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Diffstat (limited to '')
-rw-r--r-- | compiler/rustc_mir_transform/src/deref_separator.rs | 105 |
1 files changed, 105 insertions, 0 deletions
diff --git a/compiler/rustc_mir_transform/src/deref_separator.rs b/compiler/rustc_mir_transform/src/deref_separator.rs new file mode 100644 index 000000000..a00bb16f7 --- /dev/null +++ b/compiler/rustc_mir_transform/src/deref_separator.rs @@ -0,0 +1,105 @@ +use crate::MirPass; +use rustc_index::vec::IndexVec; +use rustc_middle::mir::patch::MirPatch; +use rustc_middle::mir::visit::NonUseContext::VarDebugInfo; +use rustc_middle::mir::visit::{MutVisitor, PlaceContext}; +use rustc_middle::mir::*; +use rustc_middle::ty::TyCtxt; + +pub struct Derefer; + +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>, cntxt: PlaceContext, loc: Location) { + if !place.projection.is_empty() + && cntxt != PlaceContext::NonUse(VarDebugInfo) + && place.projection[1..].contains(&ProjectionElem::Deref) + { + 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, elem) in place.projection[0..].iter().enumerate() { + if *elem == ProjectionElem::Deref { + last_deref_idx = idx; + } + } + + for (idx, (p_ref, p_elem)) in place.iter_projections().enumerate() { + if !p_ref.projection.is_empty() && p_elem == ProjectionElem::Deref { + let ty = p_ref.ty(&self.local_decls, self.tcx).ty; + let temp = self.patcher.new_local_with_info( + ty, + self.local_decls[p_ref.local].source_info.span, + Some(Box::new(LocalInfo::DerefTemp)), + ); + + 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::CopyForDeref(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 the previous 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)); + } + } + } +} + +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 { + fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { + deref_finder(tcx, body); + body.phase = MirPhase::Derefered; + } +} |