| //! 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::TryFrom; |
| use std::fmt::Write; |
| |
| use rustc_errors::ErrorReported; |
| use rustc_hir::def::Namespace; |
| use rustc_macros::HashStable; |
| use rustc_middle::ty::layout::{PrimitiveExt, TyAndLayout}; |
| use rustc_middle::ty::print::{FmtPrinter, PrettyPrinter, Printer}; |
| use rustc_middle::ty::{ConstInt, Ty}; |
| use rustc_middle::{mir, ty}; |
| use rustc_target::abi::{Abi, HasDataLayout, LayoutOf, Size, TagEncoding}; |
| use rustc_target::abi::{VariantIdx, Variants}; |
| |
| use super::{ |
| from_known_layout, mir_assign_valid_types, ConstValue, GlobalId, InterpCx, InterpResult, |
| MPlaceTy, Machine, MemPlace, Place, PlaceTy, Pointer, Scalar, ScalarMaybeUninit, |
| }; |
| |
| /// An `Immediate` 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 wide 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, PartialEq, Eq, HashStable, Hash)] |
| pub enum Immediate<Tag = ()> { |
| Scalar(ScalarMaybeUninit<Tag>), |
| ScalarPair(ScalarMaybeUninit<Tag>, ScalarMaybeUninit<Tag>), |
| } |
| |
| impl<Tag> From<ScalarMaybeUninit<Tag>> for Immediate<Tag> { |
| #[inline(always)] |
| fn from(val: ScalarMaybeUninit<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<Tag> From<Pointer<Tag>> for Immediate<Tag> { |
| #[inline(always)] |
| fn from(val: Pointer<Tag>) -> Self { |
| Immediate::Scalar(Scalar::from(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_machine_usize(len, cx).into()) |
| } |
| |
| pub fn new_dyn_trait(val: Scalar<Tag>, vtable: Pointer<Tag>) -> Self { |
| Immediate::ScalarPair(val.into(), vtable.into()) |
| } |
| |
| #[inline] |
| pub fn to_scalar_or_uninit(self) -> ScalarMaybeUninit<Tag> { |
| match self { |
| Immediate::Scalar(val) => val, |
| Immediate::ScalarPair(..) => bug!("Got a wide pointer where a scalar was expected"), |
| } |
| } |
| |
| #[inline] |
| pub fn to_scalar(self) -> InterpResult<'tcx, Scalar<Tag>> { |
| self.to_scalar_or_uninit().check_init() |
| } |
| |
| #[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.check_init()?, b.check_init()?)), |
| } |
| } |
| } |
| |
| // 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 = ()> { |
| imm: Immediate<Tag>, |
| pub layout: TyAndLayout<'tcx>, |
| } |
| |
| impl<Tag: Copy> std::fmt::Display for ImmTy<'tcx, Tag> { |
| fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { |
| /// Helper function for printing a scalar to a FmtPrinter |
| fn p<'a, 'tcx, F: std::fmt::Write, Tag>( |
| cx: FmtPrinter<'a, 'tcx, F>, |
| s: ScalarMaybeUninit<Tag>, |
| ty: Ty<'tcx>, |
| ) -> Result<FmtPrinter<'a, 'tcx, F>, std::fmt::Error> { |
| match s { |
| ScalarMaybeUninit::Scalar(s) => { |
| cx.pretty_print_const_scalar(s.erase_tag(), ty, true) |
| } |
| ScalarMaybeUninit::Uninit => cx.typed_value( |
| |mut this| { |
| this.write_str("{uninit ")?; |
| Ok(this) |
| }, |
| |this| this.print_type(ty), |
| " ", |
| ), |
| } |
| } |
| ty::tls::with(|tcx| { |
| match self.imm { |
| Immediate::Scalar(s) => { |
| if let Some(ty) = tcx.lift(&self.layout.ty) { |
| let cx = FmtPrinter::new(tcx, f, Namespace::ValueNS); |
| p(cx, s, ty)?; |
| return Ok(()); |
| } |
| write!(f, "{}: {}", s.erase_tag(), self.layout.ty) |
| } |
| Immediate::ScalarPair(a, b) => { |
| // FIXME(oli-obk): at least print tuples and slices nicely |
| write!(f, "({}, {}): {}", a.erase_tag(), b.erase_tag(), self.layout.ty,) |
| } |
| } |
| }) |
| } |
| } |
| |
| 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, PartialEq, Eq, HashStable, Hash)] |
| pub enum Operand<Tag = ()> { |
| Immediate(Immediate<Tag>), |
| Indirect(MemPlace<Tag>), |
| } |
| |
| #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)] |
| pub struct OpTy<'tcx, Tag = ()> { |
| op: Operand<Tag>, // Keep this private; it helps enforce invariants. |
| pub layout: TyAndLayout<'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: TyAndLayout<'tcx>) -> Self { |
| ImmTy { imm: val.into(), layout } |
| } |
| |
| #[inline] |
| pub fn from_immediate(imm: Immediate<Tag>, layout: TyAndLayout<'tcx>) -> Self { |
| ImmTy { imm, layout } |
| } |
| |
| #[inline] |
| pub fn try_from_uint(i: impl Into<u128>, layout: TyAndLayout<'tcx>) -> Option<Self> { |
| Some(Self::from_scalar(Scalar::try_from_uint(i, layout.size)?, layout)) |
| } |
| #[inline] |
| pub fn from_uint(i: impl Into<u128>, layout: TyAndLayout<'tcx>) -> Self { |
| Self::from_scalar(Scalar::from_uint(i, layout.size), layout) |
| } |
| |
| #[inline] |
| pub fn try_from_int(i: impl Into<i128>, layout: TyAndLayout<'tcx>) -> Option<Self> { |
| Some(Self::from_scalar(Scalar::try_from_int(i, layout.size)?, layout)) |
| } |
| |
| #[inline] |
| pub fn from_int(i: impl Into<i128>, layout: TyAndLayout<'tcx>) -> Self { |
| Self::from_scalar(Scalar::from_int(i, layout.size), layout) |
| } |
| |
| #[inline] |
| pub fn to_const_int(self) -> ConstInt { |
| assert!(self.layout.ty.is_integral()); |
| ConstInt::new( |
| self.to_scalar() |
| .expect("to_const_int doesn't work on scalar pairs") |
| .assert_bits(self.layout.size), |
| self.layout.size, |
| self.layout.ty.is_signed(), |
| self.layout.ty.is_ptr_sized_integral(), |
| ) |
| } |
| } |
| |
| impl<'mir, 'tcx: 'mir, 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(self) { |
| 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 => { |
| if let Scalar::Ptr(ptr) = mplace.ptr { |
| // We may be reading from a static. |
| // In order to ensure that `static FOO: Type = FOO;` causes a cycle error |
| // instead of magically pulling *any* ZST value from the ether, we need to |
| // actually access the referenced allocation. |
| self.memory.get_raw(ptr.alloc_id)?; |
| } |
| return Ok(Some(ImmTy { |
| // zero-sized type |
| imm: Scalar::zst().into(), |
| layout: mplace.layout, |
| })); |
| } |
| }; |
| |
| let alloc = self.memory.get_raw(ptr.alloc_id)?; |
| |
| match mplace.layout.abi { |
| Abi::Scalar(..) => { |
| let scalar = alloc.read_scalar(self, ptr, mplace.layout.size)?; |
| Ok(Some(ImmTy { imm: scalar.into(), layout: mplace.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 = alloc.read_scalar(self, a_ptr, a_size)?; |
| let b_val = alloc.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(self) { |
| 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 { |
| span_bug!(self.cur_span(), "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, ScalarMaybeUninit<M::PointerTag>> { |
| Ok(self.read_immediate(op)?.to_scalar_or_uninit()) |
| } |
| |
| // Turn the wide 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))?; |
| let str = ::std::str::from_utf8(bytes).map_err(|err| err_ub!(InvalidStr(err)))?; |
| Ok(str) |
| } |
| |
| /// Projection functions |
| pub fn operand_field( |
| &self, |
| op: OpTy<'tcx, M::PointerTag>, |
| field: usize, |
| ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> { |
| let base = match op.try_as_mplace(self) { |
| Ok(mplace) => { |
| // We can reuse the mplace field computation logic for indirect operands. |
| let field = self.mplace_field(mplace, field)?; |
| return Ok(field.into()); |
| } |
| Err(value) => value, |
| }; |
| |
| 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) => span_bug!( |
| self.cur_span(), |
| "field access on non aggregate {:#?}, {:#?}", |
| val, |
| op.layout |
| ), |
| }; |
| Ok(OpTy { op: Operand::Immediate(immediate), layout: field_layout }) |
| } |
| |
| pub fn operand_index( |
| &self, |
| op: OpTy<'tcx, M::PointerTag>, |
| index: u64, |
| ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> { |
| if let Ok(index) = usize::try_from(index) { |
| // We can just treat this as a field. |
| self.operand_field(op, index) |
| } else { |
| // Indexing into a big array. This must be an mplace. |
| let mplace = op.assert_mem_place(self); |
| Ok(self.mplace_index(mplace, index)?.into()) |
| } |
| } |
| |
| 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(self) { |
| 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_middle::mir::ProjectionElem::*; |
| Ok(match proj_elem { |
| Field(field, _) => self.operand_field(base, field.index())?, |
| Downcast(_, variant) => self.operand_downcast(base, variant)?, |
| Deref => self.deref_operand(base)?.into(), |
| Subslice { .. } | ConstantIndex { .. } | Index(_) => { |
| // 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); |
| self.mplace_projection(mplace, proj_elem)?.into() |
| } |
| }) |
| } |
| |
| /// Read from a local. Will not actually access the local if reading from a ZST. |
| /// Will not access memory, instead an indirect `Operand` is returned. |
| /// |
| /// This is public because it 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<TyAndLayout<'tcx>>, |
| ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> { |
| 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 { |
| M::access_local(&self, frame, local)? |
| }; |
| Ok(OpTy { op, layout }) |
| } |
| |
| /// Every place can be read from, so we can turn them into an operand. |
| /// This will definitely return `Indirect` if the place is a `Ptr`, i.e., this |
| /// will never actually read from memory. |
| #[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 fn eval_place_to_op( |
| &self, |
| place: mir::Place<'tcx>, |
| layout: Option<TyAndLayout<'tcx>>, |
| ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> { |
| // Do not use the layout passed in as argument if the base we are looking at |
| // here is not the entire place. |
| let layout = if place.projection.is_empty() { layout } else { None }; |
| |
| let base_op = self.access_local(self.frame(), place.local, layout)?; |
| |
| let op = place |
| .projection |
| .iter() |
| .try_fold(base_op, |op, elem| self.operand_projection(op, elem))?; |
| |
| trace!("eval_place_to_op: got {:?}", *op); |
| // Sanity-check the type we ended up with. |
| debug_assert!(mir_assign_valid_types( |
| *self.tcx, |
| self.param_env, |
| self.layout_of(self.subst_from_current_frame_and_normalize_erasing_regions( |
| place.ty(&self.frame().body.local_decls, *self.tcx).ty |
| ))?, |
| op.layout, |
| )); |
| 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<TyAndLayout<'tcx>>, |
| ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> { |
| use rustc_middle::mir::Operand::*; |
| let op = match *mir_op { |
| // FIXME: do some more logic on `move` to invalidate the old location |
| Copy(place) | Move(place) => self.eval_place_to_op(place, layout)?, |
| |
| Constant(ref constant) => { |
| let val = |
| self.subst_from_current_frame_and_normalize_erasing_regions(constant.literal); |
| self.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.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 const_to_op( |
| &self, |
| val: &ty::Const<'tcx>, |
| layout: Option<TyAndLayout<'tcx>>, |
| ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> { |
| let tag_scalar = |scalar| -> InterpResult<'tcx, _> { |
| Ok(match scalar { |
| Scalar::Ptr(ptr) => Scalar::Ptr(self.global_base_pointer(ptr)?), |
| Scalar::Raw { data, size } => Scalar::Raw { data, size }, |
| }) |
| }; |
| // Early-return cases. |
| let val_val = match val.val { |
| ty::ConstKind::Param(_) | ty::ConstKind::Bound(..) => throw_inval!(TooGeneric), |
| ty::ConstKind::Error(_) => throw_inval!(TypeckError(ErrorReported)), |
| ty::ConstKind::Unevaluated(def, substs, promoted) => { |
| let instance = self.resolve(def, substs)?; |
| return Ok(self.eval_to_allocation(GlobalId { instance, promoted })?.into()); |
| } |
| ty::ConstKind::Infer(..) | ty::ConstKind::Placeholder(..) => { |
| span_bug!(self.cur_span(), "const_to_op: Unexpected ConstKind {:?}", val) |
| } |
| ty::ConstKind::Value(val_val) => val_val, |
| }; |
| // Other cases need layout. |
| let layout = |
| from_known_layout(self.tcx, self.param_env, layout, || self.layout_of(val.ty))?; |
| let op = match val_val { |
| ConstValue::ByRef { alloc, offset } => { |
| let id = self.tcx.create_memory_alloc(alloc); |
| // We rely on mutability being set correctly in that allocation to prevent writes |
| // where none should happen. |
| let ptr = self.global_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.create_memory_alloc(data), |
| Size::from_bytes(start), // offset: `start` |
| ); |
| Operand::Immediate(Immediate::new_slice( |
| self.global_base_pointer(ptr)?.into(), |
| u64::try_from(end.checked_sub(start).unwrap()).unwrap(), // len: `end - start` |
| self, |
| )) |
| } |
| }; |
| Ok(OpTy { op, layout }) |
| } |
| |
| /// Read discriminant, return the runtime value as well as the variant index. |
| pub fn read_discriminant( |
| &self, |
| op: OpTy<'tcx, M::PointerTag>, |
| ) -> InterpResult<'tcx, (Scalar<M::PointerTag>, VariantIdx)> { |
| trace!("read_discriminant_value {:#?}", op.layout); |
| // Get type and layout of the discriminant. |
| let discr_layout = self.layout_of(op.layout.ty.discriminant_ty(*self.tcx))?; |
| trace!("discriminant type: {:?}", discr_layout.ty); |
| |
| // We use "discriminant" to refer to the value associated with a particular enum variant. |
| // This is not to be confused with its "variant index", which is just determining its position in the |
| // declared list of variants -- they can differ with explicitly assigned discriminants. |
| // We use "tag" to refer to how the discriminant is encoded in memory, which can be either |
| // straight-forward (`TagEncoding::Direct`) or with a niche (`TagEncoding::Niche`). |
| let (tag_scalar_layout, tag_encoding, tag_field) = match op.layout.variants { |
| Variants::Single { index } => { |
| let discr = match op.layout.ty.discriminant_for_variant(*self.tcx, index) { |
| Some(discr) => { |
| // This type actually has discriminants. |
| assert_eq!(discr.ty, discr_layout.ty); |
| Scalar::from_uint(discr.val, discr_layout.size) |
| } |
| None => { |
| // On a type without actual discriminants, variant is 0. |
| assert_eq!(index.as_u32(), 0); |
| Scalar::from_uint(index.as_u32(), discr_layout.size) |
| } |
| }; |
| return Ok((discr, index)); |
| } |
| Variants::Multiple { ref tag, ref tag_encoding, tag_field, .. } => { |
| (tag, tag_encoding, tag_field) |
| } |
| }; |
| |
| // There are *three* layouts that come into play here: |
| // - The discriminant has a type for typechecking. This is `discr_layout`, and is used for |
| // the `Scalar` we return. |
| // - The tag (encoded discriminant) has layout `tag_layout`. This is always an integer type, |
| // and used to interpret the value we read from the tag field. |
| // For the return value, a cast to `discr_layout` is performed. |
| // - The field storing the tag has a layout, which is very similar to `tag_layout` but |
| // may be a pointer. This is `tag_val.layout`; we just use it for sanity checks. |
| |
| // Get layout for tag. |
| let tag_layout = self.layout_of(tag_scalar_layout.value.to_int_ty(*self.tcx))?; |
| |
| // Read tag and sanity-check `tag_layout`. |
| let tag_val = self.read_immediate(self.operand_field(op, tag_field)?)?; |
| assert_eq!(tag_layout.size, tag_val.layout.size); |
| assert_eq!(tag_layout.abi.is_signed(), tag_val.layout.abi.is_signed()); |
| let tag_val = tag_val.to_scalar()?; |
| trace!("tag value: {:?}", tag_val); |
| |
| // Figure out which discriminant and variant this corresponds to. |
| Ok(match *tag_encoding { |
| TagEncoding::Direct => { |
| let tag_bits = self |
| .force_bits(tag_val, tag_layout.size) |
| .map_err(|_| err_ub!(InvalidTag(tag_val.erase_tag())))?; |
| // Cast bits from tag layout to discriminant layout. |
| let discr_val = self.cast_from_scalar(tag_bits, tag_layout, discr_layout.ty); |
| let discr_bits = discr_val.assert_bits(discr_layout.size); |
| // Convert discriminant to variant index, and catch invalid discriminants. |
| let index = match *op.layout.ty.kind() { |
| ty::Adt(adt, _) => { |
| adt.discriminants(*self.tcx).find(|(_, var)| var.val == discr_bits) |
| } |
| ty::Generator(def_id, substs, _) => { |
| let substs = substs.as_generator(); |
| substs |
| .discriminants(def_id, *self.tcx) |
| .find(|(_, var)| var.val == discr_bits) |
| } |
| _ => span_bug!(self.cur_span(), "tagged layout for non-adt non-generator"), |
| } |
| .ok_or_else(|| err_ub!(InvalidTag(tag_val.erase_tag())))?; |
| // Return the cast value, and the index. |
| (discr_val, index.0) |
| } |
| TagEncoding::Niche { dataful_variant, ref niche_variants, niche_start } => { |
| // Compute the variant this niche value/"tag" corresponds to. With niche layout, |
| // discriminant (encoded in niche/tag) and variant index are the same. |
| let variants_start = niche_variants.start().as_u32(); |
| let variants_end = niche_variants.end().as_u32(); |
| let variant = match tag_val.to_bits_or_ptr(tag_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_ub!(InvalidTag(tag_val.erase_tag())) |
| } |
| dataful_variant |
| } |
| Ok(tag_bits) => { |
| // We need to use machine arithmetic to get the relative variant idx: |
| // variant_index_relative = tag_val - niche_start_val |
| let tag_val = ImmTy::from_uint(tag_bits, tag_layout); |
| let niche_start_val = ImmTy::from_uint(niche_start, tag_layout); |
| let variant_index_relative_val = |
| self.binary_op(mir::BinOp::Sub, tag_val, niche_start_val)?; |
| let variant_index_relative = variant_index_relative_val |
| .to_scalar()? |
| .assert_bits(tag_val.layout.size); |
| // Check if this is in the range that indicates an actual discriminant. |
| if variant_index_relative <= u128::from(variants_end - variants_start) { |
| let variant_index_relative = u32::try_from(variant_index_relative) |
| .expect("we checked that this fits into a u32"); |
| // Then computing the absolute variant idx should not overflow any more. |
| let variant_index = variants_start |
| .checked_add(variant_index_relative) |
| .expect("overflow computing absolute variant idx"); |
| let variants_len = op |
| .layout |
| .ty |
| .ty_adt_def() |
| .expect("tagged layout for non adt") |
| .variants |
| .len(); |
| assert!(usize::try_from(variant_index).unwrap() < variants_len); |
| VariantIdx::from_u32(variant_index) |
| } else { |
| dataful_variant |
| } |
| } |
| }; |
| // Compute the size of the scalar we need to return. |
| // No need to cast, because the variant index directly serves as discriminant and is |
| // encoded in the tag. |
| (Scalar::from_uint(variant.as_u32(), discr_layout.size), variant) |
| } |
| }) |
| } |
| } |
