| //! 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, |
| ConstValue, Pointer, Scalar, |
| InterpResult, sign_extend, truncate, |
| }; |
| use super::{ |
| InterpCx, Machine, |
| MemPlace, MPlaceTy, PlaceTy, Place, |
| }; |
| 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<Tag> From<ScalarMaybeUndef<Tag>> for Immediate<Tag> { |
| #[inline(always)] |
| fn from(val: ScalarMaybeUndef<Tag>) -> Self { |
| Immediate::Scalar(val) |
| } |
| } |
| |
| impl<Tag> From<Scalar<Tag>> for Immediate<Tag> { |
| #[inline(always)] |
| fn from(val: Scalar<Tag>) -> Self { |
| Immediate::Scalar(val.into()) |
| } |
| } |
| |
| impl<'tcx, Tag> Immediate<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) -> InterpResult<'tcx, Scalar<Tag>> { |
| self.to_scalar_or_undef().not_undef() |
| } |
| |
| #[inline] |
| pub fn to_scalar_pair(self) -> InterpResult<'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()?)) |
| } |
| } |
| |
| /// Converts 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) -> InterpResult<'tcx, Scalar<Tag>> { |
| match self { |
| Immediate::Scalar(ptr) | |
| Immediate::ScalarPair(ptr, _) => ptr.not_undef(), |
| } |
| } |
| |
| /// Converts the value into its metadata. |
| /// Throws away the first half of a ScalarPair! |
| #[inline] |
| pub fn to_meta(self) -> InterpResult<'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=()> { |
| pub(crate) imm: 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.imm |
| } |
| } |
| |
| /// 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<Tag> Operand<Tag> { |
| #[inline] |
| pub fn assert_mem_place(self) -> MemPlace<Tag> |
| where Tag: ::std::fmt::Debug |
| { |
| match self { |
| Operand::Indirect(mplace) => mplace, |
| _ => bug!("assert_mem_place: expected Operand::Indirect, got {:?}", self), |
| |
| } |
| } |
| |
| #[inline] |
| pub fn assert_immediate(self) -> Immediate<Tag> |
| where Tag: ::std::fmt::Debug |
| { |
| match self { |
| Operand::Immediate(imm) => imm, |
| _ => bug!("assert_immediate: expected Operand::Immediate, got {:?}", self), |
| |
| } |
| } |
| } |
| |
| #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)] |
| pub struct OpTy<'tcx, Tag=()> { |
| op: Operand<Tag>, // Keep this private, it helps enforce invariants |
| 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.imm), |
| layout: val.layout |
| } |
| } |
| } |
| |
| impl<'tcx, Tag: Copy> ImmTy<'tcx, Tag> { |
| #[inline] |
| pub fn from_scalar(val: Scalar<Tag>, layout: TyLayout<'tcx>) -> Self { |
| ImmTy { imm: val.into(), layout } |
| } |
| |
| #[inline] |
| pub fn from_uint(i: impl Into<u128>, layout: TyLayout<'tcx>) -> Self { |
| Self::from_scalar(Scalar::from_uint(i, layout.size), layout) |
| } |
| |
| #[inline] |
| pub fn from_int(i: impl Into<i128>, layout: TyLayout<'tcx>) -> Self { |
| Self::from_scalar(Scalar::from_int(i, layout.size), layout) |
| } |
| |
| #[inline] |
| pub fn to_bits(self) -> InterpResult<'tcx, u128> { |
| self.to_scalar()?.to_bits(self.layout.size) |
| } |
| } |
| |
| // Use the existing layout if given (but sanity check in debug mode), |
| // or compute the layout. |
| #[inline(always)] |
| pub(super) fn from_known_layout<'tcx>( |
| layout: Option<TyLayout<'tcx>>, |
| compute: impl FnOnce() -> InterpResult<'tcx, TyLayout<'tcx>> |
| ) -> InterpResult<'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<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { |
| /// Normalice `place.ptr` to a `Pointer` if this is a place and not a ZST. |
| /// Can be helpful to avoid lots of `force_ptr` calls later, if this place is used a lot. |
| #[inline] |
| pub fn force_op_ptr( |
| &self, |
| op: OpTy<'tcx, M::PointerTag>, |
| ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> { |
| match op.try_as_mplace() { |
| Ok(mplace) => Ok(self.force_mplace_ptr(mplace)?.into()), |
| Err(imm) => Ok(imm.into()), // Nothing to cast/force |
| } |
| } |
| |
| /// Try reading an immediate in memory; this is interesting particularly for `ScalarPair`. |
| /// Returns `None` if the layout does not permit loading this as a value. |
| fn try_read_immediate_from_mplace( |
| &self, |
| mplace: MPlaceTy<'tcx, M::PointerTag>, |
| ) -> InterpResult<'tcx, Option<ImmTy<'tcx, M::PointerTag>>> { |
| if mplace.layout.is_unsized() { |
| // Don't touch unsized |
| return Ok(None); |
| } |
| |
| let ptr = match self.check_mplace_access(mplace, None) |
| .expect("places should be checked on creation") |
| { |
| Some(ptr) => ptr, |
| None => return Ok(Some(ImmTy { // zero-sized type |
| imm: Scalar::zst().into(), |
| layout: mplace.layout, |
| })), |
| }; |
| |
| match mplace.layout.abi { |
| layout::Abi::Scalar(..) => { |
| let scalar = self.memory |
| .get(ptr.alloc_id)? |
| .read_scalar(self, ptr, mplace.layout.size)?; |
| Ok(Some(ImmTy { |
| imm: scalar.into(), |
| layout: mplace.layout, |
| })) |
| } |
| layout::Abi::ScalarPair(ref a, ref b) => { |
| // We checked `ptr_align` above, so all fields will have the alignment they need. |
| // We would anyway check against `ptr_align.restrict_for_offset(b_offset)`, |
| // which `ptr.offset(b_offset)` cannot possibly fail to satisfy. |
| 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 tell apart the fields |
| 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_val = self.memory |
| .get(ptr.alloc_id)? |
| .read_scalar(self, b_ptr, b_size)?; |
| Ok(Some(ImmTy { |
| imm: Immediate::ScalarPair(a_val, b_val), |
| layout: mplace.layout, |
| })) |
| } |
| _ => 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>, |
| ) -> InterpResult<'tcx, Result<ImmTy<'tcx, M::PointerTag>, MPlaceTy<'tcx, 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> |
| ) -> InterpResult<'tcx, ImmTy<'tcx, M::PointerTag>> { |
| if let Ok(imm) = self.try_read_immediate(op)? { |
| Ok(imm) |
| } 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> |
| ) -> InterpResult<'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>, |
| ) -> InterpResult<'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| { |
| err_unsup!(ValidationFailure(err.to_string())) |
| })?; |
| Ok(str) |
| } |
| |
| /// Projection functions |
| pub fn operand_field( |
| &self, |
| op: OpTy<'tcx, M::PointerTag>, |
| field: u64, |
| ) -> InterpResult<'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 = 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::from(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, |
| ) -> InterpResult<'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>, |
| ) -> InterpResult<'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(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.assert_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 |
| pub fn access_local( |
| &self, |
| frame: &super::Frame<'mir, 'tcx, M::PointerTag, M::FrameExtra>, |
| local: mir::Local, |
| layout: Option<TyLayout<'tcx>>, |
| ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> { |
| assert_ne!(local, mir::RETURN_PLACE); |
| let layout = self.layout_of_local(frame, local, layout)?; |
| let op = if layout.is_zst() { |
| // Do not read from ZST, they might not be initialized |
| Operand::Immediate(Scalar::zst().into()) |
| } else { |
| frame.locals[local].access()? |
| }; |
| Ok(OpTy { op, layout }) |
| } |
| |
| /// Every place can be read from, so we can turn them into an operand |
| #[inline(always)] |
| pub fn place_to_op( |
| &self, |
| place: PlaceTy<'tcx, M::PointerTag> |
| ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> { |
| let op = match *place { |
| Place::Ptr(mplace) => { |
| Operand::Indirect(mplace) |
| } |
| Place::Local { frame, local } => |
| *self.access_local(&self.stack[frame], local, None)? |
| }; |
| Ok(OpTy { op, layout: place.layout }) |
| } |
| |
| // Evaluate a place with the goal of reading from it. This lets us sometimes |
| // avoid allocations. |
| pub(super) fn eval_place_to_op( |
| &self, |
| place: &mir::Place<'tcx>, |
| layout: Option<TyLayout<'tcx>>, |
| ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> { |
| use rustc::mir::PlaceBase; |
| |
| let base_op = match &place.base { |
| PlaceBase::Local(mir::RETURN_PLACE) => |
| throw_unsup!(ReadFromReturnPointer), |
| PlaceBase::Local(local) => { |
| // Do not use the layout passed in as argument if the base we are looking at |
| // here is not the entire place. |
| // FIXME use place_projection.is_empty() when is available |
| let layout = if place.projection.is_empty() { |
| layout |
| } else { |
| None |
| }; |
| |
| self.access_local(self.frame(), *local, layout)? |
| } |
| PlaceBase::Static(place_static) => { |
| self.eval_static_to_mplace(&place_static)?.into() |
| } |
| }; |
| |
| let op = place.projection.iter().try_fold( |
| base_op, |
| |op, elem| self.operand_projection(op, elem) |
| )?; |
| |
| 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 table lookups |
| /// by passing it in here. |
| pub fn eval_operand( |
| &self, |
| mir_op: &mir::Operand<'tcx>, |
| layout: Option<TyLayout<'tcx>>, |
| ) -> InterpResult<'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 val = self.subst_from_frame_and_normalize_erasing_regions(constant.literal); |
| self.eval_const_to_op(val, layout)? |
| } |
| }; |
| trace!("{:?}: {:?}", mir_op, *op); |
| Ok(op) |
| } |
| |
| /// Evaluate a bunch of operands at once |
| pub(super) fn eval_operands( |
| &self, |
| ops: &[mir::Operand<'tcx>], |
| ) -> InterpResult<'tcx, Vec<OpTy<'tcx, M::PointerTag>>> { |
| ops.into_iter() |
| .map(|op| self.eval_operand(op, None)) |
| .collect() |
| } |
| |
| // Used when the miri-engine runs into a constant and for extracting information from constants |
| // in patterns via the `const_eval` module |
| /// The `val` and `layout` are assumed to already be in our interpreter |
| /// "universe" (param_env). |
| crate fn eval_const_to_op( |
| &self, |
| val: &'tcx ty::Const<'tcx>, |
| layout: Option<TyLayout<'tcx>>, |
| ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> { |
| let tag_scalar = |scalar| match scalar { |
| Scalar::Ptr(ptr) => Scalar::Ptr(self.tag_static_base_pointer(ptr)), |
| Scalar::Raw { data, size } => Scalar::Raw { data, size }, |
| }; |
| // Early-return cases. |
| match val.val { |
| ConstValue::Param(_) => |
| throw_inval!(TooGeneric), |
| ConstValue::Unevaluated(def_id, substs) => { |
| let instance = self.resolve(def_id, substs)?; |
| return Ok(OpTy::from(self.const_eval_raw(GlobalId { |
| instance, |
| promoted: None, |
| })?)); |
| } |
| _ => {} |
| } |
| // Other cases need layout. |
| let layout = from_known_layout(layout, || { |
| self.layout_of(val.ty) |
| })?; |
| let op = match val.val { |
| ConstValue::ByRef { alloc, offset } => { |
| let id = self.tcx.alloc_map.lock().create_memory_alloc(alloc); |
| // We rely on mutability being set correctly in that allocation to prevent writes |
| // where none should happen. |
| let ptr = self.tag_static_base_pointer(Pointer::new(id, offset)); |
| Operand::Indirect(MemPlace::from_ptr(ptr, layout.align.abi)) |
| }, |
| ConstValue::Scalar(x) => |
| Operand::Immediate(tag_scalar(x).into()), |
| ConstValue::Slice { data, start, end } => { |
| // We rely on mutability being set correctly in `data` to prevent writes |
| // where none should happen. |
| let ptr = Pointer::new( |
| self.tcx.alloc_map.lock().create_memory_alloc(data), |
| Size::from_bytes(start as u64), // offset: `start` |
| ); |
| Operand::Immediate(Immediate::new_slice( |
| self.tag_static_base_pointer(ptr).into(), |
| (end - start) as u64, // len: `end - start` |
| self, |
| )) |
| } |
| ConstValue::Param(..) | |
| ConstValue::Infer(..) | |
| ConstValue::Placeholder(..) | |
| ConstValue::Unevaluated(..) => |
| bug!("eval_const_to_op: Unexpected ConstValue {:?}", val), |
| }; |
| Ok(OpTy { op, layout }) |
| } |
| |
| /// Read discriminant, return the runtime value as well as the variant index. |
| pub fn read_discriminant( |
| &self, |
| rval: OpTy<'tcx, M::PointerTag>, |
| ) -> InterpResult<'tcx, (u128, VariantIdx)> { |
| trace!("read_discriminant_value {:#?}", rval.layout); |
| |
| let (discr_kind, discr_index) = match rval.layout.variants { |
| layout::Variants::Single { index } => { |
| let discr_val = rval.layout.ty.discriminant_for_variant(*self.tcx, index).map_or( |
| index.as_u32() as u128, |
| |discr| discr.val); |
| return Ok((discr_val, index)); |
| } |
| layout::Variants::Multiple { ref discr_kind, discr_index, .. } => |
| (discr_kind, discr_index), |
| }; |
| |
| // read raw discriminant value |
| let discr_op = self.operand_field(rval, discr_index as u64)?; |
| 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 *discr_kind { |
| layout::DiscriminantKind::Tag => { |
| let bits_discr = raw_discr |
| .not_undef() |
| .and_then(|raw_discr| self.force_bits(raw_discr, discr_val.layout.size)) |
| .map_err(|_| err_unsup!(InvalidDiscriminant(raw_discr.erase_tag())))?; |
| let real_discr = if discr_val.layout.ty.is_signed() { |
| // going from layout tag type to typeck discriminant type |
| // requires first sign extending with the layout discriminant |
| let sexted = sign_extend(bits_discr, discr_val.layout.size) as i128; |
| // 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 size = layout::Integer::from_attr(self, discr_ty).size(); |
| let truncatee = sexted as u128; |
| truncate(truncatee, size) |
| } else { |
| bits_discr |
| }; |
| // Make sure we catch invalid discriminants |
| let index = match &rval.layout.ty.sty { |
| ty::Adt(adt, _) => adt |
| .discriminants(self.tcx.tcx) |
| .find(|(_, var)| var.val == real_discr), |
| ty::Generator(def_id, substs, _) => substs |
| .discriminants(*def_id, self.tcx.tcx) |
| .find(|(_, var)| var.val == real_discr), |
| _ => bug!("tagged layout for non-adt non-generator"), |
| }.ok_or_else( |
| || err_unsup!(InvalidDiscriminant(raw_discr.erase_tag())) |
| )?; |
| (real_discr, index.0) |
| }, |
| layout::DiscriminantKind::Niche { |
| 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; |
| let raw_discr = raw_discr.not_undef().map_err(|_| { |
| err_unsup!(InvalidDiscriminant(ScalarMaybeUndef::Undef)) |
| })?; |
| match raw_discr.to_bits_or_ptr(discr_val.layout.size, self) { |
| Err(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.ptr_may_be_null(ptr); |
| if !ptr_valid { |
| throw_unsup!(InvalidDiscriminant(raw_discr.erase_tag().into())) |
| } |
| (dataful_variant.as_u32() as u128, dataful_variant) |
| }, |
| Ok(raw_discr) => { |
| 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) |
| } |
| }, |
| } |
| } |
| }) |
| } |
| } |
