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Diffstat (limited to 'compiler/rustc_const_eval/src/interpret/place.rs')
| -rw-r--r-- | compiler/rustc_const_eval/src/interpret/place.rs | 900 |
1 files changed, 900 insertions, 0 deletions
diff --git a/compiler/rustc_const_eval/src/interpret/place.rs b/compiler/rustc_const_eval/src/interpret/place.rs new file mode 100644 index 000000000..f4571a1ca --- /dev/null +++ b/compiler/rustc_const_eval/src/interpret/place.rs @@ -0,0 +1,900 @@ +//! Computations on places -- field projections, going from mir::Place, and writing +//! into a place. +//! All high-level functions to write to memory work on places as destinations. + +use std::hash::Hash; + +use rustc_ast::Mutability; +use rustc_middle::mir; +use rustc_middle::ty; +use rustc_middle::ty::layout::{LayoutOf, PrimitiveExt, TyAndLayout}; +use rustc_target::abi::{self, Abi, Align, HasDataLayout, Size, TagEncoding, VariantIdx}; + +use super::{ + alloc_range, mir_assign_valid_types, AllocId, AllocRef, AllocRefMut, CheckInAllocMsg, + ConstAlloc, ImmTy, Immediate, InterpCx, InterpResult, Machine, MemoryKind, OpTy, Operand, + Pointer, Provenance, Scalar, ScalarMaybeUninit, +}; + +#[derive(Copy, Clone, Hash, PartialEq, Eq, Debug)] +/// Information required for the sound usage of a `MemPlace`. +pub enum MemPlaceMeta<Prov: Provenance = AllocId> { + /// The unsized payload (e.g. length for slices or vtable pointer for trait objects). + Meta(Scalar<Prov>), + /// `Sized` types or unsized `extern type` + None, +} + +impl<Prov: Provenance> MemPlaceMeta<Prov> { + pub fn unwrap_meta(self) -> Scalar<Prov> { + match self { + Self::Meta(s) => s, + Self::None => { + bug!("expected wide pointer extra data (e.g. slice length or trait object vtable)") + } + } + } + + pub fn has_meta(self) -> bool { + match self { + Self::Meta(_) => true, + Self::None => false, + } + } +} + +#[derive(Copy, Clone, Hash, PartialEq, Eq, Debug)] +pub struct MemPlace<Prov: Provenance = AllocId> { + /// The pointer can be a pure integer, with the `None` provenance. + pub ptr: Pointer<Option<Prov>>, + /// Metadata for unsized places. Interpretation is up to the type. + /// Must not be present for sized types, but can be missing for unsized types + /// (e.g., `extern type`). + pub meta: MemPlaceMeta<Prov>, +} + +/// A MemPlace with its layout. Constructing it is only possible in this module. +#[derive(Copy, Clone, Hash, Eq, PartialEq, Debug)] +pub struct MPlaceTy<'tcx, Prov: Provenance = AllocId> { + mplace: MemPlace<Prov>, + pub layout: TyAndLayout<'tcx>, + /// rustc does not have a proper way to represent the type of a field of a `repr(packed)` struct: + /// it needs to have a different alignment than the field type would usually have. + /// So we represent this here with a separate field that "overwrites" `layout.align`. + /// This means `layout.align` should never be used for a `MPlaceTy`! + pub align: Align, +} + +#[derive(Copy, Clone, Debug)] +pub enum Place<Prov: Provenance = AllocId> { + /// A place referring to a value allocated in the `Memory` system. + Ptr(MemPlace<Prov>), + + /// To support alloc-free locals, we are able to write directly to a local. + /// (Without that optimization, we'd just always be a `MemPlace`.) + Local { frame: usize, local: mir::Local }, +} + +#[derive(Clone, Debug)] +pub struct PlaceTy<'tcx, Prov: Provenance = AllocId> { + place: Place<Prov>, // Keep this private; it helps enforce invariants. + pub layout: TyAndLayout<'tcx>, + /// rustc does not have a proper way to represent the type of a field of a `repr(packed)` struct: + /// it needs to have a different alignment than the field type would usually have. + /// So we represent this here with a separate field that "overwrites" `layout.align`. + /// This means `layout.align` should never be used for a `PlaceTy`! + pub align: Align, +} + +impl<'tcx, Prov: Provenance> std::ops::Deref for PlaceTy<'tcx, Prov> { + type Target = Place<Prov>; + #[inline(always)] + fn deref(&self) -> &Place<Prov> { + &self.place + } +} + +impl<'tcx, Prov: Provenance> std::ops::Deref for MPlaceTy<'tcx, Prov> { + type Target = MemPlace<Prov>; + #[inline(always)] + fn deref(&self) -> &MemPlace<Prov> { + &self.mplace + } +} + +impl<'tcx, Prov: Provenance> From<MPlaceTy<'tcx, Prov>> for PlaceTy<'tcx, Prov> { + #[inline(always)] + fn from(mplace: MPlaceTy<'tcx, Prov>) -> Self { + PlaceTy { place: Place::Ptr(*mplace), layout: mplace.layout, align: mplace.align } + } +} + +impl<'tcx, Prov: Provenance> From<&'_ MPlaceTy<'tcx, Prov>> for PlaceTy<'tcx, Prov> { + #[inline(always)] + fn from(mplace: &MPlaceTy<'tcx, Prov>) -> Self { + PlaceTy { place: Place::Ptr(**mplace), layout: mplace.layout, align: mplace.align } + } +} + +impl<'tcx, Prov: Provenance> From<&'_ mut MPlaceTy<'tcx, Prov>> for PlaceTy<'tcx, Prov> { + #[inline(always)] + fn from(mplace: &mut MPlaceTy<'tcx, Prov>) -> Self { + PlaceTy { place: Place::Ptr(**mplace), layout: mplace.layout, align: mplace.align } + } +} + +impl<Prov: Provenance> MemPlace<Prov> { + #[inline(always)] + pub fn from_ptr(ptr: Pointer<Option<Prov>>) -> Self { + MemPlace { ptr, meta: MemPlaceMeta::None } + } + + /// Adjust the provenance of the main pointer (metadata is unaffected). + pub fn map_provenance(self, f: impl FnOnce(Option<Prov>) -> Option<Prov>) -> Self { + MemPlace { ptr: self.ptr.map_provenance(f), ..self } + } + + /// Turn a mplace into a (thin or wide) pointer, as a reference, pointing to the same space. + /// This is the inverse of `ref_to_mplace`. + #[inline(always)] + pub fn to_ref(self, cx: &impl HasDataLayout) -> Immediate<Prov> { + match self.meta { + MemPlaceMeta::None => Immediate::from(Scalar::from_maybe_pointer(self.ptr, cx)), + MemPlaceMeta::Meta(meta) => { + Immediate::ScalarPair(Scalar::from_maybe_pointer(self.ptr, cx).into(), meta.into()) + } + } + } + + #[inline] + pub fn offset_with_meta<'tcx>( + self, + offset: Size, + meta: MemPlaceMeta<Prov>, + cx: &impl HasDataLayout, + ) -> InterpResult<'tcx, Self> { + Ok(MemPlace { ptr: self.ptr.offset(offset, cx)?, meta }) + } +} + +impl<Prov: Provenance> Place<Prov> { + /// Asserts that this points to some local variable. + /// Returns the frame idx and the variable idx. + #[inline] + #[cfg_attr(debug_assertions, track_caller)] // only in debug builds due to perf (see #98980) + pub fn assert_local(&self) -> (usize, mir::Local) { + match self { + Place::Local { frame, local } => (*frame, *local), + _ => bug!("assert_local: expected Place::Local, got {:?}", self), + } + } +} + +impl<'tcx, Prov: Provenance> MPlaceTy<'tcx, Prov> { + /// Produces a MemPlace that works for ZST but nothing else. + /// Conceptually this is a new allocation, but it doesn't actually create an allocation so you + /// don't need to worry about memory leaks. + #[inline] + pub fn fake_alloc_zst(layout: TyAndLayout<'tcx>) -> Self { + assert!(layout.is_zst()); + let align = layout.align.abi; + let ptr = Pointer::from_addr(align.bytes()); // no provenance, absolute address + MPlaceTy { mplace: MemPlace { ptr, meta: MemPlaceMeta::None }, layout, align } + } + + #[inline] + pub fn offset_with_meta( + &self, + offset: Size, + meta: MemPlaceMeta<Prov>, + layout: TyAndLayout<'tcx>, + cx: &impl HasDataLayout, + ) -> InterpResult<'tcx, Self> { + Ok(MPlaceTy { + mplace: self.mplace.offset_with_meta(offset, meta, cx)?, + align: self.align.restrict_for_offset(offset), + layout, + }) + } + + pub fn offset( + &self, + offset: Size, + layout: TyAndLayout<'tcx>, + cx: &impl HasDataLayout, + ) -> InterpResult<'tcx, Self> { + assert!(!layout.is_unsized()); + self.offset_with_meta(offset, MemPlaceMeta::None, layout, cx) + } + + #[inline] + pub fn from_aligned_ptr(ptr: Pointer<Option<Prov>>, layout: TyAndLayout<'tcx>) -> Self { + MPlaceTy { mplace: MemPlace::from_ptr(ptr), layout, align: layout.align.abi } + } + + #[inline] + pub fn from_aligned_ptr_with_meta( + ptr: Pointer<Option<Prov>>, + layout: TyAndLayout<'tcx>, + meta: MemPlaceMeta<Prov>, + ) -> Self { + let mut mplace = MemPlace::from_ptr(ptr); + mplace.meta = meta; + + MPlaceTy { mplace, layout, align: layout.align.abi } + } + + #[inline] + pub(crate) fn len(&self, cx: &impl HasDataLayout) -> InterpResult<'tcx, u64> { + if self.layout.is_unsized() { + // We need to consult `meta` metadata + match self.layout.ty.kind() { + ty::Slice(..) | ty::Str => self.mplace.meta.unwrap_meta().to_machine_usize(cx), + _ => bug!("len not supported on unsized type {:?}", self.layout.ty), + } + } else { + // Go through the layout. There are lots of types that support a length, + // e.g., SIMD types. (But not all repr(simd) types even have FieldsShape::Array!) + match self.layout.fields { + abi::FieldsShape::Array { count, .. } => Ok(count), + _ => bug!("len not supported on sized type {:?}", self.layout.ty), + } + } + } + + #[inline] + pub(super) fn vtable(&self) -> Scalar<Prov> { + match self.layout.ty.kind() { + ty::Dynamic(..) => self.mplace.meta.unwrap_meta(), + _ => bug!("vtable not supported on type {:?}", self.layout.ty), + } + } +} + +// These are defined here because they produce a place. +impl<'tcx, Prov: Provenance> OpTy<'tcx, Prov> { + #[inline(always)] + /// Note: do not call `as_ref` on the resulting place. This function should only be used to + /// read from the resulting mplace, not to get its address back. + pub fn try_as_mplace(&self) -> Result<MPlaceTy<'tcx, Prov>, ImmTy<'tcx, Prov>> { + match **self { + Operand::Indirect(mplace) => { + Ok(MPlaceTy { mplace, layout: self.layout, align: self.align.unwrap() }) + } + Operand::Immediate(imm) => Err(ImmTy::from_immediate(imm, self.layout)), + } + } + + #[inline(always)] + #[cfg_attr(debug_assertions, track_caller)] // only in debug builds due to perf (see #98980) + /// Note: do not call `as_ref` on the resulting place. This function should only be used to + /// read from the resulting mplace, not to get its address back. + pub fn assert_mem_place(&self) -> MPlaceTy<'tcx, Prov> { + self.try_as_mplace().unwrap() + } +} + +impl<'tcx, Prov: Provenance> PlaceTy<'tcx, Prov> { + /// A place is either an mplace or some local. + #[inline] + pub fn try_as_mplace(&self) -> Result<MPlaceTy<'tcx, Prov>, (usize, mir::Local)> { + match **self { + Place::Ptr(mplace) => Ok(MPlaceTy { mplace, layout: self.layout, align: self.align }), + Place::Local { frame, local } => Err((frame, local)), + } + } + + #[inline(always)] + #[cfg_attr(debug_assertions, track_caller)] // only in debug builds due to perf (see #98980) + pub fn assert_mem_place(self) -> MPlaceTy<'tcx, Prov> { + self.try_as_mplace().unwrap() + } +} + +// FIXME: Working around https://github.com/rust-lang/rust/issues/54385 +impl<'mir, 'tcx: 'mir, Prov, M> InterpCx<'mir, 'tcx, M> +where + Prov: Provenance + Eq + Hash + 'static, + M: Machine<'mir, 'tcx, Provenance = Prov>, +{ + /// Take a value, which represents a (thin or wide) reference, and make it a place. + /// Alignment is just based on the type. This is the inverse of `MemPlace::to_ref()`. + /// + /// Only call this if you are sure the place is "valid" (aligned and inbounds), or do not + /// want to ever use the place for memory access! + /// Generally prefer `deref_operand`. + pub fn ref_to_mplace( + &self, + val: &ImmTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> { + let pointee_type = + val.layout.ty.builtin_deref(true).expect("`ref_to_mplace` called on non-ptr type").ty; + let layout = self.layout_of(pointee_type)?; + let (ptr, meta) = match **val { + Immediate::Scalar(ptr) => (ptr, MemPlaceMeta::None), + Immediate::ScalarPair(ptr, meta) => (ptr, MemPlaceMeta::Meta(meta.check_init()?)), + Immediate::Uninit => throw_ub!(InvalidUninitBytes(None)), + }; + + let mplace = MemPlace { ptr: ptr.to_pointer(self)?, meta }; + // When deref'ing a pointer, the *static* alignment given by the type is what matters. + let align = layout.align.abi; + Ok(MPlaceTy { mplace, layout, align }) + } + + /// Take an operand, representing a pointer, and dereference it to a place -- that + /// will always be a MemPlace. Lives in `place.rs` because it creates a place. + #[instrument(skip(self), level = "debug")] + pub fn deref_operand( + &self, + src: &OpTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> { + let val = self.read_immediate(src)?; + trace!("deref to {} on {:?}", val.layout.ty, *val); + + if val.layout.ty.is_box() { + bug!("dereferencing {:?}", val.layout.ty); + } + + let mplace = self.ref_to_mplace(&val)?; + self.check_mplace_access(mplace, CheckInAllocMsg::DerefTest)?; + Ok(mplace) + } + + #[inline] + pub(super) fn get_place_alloc( + &self, + place: &MPlaceTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx, Option<AllocRef<'_, 'tcx, M::Provenance, M::AllocExtra>>> { + assert!(!place.layout.is_unsized()); + assert!(!place.meta.has_meta()); + let size = place.layout.size; + self.get_ptr_alloc(place.ptr, size, place.align) + } + + #[inline] + pub(super) fn get_place_alloc_mut( + &mut self, + place: &MPlaceTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx, Option<AllocRefMut<'_, 'tcx, M::Provenance, M::AllocExtra>>> { + assert!(!place.layout.is_unsized()); + assert!(!place.meta.has_meta()); + let size = place.layout.size; + self.get_ptr_alloc_mut(place.ptr, size, place.align) + } + + /// Check if this mplace is dereferenceable and sufficiently aligned. + fn check_mplace_access( + &self, + mplace: MPlaceTy<'tcx, M::Provenance>, + msg: CheckInAllocMsg, + ) -> InterpResult<'tcx> { + let (size, align) = self + .size_and_align_of_mplace(&mplace)? + .unwrap_or((mplace.layout.size, mplace.layout.align.abi)); + assert!(mplace.align <= align, "dynamic alignment less strict than static one?"); + let align = M::enforce_alignment(self).then_some(align); + self.check_ptr_access_align(mplace.ptr, size, align.unwrap_or(Align::ONE), msg)?; + Ok(()) + } + + /// Converts a repr(simd) place into a place where `place_index` accesses the SIMD elements. + /// Also returns the number of elements. + pub fn mplace_to_simd( + &self, + mplace: &MPlaceTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx, (MPlaceTy<'tcx, M::Provenance>, u64)> { + // Basically we just transmute this place into an array following simd_size_and_type. + // (Transmuting is okay since this is an in-memory place. We also double-check the size + // stays the same.) + let (len, e_ty) = mplace.layout.ty.simd_size_and_type(*self.tcx); + let array = self.tcx.mk_array(e_ty, len); + let layout = self.layout_of(array)?; + assert_eq!(layout.size, mplace.layout.size); + Ok((MPlaceTy { layout, ..*mplace }, len)) + } + + /// Converts a repr(simd) place into a place where `place_index` accesses the SIMD elements. + /// Also returns the number of elements. + pub fn place_to_simd( + &mut self, + place: &PlaceTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx, (MPlaceTy<'tcx, M::Provenance>, u64)> { + let mplace = self.force_allocation(place)?; + self.mplace_to_simd(&mplace) + } + + pub fn local_to_place( + &self, + frame: usize, + local: mir::Local, + ) -> InterpResult<'tcx, PlaceTy<'tcx, M::Provenance>> { + let layout = self.layout_of_local(&self.stack()[frame], local, None)?; + let place = Place::Local { frame, local }; + Ok(PlaceTy { place, layout, align: layout.align.abi }) + } + + /// Computes a place. You should only use this if you intend to write into this + /// place; for reading, a more efficient alternative is `eval_place_to_op`. + #[instrument(skip(self), level = "debug")] + pub fn eval_place( + &mut self, + mir_place: mir::Place<'tcx>, + ) -> InterpResult<'tcx, PlaceTy<'tcx, M::Provenance>> { + let mut place = self.local_to_place(self.frame_idx(), mir_place.local)?; + // Using `try_fold` turned out to be bad for performance, hence the loop. + for elem in mir_place.projection.iter() { + place = self.place_projection(&place, elem)? + } + + trace!("{:?}", self.dump_place(place.place)); + // 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( + mir_place.ty(&self.frame().body.local_decls, *self.tcx).ty + )?)?, + place.layout, + ), + "eval_place of a MIR place with type {:?} produced an interpreter place with type {:?}", + mir_place.ty(&self.frame().body.local_decls, *self.tcx).ty, + place.layout.ty, + ); + Ok(place) + } + + /// Write an immediate to a place + #[inline(always)] + #[instrument(skip(self), level = "debug")] + pub fn write_immediate( + &mut self, + src: Immediate<M::Provenance>, + dest: &PlaceTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx> { + self.write_immediate_no_validate(src, dest)?; + + if M::enforce_validity(self) { + // Data got changed, better make sure it matches the type! + self.validate_operand(&self.place_to_op(dest)?)?; + } + + Ok(()) + } + + /// Write a scalar to a place + #[inline(always)] + pub fn write_scalar( + &mut self, + val: impl Into<ScalarMaybeUninit<M::Provenance>>, + dest: &PlaceTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx> { + self.write_immediate(Immediate::Scalar(val.into()), dest) + } + + /// Write a pointer to a place + #[inline(always)] + pub fn write_pointer( + &mut self, + ptr: impl Into<Pointer<Option<M::Provenance>>>, + dest: &PlaceTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx> { + self.write_scalar(Scalar::from_maybe_pointer(ptr.into(), self), dest) + } + + /// Write an immediate to a place. + /// If you use this you are responsible for validating that things got copied at the + /// right type. + fn write_immediate_no_validate( + &mut self, + src: Immediate<M::Provenance>, + dest: &PlaceTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx> { + assert!(!dest.layout.is_unsized(), "Cannot write unsized data"); + trace!("write_immediate: {:?} <- {:?}: {}", *dest, src, dest.layout.ty); + + // See if we can avoid an allocation. This is the counterpart to `read_immediate_raw`, + // but not factored as a separate function. + let mplace = match dest.place { + Place::Local { frame, local } => { + match M::access_local_mut(self, frame, local)? { + Operand::Immediate(local) => { + // Local can be updated in-place. + *local = src; + return Ok(()); + } + Operand::Indirect(mplace) => { + // The local is in memory, go on below. + *mplace + } + } + } + Place::Ptr(mplace) => mplace, // already referring to memory + }; + + // This is already in memory, write there. + self.write_immediate_to_mplace_no_validate(src, dest.layout, dest.align, mplace) + } + + /// Write an immediate to memory. + /// If you use this you are responsible for validating that things got copied at the + /// right layout. + fn write_immediate_to_mplace_no_validate( + &mut self, + value: Immediate<M::Provenance>, + layout: TyAndLayout<'tcx>, + align: Align, + dest: MemPlace<M::Provenance>, + ) -> InterpResult<'tcx> { + // Note that it is really important that the type here is the right one, and matches the + // type things are read at. In case `value` is a `ScalarPair`, we don't do any magic here + // to handle padding properly, which is only correct if we never look at this data with the + // wrong type. + + let tcx = *self.tcx; + let Some(mut alloc) = self.get_place_alloc_mut(&MPlaceTy { mplace: dest, layout, align })? else { + // zero-sized access + return Ok(()); + }; + + match value { + Immediate::Scalar(scalar) => { + let Abi::Scalar(s) = layout.abi else { span_bug!( + self.cur_span(), + "write_immediate_to_mplace: invalid Scalar layout: {layout:#?}", + ) + }; + let size = s.size(&tcx); + assert_eq!(size, layout.size, "abi::Scalar size does not match layout size"); + alloc.write_scalar(alloc_range(Size::ZERO, size), scalar) + } + Immediate::ScalarPair(a_val, b_val) => { + // 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 Abi::ScalarPair(a, b) = layout.abi else { span_bug!( + self.cur_span(), + "write_immediate_to_mplace: invalid ScalarPair layout: {:#?}", + layout + ) + }; + let (a_size, b_size) = (a.size(&tcx), b.size(&tcx)); + let b_offset = a_size.align_to(b.align(&tcx).abi); + assert!(b_offset.bytes() > 0); // in `operand_field` we use the offset to tell apart the fields + + // It is tempting to verify `b_offset` against `layout.fields.offset(1)`, + // but that does not work: We could be a newtype around a pair, then the + // fields do not match the `ScalarPair` components. + + alloc.write_scalar(alloc_range(Size::ZERO, a_size), a_val)?; + alloc.write_scalar(alloc_range(b_offset, b_size), b_val) + } + Immediate::Uninit => alloc.write_uninit(), + } + } + + pub fn write_uninit(&mut self, dest: &PlaceTy<'tcx, M::Provenance>) -> InterpResult<'tcx> { + let mplace = match dest.try_as_mplace() { + Ok(mplace) => mplace, + Err((frame, local)) => { + match M::access_local_mut(self, frame, local)? { + Operand::Immediate(local) => { + *local = Immediate::Uninit; + return Ok(()); + } + Operand::Indirect(mplace) => { + // The local is in memory, go on below. + MPlaceTy { mplace: *mplace, layout: dest.layout, align: dest.align } + } + } + } + }; + let Some(mut alloc) = self.get_place_alloc_mut(&mplace)? else { + // Zero-sized access + return Ok(()); + }; + alloc.write_uninit()?; + Ok(()) + } + + /// Copies the data from an operand to a place. + /// `allow_transmute` indicates whether the layouts may disagree. + #[inline(always)] + #[instrument(skip(self), level = "debug")] + pub fn copy_op( + &mut self, + src: &OpTy<'tcx, M::Provenance>, + dest: &PlaceTy<'tcx, M::Provenance>, + allow_transmute: bool, + ) -> InterpResult<'tcx> { + self.copy_op_no_validate(src, dest, allow_transmute)?; + + if M::enforce_validity(self) { + // Data got changed, better make sure it matches the type! + self.validate_operand(&self.place_to_op(dest)?)?; + } + + Ok(()) + } + + /// Copies the data from an operand to a place. + /// `allow_transmute` indicates whether the layouts may disagree. + /// Also, if you use this you are responsible for validating that things get copied at the + /// right type. + #[instrument(skip(self), level = "debug")] + fn copy_op_no_validate( + &mut self, + src: &OpTy<'tcx, M::Provenance>, + dest: &PlaceTy<'tcx, M::Provenance>, + allow_transmute: bool, + ) -> InterpResult<'tcx> { + // We do NOT compare the types for equality, because well-typed code can + // actually "transmute" `&mut T` to `&T` in an assignment without a cast. + let layout_compat = + mir_assign_valid_types(*self.tcx, self.param_env, src.layout, dest.layout); + if !allow_transmute && !layout_compat { + span_bug!( + self.cur_span(), + "type mismatch when copying!\nsrc: {:?},\ndest: {:?}", + src.layout.ty, + dest.layout.ty, + ); + } + + // Let us see if the layout is simple so we take a shortcut, + // avoid force_allocation. + let src = match self.read_immediate_raw(src, /*force*/ false)? { + Ok(src_val) => { + assert!(!src.layout.is_unsized(), "cannot have unsized immediates"); + assert!( + !dest.layout.is_unsized(), + "the src is sized, so the dest must also be sized" + ); + assert_eq!(src.layout.size, dest.layout.size); + // Yay, we got a value that we can write directly. + return if layout_compat { + self.write_immediate_no_validate(*src_val, dest) + } else { + // This is tricky. The problematic case is `ScalarPair`: the `src_val` was + // loaded using the offsets defined by `src.layout`. When we put this back into + // the destination, we have to use the same offsets! So (a) we make sure we + // write back to memory, and (b) we use `dest` *with the source layout*. + let dest_mem = self.force_allocation(dest)?; + self.write_immediate_to_mplace_no_validate( + *src_val, + src.layout, + dest_mem.align, + *dest_mem, + ) + }; + } + Err(mplace) => mplace, + }; + // Slow path, this does not fit into an immediate. Just memcpy. + trace!("copy_op: {:?} <- {:?}: {}", *dest, src, dest.layout.ty); + + let dest = self.force_allocation(&dest)?; + let Some((dest_size, _)) = self.size_and_align_of_mplace(&dest)? else { + span_bug!(self.cur_span(), "copy_op needs (dynamically) sized values") + }; + if cfg!(debug_assertions) { + let src_size = self.size_and_align_of_mplace(&src)?.unwrap().0; + assert_eq!(src_size, dest_size, "Cannot copy differently-sized data"); + } else { + // As a cheap approximation, we compare the fixed parts of the size. + assert_eq!(src.layout.size, dest.layout.size); + } + + self.mem_copy( + src.ptr, src.align, dest.ptr, dest.align, dest_size, /*nonoverlapping*/ false, + ) + } + + /// Ensures that a place is in memory, and returns where it is. + /// If the place currently refers to a local that doesn't yet have a matching allocation, + /// create such an allocation. + /// This is essentially `force_to_memplace`. + #[instrument(skip(self), level = "debug")] + pub fn force_allocation( + &mut self, + place: &PlaceTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> { + let mplace = match place.place { + Place::Local { frame, local } => { + match M::access_local_mut(self, frame, local)? { + &mut Operand::Immediate(local_val) => { + // We need to make an allocation. + + // We need the layout of the local. We can NOT use the layout we got, + // that might e.g., be an inner field of a struct with `Scalar` layout, + // that has different alignment than the outer field. + let local_layout = + self.layout_of_local(&self.stack()[frame], local, None)?; + if local_layout.is_unsized() { + throw_unsup_format!("unsized locals are not supported"); + } + let mplace = *self.allocate(local_layout, MemoryKind::Stack)?; + if !matches!(local_val, Immediate::Uninit) { + // Preserve old value. (As an optimization, we can skip this if it was uninit.) + // We don't have to validate as we can assume the local + // was already valid for its type. + self.write_immediate_to_mplace_no_validate( + local_val, + local_layout, + local_layout.align.abi, + mplace, + )?; + } + // Now we can call `access_mut` again, asserting it goes well, + // and actually overwrite things. + *M::access_local_mut(self, frame, local).unwrap() = + Operand::Indirect(mplace); + mplace + } + &mut Operand::Indirect(mplace) => mplace, // this already was an indirect local + } + } + Place::Ptr(mplace) => mplace, + }; + // Return with the original layout, so that the caller can go on + Ok(MPlaceTy { mplace, layout: place.layout, align: place.align }) + } + + pub fn allocate( + &mut self, + layout: TyAndLayout<'tcx>, + kind: MemoryKind<M::MemoryKind>, + ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> { + assert!(!layout.is_unsized()); + let ptr = self.allocate_ptr(layout.size, layout.align.abi, kind)?; + Ok(MPlaceTy::from_aligned_ptr(ptr.into(), layout)) + } + + /// Returns a wide MPlace of type `&'static [mut] str` to a new 1-aligned allocation. + pub fn allocate_str( + &mut self, + str: &str, + kind: MemoryKind<M::MemoryKind>, + mutbl: Mutability, + ) -> MPlaceTy<'tcx, M::Provenance> { + let ptr = self.allocate_bytes_ptr(str.as_bytes(), Align::ONE, kind, mutbl); + let meta = Scalar::from_machine_usize(u64::try_from(str.len()).unwrap(), self); + let mplace = MemPlace { ptr: ptr.into(), meta: MemPlaceMeta::Meta(meta) }; + + let ty = self.tcx.mk_ref( + self.tcx.lifetimes.re_static, + ty::TypeAndMut { ty: self.tcx.types.str_, mutbl }, + ); + let layout = self.layout_of(ty).unwrap(); + MPlaceTy { mplace, layout, align: layout.align.abi } + } + + /// Writes the discriminant of the given variant. + #[instrument(skip(self), level = "debug")] + pub fn write_discriminant( + &mut self, + variant_index: VariantIdx, + dest: &PlaceTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx> { + // This must be an enum or generator. + match dest.layout.ty.kind() { + ty::Adt(adt, _) => assert!(adt.is_enum()), + ty::Generator(..) => {} + _ => span_bug!( + self.cur_span(), + "write_discriminant called on non-variant-type (neither enum nor generator)" + ), + } + // Layout computation excludes uninhabited variants from consideration + // therefore there's no way to represent those variants in the given layout. + // Essentially, uninhabited variants do not have a tag that corresponds to their + // discriminant, so we cannot do anything here. + // When evaluating we will always error before even getting here, but ConstProp 'executes' + // dead code, so we cannot ICE here. + if dest.layout.for_variant(self, variant_index).abi.is_uninhabited() { + throw_ub!(UninhabitedEnumVariantWritten) + } + + match dest.layout.variants { + abi::Variants::Single { index } => { + assert_eq!(index, variant_index); + } + abi::Variants::Multiple { + tag_encoding: TagEncoding::Direct, + tag: tag_layout, + tag_field, + .. + } => { + // No need to validate that the discriminant here because the + // `TyAndLayout::for_variant()` call earlier already checks the variant is valid. + + let discr_val = + dest.layout.ty.discriminant_for_variant(*self.tcx, variant_index).unwrap().val; + + // raw discriminants for enums are isize or bigger during + // their computation, but the in-memory tag is the smallest possible + // representation + let size = tag_layout.size(self); + let tag_val = size.truncate(discr_val); + + let tag_dest = self.place_field(dest, tag_field)?; + self.write_scalar(Scalar::from_uint(tag_val, size), &tag_dest)?; + } + abi::Variants::Multiple { + tag_encoding: + TagEncoding::Niche { dataful_variant, ref niche_variants, niche_start }, + tag: tag_layout, + tag_field, + .. + } => { + // No need to validate that the discriminant here because the + // `TyAndLayout::for_variant()` call earlier already checks the variant is valid. + + if variant_index != dataful_variant { + let variants_start = niche_variants.start().as_u32(); + let variant_index_relative = variant_index + .as_u32() + .checked_sub(variants_start) + .expect("overflow computing relative variant idx"); + // We need to use machine arithmetic when taking into account `niche_start`: + // tag_val = variant_index_relative + niche_start_val + let tag_layout = self.layout_of(tag_layout.primitive().to_int_ty(*self.tcx))?; + let niche_start_val = ImmTy::from_uint(niche_start, tag_layout); + let variant_index_relative_val = + ImmTy::from_uint(variant_index_relative, tag_layout); + let tag_val = self.binary_op( + mir::BinOp::Add, + &variant_index_relative_val, + &niche_start_val, + )?; + // Write result. + let niche_dest = self.place_field(dest, tag_field)?; + self.write_immediate(*tag_val, &niche_dest)?; + } + } + } + + Ok(()) + } + + pub fn raw_const_to_mplace( + &self, + raw: ConstAlloc<'tcx>, + ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> { + // This must be an allocation in `tcx` + let _ = self.tcx.global_alloc(raw.alloc_id); + let ptr = self.global_base_pointer(Pointer::from(raw.alloc_id))?; + let layout = self.layout_of(raw.ty)?; + Ok(MPlaceTy::from_aligned_ptr(ptr.into(), layout)) + } + + /// Turn a place with a `dyn Trait` type into a place with the actual dynamic type. + pub(super) fn unpack_dyn_trait( + &self, + mplace: &MPlaceTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> { + let vtable = mplace.vtable().to_pointer(self)?; // also sanity checks the type + let (ty, _) = self.get_ptr_vtable(vtable)?; + let layout = self.layout_of(ty)?; + + let mplace = MPlaceTy { + mplace: MemPlace { meta: MemPlaceMeta::None, ..**mplace }, + layout, + align: layout.align.abi, + }; + Ok(mplace) + } +} + +// Some nodes are used a lot. Make sure they don't unintentionally get bigger. +#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))] +mod size_asserts { + use super::*; + // These are in alphabetical order, which is easy to maintain. + rustc_data_structures::static_assert_size!(MemPlaceMeta, 24); + rustc_data_structures::static_assert_size!(MemPlace, 40); + rustc_data_structures::static_assert_size!(MPlaceTy<'_>, 64); + rustc_data_structures::static_assert_size!(Place, 48); + rustc_data_structures::static_assert_size!(PlaceTy<'_>, 72); +} |