| //! Functions concerning immediate values and operands, and reading from operands. |
| //! All high-level functions to read from memory work on operands as sources. |
| |
| use std::convert::TryInto; |
| |
| use rustc::{mir, ty}; |
| use rustc::ty::layout::{self, Size, LayoutOf, TyLayout, HasDataLayout, IntegerExt, VariantIdx}; |
| |
| use rustc::mir::interpret::{ |
| GlobalId, AllocId, InboundsCheck, |
| ConstValue, Pointer, Scalar, |
| EvalResult, EvalErrorKind, |
| }; |
| use super::{EvalContext, Machine, MemPlace, MPlaceTy, MemoryKind}; |
| pub use rustc::mir::interpret::ScalarMaybeUndef; |
| |
| /// A `Value` represents a single immediate self-contained Rust value. |
| /// |
| /// For optimization of a few very common cases, there is also a representation for a pair of |
| /// primitive values (`ScalarPair`). It allows Miri to avoid making allocations for checked binary |
| /// operations and fat pointers. This idea was taken from rustc's codegen. |
| /// In particular, thanks to `ScalarPair`, arithmetic operations and casts can be entirely |
| /// defined on `Immediate`, and do not have to work with a `Place`. |
| #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)] |
| pub enum Immediate<Tag=(), Id=AllocId> { |
| Scalar(ScalarMaybeUndef<Tag, Id>), |
| ScalarPair(ScalarMaybeUndef<Tag, Id>, ScalarMaybeUndef<Tag, Id>), |
| } |
| |
| impl Immediate { |
| #[inline] |
| pub fn with_default_tag<Tag>(self) -> Immediate<Tag> |
| where Tag: Default |
| { |
| match self { |
| Immediate::Scalar(x) => Immediate::Scalar(x.with_default_tag()), |
| Immediate::ScalarPair(x, y) => |
| Immediate::ScalarPair(x.with_default_tag(), y.with_default_tag()), |
| } |
| } |
| } |
| |
| impl<'tcx, Tag> Immediate<Tag> { |
| #[inline] |
| pub fn erase_tag(self) -> Immediate |
| { |
| match self { |
| Immediate::Scalar(x) => Immediate::Scalar(x.erase_tag()), |
| Immediate::ScalarPair(x, y) => |
| Immediate::ScalarPair(x.erase_tag(), y.erase_tag()), |
| } |
| } |
| |
| pub fn new_slice( |
| val: Scalar<Tag>, |
| len: u64, |
| cx: &impl HasDataLayout |
| ) -> Self { |
| Immediate::ScalarPair( |
| val.into(), |
| Scalar::from_uint(len, cx.data_layout().pointer_size).into(), |
| ) |
| } |
| |
| pub fn new_dyn_trait(val: Scalar<Tag>, vtable: Pointer<Tag>) -> Self { |
| Immediate::ScalarPair(val.into(), Scalar::Ptr(vtable).into()) |
| } |
| |
| #[inline] |
| pub fn to_scalar_or_undef(self) -> ScalarMaybeUndef<Tag> { |
| match self { |
| Immediate::Scalar(val) => val, |
| Immediate::ScalarPair(..) => bug!("Got a fat pointer where a scalar was expected"), |
| } |
| } |
| |
| #[inline] |
| pub fn to_scalar(self) -> EvalResult<'tcx, Scalar<Tag>> { |
| self.to_scalar_or_undef().not_undef() |
| } |
| |
| #[inline] |
| pub fn to_scalar_pair(self) -> EvalResult<'tcx, (Scalar<Tag>, Scalar<Tag>)> { |
| match self { |
| Immediate::Scalar(..) => bug!("Got a thin pointer where a scalar pair was expected"), |
| Immediate::ScalarPair(a, b) => Ok((a.not_undef()?, b.not_undef()?)) |
| } |
| } |
| |
| /// Convert the immediate into a pointer (or a pointer-sized integer). |
| /// Throws away the second half of a ScalarPair! |
| #[inline] |
| pub fn to_scalar_ptr(self) -> EvalResult<'tcx, Scalar<Tag>> { |
| match self { |
| Immediate::Scalar(ptr) | |
| Immediate::ScalarPair(ptr, _) => ptr.not_undef(), |
| } |
| } |
| |
| /// Convert the value into its metadata. |
| /// Throws away the first half of a ScalarPair! |
| #[inline] |
| pub fn to_meta(self) -> EvalResult<'tcx, Option<Scalar<Tag>>> { |
| Ok(match self { |
| Immediate::Scalar(_) => None, |
| Immediate::ScalarPair(_, meta) => Some(meta.not_undef()?), |
| }) |
| } |
| } |
| |
| // ScalarPair needs a type to interpret, so we often have an immediate and a type together |
| // as input for binary and cast operations. |
| #[derive(Copy, Clone, Debug)] |
| pub struct ImmTy<'tcx, Tag=()> { |
| immediate: Immediate<Tag>, |
| pub layout: TyLayout<'tcx>, |
| } |
| |
| impl<'tcx, Tag> ::std::ops::Deref for ImmTy<'tcx, Tag> { |
| type Target = Immediate<Tag>; |
| #[inline(always)] |
| fn deref(&self) -> &Immediate<Tag> { |
| &self.immediate |
| } |
| } |
| |
| /// An `Operand` is the result of computing a `mir::Operand`. It can be immediate, |
| /// or still in memory. The latter is an optimization, to delay reading that chunk of |
| /// memory and to avoid having to store arbitrary-sized data here. |
| #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)] |
| pub enum Operand<Tag=(), Id=AllocId> { |
| Immediate(Immediate<Tag, Id>), |
| Indirect(MemPlace<Tag, Id>), |
| } |
| |
| impl Operand { |
| #[inline] |
| pub fn with_default_tag<Tag>(self) -> Operand<Tag> |
| where Tag: Default |
| { |
| match self { |
| Operand::Immediate(x) => Operand::Immediate(x.with_default_tag()), |
| Operand::Indirect(x) => Operand::Indirect(x.with_default_tag()), |
| } |
| } |
| } |
| |
| impl<Tag> Operand<Tag> { |
| #[inline] |
| pub fn erase_tag(self) -> Operand |
| { |
| match self { |
| Operand::Immediate(x) => Operand::Immediate(x.erase_tag()), |
| Operand::Indirect(x) => Operand::Indirect(x.erase_tag()), |
| } |
| } |
| |
| #[inline] |
| pub fn to_mem_place(self) -> MemPlace<Tag> |
| where Tag: ::std::fmt::Debug |
| { |
| match self { |
| Operand::Indirect(mplace) => mplace, |
| _ => bug!("to_mem_place: expected Operand::Indirect, got {:?}", self), |
| |
| } |
| } |
| |
| #[inline] |
| pub fn to_immediate(self) -> Immediate<Tag> |
| where Tag: ::std::fmt::Debug |
| { |
| match self { |
| Operand::Immediate(imm) => imm, |
| _ => bug!("to_immediate: expected Operand::Immediate, got {:?}", self), |
| |
| } |
| } |
| } |
| |
| #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)] |
| pub struct OpTy<'tcx, Tag=()> { |
| crate op: Operand<Tag>, // ideally we'd make this private, but const_prop needs this |
| pub layout: TyLayout<'tcx>, |
| } |
| |
| impl<'tcx, Tag> ::std::ops::Deref for OpTy<'tcx, Tag> { |
| type Target = Operand<Tag>; |
| #[inline(always)] |
| fn deref(&self) -> &Operand<Tag> { |
| &self.op |
| } |
| } |
| |
| impl<'tcx, Tag: Copy> From<MPlaceTy<'tcx, Tag>> for OpTy<'tcx, Tag> { |
| #[inline(always)] |
| fn from(mplace: MPlaceTy<'tcx, Tag>) -> Self { |
| OpTy { |
| op: Operand::Indirect(*mplace), |
| layout: mplace.layout |
| } |
| } |
| } |
| |
| impl<'tcx, Tag> From<ImmTy<'tcx, Tag>> for OpTy<'tcx, Tag> { |
| #[inline(always)] |
| fn from(val: ImmTy<'tcx, Tag>) -> Self { |
| OpTy { |
| op: Operand::Immediate(val.immediate), |
| layout: val.layout |
| } |
| } |
| } |
| |
| impl<'tcx, Tag> OpTy<'tcx, Tag> |
| { |
| #[inline] |
| pub fn erase_tag(self) -> OpTy<'tcx> |
| { |
| OpTy { |
| op: self.op.erase_tag(), |
| layout: self.layout, |
| } |
| } |
| } |
| |
| // Use the existing layout if given (but sanity check in debug mode), |
| // or compute the layout. |
| #[inline(always)] |
| fn from_known_layout<'tcx>( |
| layout: Option<TyLayout<'tcx>>, |
| compute: impl FnOnce() -> EvalResult<'tcx, TyLayout<'tcx>> |
| ) -> EvalResult<'tcx, TyLayout<'tcx>> { |
| match layout { |
| None => compute(), |
| Some(layout) => { |
| if cfg!(debug_assertions) { |
| let layout2 = compute()?; |
| assert_eq!(layout.details, layout2.details, |
| "Mismatch in layout of supposedly equal-layout types {:?} and {:?}", |
| layout.ty, layout2.ty); |
| } |
| Ok(layout) |
| } |
| } |
| } |
| |
| impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M> { |
| /// Try reading an immediate in memory; this is interesting particularly for ScalarPair. |
| /// Return None if the layout does not permit loading this as a value. |
| pub(super) fn try_read_immediate_from_mplace( |
| &self, |
| mplace: MPlaceTy<'tcx, M::PointerTag>, |
| ) -> EvalResult<'tcx, Option<Immediate<M::PointerTag>>> { |
| if mplace.layout.is_unsized() { |
| // Don't touch unsized |
| return Ok(None); |
| } |
| let (ptr, ptr_align) = mplace.to_scalar_ptr_align(); |
| |
| if mplace.layout.is_zst() { |
| // Not all ZSTs have a layout we would handle below, so just short-circuit them |
| // all here. |
| self.memory.check_align(ptr, ptr_align)?; |
| return Ok(Some(Immediate::Scalar(Scalar::zst().into()))); |
| } |
| |
| // check for integer pointers before alignment to report better errors |
| let ptr = ptr.to_ptr()?; |
| self.memory.check_align(ptr.into(), ptr_align)?; |
| match mplace.layout.abi { |
| layout::Abi::Scalar(..) => { |
| let scalar = self.memory |
| .get(ptr.alloc_id)? |
| .read_scalar(self, ptr, mplace.layout.size)?; |
| Ok(Some(Immediate::Scalar(scalar))) |
| } |
| layout::Abi::ScalarPair(ref a, ref b) => { |
| let (a, b) = (&a.value, &b.value); |
| let (a_size, b_size) = (a.size(self), b.size(self)); |
| let a_ptr = ptr; |
| let b_offset = a_size.align_to(b.align(self).abi); |
| assert!(b_offset.bytes() > 0); // we later use the offset to test which field to use |
| let b_ptr = ptr.offset(b_offset, self)?; |
| let a_val = self.memory |
| .get(ptr.alloc_id)? |
| .read_scalar(self, a_ptr, a_size)?; |
| let b_align = ptr_align.restrict_for_offset(b_offset); |
| self.memory.check_align(b_ptr.into(), b_align)?; |
| let b_val = self.memory |
| .get(ptr.alloc_id)? |
| .read_scalar(self, b_ptr, b_size)?; |
| Ok(Some(Immediate::ScalarPair(a_val, b_val))) |
| } |
| _ => Ok(None), |
| } |
| } |
| |
| /// Try returning an immediate for the operand. |
| /// If the layout does not permit loading this as an immediate, return where in memory |
| /// we can find the data. |
| /// Note that for a given layout, this operation will either always fail or always |
| /// succeed! Whether it succeeds depends on whether the layout can be represented |
| /// in a `Immediate`, not on which data is stored there currently. |
| pub(crate) fn try_read_immediate( |
| &self, |
| src: OpTy<'tcx, M::PointerTag>, |
| ) -> EvalResult<'tcx, Result<Immediate<M::PointerTag>, MemPlace<M::PointerTag>>> { |
| Ok(match src.try_as_mplace() { |
| Ok(mplace) => { |
| if let Some(val) = self.try_read_immediate_from_mplace(mplace)? { |
| Ok(val) |
| } else { |
| Err(*mplace) |
| } |
| }, |
| Err(val) => Ok(val), |
| }) |
| } |
| |
| /// Read an immediate from a place, asserting that that is possible with the given layout. |
| #[inline(always)] |
| pub fn read_immediate( |
| &self, |
| op: OpTy<'tcx, M::PointerTag> |
| ) -> EvalResult<'tcx, ImmTy<'tcx, M::PointerTag>> { |
| if let Ok(immediate) = self.try_read_immediate(op)? { |
| Ok(ImmTy { immediate, layout: op.layout }) |
| } else { |
| bug!("primitive read failed for type: {:?}", op.layout.ty); |
| } |
| } |
| |
| /// Read a scalar from a place |
| pub fn read_scalar( |
| &self, |
| op: OpTy<'tcx, M::PointerTag> |
| ) -> EvalResult<'tcx, ScalarMaybeUndef<M::PointerTag>> { |
| Ok(self.read_immediate(op)?.to_scalar_or_undef()) |
| } |
| |
| // Turn the MPlace into a string (must already be dereferenced!) |
| pub fn read_str( |
| &self, |
| mplace: MPlaceTy<'tcx, M::PointerTag>, |
| ) -> EvalResult<'tcx, &str> { |
| let len = mplace.len(self)?; |
| let bytes = self.memory.read_bytes(mplace.ptr, Size::from_bytes(len as u64))?; |
| let str = ::std::str::from_utf8(bytes) |
| .map_err(|err| EvalErrorKind::ValidationFailure(err.to_string()))?; |
| Ok(str) |
| } |
| |
| pub fn uninit_operand( |
| &mut self, |
| layout: TyLayout<'tcx> |
| ) -> EvalResult<'tcx, Operand<M::PointerTag>> { |
| // This decides which types we will use the Immediate optimization for, and hence should |
| // match what `try_read_immediate` and `eval_place_to_op` support. |
| if layout.is_zst() { |
| return Ok(Operand::Immediate(Immediate::Scalar(Scalar::zst().into()))); |
| } |
| |
| Ok(match layout.abi { |
| layout::Abi::Scalar(..) => |
| Operand::Immediate(Immediate::Scalar(ScalarMaybeUndef::Undef)), |
| layout::Abi::ScalarPair(..) => |
| Operand::Immediate(Immediate::ScalarPair( |
| ScalarMaybeUndef::Undef, |
| ScalarMaybeUndef::Undef, |
| )), |
| _ => { |
| trace!("Forcing allocation for local of type {:?}", layout.ty); |
| Operand::Indirect( |
| *self.allocate(layout, MemoryKind::Stack) |
| ) |
| } |
| }) |
| } |
| |
| /// Projection functions |
| pub fn operand_field( |
| &self, |
| op: OpTy<'tcx, M::PointerTag>, |
| field: u64, |
| ) -> EvalResult<'tcx, OpTy<'tcx, M::PointerTag>> { |
| let base = match op.try_as_mplace() { |
| Ok(mplace) => { |
| // The easy case |
| let field = self.mplace_field(mplace, field)?; |
| return Ok(field.into()); |
| }, |
| Err(value) => value |
| }; |
| |
| let field = field.try_into().unwrap(); |
| let field_layout = op.layout.field(self, field)?; |
| if field_layout.is_zst() { |
| let immediate = Immediate::Scalar(Scalar::zst().into()); |
| return Ok(OpTy { op: Operand::Immediate(immediate), layout: field_layout }); |
| } |
| let offset = op.layout.fields.offset(field); |
| let immediate = match base { |
| // the field covers the entire type |
| _ if offset.bytes() == 0 && field_layout.size == op.layout.size => base, |
| // extract fields from types with `ScalarPair` ABI |
| Immediate::ScalarPair(a, b) => { |
| let val = if offset.bytes() == 0 { a } else { b }; |
| Immediate::Scalar(val) |
| }, |
| Immediate::Scalar(val) => |
| bug!("field access on non aggregate {:#?}, {:#?}", val, op.layout), |
| }; |
| Ok(OpTy { op: Operand::Immediate(immediate), layout: field_layout }) |
| } |
| |
| pub fn operand_downcast( |
| &self, |
| op: OpTy<'tcx, M::PointerTag>, |
| variant: VariantIdx, |
| ) -> EvalResult<'tcx, OpTy<'tcx, M::PointerTag>> { |
| // Downcasts only change the layout |
| Ok(match op.try_as_mplace() { |
| Ok(mplace) => { |
| self.mplace_downcast(mplace, variant)?.into() |
| }, |
| Err(..) => { |
| let layout = op.layout.for_variant(self, variant); |
| OpTy { layout, ..op } |
| } |
| }) |
| } |
| |
| pub fn operand_projection( |
| &self, |
| base: OpTy<'tcx, M::PointerTag>, |
| proj_elem: &mir::PlaceElem<'tcx>, |
| ) -> EvalResult<'tcx, OpTy<'tcx, M::PointerTag>> { |
| use rustc::mir::ProjectionElem::*; |
| Ok(match *proj_elem { |
| Field(field, _) => self.operand_field(base, field.index() as u64)?, |
| Downcast(_, variant) => self.operand_downcast(base, variant)?, |
| Deref => self.deref_operand(base)?.into(), |
| Subslice { .. } | ConstantIndex { .. } | Index(_) => if base.layout.is_zst() { |
| OpTy { |
| op: Operand::Immediate(Immediate::Scalar(Scalar::zst().into())), |
| // the actual index doesn't matter, so we just pick a convenient one like 0 |
| layout: base.layout.field(self, 0)?, |
| } |
| } else { |
| // The rest should only occur as mplace, we do not use Immediates for types |
| // allowing such operations. This matches place_projection forcing an allocation. |
| let mplace = base.to_mem_place(); |
| self.mplace_projection(mplace, proj_elem)?.into() |
| } |
| }) |
| } |
| |
| /// This is used by [priroda](https://github.com/oli-obk/priroda) to get an OpTy from a local |
| /// |
| /// When you know the layout of the local in advance, you can pass it as last argument |
| pub fn access_local( |
| &self, |
| frame: &super::Frame<'mir, 'tcx, M::PointerTag, M::FrameExtra>, |
| local: mir::Local, |
| layout: Option<TyLayout<'tcx>>, |
| ) -> EvalResult<'tcx, OpTy<'tcx, M::PointerTag>> { |
| assert_ne!(local, mir::RETURN_PLACE); |
| let op = *frame.locals[local].access()?; |
| let layout = from_known_layout(layout, |
| || self.layout_of_local(frame, local))?; |
| Ok(OpTy { op, layout }) |
| } |
| |
| // Evaluate a place with the goal of reading from it. This lets us sometimes |
| // avoid allocations. If you already know the layout, you can pass it in |
| // to avoid looking it up again. |
| fn eval_place_to_op( |
| &self, |
| mir_place: &mir::Place<'tcx>, |
| layout: Option<TyLayout<'tcx>>, |
| ) -> EvalResult<'tcx, OpTy<'tcx, M::PointerTag>> { |
| use rustc::mir::Place::*; |
| let op = match *mir_place { |
| Local(mir::RETURN_PLACE) => return err!(ReadFromReturnPointer), |
| Local(local) => self.access_local(self.frame(), local, layout)?, |
| |
| Projection(ref proj) => { |
| let op = self.eval_place_to_op(&proj.base, None)?; |
| self.operand_projection(op, &proj.elem)? |
| } |
| |
| _ => self.eval_place_to_mplace(mir_place)?.into(), |
| }; |
| |
| trace!("eval_place_to_op: got {:?}", *op); |
| Ok(op) |
| } |
| |
| /// Evaluate the operand, returning a place where you can then find the data. |
| /// if you already know the layout, you can save two some table lookups |
| /// by passing it in here. |
| pub fn eval_operand( |
| &self, |
| mir_op: &mir::Operand<'tcx>, |
| layout: Option<TyLayout<'tcx>>, |
| ) -> EvalResult<'tcx, OpTy<'tcx, M::PointerTag>> { |
| use rustc::mir::Operand::*; |
| let op = match *mir_op { |
| // FIXME: do some more logic on `move` to invalidate the old location |
| Copy(ref place) | |
| Move(ref place) => |
| self.eval_place_to_op(place, layout)?, |
| |
| Constant(ref constant) => { |
| let layout = from_known_layout(layout, || { |
| let ty = self.monomorphize(mir_op.ty(self.mir(), *self.tcx), self.substs()); |
| self.layout_of(ty) |
| })?; |
| let op = self.const_value_to_op(*constant.literal)?; |
| OpTy { op, layout } |
| } |
| }; |
| trace!("{:?}: {:?}", mir_op, *op); |
| Ok(op) |
| } |
| |
| /// Evaluate a bunch of operands at once |
| pub(super) fn eval_operands( |
| &self, |
| ops: &[mir::Operand<'tcx>], |
| ) -> EvalResult<'tcx, Vec<OpTy<'tcx, M::PointerTag>>> { |
| ops.into_iter() |
| .map(|op| self.eval_operand(op, None)) |
| .collect() |
| } |
| |
| // Used when miri runs into a constant, and by CTFE. |
| // FIXME: CTFE should use allocations, then we can make this private (embed it into |
| // `eval_operand`, ideally). |
| pub(crate) fn const_value_to_op( |
| &self, |
| val: ty::LazyConst<'tcx>, |
| ) -> EvalResult<'tcx, Operand<M::PointerTag>> { |
| trace!("const_value_to_op: {:?}", val); |
| let val = match val { |
| ty::LazyConst::Unevaluated(def_id, substs) => { |
| let instance = self.resolve(def_id, substs)?; |
| return Ok(*OpTy::from(self.const_eval_raw(GlobalId { |
| instance, |
| promoted: None, |
| })?)); |
| }, |
| ty::LazyConst::Evaluated(c) => c, |
| }; |
| match val.val { |
| ConstValue::ByRef(id, alloc, offset) => { |
| // We rely on mutability being set correctly in that allocation to prevent writes |
| // where none should happen -- and for `static mut`, we copy on demand anyway. |
| Ok(Operand::Indirect( |
| MemPlace::from_ptr(Pointer::new(id, offset), alloc.align) |
| ).with_default_tag()) |
| }, |
| ConstValue::ScalarPair(a, b) => |
| Ok(Operand::Immediate(Immediate::ScalarPair( |
| a.into(), |
| b.into(), |
| )).with_default_tag()), |
| ConstValue::Scalar(x) => |
| Ok(Operand::Immediate(Immediate::Scalar(x.into())).with_default_tag()), |
| } |
| } |
| |
| /// Read discriminant, return the runtime value as well as the variant index. |
| pub fn read_discriminant( |
| &self, |
| rval: OpTy<'tcx, M::PointerTag>, |
| ) -> EvalResult<'tcx, (u128, VariantIdx)> { |
| trace!("read_discriminant_value {:#?}", rval.layout); |
| |
| match rval.layout.variants { |
| layout::Variants::Single { index } => { |
| let discr_val = rval.layout.ty.ty_adt_def().map_or( |
| index.as_u32() as u128, |
| |def| def.discriminant_for_variant(*self.tcx, index).val); |
| return Ok((discr_val, index)); |
| } |
| layout::Variants::Tagged { .. } | |
| layout::Variants::NicheFilling { .. } => {}, |
| } |
| // read raw discriminant value |
| let discr_op = self.operand_field(rval, 0)?; |
| let discr_val = self.read_immediate(discr_op)?; |
| let raw_discr = discr_val.to_scalar_or_undef(); |
| trace!("discr value: {:?}", raw_discr); |
| // post-process |
| Ok(match rval.layout.variants { |
| layout::Variants::Single { .. } => bug!(), |
| layout::Variants::Tagged { .. } => { |
| let bits_discr = match raw_discr.to_bits(discr_val.layout.size) { |
| Ok(raw_discr) => raw_discr, |
| Err(_) => return err!(InvalidDiscriminant(raw_discr.erase_tag())), |
| }; |
| let real_discr = if discr_val.layout.ty.is_signed() { |
| let i = bits_discr as i128; |
| // going from layout tag type to typeck discriminant type |
| // requires first sign extending with the layout discriminant |
| let shift = 128 - discr_val.layout.size.bits(); |
| let sexted = (i << shift) >> shift; |
| // and then zeroing with the typeck discriminant type |
| let discr_ty = rval.layout.ty |
| .ty_adt_def().expect("tagged layout corresponds to adt") |
| .repr |
| .discr_type(); |
| let discr_ty = layout::Integer::from_attr(self, discr_ty); |
| let shift = 128 - discr_ty.size().bits(); |
| let truncatee = sexted as u128; |
| (truncatee << shift) >> shift |
| } else { |
| bits_discr |
| }; |
| // Make sure we catch invalid discriminants |
| let index = rval.layout.ty |
| .ty_adt_def() |
| .expect("tagged layout for non adt") |
| .discriminants(self.tcx.tcx) |
| .find(|(_, var)| var.val == real_discr) |
| .ok_or_else(|| EvalErrorKind::InvalidDiscriminant(raw_discr.erase_tag()))?; |
| (real_discr, index.0) |
| }, |
| layout::Variants::NicheFilling { |
| dataful_variant, |
| ref niche_variants, |
| niche_start, |
| .. |
| } => { |
| let variants_start = niche_variants.start().as_u32() as u128; |
| let variants_end = niche_variants.end().as_u32() as u128; |
| match raw_discr { |
| ScalarMaybeUndef::Scalar(Scalar::Ptr(ptr)) => { |
| // The niche must be just 0 (which an inbounds pointer value never is) |
| let ptr_valid = niche_start == 0 && variants_start == variants_end && |
| self.memory.check_bounds_ptr(ptr, InboundsCheck::MaybeDead).is_ok(); |
| if !ptr_valid { |
| return err!(InvalidDiscriminant(raw_discr.erase_tag())); |
| } |
| (dataful_variant.as_u32() as u128, dataful_variant) |
| }, |
| ScalarMaybeUndef::Scalar(Scalar::Bits { bits: raw_discr, size }) => { |
| assert_eq!(size as u64, discr_val.layout.size.bytes()); |
| let adjusted_discr = raw_discr.wrapping_sub(niche_start) |
| .wrapping_add(variants_start); |
| if variants_start <= adjusted_discr && adjusted_discr <= variants_end { |
| let index = adjusted_discr as usize; |
| assert_eq!(index as u128, adjusted_discr); |
| assert!(index < rval.layout.ty |
| .ty_adt_def() |
| .expect("tagged layout for non adt") |
| .variants.len()); |
| (adjusted_discr, VariantIdx::from_usize(index)) |
| } else { |
| (dataful_variant.as_u32() as u128, dataful_variant) |
| } |
| }, |
| ScalarMaybeUndef::Undef => |
| return err!(InvalidDiscriminant(ScalarMaybeUndef::Undef)), |
| } |
| } |
| }) |
| } |
| |
| } |