elem in place.projection.iter() {
+            if let PlaceElem::Index(local) = elem {
+                assert_ne!(local, SELF_ARG);
             }
         }
     }
@@ -516,32 +514,51 @@ fn make_aggregate_adt<'tcx>(
 
 #[tracing::instrument(level = "trace", skip(tcx, body))]
 fn make_coroutine_state_argument_indirect<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
-    let coroutine_ty = body.local_decls.raw[1].ty;
+    let coroutine_ty = body.local_decls[SELF_ARG].ty;
 
     let ref_coroutine_ty = Ty::new_mut_ref(tcx, tcx.lifetimes.re_erased, coroutine_ty);
 
     // Replace the by value coroutine argument
-    body.local_decls.raw[1].ty = ref_coroutine_ty;
+    body.local_decls[SELF_ARG].ty = ref_coroutine_ty;
 
     // Add a deref to accesses of the coroutine state
-    SelfArgVisitor::new(tcx, ProjectionElem::Deref).visit_body(body);
+    SelfArgVisitor::new(tcx, tcx.mk_place_deref(SELF_ARG.into())).visit_body(body);
 }
 
 #[tracing::instrument(level = "trace", skip(tcx, body))]
 fn make_coroutine_state_argument_pinned<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
-    let ref_coroutine_ty = body.local_decls.raw[1].ty;
+    let coroutine_ty = body.local_decls[SELF_ARG].ty;
+
+    let ref_coroutine_ty = Ty::new_mut_ref(tcx, tcx.lifetimes.re_erased, coroutine_ty);
 
     let pin_did = tcx.require_lang_item(LangItem::Pin, body.span);
     let pin_adt_ref = tcx.adt_def(pin_did);
     let args = tcx.mk_args(&[ref_coroutine_ty.into()]);
     let pin_ref_coroutine_ty = Ty::new_adt(tcx, pin_adt_ref, args);
 
     // Replace the by ref coroutine argument
-    body.local_decls.raw[1].ty = pin_ref_coroutine_ty;
+    body.local_decls[SELF_ARG].ty = pin_ref_coroutine_ty;
+
+    let unpinned_local = body.local_decls.push(LocalDecl::new(ref_coroutine_ty, body.span));
 
     // Add the Pin field access to accesses of the coroutine state
-    SelfArgVisitor::new(tcx, ProjectionElem::Field(FieldIdx::ZERO, ref_coroutine_ty))
-        .visit_body(body);
+    SelfArgVisitor::new(tcx, tcx.mk_place_deref(unpinned_local.into())).visit_body(body);
+
+    let source_info = SourceInfo::outermost(body.span);
+    body.basic_blocks_mut()[START_BLOCK].statements.insert(
+        0,
+        Statement::new(
+            source_info,
+            StatementKind::Assign(Box::new((
+                unpinned_local.into(),
+                Rvalue::CopyForDeref(tcx.mk_place_field(
+                    SELF_ARG.into(),
+                    FieldIdx::ZERO,
+                    ref_coroutine_ty,
+                )),
+            ))),
+        ),
+    );
 }
 
 /// Transforms the `body` of the coroutine applying the following transforms:
@@ -1293,8 +1310,6 @@ fn create_coroutine_resume_function<'tcx>(
     let default_block = insert_term_block(body, TerminatorKind::Unreachable);
     insert_switch(body, cases, &transform, default_block);
 
-    make_coroutine_state_argument_indirect(tcx, body);
-
     match transform.coroutine_kind {
         CoroutineKind::Coroutine(_)
         | CoroutineKind::Desugared(CoroutineDesugaring::Async | CoroutineDesugaring::AsyncGen, _) =>
@@ -1303,7 +1318,9 @@ fn create_coroutine_resume_function<'tcx>(
         }
         // Iterator::next doesn't accept a pinned argument,
         // unlike for all other coroutine kinds.
-        CoroutineKind::Desugared(CoroutineDesugaring::Gen, _) => {}
+        CoroutineKind::Desugared(CoroutineDesugaring::Gen, _) => {
+            make_coroutine_state_argument_indirect(tcx, body);
+        }
     }
 }
 

compiler/rustc_mir_transform/src/coroutine/drop.rs

@@ -685,12 +685,13 @@ pub(super) fn create_coroutine_drop_shim_async<'tcx>(
     let poll_enum = Ty::new_adt(tcx, poll_adt_ref, tcx.mk_args(&[tcx.types.unit.into()]));
     body.local_decls[RETURN_PLACE] = LocalDecl::with_source_info(poll_enum, source_info);
 
-    make_coroutine_state_argument_indirect(tcx, &mut body);
-
     match transform.coroutine_kind {
         // Iterator::next doesn't accept a pinned argument,
         // unlike for all other coroutine kinds.
-        CoroutineKind::Desugared(CoroutineDesugaring::Gen, _) => {}
+        CoroutineKind::Desugared(CoroutineDesugaring::Gen, _) => {
+            make_coroutine_state_argument_indirect(tcx, &mut body);
+        }
+
         _ => {
             make_coroutine_state_argument_pinned(tcx, &mut body);
         }

tests/mir-opt/async_drop_live_dead.a-{closure#0}.coroutine_drop_async.0.panic-abort.mir

@@ -2,7 +2,7 @@
 
 fn a::{closure#0}(_1: Pin<&mut {async fn body of a<T>()}>, _2: &mut Context<'_>) -> Poll<()> {
     debug _task_context => _2;
-    debug x => ((*(_1.0: &mut {async fn body of a<T>()})).0: T);
+    debug x => ((*_20).0: T);
     let mut _0: std::task::Poll<()>;
     let _3: T;
     let mut _4: impl std::future::Future<Output = ()>;
@@ -21,12 +21,14 @@ fn a::{closure#0}(_1: Pin<&mut {async fn body of a<T>()}>, _2: &mut Context<'_>)
     let mut _17: isize;
     let mut _18: ();
     let mut _19: u32;
+    let mut _20: &mut {async fn body of a<T>()};
     scope 1 {
-        debug x => (((*(_1.0: &mut {async fn body of a<T>()})) as variant#4).0: T);
+        debug x => (((*_20) as variant#4).0: T);
     }
 
     bb0: {
-        _19 = discriminant((*(_1.0: &mut {async fn body of a<T>()})));
+        _20 = deref_copy (_1.0: &mut {async fn body of a<T>()});
+        _19 = discriminant((*_20));
         switchInt(move _19) -> [0: bb8, 3: bb11, 4: bb12, otherwise: bb13];
     }
 
@@ -39,13 +41,13 @@ fn a::{closure#0}(_1: Pin<&mut {async fn body of a<T>()}>, _2: &mut Context<'_>)
 
     bb2: {
         _0 = Poll::<()>::Pending;
-        discriminant((*(_1.0: &mut {async fn body of a<T>()}))) = 4;
+        discriminant((*_20)) = 4;
         return;
     }
 
     bb3: {
         StorageLive(_16);
-        _15 = &mut (((*(_1.0: &mut {async fn body of a<T>()})) as variant#4).1: impl std::future::Future<Output = ()>);
+        _15 = &mut (((*_20) as variant#4).1: impl std::future::Future<Output = ()>);
         _16 = Pin::<&mut impl Future<Output = ()>>::new_unchecked(move _15) -> [return: bb6, unwind unreachable];
     }
 
@@ -77,7 +79,7 @@ fn a::{closure#0}(_1: Pin<&mut {async fn body of a<T>()}>, _2: &mut Context<'_>)
     }
 
     bb10: {
-        drop(((*(_1.0: &mut {async fn body of a<T>()})).0: T)) -> [return: bb9, unwind unreachable];
+        drop(((*_20).0: T)) -> [return: bb9, unwind unreachable];
     }
 
     bb11: {

tests/mir-opt/async_drop_live_dead.a-{closure#0}.coroutine_drop_async.0.panic-unwind.mir

@@ -2,7 +2,7 @@
 
 fn a::{closure#0}(_1: Pin<&mut {async fn body of a<T>()}>, _2: &mut Context<'_>) -> Poll<()> {
     debug _task_context => _2;
-    debug x => ((*(_1.0: &mut {async fn body of a<T>()})).0: T);
+    debug x => ((*_20).0: T);
     let mut _0: std::task::Poll<()>;
     let _3: T;
     let mut _4: impl std::future::Future<Output = ()>;
@@ -21,12 +21,14 @@ fn a::{closure#0}(_1: Pin<&mut {async fn body of a<T>()}>, _2: &mut Context<'_>)
     let mut _17: isize;
     let mut _18: ();
     let mut _19: u32;
+    let mut _20: &mut {async fn body of a<T>()};
     scope 1 {
-        debug x => (((*(_1.0: &mut {async fn body of a<T>()})) as variant#4).0: T);
+        debug x => (((*_20) as variant#4).0: T);
     }
 
     bb0: {
-        _19 = discriminant((*(_1.0: &mut {async fn body of a<T>()})));
+        _20 = deref_copy (_1.0: &mut {async fn body of a<T>()});
+        _19 = discriminant((*_20));
         switchInt(move _19) -> [0: bb8, 2: bb15, 3: bb13, 4: bb14, otherwise: bb16];
     }
 
@@ -39,13 +41,13 @@ fn a::{closure#0}(_1: Pin<&mut {async fn body of a<T>()}>, _2: &mut Context<'_>)
 
     bb2: {
         _0 = Poll::<()>::Pending;
-        discriminant((*(_1.0: &mut {async fn body of a<T>()}))) = 4;
+        discriminant((*_20)) = 4;
         return;
     }
 
     bb3: {
         StorageLive(_16);
-        _15 = &mut (((*(_1.0: &mut {async fn body of a<T>()})) as variant#4).1: impl std::future::Future<Output = ()>);
+        _15 = &mut (((*_20) as variant#4).1: impl std::future::Future<Output = ()>);
         _16 = Pin::<&mut impl Future<Output = ()>>::new_unchecked(move _15) -> [return: bb6, unwind: bb12];
     }
 
@@ -81,11 +83,11 @@ fn a::{closure#0}(_1: Pin<&mut {async fn body of a<T>()}>, _2: &mut Context<'_>)
     }
 
     bb11: {
-        drop(((*(_1.0: &mut {async fn body of a<T>()})).0: T)) -> [return: bb10, unwind: bb9];
+        drop(((*_20).0: T)) -> [return: bb10, unwind: bb9];
     }
 
     bb12 (cleanup): {
-        discriminant((*(_1.0: &mut {async fn body of a<T>()}))) = 2;
+        discriminant((*_20)) = 2;
         resume;
     }
 

tests/mir-opt/building/async_await.a-{closure#0}.coroutine_resume.0.mir

@@ -14,9 +14,11 @@ fn a::{closure#0}(_1: Pin<&mut {async fn body of a()}>, _2: &mut Context<'_>) ->
     let mut _0: std::task::Poll<()>;
     let mut _3: ();
     let mut _4: u32;
+    let mut _5: &mut {async fn body of a()};
 
     bb0: {
-        _4 = discriminant((*(_1.0: &mut {async fn body of a()})));
+        _5 = deref_copy (_1.0: &mut {async fn body of a()});
+        _4 = discriminant((*_5));
         switchInt(move _4) -> [0: bb1, 1: bb9, otherwise: bb10];
     }
 
@@ -27,7 +29,7 @@ fn a::{closure#0}(_1: Pin<&mut {async fn body of a()}>, _2: &mut Context<'_>) ->
 
     bb2: {
         _0 = Poll::<()>::Ready(move _3);
-        discriminant((*(_1.0: &mut {async fn body of a()}))) = 1;
+        discriminant((*_5)) = 1;
         return;
     }
 

tests/mir-opt/building/async_await.b-{closure#0}.coroutine_resume.0.mir

@@ -86,23 +86,25 @@ fn b::{closure#0}(_1: Pin<&mut {async fn body of b()}>, _2: &mut Context<'_>) ->
     let mut _36: ();
     let mut _37: ();
     let mut _38: u32;
+    let mut _39: &mut {async fn body of b()};
     scope 1 {
-        debug __awaitee => (((*(_1.0: &mut {async fn body of b()})) as variant#3).0: {async fn body of a()});
+        debug __awaitee => (((*_39) as variant#3).0: {async fn body of a()});
         let _17: ();
         scope 2 {
             debug result => _17;
         }
     }
     scope 3 {
-        debug __awaitee => (((*(_1.0: &mut {async fn body of b()})) as variant#4).0: {async fn body of a()});
+        debug __awaitee => (((*_39) as variant#4).0: {async fn body of a()});
         let _33: ();
         scope 4 {
             debug result => _33;
         }
     }
 
     bb0: {
-        _38 = discriminant((*(_1.0: &mut {async fn body of b()})));
+        _39 = deref_copy (_1.0: &mut {async fn body of b()});
+        _38 = discriminant((*_39));
         switchInt(move _38) -> [0: bb1, 1: bb39, 3: bb37, 4: bb38, otherwise: bb40];
     }
 
@@ -120,7 +122,7 @@ fn b::{closure#0}(_1: Pin<&mut {async fn body of b()}>, _2: &mut Context<'_>) ->
     bb3: {
         StorageDead(_5);
         nop;
-        (((*(_1.0: &mut {async fn body of b()})) as variant#3).0: {async fn body of a()}) = move _4;
+        (((*_39) as variant#3).0: {async fn body of a()}) = move _4;
         goto -> bb4;
     }
 
@@ -130,7 +132,7 @@ fn b::{closure#0}(_1: Pin<&mut {async fn body of b()}>, _2: &mut Context<'_>) ->
         StorageLive(_10);
         StorageLive(_11);
         StorageLive(_12);
-        _12 = &mut (((*(_1.0: &mut {async fn body of b()})) as variant#3).0: {async fn body of a()});
+        _12 = &mut (((*_39) as variant#3).0: {async fn body of a()});
         _11 = &mut (*_12);
         _10 = Pin::<&mut {async fn body of a()}>::new_unchecked(move _11) -> [return: bb5, unwind unreachable];
     }
@@ -176,7 +178,7 @@ fn b::{closure#0}(_1: Pin<&mut {async fn body of b()}>, _2: &mut Context<'_>) ->
         StorageDead(_4);
         StorageDead(_19);
         StorageDead(_20);
-        discriminant((*(_1.0: &mut {async fn body of b()}))) = 3;
+        discriminant((*_39)) = 3;
         return;
     }
 
@@ -189,7 +191,7 @@ fn b::{closure#0}(_1: Pin<&mut {async fn body of b()}>, _2: &mut Context<'_>) ->
         StorageDead(_12);
         StorageDead(_9);
         StorageDead(_8);
-        drop((((*(_1.0: &mut {async fn body of b()})) as variant#3).0: {async fn body of a()})) -> [return: bb12, unwind unreachable];
+        drop((((*_39) as variant#3).0: {async fn body of a()})) -> [return: bb12, unwind unreachable];
     }
 
     bb11: {
@@ -216,7 +218,7 @@ fn b::{closure#0}(_1: Pin<&mut {async fn body of b()}>, _2: &mut Context<'_>) ->
     bb14: {
         StorageDead(_22);
         nop;
-        (((*(_1.0: &mut {async fn body of b()})) as variant#4).0: {async fn body of a()}) = move _21;
+        (((*_39) as variant#4).0: {async fn body of a()}) = move _21;
         goto -> bb15;
     }
 
@@ -226,7 +228,7 @@ fn b::{closure#0}(_1: Pin<&mut {async fn body of b()}>, _2: &mut Context<'_>) ->
         StorageLive(_26);
         StorageLive(_27);
         StorageLive(_28);
-        _28 = &mut (((*(_1.0: &mut {async fn body of b()})) as variant#4).0: {async fn body of a()});
+        _28 = &mut (((*_39) as variant#4).0: {async fn body of a()});
         _27 = &mut (*_28);
         _26 = Pin::<&mut {async fn body of a()}>::new_unchecked(move _27) -> [return: bb16, unwind unreachable];
     }
@@ -267,7 +269,7 @@ fn b::{closure#0}(_1: Pin<&mut {async fn body of b()}>, _2: &mut Context<'_>) ->
         StorageDead(_21);
         StorageDead(_35);
         StorageDead(_36);
-        discriminant((*(_1.0: &mut {async fn body of b()}))) = 4;
+        discriminant((*_39)) = 4;
         return;
     }
 
@@ -280,7 +282,7 @@ fn b::{closure#0}(_1: Pin<&mut {async fn body of b()}>, _2: &mut Context<'_>) ->
         StorageDead(_28);
         StorageDead(_25);
         StorageDead(_24);
-        drop((((*(_1.0: &mut {async fn body of b()})) as variant#4).0: {async fn body of a()})) -> [return: bb22, unwind unreachable];
+        drop((((*_39) as variant#4).0: {async fn body of a()})) -> [return: bb22, unwind unreachable];
     }
 
     bb21: {
@@ -299,14 +301,14 @@ fn b::{closure#0}(_1: Pin<&mut {async fn body of b()}>, _2: &mut Context<'_>) ->
 
     bb23: {
         _0 = Poll::<()>::Ready(move _37);
-        discriminant((*(_1.0: &mut {async fn body of b()}))) = 1;
+        discriminant((*_39)) = 1;
         return;
     }
 
     bb24: {
         StorageDead(_36);
         StorageDead(_35);
-        drop((((*(_1.0: &mut {async fn body of b()})) as variant#4).0: {async fn body of a()})) -> [return: bb25, unwind unreachable];
+        drop((((*_39) as variant#4).0: {async fn body of a()})) -> [return: bb25, unwind unreachable];
     }
 
     bb25: {
@@ -318,7 +320,7 @@ fn b::{closure#0}(_1: Pin<&mut {async fn body of b()}>, _2: &mut Context<'_>) ->
     bb26: {
         StorageDead(_20);
         StorageDead(_19);
-        drop((((*(_1.0: &mut {async fn body of b()})) as variant#3).0: {async fn body of a()})) -> [return: bb27, unwind unreachable];
+        drop((((*_39) as variant#3).0: {async fn body of a()})) -> [return: bb27, unwind unreachable];
     }
 
     bb27: {