Subpart11 for async drop (major5) - shims codegen

Author: azhogin

compiler/rustc_mir_transform/src/shim.rs

@@ -6,14 +6,15 @@ use rustc_hir::def_id::DefId;
 use rustc_hir::lang_items::LangItem;
 use rustc_index::{Idx, IndexVec};
 use rustc_middle::mir::patch::MirPatch;
+use rustc_middle::mir::visit::{MutVisitor, PlaceContext};
 use rustc_middle::mir::*;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{
     self, CoroutineArgs, CoroutineArgsExt, EarlyBinder, GenericArgs, Ty, TyCtxt,
 };
 use rustc_middle::{bug, span_bug};
 use rustc_mir_dataflow::elaborate_drops::{self, DropElaborator, DropFlagMode, DropStyle};
-use rustc_span::source_map::Spanned;
+use rustc_span::source_map::{dummy_spanned, Spanned};
 use rustc_span::{Span, DUMMY_SP};
 use rustc_target::abi::{FieldIdx, VariantIdx, FIRST_VARIANT};
 use rustc_target::spec::abi::Abi;
@@ -24,10 +25,46 @@ use crate::{
     instsimplify, mentioned_items, pass_manager as pm, remove_noop_landing_pads, simplify,
 };
 
+mod async_destructor_ctor;
+
 pub fn provide(providers: &mut Providers) {
     providers.mir_shims = make_shim;
 }
 
+// Replace Pin<&mut ImplCoroutine> accesses (_1.0) into Pin<&mut ProxyCoroutine> acceses
+struct FixProxyFutureDropVisitor<'tcx> {
+    tcx: TyCtxt<'tcx>,
+    replace_to: Local,
+}
+
+impl<'tcx> MutVisitor<'tcx> for FixProxyFutureDropVisitor<'tcx> {
+    fn tcx(&self) -> TyCtxt<'tcx> {
+        self.tcx
+    }
+
+    fn visit_place(
+        &mut self,
+        place: &mut Place<'tcx>,
+        _context: PlaceContext,
+        _location: Location,
+    ) {
+        if place.local == Local::from_u32(1) {
+            if place.projection.len() == 1 {
+                assert!(matches!(
+                    place.projection.first(),
+                    Some(ProjectionElem::Field(FieldIdx::ZERO, _))
+                ));
+                *place = Place::from(self.replace_to);
+            } else if place.projection.len() == 2 {
+                assert!(matches!(place.projection[0], ProjectionElem::Field(FieldIdx::ZERO, _)));
+                assert!(matches!(place.projection[1], ProjectionElem::Deref));
+                *place =
+                    Place::from(self.replace_to).project_deeper(&[ProjectionElem::Deref], self.tcx);
+            }
+        }
+    }
+}
+
 fn make_shim<'tcx>(tcx: TyCtxt<'tcx>, instance: ty::InstanceKind<'tcx>) -> Body<'tcx> {
     debug!("make_shim({:?})", instance);
 
@@ -127,14 +164,218 @@ fn make_shim<'tcx>(tcx: TyCtxt<'tcx>, instance: ty::InstanceKind<'tcx>) -> Body<
         ty::InstanceKind::ThreadLocalShim(..) => build_thread_local_shim(tcx, instance),
         ty::InstanceKind::CloneShim(def_id, ty) => build_clone_shim(tcx, def_id, ty),
         ty::InstanceKind::FnPtrAddrShim(def_id, ty) => build_fn_ptr_addr_shim(tcx, def_id, ty),
-        ty::InstanceKind::FutureDropPollShim(_def_id, _proxy_ty, _impl_ty) => {
-            todo!()
+        ty::InstanceKind::FutureDropPollShim(def_id, proxy_ty, impl_ty) => {
+            let ty::Coroutine(coroutine_def_id, impl_args) = impl_ty.kind() else {
+                bug!("FutureDropPollShim not for coroutine impl type: ({:?})", instance);
+            };
+
+            let span = tcx.def_span(def_id);
+            let source_info = SourceInfo::outermost(span);
+
+            let pin_proxy_layout_local = Local::new(1);
+            let cor_ref = Ty::new_mut_ref(tcx, tcx.lifetimes.re_erased, impl_ty);
+            let proxy_ref = Ty::new_mut_ref(tcx, tcx.lifetimes.re_erased, proxy_ty);
+            // taking _1.0.0 (impl from Pin, impl from proxy)
+            let proxy_ref_place = Place::from(pin_proxy_layout_local)
+                .project_deeper(&[PlaceElem::Field(FieldIdx::ZERO, proxy_ref)], tcx);
+            let impl_ref_place = |proxy_ref_local: Local| {
+                Place::from(proxy_ref_local).project_deeper(
+                    &[
+                        PlaceElem::Deref,
+                        PlaceElem::Downcast(None, VariantIdx::ZERO),
+                        PlaceElem::Field(FieldIdx::ZERO, cor_ref),
+                    ],
+                    tcx,
+                )
+            };
+
+            if tcx.is_templated_coroutine(*coroutine_def_id) {
+                // ret_ty = `Poll<()>`
+                let poll_adt_ref = tcx.adt_def(tcx.require_lang_item(LangItem::Poll, None));
+                let ret_ty = Ty::new_adt(tcx, poll_adt_ref, tcx.mk_args(&[tcx.types.unit.into()]));
+                // env_ty = `Pin<&mut proxy_ty>`
+                let pin_adt_ref = tcx.adt_def(tcx.require_lang_item(LangItem::Pin, None));
+                let env_ty = Ty::new_adt(tcx, pin_adt_ref, tcx.mk_args(&[proxy_ref.into()]));
+                // sig = `fn (Pin<&mut proxy_ty>, &mut Context) -> Poll<()>`
+                let sig = tcx.mk_fn_sig(
+                    [env_ty, Ty::new_task_context(tcx)],
+                    ret_ty,
+                    false,
+                    hir::Safety::Safe,
+                    rustc_target::spec::abi::Abi::Rust,
+                );
+                let mut locals = local_decls_for_sig(&sig, span);
+                let mut blocks = IndexVec::with_capacity(3);
+
+                let proxy_ref_local = locals.push(LocalDecl::new(proxy_ref, span));
+                let cor_ref_local = locals.push(LocalDecl::new(cor_ref, span));
+                let cor_ref_place = Place::from(cor_ref_local);
+
+                let call_bb = BasicBlock::new(1);
+                let return_bb = BasicBlock::new(2);
+
+                let assign1 = Statement {
+                    source_info,
+                    kind: StatementKind::Assign(Box::new((
+                        Place::from(proxy_ref_local),
+                        Rvalue::CopyForDeref(proxy_ref_place),
+                    ))),
+                };
+                let assign2 = Statement {
+                    source_info,
+                    kind: StatementKind::Assign(Box::new((
+                        cor_ref_place,
+                        Rvalue::CopyForDeref(impl_ref_place(proxy_ref_local)),
+                    ))),
+                };
+
+                // cor_pin_ty = `Pin<&mut cor_ref>`
+                let cor_pin_ty = Ty::new_adt(tcx, pin_adt_ref, tcx.mk_args(&[cor_ref.into()]));
+                let cor_pin_place = Place::from(locals.push(LocalDecl::new(cor_pin_ty, span)));
+
+                let pin_fn = tcx.require_lang_item(LangItem::PinNewUnchecked, Some(span));
+                // call Pin<FutTy>::new_unchecked(&mut impl_cor)
+                blocks.push(BasicBlockData {
+                    statements: vec![assign1, assign2],
+                    terminator: Some(Terminator {
+                        source_info,
+                        kind: TerminatorKind::Call {
+                            func: Operand::function_handle(tcx, pin_fn, [cor_ref.into()], span),
+                            args: [dummy_spanned(Operand::Move(cor_ref_place))].into(),
+                            destination: cor_pin_place,
+                            target: Some(call_bb),
+                            unwind: UnwindAction::Continue,
+                            call_source: CallSource::Misc,
+                            fn_span: span,
+                        },
+                    }),
+                    is_cleanup: false,
+                });
+                // When dropping async drop coroutine, we continue its execution:
+                // we call impl::poll (impl_layout, ctx)
+                let poll_fn = tcx.require_lang_item(LangItem::FuturePoll, None);
+                let resume_ctx = Place::from(Local::new(2));
+                blocks.push(BasicBlockData {
+                    statements: vec![],
+                    terminator: Some(Terminator {
+                        source_info,
+                        kind: TerminatorKind::Call {
+                            func: Operand::function_handle(tcx, poll_fn, [impl_ty.into()], span),
+                            args: [
+                                dummy_spanned(Operand::Move(cor_pin_place)),
+                                dummy_spanned(Operand::Move(resume_ctx)),
+                            ]
+                            .into(),
+                            destination: Place::return_place(),
+                            target: Some(return_bb),
+                            unwind: UnwindAction::Continue,
+                            call_source: CallSource::Misc,
+                            fn_span: span,
+                        },
+                    }),
+                    is_cleanup: false,
+                });
+                blocks.push(BasicBlockData {
+                    statements: vec![],
+                    terminator: Some(Terminator { source_info, kind: TerminatorKind::Return }),
+                    is_cleanup: false,
+                });
+
+                let source = MirSource::from_instance(instance);
+                let mut body = new_body(source, blocks, locals, sig.inputs().len(), span);
+                pm::run_passes(
+                    tcx,
+                    &mut body,
+                    &[
+                        &mentioned_items::MentionedItems,
+                        &abort_unwinding_calls::AbortUnwindingCalls,
+                        &add_call_guards::CriticalCallEdges,
+                    ],
+                    Some(MirPhase::Runtime(RuntimePhase::Optimized)),
+                );
+                return body;
+            }
+            // future drop poll for async drop must be resolved to standart poll (AsyncDropGlue)
+            assert!(!tcx.is_templated_coroutine(*coroutine_def_id));
+
+            // converting `(_1: Pin<&mut CorLayout>, _2: &mut Context<'_>) -> Poll<()>`
+            // into `(_1: Pin<&mut ProxyLayout>, _2: &mut Context<'_>) -> Poll<()>`
+            // let mut _x: &mut CorLayout = &*_1.0.0;
+            // Replace old _1.0 accesses into _x accesses;
+            let body = tcx.optimized_mir(*coroutine_def_id).future_drop_poll().unwrap();
+            let mut body: Body<'tcx> = EarlyBinder::bind(body.clone()).instantiate(tcx, impl_args);
+            body.source.instance = instance;
+            body.var_debug_info.clear();
+            let pin_adt_ref = tcx.adt_def(tcx.require_lang_item(LangItem::Pin, Some(span)));
+            let args = tcx.mk_args(&[proxy_ref.into()]);
+            let pin_proxy_ref = Ty::new_adt(tcx, pin_adt_ref, args);
+
+            let proxy_ref_local = body.local_decls.push(LocalDecl::new(proxy_ref, span));
+            let cor_ref_local = body.local_decls.push(LocalDecl::new(cor_ref, span));
+            FixProxyFutureDropVisitor { tcx, replace_to: cor_ref_local }.visit_body(&mut body);
+            // Now changing first arg from Pin<&mut ImplCoroutine> to Pin<&mut ProxyCoroutine>
+            body.local_decls[pin_proxy_layout_local] = LocalDecl::new(pin_proxy_ref, span);
+
+            {
+                let bb: &mut BasicBlockData<'tcx> = &mut body.basic_blocks_mut()[START_BLOCK];
+                // _tmp = _1.0 : Pin<&ProxyLayout> ==> &ProxyLayout
+                bb.statements.insert(
+                    0,
+                    Statement {
+                        source_info,
+                        kind: StatementKind::Assign(Box::new((
+                            Place::from(proxy_ref_local),
+                            Rvalue::CopyForDeref(proxy_ref_place),
+                        ))),
+                    },
+                );
+                bb.statements.insert(
+                    1,
+                    Statement {
+                        source_info,
+                        kind: StatementKind::Assign(Box::new((
+                            Place::from(cor_ref_local),
+                            Rvalue::CopyForDeref(impl_ref_place(proxy_ref_local)),
+                        ))),
+                    },
+                );
+            }
+
+            pm::run_passes(
+                tcx,
+                &mut body,
+                &[
+                    &mentioned_items::MentionedItems,
+                    &abort_unwinding_calls::AbortUnwindingCalls,
+                    &add_call_guards::CriticalCallEdges,
+                ],
+                Some(MirPhase::Runtime(RuntimePhase::Optimized)),
+            );
+            debug!("make_shim({:?}) = {:?}", instance, body);
+            return body;
         }
-        ty::InstanceKind::AsyncDropGlue(_def_id, _ty) => {
-            todo!()
+        ty::InstanceKind::AsyncDropGlue(def_id, ty) => {
+            let mut body = async_destructor_ctor::build_async_drop_shim(tcx, def_id, ty);
+
+            pm::run_passes(
+                tcx,
+                &mut body,
+                &[
+                    &mentioned_items::MentionedItems,
+                    &simplify::SimplifyCfg::MakeShim,
+                    &crate::reveal_all::RevealAll,
+                    &crate::coroutine::StateTransform,
+                ],
+                Some(MirPhase::Runtime(RuntimePhase::PostCleanup)),
+            );
+            debug!("make_shim({:?}) = {:?}", instance, body);
+            return body;
         }
-        ty::InstanceKind::AsyncDropGlueCtorShim(_def_id, _ty) => {
-            bug!("AsyncDropGlueCtorShim in re-working ({:?})", instance)
+
+        ty::InstanceKind::AsyncDropGlueCtorShim(def_id, ty) => {
+            let body = async_destructor_ctor::build_async_destructor_ctor_shim(tcx, def_id, ty);
+            debug!("make_shim({:?}) = {:?}", instance, body);
+            return body;
         }
         ty::InstanceKind::Virtual(..) => {
             bug!("InstanceKind::Virtual ({:?}) is for direct calls only", instance)