diff --git a/src/librustc_mir/transform/check_consts/validation.rs b/src/librustc_mir/transform/check_consts/validation.rs index 45d8e1d08b721..43973baa7a486 100644 --- a/src/librustc_mir/transform/check_consts/validation.rs +++ b/src/librustc_mir/transform/check_consts/validation.rs @@ -3,7 +3,6 @@ use rustc_errors::struct_span_err; use rustc_hir::lang_items; use rustc_hir::{def_id::DefId, HirId}; -use rustc_index::bit_set::BitSet; use rustc_infer::infer::TyCtxtInferExt; use rustc_middle::mir::visit::{MutatingUseContext, NonMutatingUseContext, PlaceContext, Visitor}; use rustc_middle::mir::*; @@ -28,70 +27,100 @@ use crate::dataflow::{self, Analysis}; // We are using `MaybeMutBorrowedLocals` as a proxy for whether an item may have been mutated // through a pointer prior to the given point. This is okay even though `MaybeMutBorrowedLocals` // kills locals upon `StorageDead` because a local will never be used after a `StorageDead`. -pub type IndirectlyMutableResults<'mir, 'tcx> = +type IndirectlyMutableResults<'mir, 'tcx> = dataflow::ResultsCursor<'mir, 'tcx, MaybeMutBorrowedLocals<'mir, 'tcx>>; -struct QualifCursor<'a, 'mir, 'tcx, Q: Qualif> { - cursor: dataflow::ResultsCursor<'mir, 'tcx, FlowSensitiveAnalysis<'a, 'mir, 'tcx, Q>>, - in_any_value_of_ty: BitSet, -} - -impl QualifCursor<'a, 'mir, 'tcx, Q> { - pub fn new(q: Q, ccx: &'a ConstCx<'mir, 'tcx>) -> Self { - let cursor = FlowSensitiveAnalysis::new(q, ccx) - .into_engine(ccx.tcx, ccx.body, ccx.def_id) - .iterate_to_fixpoint() - .into_results_cursor(ccx.body); - - let mut in_any_value_of_ty = BitSet::new_empty(ccx.body.local_decls.len()); - for (local, decl) in ccx.body.local_decls.iter_enumerated() { - if Q::in_any_value_of_ty(ccx, decl.ty) { - in_any_value_of_ty.insert(local); - } - } - - QualifCursor { cursor, in_any_value_of_ty } - } -} +type QualifResults<'mir, 'tcx, Q> = + dataflow::ResultsCursor<'mir, 'tcx, FlowSensitiveAnalysis<'mir, 'mir, 'tcx, Q>>; -pub struct Qualifs<'a, 'mir, 'tcx> { - has_mut_interior: QualifCursor<'a, 'mir, 'tcx, HasMutInterior>, - needs_drop: QualifCursor<'a, 'mir, 'tcx, NeedsDrop>, - indirectly_mutable: IndirectlyMutableResults<'mir, 'tcx>, +#[derive(Default)] +pub struct Qualifs<'mir, 'tcx> { + has_mut_interior: Option>, + needs_drop: Option>, + indirectly_mutable: Option>, } -impl Qualifs<'a, 'mir, 'tcx> { - fn indirectly_mutable(&mut self, local: Local, location: Location) -> bool { - self.indirectly_mutable.seek_before(location); - self.indirectly_mutable.get().contains(local) +impl Qualifs<'mir, 'tcx> { + fn indirectly_mutable( + &mut self, + ccx: &'mir ConstCx<'mir, 'tcx>, + local: Local, + location: Location, + ) -> bool { + let indirectly_mutable = self.indirectly_mutable.get_or_insert_with(|| { + let ConstCx { tcx, body, def_id, param_env, .. } = *ccx; + + // We can use `unsound_ignore_borrow_on_drop` here because custom drop impls are not + // allowed in a const. + // + // FIXME(ecstaticmorse): Someday we want to allow custom drop impls. How do we do this + // without breaking stable code? + MaybeMutBorrowedLocals::mut_borrows_only(tcx, &body, param_env) + .unsound_ignore_borrow_on_drop() + .into_engine(tcx, &body, def_id) + .iterate_to_fixpoint() + .into_results_cursor(&body) + }); + + indirectly_mutable.seek_before(location); + indirectly_mutable.get().contains(local) } /// Returns `true` if `local` is `NeedsDrop` at the given `Location`. /// /// Only updates the cursor if absolutely necessary - fn needs_drop(&mut self, local: Local, location: Location) -> bool { - if !self.needs_drop.in_any_value_of_ty.contains(local) { + fn needs_drop( + &mut self, + ccx: &'mir ConstCx<'mir, 'tcx>, + local: Local, + location: Location, + ) -> bool { + let ty = ccx.body.local_decls[local].ty; + if !NeedsDrop::in_any_value_of_ty(ccx, ty) { return false; } - self.needs_drop.cursor.seek_before(location); - self.needs_drop.cursor.get().contains(local) || self.indirectly_mutable(local, location) + let needs_drop = self.needs_drop.get_or_insert_with(|| { + let ConstCx { tcx, body, def_id, .. } = *ccx; + + FlowSensitiveAnalysis::new(NeedsDrop, ccx) + .into_engine(tcx, &body, def_id) + .iterate_to_fixpoint() + .into_results_cursor(&body) + }); + + needs_drop.seek_before(location); + needs_drop.get().contains(local) || self.indirectly_mutable(ccx, local, location) } /// Returns `true` if `local` is `HasMutInterior` at the given `Location`. /// /// Only updates the cursor if absolutely necessary. - fn has_mut_interior(&mut self, local: Local, location: Location) -> bool { - if !self.has_mut_interior.in_any_value_of_ty.contains(local) { + fn has_mut_interior( + &mut self, + ccx: &'mir ConstCx<'mir, 'tcx>, + local: Local, + location: Location, + ) -> bool { + let ty = ccx.body.local_decls[local].ty; + if !HasMutInterior::in_any_value_of_ty(ccx, ty) { return false; } - self.has_mut_interior.cursor.seek_before(location); - self.has_mut_interior.cursor.get().contains(local) - || self.indirectly_mutable(local, location) + let has_mut_interior = self.has_mut_interior.get_or_insert_with(|| { + let ConstCx { tcx, body, def_id, .. } = *ccx; + + FlowSensitiveAnalysis::new(HasMutInterior, ccx) + .into_engine(tcx, &body, def_id) + .iterate_to_fixpoint() + .into_results_cursor(&body) + }); + + has_mut_interior.seek_before(location); + has_mut_interior.get().contains(local) || self.indirectly_mutable(ccx, local, location) } - fn in_return_place(&mut self, ccx: &ConstCx<'_, 'tcx>) -> ConstQualifs { + fn in_return_place(&mut self, ccx: &'mir ConstCx<'mir, 'tcx>) -> ConstQualifs { // Find the `Return` terminator if one exists. // // If no `Return` terminator exists, this MIR is divergent. Just return the conservative @@ -114,21 +143,21 @@ impl Qualifs<'a, 'mir, 'tcx> { let return_loc = ccx.body.terminator_loc(return_block); ConstQualifs { - needs_drop: self.needs_drop(RETURN_PLACE, return_loc), - has_mut_interior: self.has_mut_interior(RETURN_PLACE, return_loc), + needs_drop: self.needs_drop(ccx, RETURN_PLACE, return_loc), + has_mut_interior: self.has_mut_interior(ccx, RETURN_PLACE, return_loc), } } } -pub struct Validator<'a, 'mir, 'tcx> { - ccx: &'a ConstCx<'mir, 'tcx>, - qualifs: Qualifs<'a, 'mir, 'tcx>, +pub struct Validator<'mir, 'tcx> { + ccx: &'mir ConstCx<'mir, 'tcx>, + qualifs: Qualifs<'mir, 'tcx>, /// The span of the current statement. span: Span, } -impl Deref for Validator<'_, 'mir, 'tcx> { +impl Deref for Validator<'mir, 'tcx> { type Target = ConstCx<'mir, 'tcx>; fn deref(&self) -> &Self::Target { @@ -136,27 +165,9 @@ impl Deref for Validator<'_, 'mir, 'tcx> { } } -impl Validator<'a, 'mir, 'tcx> { - pub fn new(ccx: &'a ConstCx<'mir, 'tcx>) -> Self { - let ConstCx { tcx, body, def_id, param_env, .. } = *ccx; - - let needs_drop = QualifCursor::new(NeedsDrop, ccx); - let has_mut_interior = QualifCursor::new(HasMutInterior, ccx); - - // We can use `unsound_ignore_borrow_on_drop` here because custom drop impls are not - // allowed in a const. - // - // FIXME(ecstaticmorse): Someday we want to allow custom drop impls. How do we do this - // without breaking stable code? - let indirectly_mutable = MaybeMutBorrowedLocals::mut_borrows_only(tcx, body, param_env) - .unsound_ignore_borrow_on_drop() - .into_engine(tcx, body, def_id) - .iterate_to_fixpoint() - .into_results_cursor(body); - - let qualifs = Qualifs { needs_drop, has_mut_interior, indirectly_mutable }; - - Validator { span: ccx.body.span, ccx, qualifs } +impl Validator<'mir, 'tcx> { + pub fn new(ccx: &'mir ConstCx<'mir, 'tcx>) -> Self { + Validator { span: ccx.body.span, ccx, qualifs: Default::default() } } pub fn check_body(&mut self) { @@ -239,7 +250,7 @@ impl Validator<'a, 'mir, 'tcx> { } } -impl Visitor<'tcx> for Validator<'_, 'mir, 'tcx> { +impl Visitor<'tcx> for Validator<'mir, 'tcx> { fn visit_basic_block_data(&mut self, bb: BasicBlock, block: &BasicBlockData<'tcx>) { trace!("visit_basic_block_data: bb={:?} is_cleanup={:?}", bb, block.is_cleanup); @@ -345,7 +356,7 @@ impl Visitor<'tcx> for Validator<'_, 'mir, 'tcx> { | Rvalue::AddressOf(Mutability::Not, ref place) => { let borrowed_place_has_mut_interior = qualifs::in_place::( &self.ccx, - &mut |local| self.qualifs.has_mut_interior(local, location), + &mut |local| self.qualifs.has_mut_interior(self.ccx, local, location), place.as_ref(), ); @@ -395,14 +406,31 @@ impl Visitor<'tcx> for Validator<'_, 'mir, 'tcx> { ); } - fn visit_operand(&mut self, op: &Operand<'tcx>, location: Location) { - self.super_operand(op, location); - if let Operand::Constant(c) = op { - if let Some(def_id) = c.check_static_ptr(self.tcx) { - self.check_static(def_id, self.span); + fn visit_constant(&mut self, constant: &Constant<'tcx>, location: Location) { + self.super_constant(constant, location); + + if let ty::ConstKind::Unevaluated(def_id, _, promoted) = constant.literal.val { + assert!(promoted.is_none(), "Const-checking should run before promotion"); + + // If a cyclic data dependency exists within a const initializer, try to find + // it during const-checking. This is important because MIR optimizations could + // eliminate a cycle before const-eval runs. See #71078 for an example of this. + // + // FIXME: This means we don't look for cycles involving associated constants, but we + // should handle fully monomorphized ones here at least. + if self.tcx.trait_of_item(def_id).is_none() { + let _ = self.tcx.at(self.span).mir_const_qualif(def_id); } } + + if let Some(def_id) = constant.check_static_ptr(self.tcx) { + self.check_static(def_id, self.span); + + // NOTE: Because we are allowed to refer to the address of a static within its + // initializer, we don't try to trigger cycle errors every time we see a static. + } } + fn visit_projection_elem( &mut self, place_local: Local, @@ -571,7 +599,7 @@ impl Visitor<'tcx> for Validator<'_, 'mir, 'tcx> { let needs_drop = if let Some(local) = dropped_place.as_local() { // Use the span where the local was declared as the span of the drop error. err_span = self.body.local_decls[local].source_info.span; - self.qualifs.needs_drop(local, location) + self.qualifs.needs_drop(self.ccx, local, location) } else { true };