1 //! Computations on places -- field projections, going from mir::Place, and writing
3 //! All high-level functions to write to memory work on places as destinations.
5 use std::convert::TryFrom;
10 use rustc::ty::{self, Ty};
11 use rustc::ty::layout::{self, Size, Align, LayoutOf, TyLayout, HasDataLayout, VariantIdx};
12 use rustc::ty::TypeFoldable;
15 GlobalId, AllocId, Allocation, Scalar, EvalResult, Pointer, PointerArithmetic,
16 EvalContext, Machine, AllocMap, AllocationExtra,
17 RawConst, Immediate, ImmTy, ScalarMaybeUndef, Operand, OpTy, MemoryKind
20 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
21 pub struct MemPlace<Tag=(), Id=AllocId> {
22 /// A place may have an integral pointer for ZSTs, and since it might
23 /// be turned back into a reference before ever being dereferenced.
24 /// However, it may never be undef.
25 pub ptr: Scalar<Tag, Id>,
27 /// Metadata for unsized places. Interpretation is up to the type.
28 /// Must not be present for sized types, but can be missing for unsized types
29 /// (e.g., `extern type`).
30 pub meta: Option<Scalar<Tag, Id>>,
33 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
34 pub enum Place<Tag=(), Id=AllocId> {
35 /// A place referring to a value allocated in the `Memory` system.
36 Ptr(MemPlace<Tag, Id>),
38 /// To support alloc-free locals, we are able to write directly to a local.
39 /// (Without that optimization, we'd just always be a `MemPlace`.)
46 #[derive(Copy, Clone, Debug)]
47 pub struct PlaceTy<'tcx, Tag=()> {
49 pub layout: TyLayout<'tcx>,
52 impl<'tcx, Tag> ::std::ops::Deref for PlaceTy<'tcx, Tag> {
53 type Target = Place<Tag>;
55 fn deref(&self) -> &Place<Tag> {
60 /// A MemPlace with its layout. Constructing it is only possible in this module.
61 #[derive(Copy, Clone, Debug)]
62 pub struct MPlaceTy<'tcx, Tag=()> {
63 mplace: MemPlace<Tag>,
64 pub layout: TyLayout<'tcx>,
67 impl<'tcx, Tag> ::std::ops::Deref for MPlaceTy<'tcx, Tag> {
68 type Target = MemPlace<Tag>;
70 fn deref(&self) -> &MemPlace<Tag> {
75 impl<'tcx, Tag> From<MPlaceTy<'tcx, Tag>> for PlaceTy<'tcx, Tag> {
77 fn from(mplace: MPlaceTy<'tcx, Tag>) -> Self {
79 place: Place::Ptr(mplace.mplace),
87 pub fn with_default_tag<Tag>(self) -> MemPlace<Tag>
91 ptr: self.ptr.with_default_tag(),
93 meta: self.meta.map(Scalar::with_default_tag),
98 impl<Tag> MemPlace<Tag> {
100 pub fn erase_tag(self) -> MemPlace
103 ptr: self.ptr.erase_tag(),
105 meta: self.meta.map(Scalar::erase_tag),
110 pub fn with_tag(self, new_tag: Tag) -> Self
113 ptr: self.ptr.with_tag(new_tag),
120 pub fn from_scalar_ptr(ptr: Scalar<Tag>, align: Align) -> Self {
128 /// Produces a Place that will error if attempted to be read from or written to
130 pub fn null(cx: &impl HasDataLayout) -> Self {
131 Self::from_scalar_ptr(Scalar::ptr_null(cx), Align::from_bytes(1).unwrap())
135 pub fn from_ptr(ptr: Pointer<Tag>, align: Align) -> Self {
136 Self::from_scalar_ptr(ptr.into(), align)
140 pub fn to_scalar_ptr_align(self) -> (Scalar<Tag>, Align) {
141 assert!(self.meta.is_none());
142 (self.ptr, self.align)
145 /// metact the ptr part of the mplace
147 pub fn to_ptr(self) -> EvalResult<'tcx, Pointer<Tag>> {
148 // At this point, we forget about the alignment information --
149 // the place has been turned into a reference, and no matter where it came from,
150 // it now must be aligned.
151 self.to_scalar_ptr_align().0.to_ptr()
154 /// Turn a mplace into a (thin or fat) pointer, as a reference, pointing to the same space.
155 /// This is the inverse of `ref_to_mplace`.
157 pub fn to_ref(self) -> Immediate<Tag> {
159 None => Immediate::Scalar(self.ptr.into()),
160 Some(meta) => Immediate::ScalarPair(self.ptr.into(), meta.into()),
167 meta: Option<Scalar<Tag>>,
168 cx: &impl HasDataLayout,
169 ) -> EvalResult<'tcx, Self> {
171 ptr: self.ptr.ptr_offset(offset, cx)?,
172 align: self.align.restrict_for_offset(offset),
178 impl<'tcx, Tag> MPlaceTy<'tcx, Tag> {
179 /// Produces a MemPlace that works for ZST but nothing else
181 pub fn dangling(layout: TyLayout<'tcx>, cx: &impl HasDataLayout) -> Self {
183 mplace: MemPlace::from_scalar_ptr(
184 Scalar::from_uint(layout.align.abi.bytes(), cx.pointer_size()),
192 pub fn with_tag(self, new_tag: Tag) -> Self
195 mplace: self.mplace.with_tag(new_tag),
204 meta: Option<Scalar<Tag>>,
205 layout: TyLayout<'tcx>,
206 cx: &impl HasDataLayout,
207 ) -> EvalResult<'tcx, Self> {
209 mplace: self.mplace.offset(offset, meta, cx)?,
215 fn from_aligned_ptr(ptr: Pointer<Tag>, layout: TyLayout<'tcx>) -> Self {
216 MPlaceTy { mplace: MemPlace::from_ptr(ptr, layout.align.abi), layout }
220 pub(super) fn len(self, cx: &impl HasDataLayout) -> EvalResult<'tcx, u64> {
221 if self.layout.is_unsized() {
222 // We need to consult `meta` metadata
223 match self.layout.ty.sty {
224 ty::Slice(..) | ty::Str =>
225 return self.mplace.meta.unwrap().to_usize(cx),
226 _ => bug!("len not supported on unsized type {:?}", self.layout.ty),
229 // Go through the layout. There are lots of types that support a length,
231 match self.layout.fields {
232 layout::FieldPlacement::Array { count, .. } => Ok(count),
233 _ => bug!("len not supported on sized type {:?}", self.layout.ty),
239 pub(super) fn vtable(self) -> EvalResult<'tcx, Pointer<Tag>> {
240 match self.layout.ty.sty {
241 ty::Dynamic(..) => self.mplace.meta.unwrap().to_ptr(),
242 _ => bug!("vtable not supported on type {:?}", self.layout.ty),
247 impl<'tcx, Tag: ::std::fmt::Debug> OpTy<'tcx, Tag> {
249 pub fn try_as_mplace(self) -> Result<MPlaceTy<'tcx, Tag>, Immediate<Tag>> {
251 Operand::Indirect(mplace) => Ok(MPlaceTy { mplace, layout: self.layout }),
252 Operand::Immediate(imm) => Err(imm),
257 pub fn to_mem_place(self) -> MPlaceTy<'tcx, Tag> {
258 self.try_as_mplace().unwrap()
262 impl<'tcx, Tag: ::std::fmt::Debug> Place<Tag> {
263 /// Produces a Place that will error if attempted to be read from or written to
265 pub fn null(cx: &impl HasDataLayout) -> Self {
266 Place::Ptr(MemPlace::null(cx))
270 pub fn from_scalar_ptr(ptr: Scalar<Tag>, align: Align) -> Self {
271 Place::Ptr(MemPlace::from_scalar_ptr(ptr, align))
275 pub fn from_ptr(ptr: Pointer<Tag>, align: Align) -> Self {
276 Place::Ptr(MemPlace::from_ptr(ptr, align))
280 pub fn to_mem_place(self) -> MemPlace<Tag> {
282 Place::Ptr(mplace) => mplace,
283 _ => bug!("to_mem_place: expected Place::Ptr, got {:?}", self),
289 pub fn to_scalar_ptr_align(self) -> (Scalar<Tag>, Align) {
290 self.to_mem_place().to_scalar_ptr_align()
294 pub fn to_ptr(self) -> EvalResult<'tcx, Pointer<Tag>> {
295 self.to_mem_place().to_ptr()
299 impl<'tcx, Tag: ::std::fmt::Debug> PlaceTy<'tcx, Tag> {
301 pub fn to_mem_place(self) -> MPlaceTy<'tcx, Tag> {
302 MPlaceTy { mplace: self.place.to_mem_place(), layout: self.layout }
306 // separating the pointer tag for `impl Trait`, see https://github.com/rust-lang/rust/issues/54385
307 impl<'a, 'mir, 'tcx, Tag, M> EvalContext<'a, 'mir, 'tcx, M>
309 // FIXME: Working around https://github.com/rust-lang/rust/issues/54385
310 Tag: ::std::fmt::Debug+Default+Copy+Eq+Hash+'static,
311 M: Machine<'a, 'mir, 'tcx, PointerTag=Tag>,
312 // FIXME: Working around https://github.com/rust-lang/rust/issues/24159
313 M::MemoryMap: AllocMap<AllocId, (MemoryKind<M::MemoryKinds>, Allocation<Tag, M::AllocExtra>)>,
314 M::AllocExtra: AllocationExtra<Tag, M::MemoryExtra>,
316 /// Take a value, which represents a (thin or fat) reference, and make it a place.
317 /// Alignment is just based on the type. This is the inverse of `MemPlace::to_ref()`.
318 /// This does NOT call the "deref" machine hook, so it does NOT count as a
319 /// deref as far as Stacked Borrows is concerned. Use `deref_operand` for that!
320 pub fn ref_to_mplace(
322 val: ImmTy<'tcx, M::PointerTag>,
323 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
324 let pointee_type = val.layout.ty.builtin_deref(true).unwrap().ty;
325 let layout = self.layout_of(pointee_type)?;
327 let mplace = MemPlace {
328 ptr: val.to_scalar_ptr()?,
329 align: layout.align.abi,
330 meta: val.to_meta()?,
332 Ok(MPlaceTy { mplace, layout })
335 // Take an operand, representing a pointer, and dereference it to a place -- that
336 // will always be a MemPlace. Lives in `place.rs` because it creates a place.
337 // This calls the "deref" machine hook, and counts as a deref as far as
338 // Stacked Borrows is concerned.
339 pub fn deref_operand(
341 src: OpTy<'tcx, M::PointerTag>,
342 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
343 let val = self.read_immediate(src)?;
344 trace!("deref to {} on {:?}", val.layout.ty, *val);
345 let mut place = self.ref_to_mplace(val)?;
346 // Pointer tag tracking might want to adjust the tag.
347 let mutbl = match val.layout.ty.sty {
348 // `builtin_deref` considers boxes immutable, that's useless for our purposes
349 ty::Ref(_, _, mutbl) => Some(mutbl),
350 ty::Adt(def, _) if def.is_box() => Some(hir::MutMutable),
351 ty::RawPtr(_) => None,
352 _ => bug!("Unexpected pointer type {}", val.layout.ty.sty),
354 place.mplace.ptr = M::tag_dereference(self, place, mutbl)?;
358 /// Offset a pointer to project to a field. Unlike place_field, this is always
359 /// possible without allocating, so it can take &self. Also return the field's layout.
360 /// This supports both struct and array fields.
364 base: MPlaceTy<'tcx, M::PointerTag>,
366 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
367 // Not using the layout method because we want to compute on u64
368 let offset = match base.layout.fields {
369 layout::FieldPlacement::Arbitrary { ref offsets, .. } =>
370 offsets[usize::try_from(field).unwrap()],
371 layout::FieldPlacement::Array { stride, .. } => {
372 let len = base.len(self)?;
373 assert!(field < len, "Tried to access element {} of array/slice with length {}",
377 layout::FieldPlacement::Union(count) => {
378 assert!(field < count as u64,
379 "Tried to access field {} of union with {} fields", field, count);
380 // Offset is always 0
384 // the only way conversion can fail if is this is an array (otherwise we already panicked
385 // above). In that case, all fields are equal.
386 let field_layout = base.layout.field(self, usize::try_from(field).unwrap_or(0))?;
388 // Offset may need adjustment for unsized fields
389 let (meta, offset) = if field_layout.is_unsized() {
390 // re-use parent metadata to determine dynamic field layout
391 let align = match self.size_and_align_of(base.meta, field_layout)? {
392 Some((_, align)) => align,
393 None if offset == Size::ZERO =>
394 // An extern type at offset 0, we fall back to its static alignment.
395 // FIXME: Once we have made decisions for how to handle size and alignment
396 // of `extern type`, this should be adapted. It is just a temporary hack
397 // to get some code to work that probably ought to work.
398 field_layout.align.abi,
400 bug!("Cannot compute offset for extern type field at non-0 offset"),
402 (base.meta, offset.align_to(align))
404 // base.meta could be present; we might be accessing a sized field of an unsized
409 // We do not look at `base.layout.align` nor `field_layout.align`, unlike
410 // codegen -- mostly to see if we can get away with that
411 base.offset(offset, meta, field_layout, self)
414 // Iterates over all fields of an array. Much more efficient than doing the
415 // same by repeatedly calling `mplace_array`.
416 pub fn mplace_array_fields(
418 base: MPlaceTy<'tcx, Tag>,
420 EvalResult<'tcx, impl Iterator<Item=EvalResult<'tcx, MPlaceTy<'tcx, Tag>>> + 'a>
422 let len = base.len(self)?; // also asserts that we have a type where this makes sense
423 let stride = match base.layout.fields {
424 layout::FieldPlacement::Array { stride, .. } => stride,
425 _ => bug!("mplace_array_fields: expected an array layout"),
427 let layout = base.layout.field(self, 0)?;
428 let dl = &self.tcx.data_layout;
429 Ok((0..len).map(move |i| base.offset(i * stride, None, layout, dl)))
432 pub fn mplace_subslice(
434 base: MPlaceTy<'tcx, M::PointerTag>,
437 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
438 let len = base.len(self)?; // also asserts that we have a type where this makes sense
439 assert!(from <= len - to);
441 // Not using layout method because that works with usize, and does not work with slices
442 // (that have count 0 in their layout).
443 let from_offset = match base.layout.fields {
444 layout::FieldPlacement::Array { stride, .. } =>
446 _ => bug!("Unexpected layout of index access: {:#?}", base.layout),
449 // Compute meta and new layout
450 let inner_len = len - to - from;
451 let (meta, ty) = match base.layout.ty.sty {
452 // It is not nice to match on the type, but that seems to be the only way to
454 ty::Array(inner, _) =>
455 (None, self.tcx.mk_array(inner, inner_len)),
457 let len = Scalar::from_uint(inner_len, self.pointer_size());
458 (Some(len), base.layout.ty)
461 bug!("cannot subslice non-array type: `{:?}`", base.layout.ty),
463 let layout = self.layout_of(ty)?;
464 base.offset(from_offset, meta, layout, self)
467 pub fn mplace_downcast(
469 base: MPlaceTy<'tcx, M::PointerTag>,
471 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
472 // Downcasts only change the layout
473 assert!(base.meta.is_none());
474 Ok(MPlaceTy { layout: base.layout.for_variant(self, variant), ..base })
477 /// Project into an mplace
478 pub fn mplace_projection(
480 base: MPlaceTy<'tcx, M::PointerTag>,
481 proj_elem: &mir::PlaceElem<'tcx>,
482 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
483 use rustc::mir::ProjectionElem::*;
484 Ok(match *proj_elem {
485 Field(field, _) => self.mplace_field(base, field.index() as u64)?,
486 Downcast(_, variant) => self.mplace_downcast(base, variant)?,
487 Deref => self.deref_operand(base.into())?,
490 let n = *self.frame().locals[local].access()?;
491 let n_layout = self.layout_of(self.tcx.types.usize)?;
492 let n = self.read_scalar(OpTy { op: n, layout: n_layout })?;
493 let n = n.to_bits(self.tcx.data_layout.pointer_size)?;
494 self.mplace_field(base, u64::try_from(n).unwrap())?
502 let n = base.len(self)?;
503 assert!(n >= min_length as u64);
505 let index = if from_end {
506 n - u64::from(offset)
511 self.mplace_field(base, index)?
514 Subslice { from, to } =>
515 self.mplace_subslice(base, u64::from(from), u64::from(to))?,
519 /// Gets the place of a field inside the place, and also the field's type.
520 /// Just a convenience function, but used quite a bit.
521 /// This is the only projection that might have a side-effect: We cannot project
522 /// into the field of a local `ScalarPair`, we have to first allocate it.
525 base: PlaceTy<'tcx, M::PointerTag>,
527 ) -> EvalResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
528 // FIXME: We could try to be smarter and avoid allocation for fields that span the
530 let mplace = self.force_allocation(base)?;
531 Ok(self.mplace_field(mplace, field)?.into())
534 pub fn place_downcast(
536 base: PlaceTy<'tcx, M::PointerTag>,
538 ) -> EvalResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
539 // Downcast just changes the layout
540 Ok(match base.place {
541 Place::Ptr(mplace) =>
542 self.mplace_downcast(MPlaceTy { mplace, layout: base.layout }, variant)?.into(),
543 Place::Local { .. } => {
544 let layout = base.layout.for_variant(self, variant);
545 PlaceTy { layout, ..base }
550 /// Projects into a place.
551 pub fn place_projection(
553 base: PlaceTy<'tcx, M::PointerTag>,
554 proj_elem: &mir::ProjectionElem<'tcx, mir::Local, Ty<'tcx>>,
555 ) -> EvalResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
556 use rustc::mir::ProjectionElem::*;
557 Ok(match *proj_elem {
558 Field(field, _) => self.place_field(base, field.index() as u64)?,
559 Downcast(_, variant) => self.place_downcast(base, variant)?,
560 Deref => self.deref_operand(self.place_to_op(base)?)?.into(),
561 // For the other variants, we have to force an allocation.
562 // This matches `operand_projection`.
563 Subslice { .. } | ConstantIndex { .. } | Index(_) => {
564 let mplace = self.force_allocation(base)?;
565 self.mplace_projection(mplace, proj_elem)?.into()
570 /// Evaluate statics and promoteds to an `MPlace`. Used to share some code between
571 /// `eval_place` and `eval_place_to_op`.
572 pub(super) fn eval_place_to_mplace(
574 mir_place: &mir::Place<'tcx>
575 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
576 use rustc::mir::Place::*;
577 Ok(match *mir_place {
578 Promoted(ref promoted) => {
579 let instance = self.frame().instance;
580 self.const_eval_raw(GlobalId {
582 promoted: Some(promoted.0),
586 Static(ref static_) => {
587 assert!(!static_.ty.needs_subst());
588 let layout = self.layout_of(static_.ty)?;
589 let instance = ty::Instance::mono(*self.tcx, static_.def_id);
594 // Just create a lazy reference, so we can support recursive statics.
595 // tcx takes are of assigning every static one and only one unique AllocId.
596 // When the data here is ever actually used, memory will notice,
597 // and it knows how to deal with alloc_id that are present in the
598 // global table but not in its local memory: It calls back into tcx through
599 // a query, triggering the CTFE machinery to actually turn this lazy reference
600 // into a bunch of bytes. IOW, statics are evaluated with CTFE even when
601 // this EvalContext uses another Machine (e.g., in miri). This is what we
602 // want! This way, computing statics works concistently between codegen
603 // and miri: They use the same query to eventually obtain a `ty::Const`
604 // and use that for further computation.
605 let alloc = self.tcx.alloc_map.lock().intern_static(cid.instance.def_id());
606 MPlaceTy::from_aligned_ptr(Pointer::from(alloc).with_default_tag(), layout)
609 _ => bug!("eval_place_to_mplace called on {:?}", mir_place),
613 /// Computes a place. You should only use this if you intend to write into this
614 /// place; for reading, a more efficient alternative is `eval_place_for_read`.
617 mir_place: &mir::Place<'tcx>
618 ) -> EvalResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
619 use rustc::mir::Place::*;
620 let place = match *mir_place {
621 Local(mir::RETURN_PLACE) => match self.frame().return_place {
622 Some(return_place) =>
623 // We use our layout to verify our assumption; caller will validate
624 // their layout on return.
626 place: *return_place,
627 layout: self.layout_of(self.monomorphize(self.frame().mir.return_ty())?)?,
629 None => return err!(InvalidNullPointerUsage),
631 Local(local) => PlaceTy {
632 place: Place::Local {
633 frame: self.cur_frame(),
636 layout: self.layout_of_local(self.frame(), local, None)?,
639 Projection(ref proj) => {
640 let place = self.eval_place(&proj.base)?;
641 self.place_projection(place, &proj.elem)?
644 _ => self.eval_place_to_mplace(mir_place)?.into(),
647 self.dump_place(place.place);
651 /// Write a scalar to a place
654 val: impl Into<ScalarMaybeUndef<M::PointerTag>>,
655 dest: PlaceTy<'tcx, M::PointerTag>,
656 ) -> EvalResult<'tcx> {
657 self.write_immediate(Immediate::Scalar(val.into()), dest)
660 /// Write an immediate to a place
662 pub fn write_immediate(
664 src: Immediate<M::PointerTag>,
665 dest: PlaceTy<'tcx, M::PointerTag>,
666 ) -> EvalResult<'tcx> {
667 self.write_immediate_no_validate(src, dest)?;
669 if M::enforce_validity(self) {
670 // Data got changed, better make sure it matches the type!
671 self.validate_operand(self.place_to_op(dest)?, vec![], None, /*const_mode*/false)?;
677 /// Write an immediate to a place.
678 /// If you use this you are responsible for validating that things got copied at the
680 fn write_immediate_no_validate(
682 src: Immediate<M::PointerTag>,
683 dest: PlaceTy<'tcx, M::PointerTag>,
684 ) -> EvalResult<'tcx> {
685 if cfg!(debug_assertions) {
686 // This is a very common path, avoid some checks in release mode
687 assert!(!dest.layout.is_unsized(), "Cannot write unsized data");
689 Immediate::Scalar(ScalarMaybeUndef::Scalar(Scalar::Ptr(_))) =>
690 assert_eq!(self.pointer_size(), dest.layout.size,
691 "Size mismatch when writing pointer"),
692 Immediate::Scalar(ScalarMaybeUndef::Scalar(Scalar::Bits { size, .. })) =>
693 assert_eq!(Size::from_bytes(size.into()), dest.layout.size,
694 "Size mismatch when writing bits"),
695 Immediate::Scalar(ScalarMaybeUndef::Undef) => {}, // undef can have any size
696 Immediate::ScalarPair(_, _) => {
697 // FIXME: Can we check anything here?
701 trace!("write_immediate: {:?} <- {:?}: {}", *dest, src, dest.layout.ty);
703 // See if we can avoid an allocation. This is the counterpart to `try_read_immediate`,
704 // but not factored as a separate function.
705 let mplace = match dest.place {
706 Place::Local { frame, local } => {
707 match *self.stack[frame].locals[local].access_mut()? {
708 Operand::Immediate(ref mut dest_val) => {
709 // Yay, we can just change the local directly.
713 Operand::Indirect(mplace) => mplace, // already in memory
716 Place::Ptr(mplace) => mplace, // already in memory
718 let dest = MPlaceTy { mplace, layout: dest.layout };
720 // This is already in memory, write there.
721 self.write_immediate_to_mplace_no_validate(src, dest)
724 /// Write an immediate to memory.
725 /// If you use this you are responsible for validating that things git copied at the
727 fn write_immediate_to_mplace_no_validate(
729 value: Immediate<M::PointerTag>,
730 dest: MPlaceTy<'tcx, M::PointerTag>,
731 ) -> EvalResult<'tcx> {
732 let (ptr, ptr_align) = dest.to_scalar_ptr_align();
733 // Note that it is really important that the type here is the right one, and matches the
734 // type things are read at. In case `src_val` is a `ScalarPair`, we don't do any magic here
735 // to handle padding properly, which is only correct if we never look at this data with the
738 // Nothing to do for ZSTs, other than checking alignment
739 if dest.layout.is_zst() {
740 return self.memory.check_align(ptr, ptr_align);
743 // check for integer pointers before alignment to report better errors
744 let ptr = ptr.to_ptr()?;
745 self.memory.check_align(ptr.into(), ptr_align)?;
746 let tcx = &*self.tcx;
747 // FIXME: We should check that there are dest.layout.size many bytes available in
748 // memory. The code below is not sufficient, with enough padding it might not
749 // cover all the bytes!
751 Immediate::Scalar(scalar) => {
752 match dest.layout.abi {
753 layout::Abi::Scalar(_) => {}, // fine
754 _ => bug!("write_immediate_to_mplace: invalid Scalar layout: {:#?}",
757 self.memory.get_mut(ptr.alloc_id)?.write_scalar(
758 tcx, ptr, scalar, dest.layout.size
761 Immediate::ScalarPair(a_val, b_val) => {
762 let (a, b) = match dest.layout.abi {
763 layout::Abi::ScalarPair(ref a, ref b) => (&a.value, &b.value),
764 _ => bug!("write_immediate_to_mplace: invalid ScalarPair layout: {:#?}",
767 let (a_size, b_size) = (a.size(self), b.size(self));
768 let b_offset = a_size.align_to(b.align(self).abi);
769 let b_align = ptr_align.restrict_for_offset(b_offset);
770 let b_ptr = ptr.offset(b_offset, self)?;
772 self.memory.check_align(b_ptr.into(), b_align)?;
774 // It is tempting to verify `b_offset` against `layout.fields.offset(1)`,
775 // but that does not work: We could be a newtype around a pair, then the
776 // fields do not match the `ScalarPair` components.
779 .get_mut(ptr.alloc_id)?
780 .write_scalar(tcx, ptr, a_val, a_size)?;
782 .get_mut(b_ptr.alloc_id)?
783 .write_scalar(tcx, b_ptr, b_val, b_size)
788 /// Copies the data from an operand to a place. This does not support transmuting!
789 /// Use `copy_op_transmute` if the layouts could disagree.
793 src: OpTy<'tcx, M::PointerTag>,
794 dest: PlaceTy<'tcx, M::PointerTag>,
795 ) -> EvalResult<'tcx> {
796 self.copy_op_no_validate(src, dest)?;
798 if M::enforce_validity(self) {
799 // Data got changed, better make sure it matches the type!
800 self.validate_operand(self.place_to_op(dest)?, vec![], None, /*const_mode*/false)?;
806 /// Copies the data from an operand to a place. This does not support transmuting!
807 /// Use `copy_op_transmute` if the layouts could disagree.
808 /// Also, if you use this you are responsible for validating that things git copied at the
810 fn copy_op_no_validate(
812 src: OpTy<'tcx, M::PointerTag>,
813 dest: PlaceTy<'tcx, M::PointerTag>,
814 ) -> EvalResult<'tcx> {
815 debug_assert!(!src.layout.is_unsized() && !dest.layout.is_unsized(),
816 "Cannot copy unsized data");
817 // We do NOT compare the types for equality, because well-typed code can
818 // actually "transmute" `&mut T` to `&T` in an assignment without a cast.
819 assert!(src.layout.details == dest.layout.details,
820 "Layout mismatch when copying!\nsrc: {:#?}\ndest: {:#?}", src, dest);
822 // Let us see if the layout is simple so we take a shortcut, avoid force_allocation.
823 let src = match self.try_read_immediate(src)? {
825 // Yay, we got a value that we can write directly.
826 // FIXME: Add a check to make sure that if `src` is indirect,
827 // it does not overlap with `dest`.
828 return self.write_immediate_no_validate(src_val, dest);
830 Err(mplace) => mplace,
832 // Slow path, this does not fit into an immediate. Just memcpy.
833 trace!("copy_op: {:?} <- {:?}: {}", *dest, src, dest.layout.ty);
835 let dest = self.force_allocation(dest)?;
836 let (src_ptr, src_align) = src.to_scalar_ptr_align();
837 let (dest_ptr, dest_align) = dest.to_scalar_ptr_align();
840 dest_ptr, dest_align,
842 /*nonoverlapping*/ true,
848 /// Copies the data from an operand to a place. The layouts may disagree, but they must
849 /// have the same size.
850 pub fn copy_op_transmute(
852 src: OpTy<'tcx, M::PointerTag>,
853 dest: PlaceTy<'tcx, M::PointerTag>,
854 ) -> EvalResult<'tcx> {
855 if src.layout.details == dest.layout.details {
856 // Fast path: Just use normal `copy_op`
857 return self.copy_op(src, dest);
859 // We still require the sizes to match
860 debug_assert!(!src.layout.is_unsized() && !dest.layout.is_unsized(),
861 "Cannot copy unsized data");
862 assert!(src.layout.size == dest.layout.size,
863 "Size mismatch when transmuting!\nsrc: {:#?}\ndest: {:#?}", src, dest);
865 // The hard case is `ScalarPair`. `src` is already read from memory in this case,
866 // using `src.layout` to figure out which bytes to use for the 1st and 2nd field.
867 // We have to write them to `dest` at the offsets they were *read at*, which is
868 // not necessarily the same as the offsets in `dest.layout`!
869 // Hence we do the copy with the source layout on both sides. We also make sure to write
870 // into memory, because if `dest` is a local we would not even have a way to write
871 // at the `src` offsets; the fact that we came from a different layout would
873 let dest = self.force_allocation(dest)?;
874 self.copy_op_no_validate(
876 PlaceTy::from(MPlaceTy { mplace: *dest, layout: src.layout }),
879 if M::enforce_validity(self) {
880 // Data got changed, better make sure it matches the type!
881 self.validate_operand(dest.into(), vec![], None, /*const_mode*/false)?;
887 /// Ensures that a place is in memory, and returns where it is.
888 /// If the place currently refers to a local that doesn't yet have a matching allocation,
889 /// create such an allocation.
890 /// This is essentially `force_to_memplace`.
891 pub fn force_allocation(
893 place: PlaceTy<'tcx, M::PointerTag>,
894 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
895 let mplace = match place.place {
896 Place::Local { frame, local } => {
897 match *self.stack[frame].locals[local].access()? {
898 Operand::Indirect(mplace) => mplace,
899 Operand::Immediate(value) => {
900 // We need to make an allocation.
901 // FIXME: Consider not doing anything for a ZST, and just returning
902 // a fake pointer? Are we even called for ZST?
904 // We need the layout of the local. We can NOT use the layout we got,
905 // that might e.g., be an inner field of a struct with `Scalar` layout,
906 // that has different alignment than the outer field.
907 let local_layout = self.layout_of_local(&self.stack[frame], local, None)?;
908 let ptr = self.allocate(local_layout, MemoryKind::Stack);
909 // We don't have to validate as we can assume the local
910 // was already valid for its type.
911 self.write_immediate_to_mplace_no_validate(value, ptr)?;
912 let mplace = ptr.mplace;
914 *self.stack[frame].locals[local].access_mut()? =
915 Operand::Indirect(mplace);
920 Place::Ptr(mplace) => mplace
922 // Return with the original layout, so that the caller can go on
923 Ok(MPlaceTy { mplace, layout: place.layout })
928 layout: TyLayout<'tcx>,
929 kind: MemoryKind<M::MemoryKinds>,
930 ) -> MPlaceTy<'tcx, M::PointerTag> {
931 if layout.is_unsized() {
932 assert!(self.tcx.features().unsized_locals, "cannot alloc memory for unsized type");
933 // FIXME: What should we do here? We should definitely also tag!
934 MPlaceTy::dangling(layout, self)
936 let ptr = self.memory.allocate(layout.size, layout.align.abi, kind);
937 let ptr = M::tag_new_allocation(self, ptr, kind);
938 MPlaceTy::from_aligned_ptr(ptr, layout)
942 pub fn write_discriminant_index(
944 variant_index: VariantIdx,
945 dest: PlaceTy<'tcx, M::PointerTag>,
946 ) -> EvalResult<'tcx> {
947 match dest.layout.variants {
948 layout::Variants::Single { index } => {
949 assert_eq!(index, variant_index);
951 layout::Variants::Tagged { ref tag, .. } => {
952 let adt_def = dest.layout.ty.ty_adt_def().unwrap();
953 assert!(variant_index.as_usize() < adt_def.variants.len());
954 let discr_val = adt_def
955 .discriminant_for_variant(*self.tcx, variant_index)
958 // raw discriminants for enums are isize or bigger during
959 // their computation, but the in-memory tag is the smallest possible
961 let size = tag.value.size(self);
962 let shift = 128 - size.bits();
963 let discr_val = (discr_val << shift) >> shift;
965 let discr_dest = self.place_field(dest, 0)?;
966 self.write_scalar(Scalar::from_uint(discr_val, size), discr_dest)?;
968 layout::Variants::NicheFilling {
975 variant_index.as_usize() < dest.layout.ty.ty_adt_def().unwrap().variants.len(),
977 if variant_index != dataful_variant {
979 self.place_field(dest, 0)?;
980 let niche_value = variant_index.as_u32() - niche_variants.start().as_u32();
981 let niche_value = (niche_value as u128)
982 .wrapping_add(niche_start);
984 Scalar::from_uint(niche_value, niche_dest.layout.size),
994 /// Every place can be read from, so we can turm them into an operand
998 place: PlaceTy<'tcx, M::PointerTag>
999 ) -> EvalResult<'tcx, OpTy<'tcx, M::PointerTag>> {
1000 let op = match place.place {
1001 Place::Ptr(mplace) => {
1002 Operand::Indirect(mplace)
1004 Place::Local { frame, local } =>
1005 *self.stack[frame].locals[local].access()?
1007 Ok(OpTy { op, layout: place.layout })
1010 pub fn raw_const_to_mplace(
1012 raw: RawConst<'tcx>,
1013 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
1014 // This must be an allocation in `tcx`
1015 assert!(self.tcx.alloc_map.lock().get(raw.alloc_id).is_some());
1016 let layout = self.layout_of(raw.ty)?;
1017 Ok(MPlaceTy::from_aligned_ptr(
1018 Pointer::new(raw.alloc_id, Size::ZERO).with_default_tag(),
1023 /// Turn a place with a `dyn Trait` type into a place with the actual dynamic type.
1024 /// Also return some more information so drop doesn't have to run the same code twice.
1025 pub(super) fn unpack_dyn_trait(&self, mplace: MPlaceTy<'tcx, M::PointerTag>)
1026 -> EvalResult<'tcx, (ty::Instance<'tcx>, MPlaceTy<'tcx, M::PointerTag>)> {
1027 let vtable = mplace.vtable()?; // also sanity checks the type
1028 let (instance, ty) = self.read_drop_type_from_vtable(vtable)?;
1029 let layout = self.layout_of(ty)?;
1031 // More sanity checks
1032 if cfg!(debug_assertions) {
1033 let (size, align) = self.read_size_and_align_from_vtable(vtable)?;
1034 assert_eq!(size, layout.size);
1035 // only ABI alignment is preserved
1036 assert_eq!(align, layout.align.abi);
1039 let mplace = MPlaceTy {
1040 mplace: MemPlace { meta: None, ..*mplace },
1043 Ok((instance, mplace))