| //! Propagates constants for early reporting of statically known |
| //! assertion failures |
| |
| use std::cell::Cell; |
| |
| use either::{Left, Right}; |
| |
| use rustc_const_eval::interpret::Immediate; |
| use rustc_const_eval::interpret::{ |
| self, InterpCx, InterpResult, LocalState, LocalValue, MemoryKind, OpTy, Scalar, StackPopCleanup, |
| }; |
| use rustc_hir::def::DefKind; |
| use rustc_hir::HirId; |
| use rustc_index::bit_set::BitSet; |
| use rustc_index::vec::IndexVec; |
| use rustc_middle::mir::visit::Visitor; |
| use rustc_middle::mir::{ |
| AssertKind, BinOp, Body, Constant, Local, LocalDecl, Location, Operand, Place, Rvalue, |
| SourceInfo, SourceScope, SourceScopeData, Statement, StatementKind, Terminator, TerminatorKind, |
| UnOp, RETURN_PLACE, |
| }; |
| use rustc_middle::ty::layout::{LayoutError, LayoutOf, LayoutOfHelpers, TyAndLayout}; |
| use rustc_middle::ty::InternalSubsts; |
| use rustc_middle::ty::{ |
| self, ConstInt, Instance, ParamEnv, ScalarInt, Ty, TyCtxt, TypeVisitableExt, |
| }; |
| use rustc_session::lint; |
| use rustc_span::Span; |
| use rustc_target::abi::{HasDataLayout, Size, TargetDataLayout}; |
| use rustc_trait_selection::traits; |
| |
| use crate::const_prop::CanConstProp; |
| use crate::const_prop::ConstPropMachine; |
| use crate::const_prop::ConstPropMode; |
| use crate::MirLint; |
| |
| /// The maximum number of bytes that we'll allocate space for a local or the return value. |
| /// Needed for #66397, because otherwise we eval into large places and that can cause OOM or just |
| /// Severely regress performance. |
| const MAX_ALLOC_LIMIT: u64 = 1024; |
| |
| pub struct ConstProp; |
| |
| impl<'tcx> MirLint<'tcx> for ConstProp { |
| fn run_lint(&self, tcx: TyCtxt<'tcx>, body: &Body<'tcx>) { |
| // will be evaluated by miri and produce its errors there |
| if body.source.promoted.is_some() { |
| return; |
| } |
| |
| let def_id = body.source.def_id().expect_local(); |
| let is_fn_like = tcx.def_kind(def_id).is_fn_like(); |
| let is_assoc_const = tcx.def_kind(def_id) == DefKind::AssocConst; |
| |
| // Only run const prop on functions, methods, closures and associated constants |
| if !is_fn_like && !is_assoc_const { |
| // skip anon_const/statics/consts because they'll be evaluated by miri anyway |
| trace!("ConstProp skipped for {:?}", def_id); |
| return; |
| } |
| |
| let is_generator = tcx.type_of(def_id.to_def_id()).subst_identity().is_generator(); |
| // FIXME(welseywiser) const prop doesn't work on generators because of query cycles |
| // computing their layout. |
| if is_generator { |
| trace!("ConstProp skipped for generator {:?}", def_id); |
| return; |
| } |
| |
| // Check if it's even possible to satisfy the 'where' clauses |
| // for this item. |
| // This branch will never be taken for any normal function. |
| // However, it's possible to `#!feature(trivial_bounds)]` to write |
| // a function with impossible to satisfy clauses, e.g.: |
| // `fn foo() where String: Copy {}` |
| // |
| // We don't usually need to worry about this kind of case, |
| // since we would get a compilation error if the user tried |
| // to call it. However, since we can do const propagation |
| // even without any calls to the function, we need to make |
| // sure that it even makes sense to try to evaluate the body. |
| // If there are unsatisfiable where clauses, then all bets are |
| // off, and we just give up. |
| // |
| // We manually filter the predicates, skipping anything that's not |
| // "global". We are in a potentially generic context |
| // (e.g. we are evaluating a function without substituting generic |
| // parameters, so this filtering serves two purposes: |
| // |
| // 1. We skip evaluating any predicates that we would |
| // never be able prove are unsatisfiable (e.g. `<T as Foo>` |
| // 2. We avoid trying to normalize predicates involving generic |
| // parameters (e.g. `<T as Foo>::MyItem`). This can confuse |
| // the normalization code (leading to cycle errors), since |
| // it's usually never invoked in this way. |
| let predicates = tcx |
| .predicates_of(def_id.to_def_id()) |
| .predicates |
| .iter() |
| .filter_map(|(p, _)| if p.is_global() { Some(*p) } else { None }); |
| if traits::impossible_predicates( |
| tcx, |
| traits::elaborate_predicates(tcx, predicates).map(|o| o.predicate).collect(), |
| ) { |
| trace!("ConstProp skipped for {:?}: found unsatisfiable predicates", def_id); |
| return; |
| } |
| |
| trace!("ConstProp starting for {:?}", def_id); |
| |
| let dummy_body = &Body::new( |
| body.source, |
| (*body.basic_blocks).clone(), |
| body.source_scopes.clone(), |
| body.local_decls.clone(), |
| Default::default(), |
| body.arg_count, |
| Default::default(), |
| body.span, |
| body.generator_kind(), |
| body.tainted_by_errors, |
| ); |
| |
| // FIXME(oli-obk, eddyb) Optimize locals (or even local paths) to hold |
| // constants, instead of just checking for const-folding succeeding. |
| // That would require a uniform one-def no-mutation analysis |
| // and RPO (or recursing when needing the value of a local). |
| let mut optimization_finder = ConstPropagator::new(body, dummy_body, tcx); |
| optimization_finder.visit_body(body); |
| |
| trace!("ConstProp done for {:?}", def_id); |
| } |
| } |
| |
| /// Finds optimization opportunities on the MIR. |
| struct ConstPropagator<'mir, 'tcx> { |
| ecx: InterpCx<'mir, 'tcx, ConstPropMachine<'mir, 'tcx>>, |
| tcx: TyCtxt<'tcx>, |
| param_env: ParamEnv<'tcx>, |
| source_scopes: &'mir IndexVec<SourceScope, SourceScopeData<'tcx>>, |
| local_decls: &'mir IndexVec<Local, LocalDecl<'tcx>>, |
| // Because we have `MutVisitor` we can't obtain the `SourceInfo` from a `Location`. So we store |
| // the last known `SourceInfo` here and just keep revisiting it. |
| source_info: Option<SourceInfo>, |
| } |
| |
| impl<'tcx> LayoutOfHelpers<'tcx> for ConstPropagator<'_, 'tcx> { |
| type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>; |
| |
| #[inline] |
| fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> { |
| err |
| } |
| } |
| |
| impl HasDataLayout for ConstPropagator<'_, '_> { |
| #[inline] |
| fn data_layout(&self) -> &TargetDataLayout { |
| &self.tcx.data_layout |
| } |
| } |
| |
| impl<'tcx> ty::layout::HasTyCtxt<'tcx> for ConstPropagator<'_, 'tcx> { |
| #[inline] |
| fn tcx(&self) -> TyCtxt<'tcx> { |
| self.tcx |
| } |
| } |
| |
| impl<'tcx> ty::layout::HasParamEnv<'tcx> for ConstPropagator<'_, 'tcx> { |
| #[inline] |
| fn param_env(&self) -> ty::ParamEnv<'tcx> { |
| self.param_env |
| } |
| } |
| |
| impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> { |
| fn new( |
| body: &Body<'tcx>, |
| dummy_body: &'mir Body<'tcx>, |
| tcx: TyCtxt<'tcx>, |
| ) -> ConstPropagator<'mir, 'tcx> { |
| let def_id = body.source.def_id(); |
| let substs = &InternalSubsts::identity_for_item(tcx, def_id); |
| let param_env = tcx.param_env_reveal_all_normalized(def_id); |
| |
| let can_const_prop = CanConstProp::check(tcx, param_env, body); |
| let mut only_propagate_inside_block_locals = BitSet::new_empty(can_const_prop.len()); |
| for (l, mode) in can_const_prop.iter_enumerated() { |
| if *mode == ConstPropMode::OnlyInsideOwnBlock { |
| only_propagate_inside_block_locals.insert(l); |
| } |
| } |
| let mut ecx = InterpCx::new( |
| tcx, |
| tcx.def_span(def_id), |
| param_env, |
| ConstPropMachine::new(only_propagate_inside_block_locals, can_const_prop), |
| ); |
| |
| let ret_layout = ecx |
| .layout_of(body.bound_return_ty().subst(tcx, substs)) |
| .ok() |
| // Don't bother allocating memory for large values. |
| // I don't know how return types can seem to be unsized but this happens in the |
| // `type/type-unsatisfiable.rs` test. |
| .filter(|ret_layout| { |
| ret_layout.is_sized() && ret_layout.size < Size::from_bytes(MAX_ALLOC_LIMIT) |
| }) |
| .unwrap_or_else(|| ecx.layout_of(tcx.types.unit).unwrap()); |
| |
| let ret = ecx |
| .allocate(ret_layout, MemoryKind::Stack) |
| .expect("couldn't perform small allocation") |
| .into(); |
| |
| ecx.push_stack_frame( |
| Instance::new(def_id, substs), |
| dummy_body, |
| &ret, |
| StackPopCleanup::Root { cleanup: false }, |
| ) |
| .expect("failed to push initial stack frame"); |
| |
| ConstPropagator { |
| ecx, |
| tcx, |
| param_env, |
| source_scopes: &dummy_body.source_scopes, |
| local_decls: &dummy_body.local_decls, |
| source_info: None, |
| } |
| } |
| |
| fn get_const(&self, place: Place<'tcx>) -> Option<OpTy<'tcx>> { |
| let op = match self.ecx.eval_place_to_op(place, None) { |
| Ok(op) => { |
| if matches!(*op, interpret::Operand::Immediate(Immediate::Uninit)) { |
| // Make sure nobody accidentally uses this value. |
| return None; |
| } |
| op |
| } |
| Err(e) => { |
| trace!("get_const failed: {}", e); |
| return None; |
| } |
| }; |
| |
| // Try to read the local as an immediate so that if it is representable as a scalar, we can |
| // handle it as such, but otherwise, just return the value as is. |
| Some(match self.ecx.read_immediate_raw(&op) { |
| Ok(Left(imm)) => imm.into(), |
| _ => op, |
| }) |
| } |
| |
| /// Remove `local` from the pool of `Locals`. Allows writing to them, |
| /// but not reading from them anymore. |
| fn remove_const(ecx: &mut InterpCx<'mir, 'tcx, ConstPropMachine<'mir, 'tcx>>, local: Local) { |
| ecx.frame_mut().locals[local] = LocalState { |
| value: LocalValue::Live(interpret::Operand::Immediate(interpret::Immediate::Uninit)), |
| layout: Cell::new(None), |
| }; |
| } |
| |
| fn lint_root(&self, source_info: SourceInfo) -> Option<HirId> { |
| source_info.scope.lint_root(self.source_scopes) |
| } |
| |
| fn use_ecx<F, T>(&mut self, source_info: SourceInfo, f: F) -> Option<T> |
| where |
| F: FnOnce(&mut Self) -> InterpResult<'tcx, T>, |
| { |
| // Overwrite the PC -- whatever the interpreter does to it does not make any sense anyway. |
| self.ecx.frame_mut().loc = Right(source_info.span); |
| match f(self) { |
| Ok(val) => Some(val), |
| Err(error) => { |
| trace!("InterpCx operation failed: {:?}", error); |
| // Some errors shouldn't come up because creating them causes |
| // an allocation, which we should avoid. When that happens, |
| // dedicated error variants should be introduced instead. |
| assert!( |
| !error.kind().formatted_string(), |
| "const-prop encountered formatting error: {}", |
| error |
| ); |
| None |
| } |
| } |
| } |
| |
| /// Returns the value, if any, of evaluating `c`. |
| fn eval_constant(&mut self, c: &Constant<'tcx>, source_info: SourceInfo) -> Option<OpTy<'tcx>> { |
| // FIXME we need to revisit this for #67176 |
| if c.needs_subst() { |
| return None; |
| } |
| |
| // Normalization needed b/c const prop lint runs in |
| // `mir_drops_elaborated_and_const_checked`, which happens before |
| // optimized MIR. Only after optimizing the MIR can we guarantee |
| // that the `RevealAll` pass has happened and that the body's consts |
| // are normalized, so any call to resolve before that needs to be |
| // manually normalized. |
| let val = self.tcx.try_normalize_erasing_regions(self.param_env, c.literal).ok()?; |
| |
| self.use_ecx(source_info, |this| this.ecx.eval_mir_constant(&val, Some(c.span), None)) |
| } |
| |
| /// Returns the value, if any, of evaluating `place`. |
| fn eval_place(&mut self, place: Place<'tcx>, source_info: SourceInfo) -> Option<OpTy<'tcx>> { |
| trace!("eval_place(place={:?})", place); |
| self.use_ecx(source_info, |this| this.ecx.eval_place_to_op(place, None)) |
| } |
| |
| /// Returns the value, if any, of evaluating `op`. Calls upon `eval_constant` |
| /// or `eval_place`, depending on the variant of `Operand` used. |
| fn eval_operand(&mut self, op: &Operand<'tcx>, source_info: SourceInfo) -> Option<OpTy<'tcx>> { |
| match *op { |
| Operand::Constant(ref c) => self.eval_constant(c, source_info), |
| Operand::Move(place) | Operand::Copy(place) => self.eval_place(place, source_info), |
| } |
| } |
| |
| fn report_assert_as_lint( |
| &self, |
| lint: &'static lint::Lint, |
| source_info: SourceInfo, |
| message: &'static str, |
| panic: AssertKind<impl std::fmt::Debug>, |
| ) { |
| if let Some(lint_root) = self.lint_root(source_info) { |
| self.tcx.struct_span_lint_hir(lint, lint_root, source_info.span, message, |lint| { |
| lint.span_label(source_info.span, format!("{:?}", panic)) |
| }); |
| } |
| } |
| |
| fn check_unary_op( |
| &mut self, |
| op: UnOp, |
| arg: &Operand<'tcx>, |
| source_info: SourceInfo, |
| ) -> Option<()> { |
| if let (val, true) = self.use_ecx(source_info, |this| { |
| let val = this.ecx.read_immediate(&this.ecx.eval_operand(arg, None)?)?; |
| let (_res, overflow, _ty) = this.ecx.overflowing_unary_op(op, &val)?; |
| Ok((val, overflow)) |
| })? { |
| // `AssertKind` only has an `OverflowNeg` variant, so make sure that is |
| // appropriate to use. |
| assert_eq!(op, UnOp::Neg, "Neg is the only UnOp that can overflow"); |
| self.report_assert_as_lint( |
| lint::builtin::ARITHMETIC_OVERFLOW, |
| source_info, |
| "this arithmetic operation will overflow", |
| AssertKind::OverflowNeg(val.to_const_int()), |
| ); |
| return None; |
| } |
| |
| Some(()) |
| } |
| |
| fn check_binary_op( |
| &mut self, |
| op: BinOp, |
| left: &Operand<'tcx>, |
| right: &Operand<'tcx>, |
| source_info: SourceInfo, |
| ) -> Option<()> { |
| let r = self.use_ecx(source_info, |this| { |
| this.ecx.read_immediate(&this.ecx.eval_operand(right, None)?) |
| }); |
| let l = self.use_ecx(source_info, |this| { |
| this.ecx.read_immediate(&this.ecx.eval_operand(left, None)?) |
| }); |
| // Check for exceeding shifts *even if* we cannot evaluate the LHS. |
| if matches!(op, BinOp::Shr | BinOp::Shl) { |
| let r = r.clone()?; |
| // We need the type of the LHS. We cannot use `place_layout` as that is the type |
| // of the result, which for checked binops is not the same! |
| let left_ty = left.ty(self.local_decls, self.tcx); |
| let left_size = self.ecx.layout_of(left_ty).ok()?.size; |
| let right_size = r.layout.size; |
| let r_bits = r.to_scalar().to_bits(right_size).ok(); |
| if r_bits.map_or(false, |b| b >= left_size.bits() as u128) { |
| debug!("check_binary_op: reporting assert for {:?}", source_info); |
| self.report_assert_as_lint( |
| lint::builtin::ARITHMETIC_OVERFLOW, |
| source_info, |
| "this arithmetic operation will overflow", |
| AssertKind::Overflow( |
| op, |
| match l { |
| Some(l) => l.to_const_int(), |
| // Invent a dummy value, the diagnostic ignores it anyway |
| None => ConstInt::new( |
| ScalarInt::try_from_uint(1_u8, left_size).unwrap(), |
| left_ty.is_signed(), |
| left_ty.is_ptr_sized_integral(), |
| ), |
| }, |
| r.to_const_int(), |
| ), |
| ); |
| return None; |
| } |
| } |
| |
| if let (Some(l), Some(r)) = (l, r) { |
| // The remaining operators are handled through `overflowing_binary_op`. |
| if self.use_ecx(source_info, |this| { |
| let (_res, overflow, _ty) = this.ecx.overflowing_binary_op(op, &l, &r)?; |
| Ok(overflow) |
| })? { |
| self.report_assert_as_lint( |
| lint::builtin::ARITHMETIC_OVERFLOW, |
| source_info, |
| "this arithmetic operation will overflow", |
| AssertKind::Overflow(op, l.to_const_int(), r.to_const_int()), |
| ); |
| return None; |
| } |
| } |
| Some(()) |
| } |
| |
| fn const_prop( |
| &mut self, |
| rvalue: &Rvalue<'tcx>, |
| source_info: SourceInfo, |
| place: Place<'tcx>, |
| ) -> Option<()> { |
| // Perform any special handling for specific Rvalue types. |
| // Generally, checks here fall into one of two categories: |
| // 1. Additional checking to provide useful lints to the user |
| // - In this case, we will do some validation and then fall through to the |
| // end of the function which evals the assignment. |
| // 2. Working around bugs in other parts of the compiler |
| // - In this case, we'll return `None` from this function to stop evaluation. |
| match rvalue { |
| // Additional checking: give lints to the user if an overflow would occur. |
| // We do this here and not in the `Assert` terminator as that terminator is |
| // only sometimes emitted (overflow checks can be disabled), but we want to always |
| // lint. |
| Rvalue::UnaryOp(op, arg) => { |
| trace!("checking UnaryOp(op = {:?}, arg = {:?})", op, arg); |
| self.check_unary_op(*op, arg, source_info)?; |
| } |
| Rvalue::BinaryOp(op, box (left, right)) => { |
| trace!("checking BinaryOp(op = {:?}, left = {:?}, right = {:?})", op, left, right); |
| self.check_binary_op(*op, left, right, source_info)?; |
| } |
| Rvalue::CheckedBinaryOp(op, box (left, right)) => { |
| trace!( |
| "checking CheckedBinaryOp(op = {:?}, left = {:?}, right = {:?})", |
| op, |
| left, |
| right |
| ); |
| self.check_binary_op(*op, left, right, source_info)?; |
| } |
| |
| // Do not try creating references (#67862) |
| Rvalue::AddressOf(_, place) | Rvalue::Ref(_, _, place) => { |
| trace!("skipping AddressOf | Ref for {:?}", place); |
| |
| // This may be creating mutable references or immutable references to cells. |
| // If that happens, the pointed to value could be mutated via that reference. |
| // Since we aren't tracking references, the const propagator loses track of what |
| // value the local has right now. |
| // Thus, all locals that have their reference taken |
| // must not take part in propagation. |
| Self::remove_const(&mut self.ecx, place.local); |
| |
| return None; |
| } |
| Rvalue::ThreadLocalRef(def_id) => { |
| trace!("skipping ThreadLocalRef({:?})", def_id); |
| |
| return None; |
| } |
| |
| // There's no other checking to do at this time. |
| Rvalue::Aggregate(..) |
| | Rvalue::Use(..) |
| | Rvalue::CopyForDeref(..) |
| | Rvalue::Repeat(..) |
| | Rvalue::Len(..) |
| | Rvalue::Cast(..) |
| | Rvalue::ShallowInitBox(..) |
| | Rvalue::Discriminant(..) |
| | Rvalue::NullaryOp(..) => {} |
| } |
| |
| // FIXME we need to revisit this for #67176 |
| if rvalue.needs_subst() { |
| return None; |
| } |
| if !rvalue |
| .ty(&self.ecx.frame().body.local_decls, *self.ecx.tcx) |
| .is_sized(*self.ecx.tcx, self.param_env) |
| { |
| // the interpreter doesn't support unsized locals (only unsized arguments), |
| // but rustc does (in a kinda broken way), so we have to skip them here |
| return None; |
| } |
| |
| self.use_ecx(source_info, |this| this.ecx.eval_rvalue_into_place(rvalue, place)) |
| } |
| } |
| |
| impl<'tcx> Visitor<'tcx> for ConstPropagator<'_, 'tcx> { |
| fn visit_body(&mut self, body: &Body<'tcx>) { |
| for (bb, data) in body.basic_blocks.iter_enumerated() { |
| self.visit_basic_block_data(bb, data); |
| } |
| } |
| |
| fn visit_operand(&mut self, operand: &Operand<'tcx>, location: Location) { |
| self.super_operand(operand, location); |
| } |
| |
| fn visit_constant(&mut self, constant: &Constant<'tcx>, location: Location) { |
| trace!("visit_constant: {:?}", constant); |
| self.super_constant(constant, location); |
| self.eval_constant(constant, self.source_info.unwrap()); |
| } |
| |
| fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) { |
| trace!("visit_statement: {:?}", statement); |
| let source_info = statement.source_info; |
| self.source_info = Some(source_info); |
| if let StatementKind::Assign(box (place, ref rval)) = statement.kind { |
| let can_const_prop = self.ecx.machine.can_const_prop[place.local]; |
| if let Some(()) = self.const_prop(rval, source_info, place) { |
| match can_const_prop { |
| ConstPropMode::OnlyInsideOwnBlock => { |
| trace!( |
| "found local restricted to its block. \ |
| Will remove it from const-prop after block is finished. Local: {:?}", |
| place.local |
| ); |
| } |
| ConstPropMode::OnlyPropagateInto | ConstPropMode::NoPropagation => { |
| trace!("can't propagate into {:?}", place); |
| if place.local != RETURN_PLACE { |
| Self::remove_const(&mut self.ecx, place.local); |
| } |
| } |
| ConstPropMode::FullConstProp => {} |
| } |
| } else { |
| // Const prop failed, so erase the destination, ensuring that whatever happens |
| // from here on, does not know about the previous value. |
| // This is important in case we have |
| // ```rust |
| // let mut x = 42; |
| // x = SOME_MUTABLE_STATIC; |
| // // x must now be uninit |
| // ``` |
| // FIXME: we overzealously erase the entire local, because that's easier to |
| // implement. |
| trace!( |
| "propagation into {:?} failed. |
| Nuking the entire site from orbit, it's the only way to be sure", |
| place, |
| ); |
| Self::remove_const(&mut self.ecx, place.local); |
| } |
| } else { |
| match statement.kind { |
| StatementKind::SetDiscriminant { ref place, .. } => { |
| match self.ecx.machine.can_const_prop[place.local] { |
| ConstPropMode::FullConstProp | ConstPropMode::OnlyInsideOwnBlock => { |
| if self |
| .use_ecx(source_info, |this| this.ecx.statement(statement)) |
| .is_some() |
| { |
| trace!("propped discriminant into {:?}", place); |
| } else { |
| Self::remove_const(&mut self.ecx, place.local); |
| } |
| } |
| ConstPropMode::OnlyPropagateInto | ConstPropMode::NoPropagation => { |
| Self::remove_const(&mut self.ecx, place.local); |
| } |
| } |
| } |
| StatementKind::StorageLive(local) | StatementKind::StorageDead(local) => { |
| let frame = self.ecx.frame_mut(); |
| frame.locals[local].value = |
| if let StatementKind::StorageLive(_) = statement.kind { |
| LocalValue::Live(interpret::Operand::Immediate( |
| interpret::Immediate::Uninit, |
| )) |
| } else { |
| LocalValue::Dead |
| }; |
| } |
| _ => {} |
| } |
| } |
| |
| self.super_statement(statement, location); |
| } |
| |
| fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) { |
| let source_info = terminator.source_info; |
| self.source_info = Some(source_info); |
| self.super_terminator(terminator, location); |
| match &terminator.kind { |
| TerminatorKind::Assert { expected, ref msg, ref cond, .. } => { |
| if let Some(ref value) = self.eval_operand(&cond, source_info) { |
| trace!("assertion on {:?} should be {:?}", value, expected); |
| let expected = Scalar::from_bool(*expected); |
| let Ok(value_const) = self.ecx.read_scalar(&value) else { |
| // FIXME should be used use_ecx rather than a local match... but we have |
| // quite a few of these read_scalar/read_immediate that need fixing. |
| return |
| }; |
| if expected != value_const { |
| enum DbgVal<T> { |
| Val(T), |
| Underscore, |
| } |
| impl<T: std::fmt::Debug> std::fmt::Debug for DbgVal<T> { |
| fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { |
| match self { |
| Self::Val(val) => val.fmt(fmt), |
| Self::Underscore => fmt.write_str("_"), |
| } |
| } |
| } |
| let mut eval_to_int = |op| { |
| // This can be `None` if the lhs wasn't const propagated and we just |
| // triggered the assert on the value of the rhs. |
| self.eval_operand(op, source_info) |
| .and_then(|op| self.ecx.read_immediate(&op).ok()) |
| .map_or(DbgVal::Underscore, |op| DbgVal::Val(op.to_const_int())) |
| }; |
| let msg = match msg { |
| AssertKind::DivisionByZero(op) => { |
| Some(AssertKind::DivisionByZero(eval_to_int(op))) |
| } |
| AssertKind::RemainderByZero(op) => { |
| Some(AssertKind::RemainderByZero(eval_to_int(op))) |
| } |
| AssertKind::Overflow(bin_op @ (BinOp::Div | BinOp::Rem), op1, op2) => { |
| // Division overflow is *UB* in the MIR, and different than the |
| // other overflow checks. |
| Some(AssertKind::Overflow( |
| *bin_op, |
| eval_to_int(op1), |
| eval_to_int(op2), |
| )) |
| } |
| AssertKind::BoundsCheck { ref len, ref index } => { |
| let len = eval_to_int(len); |
| let index = eval_to_int(index); |
| Some(AssertKind::BoundsCheck { len, index }) |
| } |
| // Remaining overflow errors are already covered by checks on the binary operators. |
| AssertKind::Overflow(..) | AssertKind::OverflowNeg(_) => None, |
| // Need proper const propagator for these. |
| _ => None, |
| }; |
| // Poison all places this operand references so that further code |
| // doesn't use the invalid value |
| match cond { |
| Operand::Move(ref place) | Operand::Copy(ref place) => { |
| Self::remove_const(&mut self.ecx, place.local); |
| } |
| Operand::Constant(_) => {} |
| } |
| if let Some(msg) = msg { |
| self.report_assert_as_lint( |
| lint::builtin::UNCONDITIONAL_PANIC, |
| source_info, |
| "this operation will panic at runtime", |
| msg, |
| ); |
| } |
| } |
| } |
| } |
| // None of these have Operands to const-propagate. |
| TerminatorKind::Goto { .. } |
| | TerminatorKind::Resume |
| | TerminatorKind::Abort |
| | TerminatorKind::Return |
| | TerminatorKind::Unreachable |
| | TerminatorKind::Drop { .. } |
| | TerminatorKind::DropAndReplace { .. } |
| | TerminatorKind::Yield { .. } |
| | TerminatorKind::GeneratorDrop |
| | TerminatorKind::FalseEdge { .. } |
| | TerminatorKind::FalseUnwind { .. } |
| | TerminatorKind::SwitchInt { .. } |
| | TerminatorKind::Call { .. } |
| | TerminatorKind::InlineAsm { .. } => {} |
| } |
| |
| // We remove all Locals which are restricted in propagation to their containing blocks and |
| // which were modified in the current block. |
| // Take it out of the ecx so we can get a mutable reference to the ecx for `remove_const`. |
| let mut locals = std::mem::take(&mut self.ecx.machine.written_only_inside_own_block_locals); |
| for &local in locals.iter() { |
| Self::remove_const(&mut self.ecx, local); |
| } |
| locals.clear(); |
| // Put it back so we reuse the heap of the storage |
| self.ecx.machine.written_only_inside_own_block_locals = locals; |
| if cfg!(debug_assertions) { |
| // Ensure we are correctly erasing locals with the non-debug-assert logic. |
| for local in self.ecx.machine.only_propagate_inside_block_locals.iter() { |
| assert!( |
| self.get_const(local.into()).is_none() |
| || self |
| .layout_of(self.local_decls[local].ty) |
| .map_or(true, |layout| layout.is_zst()) |
| ) |
| } |
| } |
| } |
| } |