diff options
Diffstat (limited to 'compiler/rustc_mir_transform/src/const_prop_lint.rs')
| -rw-r--r-- | compiler/rustc_mir_transform/src/const_prop_lint.rs | 477 |
1 files changed, 241 insertions, 236 deletions
diff --git a/compiler/rustc_mir_transform/src/const_prop_lint.rs b/compiler/rustc_mir_transform/src/const_prop_lint.rs index fd9475748..699fe4489 100644 --- a/compiler/rustc_mir_transform/src/const_prop_lint.rs +++ b/compiler/rustc_mir_transform/src/const_prop_lint.rs @@ -1,24 +1,17 @@ //! Propagates constants for early reporting of statically known //! assertion failures -use std::cell::Cell; - -use either::{Left, Right}; +use either::Left; use rustc_const_eval::interpret::Immediate; use rustc_const_eval::interpret::{ - self, InterpCx, InterpResult, LocalState, LocalValue, MemoryKind, OpTy, Scalar, StackPopCleanup, + self, InterpCx, InterpResult, 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::mir::*; use rustc_middle::ty::layout::{LayoutError, LayoutOf, LayoutOfHelpers, TyAndLayout}; use rustc_middle::ty::InternalSubsts; use rustc_middle::ty::{ @@ -98,10 +91,7 @@ impl<'tcx> MirLint<'tcx> for ConstProp { .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(), - ) { + if traits::impossible_predicates(tcx, traits::elaborate(tcx, predicates).collect()) { trace!("ConstProp skipped for {:?}: found unsatisfiable predicates", def_id); return; } @@ -110,7 +100,7 @@ impl<'tcx> MirLint<'tcx> for ConstProp { let dummy_body = &Body::new( body.source, - (*body.basic_blocks).clone(), + (*body.basic_blocks).to_owned(), body.source_scopes.clone(), body.local_decls.clone(), Default::default(), @@ -137,11 +127,8 @@ 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>, + worklist: Vec<BasicBlock>, + visited_blocks: BitSet<BasicBlock>, } impl<'tcx> LayoutOfHelpers<'tcx> for ConstPropagator<'_, 'tcx> { @@ -185,17 +172,11 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> { 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), + ConstPropMachine::new(can_const_prop), ); let ret_layout = ecx @@ -226,12 +207,19 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> { ecx, tcx, param_env, - source_scopes: &dummy_body.source_scopes, - local_decls: &dummy_body.local_decls, - source_info: None, + worklist: vec![START_BLOCK], + visited_blocks: BitSet::new_empty(body.basic_blocks.len()), } } + fn body(&self) -> &'mir Body<'tcx> { + self.ecx.frame().body + } + + fn local_decls(&self) -> &'mir LocalDecls<'tcx> { + &self.body().local_decls + } + fn get_const(&self, place: Place<'tcx>) -> Option<OpTy<'tcx>> { let op = match self.ecx.eval_place_to_op(place, None) { Ok(op) => { @@ -258,22 +246,21 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> { /// 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), - }; + ecx.frame_mut().locals[local].value = + LocalValue::Live(interpret::Operand::Immediate(interpret::Immediate::Uninit)); + ecx.machine.written_only_inside_own_block_locals.remove(&local); } fn lint_root(&self, source_info: SourceInfo) -> Option<HirId> { - source_info.scope.lint_root(self.source_scopes) + source_info.scope.lint_root(&self.body().source_scopes) } - fn use_ecx<F, T>(&mut self, source_info: SourceInfo, f: F) -> Option<T> + fn use_ecx<F, T>(&mut self, location: Location, 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); + self.ecx.frame_mut().loc = Left(location); match f(self) { Ok(val) => Some(val), Err(error) => { @@ -292,7 +279,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> { } /// Returns the value, if any, of evaluating `c`. - fn eval_constant(&mut self, c: &Constant<'tcx>, source_info: SourceInfo) -> Option<OpTy<'tcx>> { + fn eval_constant(&mut self, c: &Constant<'tcx>, location: Location) -> Option<OpTy<'tcx>> { // FIXME we need to revisit this for #67176 if c.needs_subst() { return None; @@ -306,45 +293,41 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> { // 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)) + self.use_ecx(location, |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>> { + fn eval_place(&mut self, place: Place<'tcx>, location: Location) -> Option<OpTy<'tcx>> { trace!("eval_place(place={:?})", place); - self.use_ecx(source_info, |this| this.ecx.eval_place_to_op(place, None)) + self.use_ecx(location, |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>> { + fn eval_operand(&mut self, op: &Operand<'tcx>, location: Location) -> 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), + Operand::Constant(ref c) => self.eval_constant(c, location), + Operand::Move(place) | Operand::Copy(place) => self.eval_place(place, location), } } fn report_assert_as_lint( &self, lint: &'static lint::Lint, - source_info: SourceInfo, + location: Location, message: &'static str, panic: AssertKind<impl std::fmt::Debug>, ) { - if let Some(lint_root) = self.lint_root(source_info) { + let source_info = self.body().source_info(location); + 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| { + fn check_unary_op(&mut self, op: UnOp, arg: &Operand<'tcx>, location: Location) -> Option<()> { + if let (val, true) = self.use_ecx(location, |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)) @@ -354,7 +337,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> { assert_eq!(op, UnOp::Neg, "Neg is the only UnOp that can overflow"); self.report_assert_as_lint( lint::builtin::ARITHMETIC_OVERFLOW, - source_info, + location, "this arithmetic operation will overflow", AssertKind::OverflowNeg(val.to_const_int()), ); @@ -369,28 +352,27 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> { op: BinOp, left: &Operand<'tcx>, right: &Operand<'tcx>, - source_info: SourceInfo, + location: Location, ) -> Option<()> { - let r = self.use_ecx(source_info, |this| { + let r = self.use_ecx(location, |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)?) - }); + let l = self + .use_ecx(location, |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_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); + debug!("check_binary_op: reporting assert for {:?}", location); self.report_assert_as_lint( lint::builtin::ARITHMETIC_OVERFLOW, - source_info, + location, "this arithmetic operation will overflow", AssertKind::Overflow( op, @@ -412,13 +394,13 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> { if let (Some(l), Some(r)) = (l, r) { // The remaining operators are handled through `overflowing_binary_op`. - if self.use_ecx(source_info, |this| { + if self.use_ecx(location, |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, + location, "this arithmetic operation will overflow", AssertKind::Overflow(op, l.to_const_int(), r.to_const_int()), ); @@ -428,12 +410,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> { Some(()) } - fn const_prop( - &mut self, - rvalue: &Rvalue<'tcx>, - source_info: SourceInfo, - place: Place<'tcx>, - ) -> Option<()> { + fn check_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) -> 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 @@ -448,11 +425,11 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> { // lint. Rvalue::UnaryOp(op, arg) => { trace!("checking UnaryOp(op = {:?}, arg = {:?})", op, arg); - self.check_unary_op(*op, arg, source_info)?; + self.check_unary_op(*op, arg, location)?; } Rvalue::BinaryOp(op, box (left, right)) => { trace!("checking BinaryOp(op = {:?}, left = {:?}, right = {:?})", op, left, right); - self.check_binary_op(*op, left, right, source_info)?; + self.check_binary_op(*op, left, right, location)?; } Rvalue::CheckedBinaryOp(op, box (left, right)) => { trace!( @@ -461,7 +438,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> { left, right ); - self.check_binary_op(*op, left, right, source_info)?; + self.check_binary_op(*op, left, right, location)?; } // Do not try creating references (#67862) @@ -500,22 +477,105 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> { 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) - { + if !rvalue.ty(self.local_decls(), self.tcx).is_sized(self.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)) + Some(()) + } + + fn check_assertion( + &mut self, + expected: bool, + msg: &AssertKind<Operand<'tcx>>, + cond: &Operand<'tcx>, + location: Location, + ) -> Option<!> { + let ref value = self.eval_operand(&cond, location)?; + trace!("assertion on {:?} should be {:?}", value, expected); + + let expected = Scalar::from_bool(expected); + let value_const = self.use_ecx(location, |this| this.ecx.read_scalar(&value))?; + + if expected != value_const { + // Poison all places this operand references so that further code + // doesn't use the invalid value + if let Some(place) = cond.place() { + Self::remove_const(&mut self.ecx, place.local); + } + + 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, location) + .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) => AssertKind::DivisionByZero(eval_to_int(op)), + AssertKind::RemainderByZero(op) => 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. + 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); + AssertKind::BoundsCheck { len, index } + } + // Remaining overflow errors are already covered by checks on the binary operators. + AssertKind::Overflow(..) | AssertKind::OverflowNeg(_) => return None, + // Need proper const propagator for these. + _ => return None, + }; + self.report_assert_as_lint( + lint::builtin::UNCONDITIONAL_PANIC, + location, + "this operation will panic at runtime", + msg, + ); + } + + None + } + + fn ensure_not_propagated(&self, local: Local) { + if cfg!(debug_assertions) { + assert!( + self.get_const(local.into()).is_none() + || self + .layout_of(self.local_decls()[local].ty) + .map_or(true, |layout| layout.is_zst()), + "failed to remove values for `{local:?}`, value={:?}", + self.get_const(local.into()), + ) + } } } impl<'tcx> Visitor<'tcx> for ConstPropagator<'_, 'tcx> { fn visit_body(&mut self, body: &Body<'tcx>) { - for (bb, data) in body.basic_blocks.iter_enumerated() { + while let Some(bb) = self.worklist.pop() { + if !self.visited_blocks.insert(bb) { + continue; + } + + let data = &body.basic_blocks[bb]; self.visit_basic_block_data(bb, data); } } @@ -527,202 +587,147 @@ impl<'tcx> Visitor<'tcx> for ConstPropagator<'_, 'tcx> { 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()); + self.eval_constant(constant, location); + } + + fn visit_assign(&mut self, place: &Place<'tcx>, rvalue: &Rvalue<'tcx>, location: Location) { + self.super_assign(place, rvalue, location); + + let Some(()) = self.check_rvalue(rvalue, location) else { return }; + + match self.ecx.machine.can_const_prop[place.local] { + // Do nothing if the place is indirect. + _ if place.is_indirect() => {} + ConstPropMode::NoPropagation => self.ensure_not_propagated(place.local), + ConstPropMode::OnlyInsideOwnBlock | ConstPropMode::FullConstProp => { + if self + .use_ecx(location, |this| this.ecx.eval_rvalue_into_place(rvalue, *place)) + .is_none() + { + // 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); + } + } + } } 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 { + + // We want to evaluate operands before any change to the assigned-to value, + // so we recurse first. + self.super_statement(statement, location); + + match statement.kind { + StatementKind::SetDiscriminant { ref place, .. } => { + match self.ecx.machine.can_const_prop[place.local] { + // Do nothing if the place is indirect. + _ if place.is_indirect() => {} + ConstPropMode::NoPropagation => self.ensure_not_propagated(place.local), + ConstPropMode::FullConstProp | ConstPropMode::OnlyInsideOwnBlock => { + if self.use_ecx(location, |this| this.ecx.statement(statement)).is_some() { + trace!("propped discriminant into {:?}", place); + } else { 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 - }; - } - _ => {} + StatementKind::StorageLive(local) => { + let frame = self.ecx.frame_mut(); + frame.locals[local].value = + LocalValue::Live(interpret::Operand::Immediate(interpret::Immediate::Uninit)); + } + StatementKind::StorageDead(local) => { + let frame = self.ecx.frame_mut(); + frame.locals[local].value = 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, - ); - } - } + self.check_assertion(*expected, msg, cond, location); + } + TerminatorKind::SwitchInt { ref discr, ref targets } => { + if let Some(ref value) = self.eval_operand(&discr, location) + && let Some(value_const) = self.use_ecx(location, |this| this.ecx.read_scalar(&value)) + && let Ok(constant) = value_const.try_to_int() + && let Ok(constant) = constant.to_bits(constant.size()) + { + // We managed to evaluate the discriminant, so we know we only need to visit + // one target. + let target = targets.target_for_value(constant); + self.worklist.push(target); + return; } + // We failed to evaluate the discriminant, fallback to visiting all successors. } // None of these have Operands to const-propagate. TerminatorKind::Goto { .. } | TerminatorKind::Resume - | TerminatorKind::Abort + | TerminatorKind::Terminate | TerminatorKind::Return | TerminatorKind::Unreachable | TerminatorKind::Drop { .. } - | TerminatorKind::DropAndReplace { .. } | TerminatorKind::Yield { .. } | TerminatorKind::GeneratorDrop | TerminatorKind::FalseEdge { .. } | TerminatorKind::FalseUnwind { .. } - | TerminatorKind::SwitchInt { .. } | TerminatorKind::Call { .. } | TerminatorKind::InlineAsm { .. } => {} } + self.worklist.extend(terminator.successors()); + } + + fn visit_basic_block_data(&mut self, block: BasicBlock, data: &BasicBlockData<'tcx>) { + self.super_basic_block_data(block, data); + // 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() { + let mut written_only_inside_own_block_locals = + std::mem::take(&mut self.ecx.machine.written_only_inside_own_block_locals); + + // This loop can get very hot for some bodies: it check each local in each bb. + // To avoid this quadratic behaviour, we only clear the locals that were modified inside + // the current block. + for local in written_only_inside_own_block_locals.drain() { + debug_assert_eq!( + self.ecx.machine.can_const_prop[local], + ConstPropMode::OnlyInsideOwnBlock + ); 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; + self.ecx.machine.written_only_inside_own_block_locals = + written_only_inside_own_block_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()) - ) + for (local, &mode) in self.ecx.machine.can_const_prop.iter_enumerated() { + match mode { + ConstPropMode::FullConstProp => {} + ConstPropMode::NoPropagation | ConstPropMode::OnlyInsideOwnBlock => { + self.ensure_not_propagated(local); + } + } } } } |