remove box derefs from codgen
This commit is contained in:
DrMeepster
parent
3e9d3d917a
commit
cb417881a9
16 changed files with 385 additions and 146 deletions
130
compiler/rustc_mir_transform/src/elaborate_box_derefs.rs
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130
compiler/rustc_mir_transform/src/elaborate_box_derefs.rs
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@ -0,0 +1,130 @@
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//! This pass transforms derefs of Box into a deref of the pointer inside Box
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//! Codegen does not allow box to be directly dereferenced
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use crate::MirPass;
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use rustc_hir::def_id::DefId;
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use rustc_index::vec::Idx;
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use rustc_middle::mir::patch::MirPatch;
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use rustc_middle::mir::visit::MutVisitor;
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use rustc_middle::mir::*;
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use rustc_middle::ty::subst::Subst;
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use rustc_middle::ty::TyCtxt;
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struct ElaborateBoxDerefVistor<'tcx, 'a> {
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tcx: TyCtxt<'tcx>,
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unique_did: DefId,
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nonnull_did: DefId,
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local_decls: &'a mut LocalDecls<'tcx>,
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patch: MirPatch<'tcx>,
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}
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impl<'tcx, 'a> MutVisitor<'tcx> for ElaborateBoxDerefVistor<'tcx, 'a> {
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fn tcx(&self) -> TyCtxt<'tcx> {
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self.tcx
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}
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fn visit_place(
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&mut self,
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place: &mut Place<'tcx>,
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context: visit::PlaceContext,
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location: Location,
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) {
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let tcx = self.tcx;
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let base_ty = self.local_decls[place.local].ty;
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// Derefer ensures that derefs are always the first projection
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if place.projection.first() == Some(&PlaceElem::Deref) && base_ty.is_box() {
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let source_info = self.local_decls[place.local].source_info;
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let substs = tcx.intern_substs(&[base_ty.boxed_ty().into()]);
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let unique_ty = tcx.bound_type_of(self.unique_did).subst(tcx, substs);
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let nonnull_ty = tcx.bound_type_of(self.nonnull_did).subst(tcx, substs);
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let ptr_ty = tcx.mk_imm_ptr(base_ty.boxed_ty());
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let ptr_local = self.patch.new_temp(ptr_ty, source_info.span);
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self.local_decls.push(LocalDecl::new(ptr_ty, source_info.span));
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self.patch.add_statement(location, StatementKind::StorageLive(ptr_local));
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self.patch.add_assign(
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location,
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Place::from(ptr_local),
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Rvalue::Use(Operand::Copy(Place::from(place.local).project_deeper(
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&[
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PlaceElem::Field(Field::new(0), unique_ty),
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PlaceElem::Field(Field::new(0), nonnull_ty),
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PlaceElem::Field(Field::new(0), ptr_ty),
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],
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tcx,
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))),
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);
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place.local = ptr_local;
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self.patch.add_statement(
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Location { block: location.block, statement_index: location.statement_index + 1 },
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StatementKind::StorageDead(ptr_local),
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);
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}
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self.super_place(place, context, location);
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}
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}
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pub struct ElaborateBoxDerefs;
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impl<'tcx> MirPass<'tcx> for ElaborateBoxDerefs {
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fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
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if let Some(def_id) = tcx.lang_items().owned_box() {
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let unique_did = tcx.adt_def(def_id).non_enum_variant().fields[0].did;
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let Some(nonnull_def) = tcx.type_of(unique_did).ty_adt_def() else {
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span_bug!(tcx.def_span(unique_did), "expected Box to contain Unique")
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};
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let nonnull_did = nonnull_def.non_enum_variant().fields[0].did;
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let patch = MirPatch::new(body);
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let (basic_blocks, local_decls) = body.basic_blocks_and_local_decls_mut();
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let mut visitor =
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ElaborateBoxDerefVistor { tcx, unique_did, nonnull_did, local_decls, patch };
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for (block, BasicBlockData { statements, terminator, .. }) in
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basic_blocks.iter_enumerated_mut()
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{
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let mut index = 0;
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for statement in statements {
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let location = Location { block, statement_index: index };
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visitor.visit_statement(statement, location);
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index += 1;
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}
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if let Some(terminator) = terminator
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&& !matches!(terminator.kind, TerminatorKind::Yield{..})
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{
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let location = Location { block, statement_index: index };
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visitor.visit_terminator(terminator, location);
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}
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let location = Location { block, statement_index: index };
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match terminator {
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// yielding into a box is handed when lowering generators
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Some(Terminator { kind: TerminatorKind::Yield { value, .. }, .. }) => {
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visitor.visit_operand(value, location);
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}
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Some(terminator) => {
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visitor.visit_terminator(terminator, location);
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}
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None => {}
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}
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}
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visitor.patch.apply(body);
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} else {
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// box is not present, this pass doesn't need to do anything
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}
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}
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}
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@ -56,7 +56,7 @@ use crate::MirPass;
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use rustc_data_structures::fx::FxHashMap;
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use rustc_hir as hir;
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use rustc_hir::lang_items::LangItem;
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use rustc_index::bit_set::{BitMatrix, BitSet};
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use rustc_index::bit_set::{BitMatrix, BitSet, GrowableBitSet};
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use rustc_index::vec::{Idx, IndexVec};
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use rustc_middle::mir::dump_mir;
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use rustc_middle::mir::visit::{MutVisitor, PlaceContext, Visitor};
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@ -206,7 +206,7 @@ struct SuspensionPoint<'tcx> {
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/// Which block to jump to if the generator is dropped in this state.
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drop: Option<BasicBlock>,
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/// Set of locals that have live storage while at this suspension point.
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storage_liveness: BitSet<Local>,
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storage_liveness: GrowableBitSet<Local>,
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}
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struct TransformVisitor<'tcx> {
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@ -362,7 +362,7 @@ impl<'tcx> MutVisitor<'tcx> for TransformVisitor<'tcx> {
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resume,
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resume_arg,
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drop,
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storage_liveness: self.storage_liveness[block].clone().unwrap(),
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storage_liveness: self.storage_liveness[block].clone().unwrap().into(),
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});
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VariantIdx::new(state)
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@ -1177,6 +1177,8 @@ fn create_cases<'tcx>(
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transform: &TransformVisitor<'tcx>,
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operation: Operation,
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) -> Vec<(usize, BasicBlock)> {
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let tcx = transform.tcx;
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let source_info = SourceInfo::outermost(body.span);
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transform
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@ -1209,13 +1211,84 @@ fn create_cases<'tcx>(
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if operation == Operation::Resume {
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// Move the resume argument to the destination place of the `Yield` terminator
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let resume_arg = Local::new(2); // 0 = return, 1 = self
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statements.push(Statement {
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source_info,
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kind: StatementKind::Assign(Box::new((
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point.resume_arg,
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Rvalue::Use(Operand::Move(resume_arg.into())),
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))),
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});
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// handle `box yield` properly
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let box_place = if let [projection @ .., ProjectionElem::Deref] =
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&**point.resume_arg.projection
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{
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let box_place =
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Place::from(point.resume_arg.local).project_deeper(projection, tcx);
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let box_ty = box_place.ty(&body.local_decls, tcx).ty;
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if box_ty.is_box() { Some((box_place, box_ty)) } else { None }
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} else {
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None
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};
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if let Some((box_place, box_ty)) = box_place {
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let unique_did = box_ty
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.ty_adt_def()
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.expect("expected Box to be an Adt")
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.non_enum_variant()
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.fields[0]
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.did;
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let Some(nonnull_def) = tcx.type_of(unique_did).ty_adt_def() else {
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span_bug!(tcx.def_span(unique_did), "expected Box to contain Unique")
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};
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let nonnull_did = nonnull_def.non_enum_variant().fields[0].did;
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let substs = tcx.intern_substs(&[box_ty.boxed_ty().into()]);
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let unique_ty = tcx.bound_type_of(unique_did).subst(tcx, substs);
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let nonnull_ty = tcx.bound_type_of(nonnull_did).subst(tcx, substs);
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let ptr_ty = tcx.mk_imm_ptr(box_ty.boxed_ty());
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let ptr_local = body.local_decls.push(LocalDecl::new(ptr_ty, body.span));
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statements.push(Statement {
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source_info,
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kind: StatementKind::StorageLive(ptr_local),
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});
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statements.push(Statement {
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source_info,
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kind: StatementKind::Assign(Box::new((
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Place::from(ptr_local),
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Rvalue::Use(Operand::Copy(box_place.project_deeper(
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&[
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PlaceElem::Field(Field::new(0), unique_ty),
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PlaceElem::Field(Field::new(0), nonnull_ty),
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PlaceElem::Field(Field::new(0), ptr_ty),
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],
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tcx,
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))),
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))),
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});
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statements.push(Statement {
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source_info,
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kind: StatementKind::Assign(Box::new((
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Place::from(ptr_local)
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.project_deeper(&[ProjectionElem::Deref], tcx),
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Rvalue::Use(Operand::Move(resume_arg.into())),
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))),
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});
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statements.push(Statement {
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source_info,
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kind: StatementKind::StorageDead(ptr_local),
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});
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} else {
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statements.push(Statement {
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source_info,
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kind: StatementKind::Assign(Box::new((
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point.resume_arg,
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Rvalue::Use(Operand::Move(resume_arg.into())),
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))),
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});
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}
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}
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// Then jump to the real target
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@ -57,6 +57,7 @@ mod deref_separator;
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mod dest_prop;
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pub mod dump_mir;
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mod early_otherwise_branch;
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mod elaborate_box_derefs;
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mod elaborate_drops;
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mod function_item_references;
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mod generator;
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@ -427,6 +428,7 @@ fn run_post_borrowck_cleanup_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tc
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// `AddRetag` needs to run after `ElaborateDrops`. Otherwise it should run fairly late,
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// but before optimizations begin.
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&deref_separator::Derefer,
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&elaborate_box_derefs::ElaborateBoxDerefs,
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&add_retag::AddRetag,
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&lower_intrinsics::LowerIntrinsics,
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&simplify::SimplifyCfg::new("elaborate-drops"),
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