| use rustc::mir; |
| use rustc::ty::layout::HasTyCtxt; |
| use rustc::ty::{self, Ty, TyCtxt}; |
| use rustc_hir::def_id::DefId; |
| use std::borrow::{Borrow, Cow}; |
| use std::collections::hash_map::Entry; |
| use std::hash::Hash; |
| |
| use rustc_data_structures::fx::FxHashMap; |
| |
| use rustc_span::source_map::Span; |
| |
| use crate::interpret::{ |
| self, snapshot, AllocId, Allocation, AssertMessage, GlobalId, ImmTy, InterpCx, InterpResult, |
| Memory, MemoryKind, OpTy, PlaceTy, Pointer, Scalar, |
| }; |
| |
| use super::error::*; |
| |
| impl<'mir, 'tcx> InterpCx<'mir, 'tcx, CompileTimeInterpreter<'mir, 'tcx>> { |
| /// Evaluate a const function where all arguments (if any) are zero-sized types. |
| /// The evaluation is memoized thanks to the query system. |
| /// |
| /// Returns `true` if the call has been evaluated. |
| fn try_eval_const_fn_call( |
| &mut self, |
| instance: ty::Instance<'tcx>, |
| ret: Option<(PlaceTy<'tcx>, mir::BasicBlock)>, |
| args: &[OpTy<'tcx>], |
| ) -> InterpResult<'tcx, bool> { |
| trace!("try_eval_const_fn_call: {:?}", instance); |
| // Because `#[track_caller]` adds an implicit non-ZST argument, we also cannot |
| // perform this optimization on items tagged with it. |
| if instance.def.requires_caller_location(self.tcx()) { |
| return Ok(false); |
| } |
| // For the moment we only do this for functions which take no arguments |
| // (or all arguments are ZSTs) so that we don't memoize too much. |
| if args.iter().any(|a| !a.layout.is_zst()) { |
| return Ok(false); |
| } |
| |
| let dest = match ret { |
| Some((dest, _)) => dest, |
| // Don't memoize diverging function calls. |
| None => return Ok(false), |
| }; |
| |
| let gid = GlobalId { instance, promoted: None }; |
| |
| let place = self.const_eval_raw(gid)?; |
| |
| self.copy_op(place.into(), dest)?; |
| |
| self.return_to_block(ret.map(|r| r.1))?; |
| self.dump_place(*dest); |
| return Ok(true); |
| } |
| } |
| |
| /// Number of steps until the detector even starts doing anything. |
| /// Also, a warning is shown to the user when this number is reached. |
| const STEPS_UNTIL_DETECTOR_ENABLED: isize = 1_000_000; |
| /// The number of steps between loop detector snapshots. |
| /// Should be a power of two for performance reasons. |
| const DETECTOR_SNAPSHOT_PERIOD: isize = 256; |
| |
| // Extra machine state for CTFE, and the Machine instance |
| pub struct CompileTimeInterpreter<'mir, 'tcx> { |
| /// When this value is negative, it indicates the number of interpreter |
| /// steps *until* the loop detector is enabled. When it is positive, it is |
| /// the number of steps after the detector has been enabled modulo the loop |
| /// detector period. |
| pub(super) steps_since_detector_enabled: isize, |
| |
| /// Extra state to detect loops. |
| pub(super) loop_detector: snapshot::InfiniteLoopDetector<'mir, 'tcx>, |
| } |
| |
| #[derive(Copy, Clone, Debug)] |
| pub struct MemoryExtra { |
| /// Whether this machine may read from statics |
| pub(super) can_access_statics: bool, |
| } |
| |
| impl<'mir, 'tcx> CompileTimeInterpreter<'mir, 'tcx> { |
| pub(super) fn new() -> Self { |
| CompileTimeInterpreter { |
| loop_detector: Default::default(), |
| steps_since_detector_enabled: -STEPS_UNTIL_DETECTOR_ENABLED, |
| } |
| } |
| } |
| |
| impl<K: Hash + Eq, V> interpret::AllocMap<K, V> for FxHashMap<K, V> { |
| #[inline(always)] |
| fn contains_key<Q: ?Sized + Hash + Eq>(&mut self, k: &Q) -> bool |
| where |
| K: Borrow<Q>, |
| { |
| FxHashMap::contains_key(self, k) |
| } |
| |
| #[inline(always)] |
| fn insert(&mut self, k: K, v: V) -> Option<V> { |
| FxHashMap::insert(self, k, v) |
| } |
| |
| #[inline(always)] |
| fn remove<Q: ?Sized + Hash + Eq>(&mut self, k: &Q) -> Option<V> |
| where |
| K: Borrow<Q>, |
| { |
| FxHashMap::remove(self, k) |
| } |
| |
| #[inline(always)] |
| fn filter_map_collect<T>(&self, mut f: impl FnMut(&K, &V) -> Option<T>) -> Vec<T> { |
| self.iter().filter_map(move |(k, v)| f(k, &*v)).collect() |
| } |
| |
| #[inline(always)] |
| fn get_or<E>(&self, k: K, vacant: impl FnOnce() -> Result<V, E>) -> Result<&V, E> { |
| match self.get(&k) { |
| Some(v) => Ok(v), |
| None => { |
| vacant()?; |
| bug!("The CTFE machine shouldn't ever need to extend the alloc_map when reading") |
| } |
| } |
| } |
| |
| #[inline(always)] |
| fn get_mut_or<E>(&mut self, k: K, vacant: impl FnOnce() -> Result<V, E>) -> Result<&mut V, E> { |
| match self.entry(k) { |
| Entry::Occupied(e) => Ok(e.into_mut()), |
| Entry::Vacant(e) => { |
| let v = vacant()?; |
| Ok(e.insert(v)) |
| } |
| } |
| } |
| } |
| |
| crate type CompileTimeEvalContext<'mir, 'tcx> = |
| InterpCx<'mir, 'tcx, CompileTimeInterpreter<'mir, 'tcx>>; |
| |
| impl interpret::MayLeak for ! { |
| #[inline(always)] |
| fn may_leak(self) -> bool { |
| // `self` is uninhabited |
| self |
| } |
| } |
| |
| impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir, 'tcx> { |
| type MemoryKinds = !; |
| type PointerTag = (); |
| type ExtraFnVal = !; |
| |
| type FrameExtra = (); |
| type MemoryExtra = MemoryExtra; |
| type AllocExtra = (); |
| |
| type MemoryMap = FxHashMap<AllocId, (MemoryKind<!>, Allocation)>; |
| |
| const STATIC_KIND: Option<!> = None; // no copying of statics allowed |
| |
| // We do not check for alignment to avoid having to carry an `Align` |
| // in `ConstValue::ByRef`. |
| const CHECK_ALIGN: bool = false; |
| |
| #[inline(always)] |
| fn enforce_validity(_ecx: &InterpCx<'mir, 'tcx, Self>) -> bool { |
| false // for now, we don't enforce validity |
| } |
| |
| fn find_mir_or_eval_fn( |
| ecx: &mut InterpCx<'mir, 'tcx, Self>, |
| span: Span, |
| instance: ty::Instance<'tcx>, |
| args: &[OpTy<'tcx>], |
| ret: Option<(PlaceTy<'tcx>, mir::BasicBlock)>, |
| _unwind: Option<mir::BasicBlock>, // unwinding is not supported in consts |
| ) -> InterpResult<'tcx, Option<&'mir mir::Body<'tcx>>> { |
| debug!("find_mir_or_eval_fn: {:?}", instance); |
| |
| // Only check non-glue functions |
| if let ty::InstanceDef::Item(def_id) = instance.def { |
| // Execution might have wandered off into other crates, so we cannot do a stability- |
| // sensitive check here. But we can at least rule out functions that are not const |
| // at all. |
| if ecx.tcx.is_const_fn_raw(def_id) { |
| // If this function is a `const fn` then under certain circumstances we |
| // can evaluate call via the query system, thus memoizing all future calls. |
| if ecx.try_eval_const_fn_call(instance, ret, args)? { |
| return Ok(None); |
| } |
| } else { |
| // Some functions we support even if they are non-const -- but avoid testing |
| // that for const fn! We certainly do *not* want to actually call the fn |
| // though, so be sure we return here. |
| return if ecx.hook_panic_fn(span, instance, args)? { |
| Ok(None) |
| } else { |
| throw_unsup_format!("calling non-const function `{}`", instance) |
| }; |
| } |
| } |
| // This is a const fn. Call it. |
| Ok(Some(match ecx.load_mir(instance.def, None) { |
| Ok(body) => *body, |
| Err(err) => { |
| if let err_unsup!(NoMirFor(ref path)) = err.kind { |
| return Err(ConstEvalError::NeedsRfc(format!( |
| "calling extern function `{}`", |
| path |
| )) |
| .into()); |
| } |
| return Err(err); |
| } |
| })) |
| } |
| |
| fn call_extra_fn( |
| _ecx: &mut InterpCx<'mir, 'tcx, Self>, |
| fn_val: !, |
| _args: &[OpTy<'tcx>], |
| _ret: Option<(PlaceTy<'tcx>, mir::BasicBlock)>, |
| _unwind: Option<mir::BasicBlock>, |
| ) -> InterpResult<'tcx> { |
| match fn_val {} |
| } |
| |
| fn call_intrinsic( |
| ecx: &mut InterpCx<'mir, 'tcx, Self>, |
| span: Span, |
| instance: ty::Instance<'tcx>, |
| args: &[OpTy<'tcx>], |
| ret: Option<(PlaceTy<'tcx>, mir::BasicBlock)>, |
| _unwind: Option<mir::BasicBlock>, |
| ) -> InterpResult<'tcx> { |
| if ecx.emulate_intrinsic(span, instance, args, ret)? { |
| return Ok(()); |
| } |
| // An intrinsic that we do not support |
| let intrinsic_name = ecx.tcx.item_name(instance.def_id()); |
| Err(ConstEvalError::NeedsRfc(format!("calling intrinsic `{}`", intrinsic_name)).into()) |
| } |
| |
| fn assert_panic( |
| ecx: &mut InterpCx<'mir, 'tcx, Self>, |
| _span: Span, |
| msg: &AssertMessage<'tcx>, |
| _unwind: Option<mir::BasicBlock>, |
| ) -> InterpResult<'tcx> { |
| use rustc::mir::interpret::PanicInfo::*; |
| Err(match msg { |
| BoundsCheck { ref len, ref index } => { |
| let len = ecx |
| .read_immediate(ecx.eval_operand(len, None)?) |
| .expect("can't eval len") |
| .to_scalar()? |
| .to_machine_usize(&*ecx)?; |
| let index = ecx |
| .read_immediate(ecx.eval_operand(index, None)?) |
| .expect("can't eval index") |
| .to_scalar()? |
| .to_machine_usize(&*ecx)?; |
| err_panic!(BoundsCheck { len, index }) |
| } |
| Overflow(op) => err_panic!(Overflow(*op)), |
| OverflowNeg => err_panic!(OverflowNeg), |
| DivisionByZero => err_panic!(DivisionByZero), |
| RemainderByZero => err_panic!(RemainderByZero), |
| ResumedAfterReturn(generator_kind) => err_panic!(ResumedAfterReturn(*generator_kind)), |
| ResumedAfterPanic(generator_kind) => err_panic!(ResumedAfterPanic(*generator_kind)), |
| Panic { .. } => bug!("`Panic` variant cannot occur in MIR"), |
| } |
| .into()) |
| } |
| |
| fn ptr_to_int(_mem: &Memory<'mir, 'tcx, Self>, _ptr: Pointer) -> InterpResult<'tcx, u64> { |
| Err(ConstEvalError::NeedsRfc("pointer-to-integer cast".to_string()).into()) |
| } |
| |
| fn binary_ptr_op( |
| _ecx: &InterpCx<'mir, 'tcx, Self>, |
| _bin_op: mir::BinOp, |
| _left: ImmTy<'tcx>, |
| _right: ImmTy<'tcx>, |
| ) -> InterpResult<'tcx, (Scalar, bool, Ty<'tcx>)> { |
| Err(ConstEvalError::NeedsRfc("pointer arithmetic or comparison".to_string()).into()) |
| } |
| |
| fn find_foreign_static( |
| _tcx: TyCtxt<'tcx>, |
| _def_id: DefId, |
| ) -> InterpResult<'tcx, Cow<'tcx, Allocation<Self::PointerTag>>> { |
| throw_unsup!(ReadForeignStatic) |
| } |
| |
| #[inline(always)] |
| fn init_allocation_extra<'b>( |
| _memory_extra: &MemoryExtra, |
| _id: AllocId, |
| alloc: Cow<'b, Allocation>, |
| _kind: Option<MemoryKind<!>>, |
| ) -> (Cow<'b, Allocation<Self::PointerTag>>, Self::PointerTag) { |
| // We do not use a tag so we can just cheaply forward the allocation |
| (alloc, ()) |
| } |
| |
| #[inline(always)] |
| fn tag_static_base_pointer(_memory_extra: &MemoryExtra, _id: AllocId) -> Self::PointerTag { |
| () |
| } |
| |
| fn box_alloc( |
| _ecx: &mut InterpCx<'mir, 'tcx, Self>, |
| _dest: PlaceTy<'tcx>, |
| ) -> InterpResult<'tcx> { |
| Err(ConstEvalError::NeedsRfc("heap allocations via `box` keyword".to_string()).into()) |
| } |
| |
| fn before_terminator(ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'tcx> { |
| { |
| let steps = &mut ecx.machine.steps_since_detector_enabled; |
| |
| *steps += 1; |
| if *steps < 0 { |
| return Ok(()); |
| } |
| |
| *steps %= DETECTOR_SNAPSHOT_PERIOD; |
| if *steps != 0 { |
| return Ok(()); |
| } |
| } |
| |
| let span = ecx.frame().span; |
| ecx.machine.loop_detector.observe_and_analyze(*ecx.tcx, span, &ecx.memory, &ecx.stack[..]) |
| } |
| |
| #[inline(always)] |
| fn stack_push(_ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'tcx> { |
| Ok(()) |
| } |
| |
| fn before_access_static( |
| memory_extra: &MemoryExtra, |
| _allocation: &Allocation, |
| ) -> InterpResult<'tcx> { |
| if memory_extra.can_access_statics { |
| Ok(()) |
| } else { |
| Err(ConstEvalError::ConstAccessesStatic.into()) |
| } |
| } |
| } |
| |
| // Please do not add any code below the above `Machine` trait impl. I (oli-obk) plan more cleanups |
| // so we can end up having a file with just that impl, but for now, let's keep the impl discoverable |
| // at the bottom of this file. |