diff options
Diffstat (limited to 'compiler/rustc_mir/src/interpret/eval_context.rs')
| -rw-r--r-- | compiler/rustc_mir/src/interpret/eval_context.rs | 1039 |
1 files changed, 1039 insertions, 0 deletions
diff --git a/compiler/rustc_mir/src/interpret/eval_context.rs b/compiler/rustc_mir/src/interpret/eval_context.rs new file mode 100644 index 00000000000..525da87463a --- /dev/null +++ b/compiler/rustc_mir/src/interpret/eval_context.rs @@ -0,0 +1,1039 @@ +use std::cell::Cell; +use std::fmt; +use std::mem; + +use rustc_data_structures::fx::FxHashMap; +use rustc_data_structures::stable_hasher::{HashStable, StableHasher}; +use rustc_hir::{self as hir, def::DefKind, def_id::DefId, definitions::DefPathData}; +use rustc_index::vec::IndexVec; +use rustc_macros::HashStable; +use rustc_middle::ich::StableHashingContext; +use rustc_middle::mir; +use rustc_middle::mir::interpret::{ + sign_extend, truncate, GlobalId, InterpResult, Pointer, Scalar, +}; +use rustc_middle::ty::layout::{self, TyAndLayout}; +use rustc_middle::ty::{ + self, query::TyCtxtAt, subst::SubstsRef, ParamEnv, Ty, TyCtxt, TypeFoldable, +}; +use rustc_span::{Pos, Span}; +use rustc_target::abi::{Align, HasDataLayout, LayoutOf, Size, TargetDataLayout}; + +use super::{ + Immediate, MPlaceTy, Machine, MemPlace, MemPlaceMeta, Memory, OpTy, Operand, Place, PlaceTy, + ScalarMaybeUninit, StackPopJump, +}; +use crate::transform::validate::equal_up_to_regions; +use crate::util::storage::AlwaysLiveLocals; + +pub struct InterpCx<'mir, 'tcx, M: Machine<'mir, 'tcx>> { + /// Stores the `Machine` instance. + /// + /// Note: the stack is provided by the machine. + pub machine: M, + + /// The results of the type checker, from rustc. + /// The span in this is the "root" of the evaluation, i.e., the const + /// we are evaluating (if this is CTFE). + pub tcx: TyCtxtAt<'tcx>, + + /// Bounds in scope for polymorphic evaluations. + pub(crate) param_env: ty::ParamEnv<'tcx>, + + /// The virtual memory system. + pub memory: Memory<'mir, 'tcx, M>, + + /// A cache for deduplicating vtables + pub(super) vtables: + FxHashMap<(Ty<'tcx>, Option<ty::PolyExistentialTraitRef<'tcx>>), Pointer<M::PointerTag>>, +} + +/// A stack frame. +#[derive(Clone)] +pub struct Frame<'mir, 'tcx, Tag = (), Extra = ()> { + //////////////////////////////////////////////////////////////////////////////// + // Function and callsite information + //////////////////////////////////////////////////////////////////////////////// + /// The MIR for the function called on this frame. + pub body: &'mir mir::Body<'tcx>, + + /// The def_id and substs of the current function. + pub instance: ty::Instance<'tcx>, + + /// Extra data for the machine. + pub extra: Extra, + + //////////////////////////////////////////////////////////////////////////////// + // Return place and locals + //////////////////////////////////////////////////////////////////////////////// + /// Work to perform when returning from this function. + pub return_to_block: StackPopCleanup, + + /// The location where the result of the current stack frame should be written to, + /// and its layout in the caller. + pub return_place: Option<PlaceTy<'tcx, Tag>>, + + /// The list of locals for this stack frame, stored in order as + /// `[return_ptr, arguments..., variables..., temporaries...]`. + /// The locals are stored as `Option<Value>`s. + /// `None` represents a local that is currently dead, while a live local + /// can either directly contain `Scalar` or refer to some part of an `Allocation`. + pub locals: IndexVec<mir::Local, LocalState<'tcx, Tag>>, + + //////////////////////////////////////////////////////////////////////////////// + // Current position within the function + //////////////////////////////////////////////////////////////////////////////// + /// If this is `Err`, we are not currently executing any particular statement in + /// this frame (can happen e.g. during frame initialization, and during unwinding on + /// frames without cleanup code). + /// We basically abuse `Result` as `Either`. + pub(super) loc: Result<mir::Location, Span>, +} + +/// What we store about a frame in an interpreter backtrace. +#[derive(Debug)] +pub struct FrameInfo<'tcx> { + pub instance: ty::Instance<'tcx>, + pub span: Span, + pub lint_root: Option<hir::HirId>, +} + +#[derive(Clone, Eq, PartialEq, Debug, HashStable)] // Miri debug-prints these +pub enum StackPopCleanup { + /// Jump to the next block in the caller, or cause UB if None (that's a function + /// that may never return). Also store layout of return place so + /// we can validate it at that layout. + /// `ret` stores the block we jump to on a normal return, while `unwind` + /// stores the block used for cleanup during unwinding. + Goto { ret: Option<mir::BasicBlock>, unwind: Option<mir::BasicBlock> }, + /// Just do nothing: Used by Main and for the `box_alloc` hook in miri. + /// `cleanup` says whether locals are deallocated. Static computation + /// wants them leaked to intern what they need (and just throw away + /// the entire `ecx` when it is done). + None { cleanup: bool }, +} + +/// State of a local variable including a memoized layout +#[derive(Clone, PartialEq, Eq, HashStable)] +pub struct LocalState<'tcx, Tag = ()> { + pub value: LocalValue<Tag>, + /// Don't modify if `Some`, this is only used to prevent computing the layout twice + #[stable_hasher(ignore)] + pub layout: Cell<Option<TyAndLayout<'tcx>>>, +} + +/// Current value of a local variable +#[derive(Copy, Clone, PartialEq, Eq, Debug, HashStable)] // Miri debug-prints these +pub enum LocalValue<Tag = ()> { + /// This local is not currently alive, and cannot be used at all. + Dead, + /// This local is alive but not yet initialized. It can be written to + /// but not read from or its address taken. Locals get initialized on + /// first write because for unsized locals, we do not know their size + /// before that. + Uninitialized, + /// A normal, live local. + /// Mostly for convenience, we re-use the `Operand` type here. + /// This is an optimization over just always having a pointer here; + /// we can thus avoid doing an allocation when the local just stores + /// immediate values *and* never has its address taken. + Live(Operand<Tag>), +} + +impl<'tcx, Tag: Copy + 'static> LocalState<'tcx, Tag> { + /// Read the local's value or error if the local is not yet live or not live anymore. + /// + /// Note: This may only be invoked from the `Machine::access_local` hook and not from + /// anywhere else. You may be invalidating machine invariants if you do! + pub fn access(&self) -> InterpResult<'tcx, Operand<Tag>> { + match self.value { + LocalValue::Dead => throw_ub!(DeadLocal), + LocalValue::Uninitialized => { + bug!("The type checker should prevent reading from a never-written local") + } + LocalValue::Live(val) => Ok(val), + } + } + + /// Overwrite the local. If the local can be overwritten in place, return a reference + /// to do so; otherwise return the `MemPlace` to consult instead. + /// + /// Note: This may only be invoked from the `Machine::access_local_mut` hook and not from + /// anywhere else. You may be invalidating machine invariants if you do! + pub fn access_mut( + &mut self, + ) -> InterpResult<'tcx, Result<&mut LocalValue<Tag>, MemPlace<Tag>>> { + match self.value { + LocalValue::Dead => throw_ub!(DeadLocal), + LocalValue::Live(Operand::Indirect(mplace)) => Ok(Err(mplace)), + ref mut + local @ (LocalValue::Live(Operand::Immediate(_)) | LocalValue::Uninitialized) => { + Ok(Ok(local)) + } + } + } +} + +impl<'mir, 'tcx, Tag> Frame<'mir, 'tcx, Tag> { + pub fn with_extra<Extra>(self, extra: Extra) -> Frame<'mir, 'tcx, Tag, Extra> { + Frame { + body: self.body, + instance: self.instance, + return_to_block: self.return_to_block, + return_place: self.return_place, + locals: self.locals, + loc: self.loc, + extra, + } + } +} + +impl<'mir, 'tcx, Tag, Extra> Frame<'mir, 'tcx, Tag, Extra> { + /// Return the `SourceInfo` of the current instruction. + pub fn current_source_info(&self) -> Option<&mir::SourceInfo> { + self.loc.ok().map(|loc| self.body.source_info(loc)) + } + + pub fn current_span(&self) -> Span { + match self.loc { + Ok(loc) => self.body.source_info(loc).span, + Err(span) => span, + } + } +} + +impl<'tcx> fmt::Display for FrameInfo<'tcx> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + ty::tls::with(|tcx| { + if tcx.def_key(self.instance.def_id()).disambiguated_data.data + == DefPathData::ClosureExpr + { + write!(f, "inside closure")?; + } else { + write!(f, "inside `{}`", self.instance)?; + } + if !self.span.is_dummy() { + let lo = tcx.sess.source_map().lookup_char_pos(self.span.lo()); + write!(f, " at {}:{}:{}", lo.file.name, lo.line, lo.col.to_usize() + 1)?; + } + Ok(()) + }) + } +} + +impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> HasDataLayout for InterpCx<'mir, 'tcx, M> { + #[inline] + fn data_layout(&self) -> &TargetDataLayout { + &self.tcx.data_layout + } +} + +impl<'mir, 'tcx, M> layout::HasTyCtxt<'tcx> for InterpCx<'mir, 'tcx, M> +where + M: Machine<'mir, 'tcx>, +{ + #[inline] + fn tcx(&self) -> TyCtxt<'tcx> { + *self.tcx + } +} + +impl<'mir, 'tcx, M> layout::HasParamEnv<'tcx> for InterpCx<'mir, 'tcx, M> +where + M: Machine<'mir, 'tcx>, +{ + fn param_env(&self) -> ty::ParamEnv<'tcx> { + self.param_env + } +} + +impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> LayoutOf for InterpCx<'mir, 'tcx, M> { + type Ty = Ty<'tcx>; + type TyAndLayout = InterpResult<'tcx, TyAndLayout<'tcx>>; + + #[inline] + fn layout_of(&self, ty: Ty<'tcx>) -> Self::TyAndLayout { + self.tcx + .layout_of(self.param_env.and(ty)) + .map_err(|layout| err_inval!(Layout(layout)).into()) + } +} + +/// Test if it is valid for a MIR assignment to assign `src`-typed place to `dest`-typed value. +/// This test should be symmetric, as it is primarily about layout compatibility. +pub(super) fn mir_assign_valid_types<'tcx>( + tcx: TyCtxt<'tcx>, + param_env: ParamEnv<'tcx>, + src: TyAndLayout<'tcx>, + dest: TyAndLayout<'tcx>, +) -> bool { + // Type-changing assignments can happen when subtyping is used. While + // all normal lifetimes are erased, higher-ranked types with their + // late-bound lifetimes are still around and can lead to type + // differences. So we compare ignoring lifetimes. + if equal_up_to_regions(tcx, param_env, src.ty, dest.ty) { + // Make sure the layout is equal, too -- just to be safe. Miri really + // needs layout equality. For performance reason we skip this check when + // the types are equal. Equal types *can* have different layouts when + // enum downcast is involved (as enum variants carry the type of the + // enum), but those should never occur in assignments. + if cfg!(debug_assertions) || src.ty != dest.ty { + assert_eq!(src.layout, dest.layout); + } + true + } else { + false + } +} + +/// Use the already known layout if given (but sanity check in debug mode), +/// or compute the layout. +#[cfg_attr(not(debug_assertions), inline(always))] +pub(super) fn from_known_layout<'tcx>( + tcx: TyCtxtAt<'tcx>, + param_env: ParamEnv<'tcx>, + known_layout: Option<TyAndLayout<'tcx>>, + compute: impl FnOnce() -> InterpResult<'tcx, TyAndLayout<'tcx>>, +) -> InterpResult<'tcx, TyAndLayout<'tcx>> { + match known_layout { + None => compute(), + Some(known_layout) => { + if cfg!(debug_assertions) { + let check_layout = compute()?; + if !mir_assign_valid_types(tcx.tcx, param_env, check_layout, known_layout) { + span_bug!( + tcx.span, + "expected type differs from actual type.\nexpected: {:?}\nactual: {:?}", + known_layout.ty, + check_layout.ty, + ); + } + } + Ok(known_layout) + } + } +} + +impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { + pub fn new( + tcx: TyCtxt<'tcx>, + root_span: Span, + param_env: ty::ParamEnv<'tcx>, + machine: M, + memory_extra: M::MemoryExtra, + ) -> Self { + InterpCx { + machine, + tcx: tcx.at(root_span), + param_env, + memory: Memory::new(tcx, memory_extra), + vtables: FxHashMap::default(), + } + } + + #[inline(always)] + pub fn cur_span(&self) -> Span { + self.stack().last().map(|f| f.current_span()).unwrap_or(self.tcx.span) + } + + #[inline(always)] + pub fn force_ptr( + &self, + scalar: Scalar<M::PointerTag>, + ) -> InterpResult<'tcx, Pointer<M::PointerTag>> { + self.memory.force_ptr(scalar) + } + + #[inline(always)] + pub fn force_bits( + &self, + scalar: Scalar<M::PointerTag>, + size: Size, + ) -> InterpResult<'tcx, u128> { + self.memory.force_bits(scalar, size) + } + + /// Call this to turn untagged "global" pointers (obtained via `tcx`) into + /// the machine pointer to the allocation. Must never be used + /// for any other pointers, nor for TLS statics. + /// + /// Using the resulting pointer represents a *direct* access to that memory + /// (e.g. by directly using a `static`), + /// as opposed to access through a pointer that was created by the program. + /// + /// This function can fail only if `ptr` points to an `extern static`. + #[inline(always)] + pub fn global_base_pointer(&self, ptr: Pointer) -> InterpResult<'tcx, Pointer<M::PointerTag>> { + self.memory.global_base_pointer(ptr) + } + + #[inline(always)] + pub(crate) fn stack(&self) -> &[Frame<'mir, 'tcx, M::PointerTag, M::FrameExtra>] { + M::stack(self) + } + + #[inline(always)] + pub(crate) fn stack_mut( + &mut self, + ) -> &mut Vec<Frame<'mir, 'tcx, M::PointerTag, M::FrameExtra>> { + M::stack_mut(self) + } + + #[inline(always)] + pub fn frame_idx(&self) -> usize { + let stack = self.stack(); + assert!(!stack.is_empty()); + stack.len() - 1 + } + + #[inline(always)] + pub fn frame(&self) -> &Frame<'mir, 'tcx, M::PointerTag, M::FrameExtra> { + self.stack().last().expect("no call frames exist") + } + + #[inline(always)] + pub fn frame_mut(&mut self) -> &mut Frame<'mir, 'tcx, M::PointerTag, M::FrameExtra> { + self.stack_mut().last_mut().expect("no call frames exist") + } + + #[inline(always)] + pub(super) fn body(&self) -> &'mir mir::Body<'tcx> { + self.frame().body + } + + #[inline(always)] + pub fn sign_extend(&self, value: u128, ty: TyAndLayout<'_>) -> u128 { + assert!(ty.abi.is_signed()); + sign_extend(value, ty.size) + } + + #[inline(always)] + pub fn truncate(&self, value: u128, ty: TyAndLayout<'_>) -> u128 { + truncate(value, ty.size) + } + + #[inline] + pub fn type_is_sized(&self, ty: Ty<'tcx>) -> bool { + ty.is_sized(self.tcx, self.param_env) + } + + #[inline] + pub fn type_is_freeze(&self, ty: Ty<'tcx>) -> bool { + ty.is_freeze(self.tcx, self.param_env) + } + + pub fn load_mir( + &self, + instance: ty::InstanceDef<'tcx>, + promoted: Option<mir::Promoted>, + ) -> InterpResult<'tcx, &'tcx mir::Body<'tcx>> { + // do not continue if typeck errors occurred (can only occur in local crate) + let def = instance.with_opt_param(); + if let Some(def) = def.as_local() { + if self.tcx.has_typeck_results(def.did) { + if let Some(error_reported) = self.tcx.typeck_opt_const_arg(def).tainted_by_errors { + throw_inval!(TypeckError(error_reported)) + } + } + } + trace!("load mir(instance={:?}, promoted={:?})", instance, promoted); + if let Some(promoted) = promoted { + return Ok(&self.tcx.promoted_mir_of_opt_const_arg(def)[promoted]); + } + match instance { + ty::InstanceDef::Item(def) => { + if self.tcx.is_mir_available(def.did) { + if let Some((did, param_did)) = def.as_const_arg() { + Ok(self.tcx.optimized_mir_of_const_arg((did, param_did))) + } else { + Ok(self.tcx.optimized_mir(def.did)) + } + } else { + throw_unsup!(NoMirFor(def.did)) + } + } + _ => Ok(self.tcx.instance_mir(instance)), + } + } + + /// Call this on things you got out of the MIR (so it is as generic as the current + /// stack frame), to bring it into the proper environment for this interpreter. + pub(super) fn subst_from_current_frame_and_normalize_erasing_regions<T: TypeFoldable<'tcx>>( + &self, + value: T, + ) -> T { + self.subst_from_frame_and_normalize_erasing_regions(self.frame(), value) + } + + /// Call this on things you got out of the MIR (so it is as generic as the provided + /// stack frame), to bring it into the proper environment for this interpreter. + pub(super) fn subst_from_frame_and_normalize_erasing_regions<T: TypeFoldable<'tcx>>( + &self, + frame: &Frame<'mir, 'tcx, M::PointerTag, M::FrameExtra>, + value: T, + ) -> T { + if let Some(substs) = frame.instance.substs_for_mir_body() { + self.tcx.subst_and_normalize_erasing_regions(substs, self.param_env, &value) + } else { + self.tcx.normalize_erasing_regions(self.param_env, value) + } + } + + /// The `substs` are assumed to already be in our interpreter "universe" (param_env). + pub(super) fn resolve( + &self, + def_id: DefId, + substs: SubstsRef<'tcx>, + ) -> InterpResult<'tcx, ty::Instance<'tcx>> { + trace!("resolve: {:?}, {:#?}", def_id, substs); + trace!("param_env: {:#?}", self.param_env); + trace!("substs: {:#?}", substs); + match ty::Instance::resolve(*self.tcx, self.param_env, def_id, substs) { + Ok(Some(instance)) => Ok(instance), + Ok(None) => throw_inval!(TooGeneric), + + // FIXME(eddyb) this could be a bit more specific than `TypeckError`. + Err(error_reported) => throw_inval!(TypeckError(error_reported)), + } + } + + pub fn layout_of_local( + &self, + frame: &Frame<'mir, 'tcx, M::PointerTag, M::FrameExtra>, + local: mir::Local, + layout: Option<TyAndLayout<'tcx>>, + ) -> InterpResult<'tcx, TyAndLayout<'tcx>> { + // `const_prop` runs into this with an invalid (empty) frame, so we + // have to support that case (mostly by skipping all caching). + match frame.locals.get(local).and_then(|state| state.layout.get()) { + None => { + let layout = from_known_layout(self.tcx, self.param_env, layout, || { + let local_ty = frame.body.local_decls[local].ty; + let local_ty = + self.subst_from_frame_and_normalize_erasing_regions(frame, local_ty); + self.layout_of(local_ty) + })?; + if let Some(state) = frame.locals.get(local) { + // Layouts of locals are requested a lot, so we cache them. + state.layout.set(Some(layout)); + } + Ok(layout) + } + Some(layout) => Ok(layout), + } + } + + /// Returns the actual dynamic size and alignment of the place at the given type. + /// Only the "meta" (metadata) part of the place matters. + /// This can fail to provide an answer for extern types. + pub(super) fn size_and_align_of( + &self, + metadata: MemPlaceMeta<M::PointerTag>, + layout: TyAndLayout<'tcx>, + ) -> InterpResult<'tcx, Option<(Size, Align)>> { + if !layout.is_unsized() { + return Ok(Some((layout.size, layout.align.abi))); + } + match layout.ty.kind { + ty::Adt(..) | ty::Tuple(..) => { + // First get the size of all statically known fields. + // Don't use type_of::sizing_type_of because that expects t to be sized, + // and it also rounds up to alignment, which we want to avoid, + // as the unsized field's alignment could be smaller. + assert!(!layout.ty.is_simd()); + assert!(layout.fields.count() > 0); + trace!("DST layout: {:?}", layout); + + let sized_size = layout.fields.offset(layout.fields.count() - 1); + let sized_align = layout.align.abi; + trace!( + "DST {} statically sized prefix size: {:?} align: {:?}", + layout.ty, + sized_size, + sized_align + ); + + // Recurse to get the size of the dynamically sized field (must be + // the last field). Can't have foreign types here, how would we + // adjust alignment and size for them? + let field = layout.field(self, layout.fields.count() - 1)?; + let (unsized_size, unsized_align) = match self.size_and_align_of(metadata, field)? { + Some(size_and_align) => size_and_align, + None => { + // A field with extern type. If this field is at offset 0, we behave + // like the underlying extern type. + // FIXME: Once we have made decisions for how to handle size and alignment + // of `extern type`, this should be adapted. It is just a temporary hack + // to get some code to work that probably ought to work. + if sized_size == Size::ZERO { + return Ok(None); + } else { + span_bug!( + self.cur_span(), + "Fields cannot be extern types, unless they are at offset 0" + ) + } + } + }; + + // FIXME (#26403, #27023): We should be adding padding + // to `sized_size` (to accommodate the `unsized_align` + // required of the unsized field that follows) before + // summing it with `sized_size`. (Note that since #26403 + // is unfixed, we do not yet add the necessary padding + // here. But this is where the add would go.) + + // Return the sum of sizes and max of aligns. + let size = sized_size + unsized_size; // `Size` addition + + // Choose max of two known alignments (combined value must + // be aligned according to more restrictive of the two). + let align = sized_align.max(unsized_align); + + // Issue #27023: must add any necessary padding to `size` + // (to make it a multiple of `align`) before returning it. + let size = size.align_to(align); + + // Check if this brought us over the size limit. + if size.bytes() >= self.tcx.data_layout.obj_size_bound() { + throw_ub!(InvalidMeta("total size is bigger than largest supported object")); + } + Ok(Some((size, align))) + } + ty::Dynamic(..) => { + let vtable = metadata.unwrap_meta(); + // Read size and align from vtable (already checks size). + Ok(Some(self.read_size_and_align_from_vtable(vtable)?)) + } + + ty::Slice(_) | ty::Str => { + let len = metadata.unwrap_meta().to_machine_usize(self)?; + let elem = layout.field(self, 0)?; + + // Make sure the slice is not too big. + let size = elem.size.checked_mul(len, self).ok_or_else(|| { + err_ub!(InvalidMeta("slice is bigger than largest supported object")) + })?; + Ok(Some((size, elem.align.abi))) + } + + ty::Foreign(_) => Ok(None), + + _ => span_bug!(self.cur_span(), "size_and_align_of::<{:?}> not supported", layout.ty), + } + } + #[inline] + pub fn size_and_align_of_mplace( + &self, + mplace: MPlaceTy<'tcx, M::PointerTag>, + ) -> InterpResult<'tcx, Option<(Size, Align)>> { + self.size_and_align_of(mplace.meta, mplace.layout) + } + + pub fn push_stack_frame( + &mut self, + instance: ty::Instance<'tcx>, + body: &'mir mir::Body<'tcx>, + return_place: Option<PlaceTy<'tcx, M::PointerTag>>, + return_to_block: StackPopCleanup, + ) -> InterpResult<'tcx> { + if !self.stack().is_empty() { + info!("PAUSING({}) {}", self.frame_idx(), self.frame().instance); + } + ::log_settings::settings().indentation += 1; + + // first push a stack frame so we have access to the local substs + let pre_frame = Frame { + body, + loc: Err(body.span), // Span used for errors caused during preamble. + return_to_block, + return_place, + // empty local array, we fill it in below, after we are inside the stack frame and + // all methods actually know about the frame + locals: IndexVec::new(), + instance, + extra: (), + }; + let frame = M::init_frame_extra(self, pre_frame)?; + self.stack_mut().push(frame); + + // Make sure all the constants required by this frame evaluate successfully (post-monomorphization check). + for const_ in &body.required_consts { + let span = const_.span; + let const_ = + self.subst_from_current_frame_and_normalize_erasing_regions(const_.literal); + self.const_to_op(const_, None).map_err(|err| { + // If there was an error, set the span of the current frame to this constant. + // Avoiding doing this when evaluation succeeds. + self.frame_mut().loc = Err(span); + err + })?; + } + + // Locals are initially uninitialized. + let dummy = LocalState { value: LocalValue::Uninitialized, layout: Cell::new(None) }; + let mut locals = IndexVec::from_elem(dummy, &body.local_decls); + + // Now mark those locals as dead that we do not want to initialize + match self.tcx.def_kind(instance.def_id()) { + // statics and constants don't have `Storage*` statements, no need to look for them + // + // FIXME: The above is likely untrue. See + // <https://github.com/rust-lang/rust/pull/70004#issuecomment-602022110>. Is it + // okay to ignore `StorageDead`/`StorageLive` annotations during CTFE? + DefKind::Static | DefKind::Const | DefKind::AssocConst => {} + _ => { + // Mark locals that use `Storage*` annotations as dead on function entry. + let always_live = AlwaysLiveLocals::new(self.body()); + for local in locals.indices() { + if !always_live.contains(local) { + locals[local].value = LocalValue::Dead; + } + } + } + } + // done + self.frame_mut().locals = locals; + M::after_stack_push(self)?; + self.frame_mut().loc = Ok(mir::Location::START); + info!("ENTERING({}) {}", self.frame_idx(), self.frame().instance); + + Ok(()) + } + + /// Jump to the given block. + #[inline] + pub fn go_to_block(&mut self, target: mir::BasicBlock) { + self.frame_mut().loc = Ok(mir::Location { block: target, statement_index: 0 }); + } + + /// *Return* to the given `target` basic block. + /// Do *not* use for unwinding! Use `unwind_to_block` instead. + /// + /// If `target` is `None`, that indicates the function cannot return, so we raise UB. + pub fn return_to_block(&mut self, target: Option<mir::BasicBlock>) -> InterpResult<'tcx> { + if let Some(target) = target { + self.go_to_block(target); + Ok(()) + } else { + throw_ub!(Unreachable) + } + } + + /// *Unwind* to the given `target` basic block. + /// Do *not* use for returning! Use `return_to_block` instead. + /// + /// If `target` is `None`, that indicates the function does not need cleanup during + /// unwinding, and we will just keep propagating that upwards. + pub fn unwind_to_block(&mut self, target: Option<mir::BasicBlock>) { + self.frame_mut().loc = match target { + Some(block) => Ok(mir::Location { block, statement_index: 0 }), + None => Err(self.frame_mut().body.span), + }; + } + + /// Pops the current frame from the stack, deallocating the + /// memory for allocated locals. + /// + /// If `unwinding` is `false`, then we are performing a normal return + /// from a function. In this case, we jump back into the frame of the caller, + /// and continue execution as normal. + /// + /// If `unwinding` is `true`, then we are in the middle of a panic, + /// and need to unwind this frame. In this case, we jump to the + /// `cleanup` block for the function, which is responsible for running + /// `Drop` impls for any locals that have been initialized at this point. + /// The cleanup block ends with a special `Resume` terminator, which will + /// cause us to continue unwinding. + pub(super) fn pop_stack_frame(&mut self, unwinding: bool) -> InterpResult<'tcx> { + info!( + "LEAVING({}) {} (unwinding = {})", + self.frame_idx(), + self.frame().instance, + unwinding + ); + + // Sanity check `unwinding`. + assert_eq!( + unwinding, + match self.frame().loc { + Ok(loc) => self.body().basic_blocks()[loc.block].is_cleanup, + Err(_) => true, + } + ); + + if unwinding && self.frame_idx() == 0 { + throw_ub_format!("unwinding past the topmost frame of the stack"); + } + + ::log_settings::settings().indentation -= 1; + let frame = + self.stack_mut().pop().expect("tried to pop a stack frame, but there were none"); + + if !unwinding { + // Copy the return value to the caller's stack frame. + if let Some(return_place) = frame.return_place { + let op = self.access_local(&frame, mir::RETURN_PLACE, None)?; + self.copy_op_transmute(op, return_place)?; + trace!("{:?}", self.dump_place(*return_place)); + } else { + throw_ub!(Unreachable); + } + } + + // Now where do we jump next? + + // Usually we want to clean up (deallocate locals), but in a few rare cases we don't. + // In that case, we return early. We also avoid validation in that case, + // because this is CTFE and the final value will be thoroughly validated anyway. + let (cleanup, next_block) = match frame.return_to_block { + StackPopCleanup::Goto { ret, unwind } => { + (true, Some(if unwinding { unwind } else { ret })) + } + StackPopCleanup::None { cleanup, .. } => (cleanup, None), + }; + + if !cleanup { + assert!(self.stack().is_empty(), "only the topmost frame should ever be leaked"); + assert!(next_block.is_none(), "tried to skip cleanup when we have a next block!"); + assert!(!unwinding, "tried to skip cleanup during unwinding"); + // Leak the locals, skip validation, skip machine hook. + return Ok(()); + } + + // Cleanup: deallocate all locals that are backed by an allocation. + for local in &frame.locals { + self.deallocate_local(local.value)?; + } + + if M::after_stack_pop(self, frame, unwinding)? == StackPopJump::NoJump { + // The hook already did everything. + // We want to skip the `info!` below, hence early return. + return Ok(()); + } + // Normal return, figure out where to jump. + if unwinding { + // Follow the unwind edge. + let unwind = next_block.expect("Encountered StackPopCleanup::None when unwinding!"); + self.unwind_to_block(unwind); + } else { + // Follow the normal return edge. + if let Some(ret) = next_block { + self.return_to_block(ret)?; + } + } + + if !self.stack().is_empty() { + info!( + "CONTINUING({}) {} (unwinding = {})", + self.frame_idx(), + self.frame().instance, + unwinding + ); + } + + Ok(()) + } + + /// Mark a storage as live, killing the previous content and returning it. + /// Remember to deallocate that! + pub fn storage_live( + &mut self, + local: mir::Local, + ) -> InterpResult<'tcx, LocalValue<M::PointerTag>> { + assert!(local != mir::RETURN_PLACE, "Cannot make return place live"); + trace!("{:?} is now live", local); + + let local_val = LocalValue::Uninitialized; + // StorageLive *always* kills the value that's currently stored. + // However, we do not error if the variable already is live; + // see <https://github.com/rust-lang/rust/issues/42371>. + Ok(mem::replace(&mut self.frame_mut().locals[local].value, local_val)) + } + + /// Returns the old value of the local. + /// Remember to deallocate that! + pub fn storage_dead(&mut self, local: mir::Local) -> LocalValue<M::PointerTag> { + assert!(local != mir::RETURN_PLACE, "Cannot make return place dead"); + trace!("{:?} is now dead", local); + + mem::replace(&mut self.frame_mut().locals[local].value, LocalValue::Dead) + } + + pub(super) fn deallocate_local( + &mut self, + local: LocalValue<M::PointerTag>, + ) -> InterpResult<'tcx> { + // FIXME: should we tell the user that there was a local which was never written to? + if let LocalValue::Live(Operand::Indirect(MemPlace { ptr, .. })) = local { + // All locals have a backing allocation, even if the allocation is empty + // due to the local having ZST type. + let ptr = ptr.assert_ptr(); + trace!("deallocating local: {:?}", self.memory.dump_alloc(ptr.alloc_id)); + self.memory.deallocate_local(ptr)?; + }; + Ok(()) + } + + pub(super) fn const_eval( + &self, + gid: GlobalId<'tcx>, + ty: Ty<'tcx>, + ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> { + // For statics we pick `ParamEnv::reveal_all`, because statics don't have generics + // and thus don't care about the parameter environment. While we could just use + // `self.param_env`, that would mean we invoke the query to evaluate the static + // with different parameter environments, thus causing the static to be evaluated + // multiple times. + let param_env = if self.tcx.is_static(gid.instance.def_id()) { + ty::ParamEnv::reveal_all() + } else { + self.param_env + }; + let val = self.tcx.const_eval_global_id(param_env, gid, Some(self.tcx.span))?; + + // Even though `ecx.const_eval` is called from `const_to_op` we can never have a + // recursion deeper than one level, because the `tcx.const_eval` above is guaranteed to not + // return `ConstValue::Unevaluated`, which is the only way that `const_to_op` will call + // `ecx.const_eval`. + let const_ = ty::Const { val: ty::ConstKind::Value(val), ty }; + self.const_to_op(&const_, None) + } + + pub fn const_eval_raw( + &self, + gid: GlobalId<'tcx>, + ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> { + // For statics we pick `ParamEnv::reveal_all`, because statics don't have generics + // and thus don't care about the parameter environment. While we could just use + // `self.param_env`, that would mean we invoke the query to evaluate the static + // with different parameter environments, thus causing the static to be evaluated + // multiple times. + let param_env = if self.tcx.is_static(gid.instance.def_id()) { + ty::ParamEnv::reveal_all() + } else { + self.param_env + }; + // We use `const_eval_raw` here, and get an unvalidated result. That is okay: + // Our result will later be validated anyway, and there seems no good reason + // to have to fail early here. This is also more consistent with + // `Memory::get_static_alloc` which has to use `const_eval_raw` to avoid cycles. + // FIXME: We can hit delay_span_bug if this is an invalid const, interning finds + // that problem, but we never run validation to show an error. Can we ensure + // this does not happen? + let val = self.tcx.const_eval_raw(param_env.and(gid))?; + self.raw_const_to_mplace(val) + } + + #[must_use] + pub fn dump_place(&'a self, place: Place<M::PointerTag>) -> PlacePrinter<'a, 'mir, 'tcx, M> { + PlacePrinter { ecx: self, place } + } + + #[must_use] + pub fn generate_stacktrace(&self) -> Vec<FrameInfo<'tcx>> { + let mut frames = Vec::new(); + for frame in self.stack().iter().rev() { + let lint_root = frame.current_source_info().and_then(|source_info| { + match &frame.body.source_scopes[source_info.scope].local_data { + mir::ClearCrossCrate::Set(data) => Some(data.lint_root), + mir::ClearCrossCrate::Clear => None, + } + }); + let span = frame.current_span(); + + frames.push(FrameInfo { span, instance: frame.instance, lint_root }); + } + trace!("generate stacktrace: {:#?}", frames); + frames + } +} + +#[doc(hidden)] +/// Helper struct for the `dump_place` function. +pub struct PlacePrinter<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> { + ecx: &'a InterpCx<'mir, 'tcx, M>, + place: Place<M::PointerTag>, +} + +impl<'a, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> std::fmt::Debug + for PlacePrinter<'a, 'mir, 'tcx, M> +{ + fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { + match self.place { + Place::Local { frame, local } => { + let mut allocs = Vec::new(); + write!(fmt, "{:?}", local)?; + if frame != self.ecx.frame_idx() { + write!(fmt, " ({} frames up)", self.ecx.frame_idx() - frame)?; + } + write!(fmt, ":")?; + + match self.ecx.stack()[frame].locals[local].value { + LocalValue::Dead => write!(fmt, " is dead")?, + LocalValue::Uninitialized => write!(fmt, " is uninitialized")?, + LocalValue::Live(Operand::Indirect(mplace)) => match mplace.ptr { + Scalar::Ptr(ptr) => { + write!( + fmt, + " by align({}){} ref:", + mplace.align.bytes(), + match mplace.meta { + MemPlaceMeta::Meta(meta) => format!(" meta({:?})", meta), + MemPlaceMeta::Poison | MemPlaceMeta::None => String::new(), + } + )?; + allocs.push(ptr.alloc_id); + } + ptr => write!(fmt, " by integral ref: {:?}", ptr)?, + }, + LocalValue::Live(Operand::Immediate(Immediate::Scalar(val))) => { + write!(fmt, " {:?}", val)?; + if let ScalarMaybeUninit::Scalar(Scalar::Ptr(ptr)) = val { + allocs.push(ptr.alloc_id); + } + } + LocalValue::Live(Operand::Immediate(Immediate::ScalarPair(val1, val2))) => { + write!(fmt, " ({:?}, {:?})", val1, val2)?; + if let ScalarMaybeUninit::Scalar(Scalar::Ptr(ptr)) = val1 { + allocs.push(ptr.alloc_id); + } + if let ScalarMaybeUninit::Scalar(Scalar::Ptr(ptr)) = val2 { + allocs.push(ptr.alloc_id); + } + } + } + + write!(fmt, ": {:?}", self.ecx.memory.dump_allocs(allocs)) + } + Place::Ptr(mplace) => match mplace.ptr { + Scalar::Ptr(ptr) => write!( + fmt, + "by align({}) ref: {:?}", + mplace.align.bytes(), + self.ecx.memory.dump_alloc(ptr.alloc_id) + ), + ptr => write!(fmt, " integral by ref: {:?}", ptr), + }, + } + } +} + +impl<'ctx, 'mir, 'tcx, Tag, Extra> HashStable<StableHashingContext<'ctx>> + for Frame<'mir, 'tcx, Tag, Extra> +where + Extra: HashStable<StableHashingContext<'ctx>>, + Tag: HashStable<StableHashingContext<'ctx>>, +{ + fn hash_stable(&self, hcx: &mut StableHashingContext<'ctx>, hasher: &mut StableHasher) { + // Exhaustive match on fields to make sure we forget no field. + let Frame { body, instance, return_to_block, return_place, locals, loc, extra } = self; + body.hash_stable(hcx, hasher); + instance.hash_stable(hcx, hasher); + return_to_block.hash_stable(hcx, hasher); + return_place.as_ref().map(|r| &**r).hash_stable(hcx, hasher); + locals.hash_stable(hcx, hasher); + loc.hash_stable(hcx, hasher); + extra.hash_stable(hcx, hasher); + } +} |