diff options
Diffstat (limited to 'compiler/rustc_mir_transform/src')
| -rw-r--r-- | compiler/rustc_mir_transform/src/deref_separator.rs | 131 |
1 files changed, 76 insertions, 55 deletions
diff --git a/compiler/rustc_mir_transform/src/deref_separator.rs b/compiler/rustc_mir_transform/src/deref_separator.rs index 24b626ad966..7d81bb74cd6 100644 --- a/compiler/rustc_mir_transform/src/deref_separator.rs +++ b/compiler/rustc_mir_transform/src/deref_separator.rs @@ -1,68 +1,89 @@ use crate::MirPass; +use rustc_index::vec::IndexVec; use rustc_middle::mir::patch::MirPatch; +use rustc_middle::mir::visit::{MutVisitor, PlaceContext}; use rustc_middle::mir::*; use rustc_middle::ty::TyCtxt; pub struct Derefer; -pub fn deref_finder<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { - let mut patch = MirPatch::new(body); - let (basic_blocks, local_decl) = body.basic_blocks_and_local_decls_mut(); - for (block, data) in basic_blocks.iter_enumerated_mut() { - for (i, stmt) in data.statements.iter_mut().enumerate() { - match stmt.kind { - StatementKind::Assign(box (og_place, Rvalue::Ref(region, borrow_knd, place))) => { - let mut place_local = place.local; - let mut last_len = 0; - for (idx, (p_ref, p_elem)) in place.iter_projections().enumerate() { - if p_elem == ProjectionElem::Deref && !p_ref.projection.is_empty() { - // The type that we are derefing. - let ty = p_ref.ty(local_decl, tcx).ty; - let temp = patch.new_temp(ty, stmt.source_info.span); - - // Because we are assigning this right before original statement - // we are using index i of statement. - let loc = Location { block: block, statement_index: i }; - patch.add_statement(loc, StatementKind::StorageLive(temp)); - - // We are adding current p_ref's projections to our - // temp value, excluding projections we already covered. - let deref_place = Place::from(place_local) - .project_deeper(&p_ref.projection[last_len..], tcx); - patch.add_assign( - loc, - Place::from(temp), - Rvalue::Use(Operand::Move(deref_place)), - ); - - place_local = temp; - last_len = p_ref.projection.len(); - - // We are creating a place by using our temp value's location - // and copying derefed values which we need to create new statement. - let temp_place = - Place::from(temp).project_deeper(&place.projection[idx..], tcx); - let new_stmt = Statement { - source_info: stmt.source_info, - kind: StatementKind::Assign(Box::new(( - og_place, - Rvalue::Ref(region, borrow_knd, temp_place), - ))), - }; - - // Replace current statement with newly created one. - *stmt = new_stmt; - - // Since our job with the temp is done it should be gone - let loc = Location { block: block, statement_index: i + 1 }; - patch.add_statement(loc, StatementKind::StorageDead(temp)); - } - } +pub struct DerefChecker<'tcx> { + tcx: TyCtxt<'tcx>, + patcher: MirPatch<'tcx>, + local_decls: IndexVec<Local, LocalDecl<'tcx>>, +} + +impl<'tcx> MutVisitor<'tcx> for DerefChecker<'tcx> { + fn tcx(&self) -> TyCtxt<'tcx> { + self.tcx + } + + fn visit_place(&mut self, place: &mut Place<'tcx>, _: PlaceContext, loc: Location) { + let mut place_local = place.local; + let mut last_len = 0; + let mut last_deref_idx = 0; + + let mut prev_temp: Option<Local> = None; + + for (idx, (p_ref, p_elem)) in place.iter_projections().enumerate() { + if p_elem == ProjectionElem::Deref && !p_ref.projection.is_empty() { + last_deref_idx = idx; + } + } + + for (idx, (p_ref, p_elem)) in place.iter_projections().enumerate() { + if p_elem == ProjectionElem::Deref && !p_ref.projection.is_empty() { + let ty = p_ref.ty(&self.local_decls, self.tcx).ty; + let temp = + self.patcher.new_temp(ty, self.local_decls[p_ref.local].source_info.span); + + self.patcher.add_statement(loc, StatementKind::StorageLive(temp)); + + // We are adding current p_ref's projections to our + // temp value, excluding projections we already covered. + let deref_place = Place::from(place_local) + .project_deeper(&p_ref.projection[last_len..], self.tcx); + self.patcher.add_assign( + loc, + Place::from(temp), + Rvalue::Use(Operand::Move(deref_place)), + ); + + place_local = temp; + last_len = p_ref.projection.len(); + + // Change `Place` only if we are actually at the Place's last deref + if idx == last_deref_idx { + let temp_place = + Place::from(temp).project_deeper(&place.projection[idx..], self.tcx); + *place = temp_place; + } + + // We are destroying last temp since it's no longer used. + if let Some(prev_temp) = prev_temp { + self.patcher.add_statement(loc, StatementKind::StorageDead(prev_temp)); } - _ => (), + + prev_temp = Some(temp); } } + + // Since we won't be able to reach final temp, we destroy it outside the loop. + if let Some(prev_temp) = prev_temp { + let last_loc = Location { block: loc.block, statement_index: loc.statement_index + 1 }; + self.patcher.add_statement(last_loc, StatementKind::StorageDead(prev_temp)); + } } - patch.apply(body); +} + +pub fn deref_finder<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { + let patch = MirPatch::new(body); + let mut checker = DerefChecker { tcx, patcher: patch, local_decls: body.local_decls.clone() }; + + for (bb, data) in body.basic_blocks_mut().iter_enumerated_mut() { + checker.visit_basic_block_data(bb, data); + } + + checker.patcher.apply(body); } impl<'tcx> MirPass<'tcx> for Derefer { |