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 either::{Either, Left, Right};
7 use rustc_ast::Mutability;
10 use rustc_middle::ty::layout::{LayoutOf, PrimitiveExt, TyAndLayout};
11 use rustc_target::abi::{self, Abi, Align, HasDataLayout, Size, TagEncoding, VariantIdx};
14 alloc_range, mir_assign_valid_types, AllocId, AllocRef, AllocRefMut, CheckInAllocMsg,
15 ConstAlloc, ImmTy, Immediate, InterpCx, InterpResult, Machine, MemoryKind, OpTy, Operand,
16 Pointer, Provenance, Scalar,
19 #[derive(Copy, Clone, Hash, PartialEq, Eq, Debug)]
20 /// Information required for the sound usage of a `MemPlace`.
21 pub enum MemPlaceMeta<Prov: Provenance = AllocId> {
22 /// The unsized payload (e.g. length for slices or vtable pointer for trait objects).
24 /// `Sized` types or unsized `extern type`
28 impl<Prov: Provenance> MemPlaceMeta<Prov> {
29 pub fn unwrap_meta(self) -> Scalar<Prov> {
33 bug!("expected wide pointer extra data (e.g. slice length or trait object vtable)")
38 pub fn has_meta(self) -> bool {
40 Self::Meta(_) => true,
46 #[derive(Copy, Clone, Hash, PartialEq, Eq, Debug)]
47 pub struct MemPlace<Prov: Provenance = AllocId> {
48 /// The pointer can be a pure integer, with the `None` provenance.
49 pub ptr: Pointer<Option<Prov>>,
50 /// Metadata for unsized places. Interpretation is up to the type.
51 /// Must not be present for sized types, but can be missing for unsized types
52 /// (e.g., `extern type`).
53 pub meta: MemPlaceMeta<Prov>,
56 /// A MemPlace with its layout. Constructing it is only possible in this module.
57 #[derive(Copy, Clone, Hash, Eq, PartialEq, Debug)]
58 pub struct MPlaceTy<'tcx, Prov: Provenance = AllocId> {
59 mplace: MemPlace<Prov>,
60 pub layout: TyAndLayout<'tcx>,
61 /// rustc does not have a proper way to represent the type of a field of a `repr(packed)` struct:
62 /// it needs to have a different alignment than the field type would usually have.
63 /// So we represent this here with a separate field that "overwrites" `layout.align`.
64 /// This means `layout.align` should never be used for a `MPlaceTy`!
68 #[derive(Copy, Clone, Debug)]
69 pub enum Place<Prov: Provenance = AllocId> {
70 /// A place referring to a value allocated in the `Memory` system.
73 /// To support alloc-free locals, we are able to write directly to a local.
74 /// (Without that optimization, we'd just always be a `MemPlace`.)
75 Local { frame: usize, local: mir::Local },
78 #[derive(Clone, Debug)]
79 pub struct PlaceTy<'tcx, Prov: Provenance = AllocId> {
80 place: Place<Prov>, // Keep this private; it helps enforce invariants.
81 pub layout: TyAndLayout<'tcx>,
82 /// rustc does not have a proper way to represent the type of a field of a `repr(packed)` struct:
83 /// it needs to have a different alignment than the field type would usually have.
84 /// So we represent this here with a separate field that "overwrites" `layout.align`.
85 /// This means `layout.align` should never be used for a `PlaceTy`!
89 impl<'tcx, Prov: Provenance> std::ops::Deref for PlaceTy<'tcx, Prov> {
90 type Target = Place<Prov>;
92 fn deref(&self) -> &Place<Prov> {
97 impl<'tcx, Prov: Provenance> std::ops::Deref for MPlaceTy<'tcx, Prov> {
98 type Target = MemPlace<Prov>;
100 fn deref(&self) -> &MemPlace<Prov> {
105 impl<'tcx, Prov: Provenance> From<MPlaceTy<'tcx, Prov>> for PlaceTy<'tcx, Prov> {
107 fn from(mplace: MPlaceTy<'tcx, Prov>) -> Self {
108 PlaceTy { place: Place::Ptr(*mplace), layout: mplace.layout, align: mplace.align }
112 impl<'tcx, Prov: Provenance> From<&'_ MPlaceTy<'tcx, Prov>> for PlaceTy<'tcx, Prov> {
114 fn from(mplace: &MPlaceTy<'tcx, Prov>) -> Self {
115 PlaceTy { place: Place::Ptr(**mplace), layout: mplace.layout, align: mplace.align }
119 impl<'tcx, Prov: Provenance> From<&'_ mut MPlaceTy<'tcx, Prov>> for PlaceTy<'tcx, Prov> {
121 fn from(mplace: &mut MPlaceTy<'tcx, Prov>) -> Self {
122 PlaceTy { place: Place::Ptr(**mplace), layout: mplace.layout, align: mplace.align }
126 impl<Prov: Provenance> MemPlace<Prov> {
128 pub fn from_ptr(ptr: Pointer<Option<Prov>>) -> Self {
129 MemPlace { ptr, meta: MemPlaceMeta::None }
132 /// Adjust the provenance of the main pointer (metadata is unaffected).
133 pub fn map_provenance(self, f: impl FnOnce(Option<Prov>) -> Option<Prov>) -> Self {
134 MemPlace { ptr: self.ptr.map_provenance(f), ..self }
137 /// Turn a mplace into a (thin or wide) pointer, as a reference, pointing to the same space.
138 /// This is the inverse of `ref_to_mplace`.
140 pub fn to_ref(self, cx: &impl HasDataLayout) -> Immediate<Prov> {
142 MemPlaceMeta::None => Immediate::from(Scalar::from_maybe_pointer(self.ptr, cx)),
143 MemPlaceMeta::Meta(meta) => {
144 Immediate::ScalarPair(Scalar::from_maybe_pointer(self.ptr, cx), meta)
150 pub fn offset_with_meta<'tcx>(
153 meta: MemPlaceMeta<Prov>,
154 cx: &impl HasDataLayout,
155 ) -> InterpResult<'tcx, Self> {
156 Ok(MemPlace { ptr: self.ptr.offset(offset, cx)?, meta })
160 impl<Prov: Provenance> Place<Prov> {
161 /// Asserts that this points to some local variable.
162 /// Returns the frame idx and the variable idx.
164 #[cfg_attr(debug_assertions, track_caller)] // only in debug builds due to perf (see #98980)
165 pub fn assert_local(&self) -> (usize, mir::Local) {
167 Place::Local { frame, local } => (*frame, *local),
168 _ => bug!("assert_local: expected Place::Local, got {:?}", self),
173 impl<'tcx, Prov: Provenance> MPlaceTy<'tcx, Prov> {
174 /// Produces a MemPlace that works for ZST but nothing else.
175 /// Conceptually this is a new allocation, but it doesn't actually create an allocation so you
176 /// don't need to worry about memory leaks.
178 pub fn fake_alloc_zst(layout: TyAndLayout<'tcx>) -> Self {
179 assert!(layout.is_zst());
180 let align = layout.align.abi;
181 let ptr = Pointer::from_addr(align.bytes()); // no provenance, absolute address
182 MPlaceTy { mplace: MemPlace { ptr, meta: MemPlaceMeta::None }, layout, align }
186 pub fn offset_with_meta(
189 meta: MemPlaceMeta<Prov>,
190 layout: TyAndLayout<'tcx>,
191 cx: &impl HasDataLayout,
192 ) -> InterpResult<'tcx, Self> {
194 mplace: self.mplace.offset_with_meta(offset, meta, cx)?,
195 align: self.align.restrict_for_offset(offset),
203 layout: TyAndLayout<'tcx>,
204 cx: &impl HasDataLayout,
205 ) -> InterpResult<'tcx, Self> {
206 assert!(layout.is_sized());
207 self.offset_with_meta(offset, MemPlaceMeta::None, layout, cx)
211 pub fn from_aligned_ptr(ptr: Pointer<Option<Prov>>, layout: TyAndLayout<'tcx>) -> Self {
212 MPlaceTy { mplace: MemPlace::from_ptr(ptr), layout, align: layout.align.abi }
216 pub fn from_aligned_ptr_with_meta(
217 ptr: Pointer<Option<Prov>>,
218 layout: TyAndLayout<'tcx>,
219 meta: MemPlaceMeta<Prov>,
221 let mut mplace = MemPlace::from_ptr(ptr);
224 MPlaceTy { mplace, layout, align: layout.align.abi }
228 pub(crate) fn len(&self, cx: &impl HasDataLayout) -> InterpResult<'tcx, u64> {
229 if self.layout.is_unsized() {
230 // We need to consult `meta` metadata
231 match self.layout.ty.kind() {
232 ty::Slice(..) | ty::Str => self.mplace.meta.unwrap_meta().to_machine_usize(cx),
233 _ => bug!("len not supported on unsized type {:?}", self.layout.ty),
236 // Go through the layout. There are lots of types that support a length,
237 // e.g., SIMD types. (But not all repr(simd) types even have FieldsShape::Array!)
238 match self.layout.fields {
239 abi::FieldsShape::Array { count, .. } => Ok(count),
240 _ => bug!("len not supported on sized type {:?}", self.layout.ty),
246 pub(super) fn vtable(&self) -> Scalar<Prov> {
247 match self.layout.ty.kind() {
248 ty::Dynamic(..) => self.mplace.meta.unwrap_meta(),
249 _ => bug!("vtable not supported on type {:?}", self.layout.ty),
254 // These are defined here because they produce a place.
255 impl<'tcx, Prov: Provenance> OpTy<'tcx, Prov> {
257 pub fn as_mplace_or_imm(&self) -> Either<MPlaceTy<'tcx, Prov>, ImmTy<'tcx, Prov>> {
259 Operand::Indirect(mplace) => {
260 Left(MPlaceTy { mplace, layout: self.layout, align: self.align.unwrap() })
262 Operand::Immediate(imm) => Right(ImmTy::from_immediate(imm, self.layout)),
267 #[cfg_attr(debug_assertions, track_caller)] // only in debug builds due to perf (see #98980)
268 pub fn assert_mem_place(&self) -> MPlaceTy<'tcx, Prov> {
269 self.as_mplace_or_imm().left().unwrap()
273 impl<'tcx, Prov: Provenance> PlaceTy<'tcx, Prov> {
274 /// A place is either an mplace or some local.
276 pub fn as_mplace_or_local(&self) -> Either<MPlaceTy<'tcx, Prov>, (usize, mir::Local)> {
278 Place::Ptr(mplace) => Left(MPlaceTy { mplace, layout: self.layout, align: self.align }),
279 Place::Local { frame, local } => Right((frame, local)),
284 #[cfg_attr(debug_assertions, track_caller)] // only in debug builds due to perf (see #98980)
285 pub fn assert_mem_place(&self) -> MPlaceTy<'tcx, Prov> {
286 self.as_mplace_or_local().left().unwrap()
290 // FIXME: Working around https://github.com/rust-lang/rust/issues/54385
291 impl<'mir, 'tcx: 'mir, Prov, M> InterpCx<'mir, 'tcx, M>
293 Prov: Provenance + 'static,
294 M: Machine<'mir, 'tcx, Provenance = Prov>,
296 pub fn increment_const_eval_counter(&mut self) {
297 self.const_eval_counter = self.const_eval_counter + 1;
298 if self.const_eval_counter == self.const_eval_limit {
299 let mut warn = self.tcx.sess.struct_warn(format!(
300 "Const eval counter limit ({}) has been crossed",
301 self.const_eval_limit
307 /// Take a value, which represents a (thin or wide) reference, and make it a place.
308 /// Alignment is just based on the type. This is the inverse of `MemPlace::to_ref()`.
310 /// Only call this if you are sure the place is "valid" (aligned and inbounds), or do not
311 /// want to ever use the place for memory access!
312 /// Generally prefer `deref_operand`.
313 pub fn ref_to_mplace(
315 val: &ImmTy<'tcx, M::Provenance>,
316 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
318 val.layout.ty.builtin_deref(true).expect("`ref_to_mplace` called on non-ptr type").ty;
319 let layout = self.layout_of(pointee_type)?;
320 let (ptr, meta) = match **val {
321 Immediate::Scalar(ptr) => (ptr, MemPlaceMeta::None),
322 Immediate::ScalarPair(ptr, meta) => (ptr, MemPlaceMeta::Meta(meta)),
323 Immediate::Uninit => throw_ub!(InvalidUninitBytes(None)),
326 let mplace = MemPlace { ptr: ptr.to_pointer(self)?, meta };
327 // When deref'ing a pointer, the *static* alignment given by the type is what matters.
328 let align = layout.align.abi;
329 Ok(MPlaceTy { mplace, layout, align })
332 /// Take an operand, representing a pointer, and dereference it to a place.
333 #[instrument(skip(self), level = "debug")]
334 pub fn deref_operand(
336 src: &OpTy<'tcx, M::Provenance>,
337 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
338 let val = self.read_immediate(src)?;
339 trace!("deref to {} on {:?}", val.layout.ty, *val);
341 if val.layout.ty.is_box() {
342 bug!("dereferencing {:?}", val.layout.ty);
345 let mplace = self.ref_to_mplace(&val)?;
346 self.check_mplace(mplace)?;
351 pub(super) fn get_place_alloc(
353 place: &MPlaceTy<'tcx, M::Provenance>,
354 ) -> InterpResult<'tcx, Option<AllocRef<'_, 'tcx, M::Provenance, M::AllocExtra>>> {
355 assert!(place.layout.is_sized());
356 assert!(!place.meta.has_meta());
357 let size = place.layout.size;
358 self.get_ptr_alloc(place.ptr, size, place.align)
362 pub(super) fn get_place_alloc_mut(
364 place: &MPlaceTy<'tcx, M::Provenance>,
365 ) -> InterpResult<'tcx, Option<AllocRefMut<'_, 'tcx, M::Provenance, M::AllocExtra>>> {
366 assert!(place.layout.is_sized());
367 assert!(!place.meta.has_meta());
368 let size = place.layout.size;
369 self.get_ptr_alloc_mut(place.ptr, size, place.align)
372 /// Check if this mplace is dereferenceable and sufficiently aligned.
373 pub fn check_mplace(&self, mplace: MPlaceTy<'tcx, M::Provenance>) -> InterpResult<'tcx> {
374 let (size, align) = self
375 .size_and_align_of_mplace(&mplace)?
376 .unwrap_or((mplace.layout.size, mplace.layout.align.abi));
377 assert!(mplace.align <= align, "dynamic alignment less strict than static one?");
378 let align = if M::enforce_alignment(self).should_check() { align } else { Align::ONE };
379 self.check_ptr_access_align(mplace.ptr, size, align, CheckInAllocMsg::DerefTest)?;
383 /// Converts a repr(simd) place into a place where `place_index` accesses the SIMD elements.
384 /// Also returns the number of elements.
385 pub fn mplace_to_simd(
387 mplace: &MPlaceTy<'tcx, M::Provenance>,
388 ) -> InterpResult<'tcx, (MPlaceTy<'tcx, M::Provenance>, u64)> {
389 // Basically we just transmute this place into an array following simd_size_and_type.
390 // (Transmuting is okay since this is an in-memory place. We also double-check the size
392 let (len, e_ty) = mplace.layout.ty.simd_size_and_type(*self.tcx);
393 let array = self.tcx.mk_array(e_ty, len);
394 let layout = self.layout_of(array)?;
395 assert_eq!(layout.size, mplace.layout.size);
396 Ok((MPlaceTy { layout, ..*mplace }, len))
399 /// Converts a repr(simd) place into a place where `place_index` accesses the SIMD elements.
400 /// Also returns the number of elements.
401 pub fn place_to_simd(
403 place: &PlaceTy<'tcx, M::Provenance>,
404 ) -> InterpResult<'tcx, (MPlaceTy<'tcx, M::Provenance>, u64)> {
405 let mplace = self.force_allocation(place)?;
406 self.mplace_to_simd(&mplace)
409 pub fn local_to_place(
413 ) -> InterpResult<'tcx, PlaceTy<'tcx, M::Provenance>> {
414 let layout = self.layout_of_local(&self.stack()[frame], local, None)?;
415 let place = Place::Local { frame, local };
416 Ok(PlaceTy { place, layout, align: layout.align.abi })
419 /// Computes a place. You should only use this if you intend to write into this
420 /// place; for reading, a more efficient alternative is `eval_place_to_op`.
421 #[instrument(skip(self), level = "debug")]
424 mir_place: mir::Place<'tcx>,
425 ) -> InterpResult<'tcx, PlaceTy<'tcx, M::Provenance>> {
426 let mut place = self.local_to_place(self.frame_idx(), mir_place.local)?;
427 // Using `try_fold` turned out to be bad for performance, hence the loop.
428 for elem in mir_place.projection.iter() {
429 place = self.place_projection(&place, elem)?
432 trace!("{:?}", self.dump_place(place.place));
433 // Sanity-check the type we ended up with.
435 mir_assign_valid_types(
438 self.layout_of(self.subst_from_current_frame_and_normalize_erasing_regions(
439 mir_place.ty(&self.frame().body.local_decls, *self.tcx).ty
443 "eval_place of a MIR place with type {:?} produced an interpreter place with type {:?}",
444 mir_place.ty(&self.frame().body.local_decls, *self.tcx).ty,
450 /// Write an immediate to a place
452 #[instrument(skip(self), level = "debug")]
453 pub fn write_immediate(
455 src: Immediate<M::Provenance>,
456 dest: &PlaceTy<'tcx, M::Provenance>,
457 ) -> InterpResult<'tcx> {
458 self.write_immediate_no_validate(src, dest)?;
460 if M::enforce_validity(self) {
461 // Data got changed, better make sure it matches the type!
462 self.validate_operand(&self.place_to_op(dest)?)?;
468 /// Write a scalar to a place
472 val: impl Into<Scalar<M::Provenance>>,
473 dest: &PlaceTy<'tcx, M::Provenance>,
474 ) -> InterpResult<'tcx> {
475 self.write_immediate(Immediate::Scalar(val.into()), dest)
478 /// Write a pointer to a place
480 pub fn write_pointer(
482 ptr: impl Into<Pointer<Option<M::Provenance>>>,
483 dest: &PlaceTy<'tcx, M::Provenance>,
484 ) -> InterpResult<'tcx> {
485 self.write_scalar(Scalar::from_maybe_pointer(ptr.into(), self), dest)
488 /// Write an immediate to a place.
489 /// If you use this you are responsible for validating that things got copied at the
491 fn write_immediate_no_validate(
493 src: Immediate<M::Provenance>,
494 dest: &PlaceTy<'tcx, M::Provenance>,
495 ) -> InterpResult<'tcx> {
496 assert!(dest.layout.is_sized(), "Cannot write unsized data");
497 trace!("write_immediate: {:?} <- {:?}: {}", *dest, src, dest.layout.ty);
499 // See if we can avoid an allocation. This is the counterpart to `read_immediate_raw`,
500 // but not factored as a separate function.
501 let mplace = match dest.place {
502 Place::Local { frame, local } => {
503 match M::access_local_mut(self, frame, local)? {
504 Operand::Immediate(local) => {
505 // Local can be updated in-place.
509 Operand::Indirect(mplace) => {
510 // The local is in memory, go on below.
515 Place::Ptr(mplace) => mplace, // already referring to memory
518 // This is already in memory, write there.
519 self.write_immediate_to_mplace_no_validate(src, dest.layout, dest.align, mplace)
522 /// Write an immediate to memory.
523 /// If you use this you are responsible for validating that things got copied at the
525 fn write_immediate_to_mplace_no_validate(
527 value: Immediate<M::Provenance>,
528 layout: TyAndLayout<'tcx>,
530 dest: MemPlace<M::Provenance>,
531 ) -> InterpResult<'tcx> {
532 // Note that it is really important that the type here is the right one, and matches the
533 // type things are read at. In case `value` is a `ScalarPair`, we don't do any magic here
534 // to handle padding properly, which is only correct if we never look at this data with the
538 let Some(mut alloc) = self.get_place_alloc_mut(&MPlaceTy { mplace: dest, layout, align })? else {
544 Immediate::Scalar(scalar) => {
545 let Abi::Scalar(s) = layout.abi else { span_bug!(
547 "write_immediate_to_mplace: invalid Scalar layout: {layout:#?}",
550 let size = s.size(&tcx);
551 assert_eq!(size, layout.size, "abi::Scalar size does not match layout size");
552 alloc.write_scalar(alloc_range(Size::ZERO, size), scalar)
554 Immediate::ScalarPair(a_val, b_val) => {
555 // We checked `ptr_align` above, so all fields will have the alignment they need.
556 // We would anyway check against `ptr_align.restrict_for_offset(b_offset)`,
557 // which `ptr.offset(b_offset)` cannot possibly fail to satisfy.
558 let Abi::ScalarPair(a, b) = layout.abi else { span_bug!(
560 "write_immediate_to_mplace: invalid ScalarPair layout: {:#?}",
564 let (a_size, b_size) = (a.size(&tcx), b.size(&tcx));
565 let b_offset = a_size.align_to(b.align(&tcx).abi);
566 assert!(b_offset.bytes() > 0); // in `operand_field` we use the offset to tell apart the fields
568 // It is tempting to verify `b_offset` against `layout.fields.offset(1)`,
569 // but that does not work: We could be a newtype around a pair, then the
570 // fields do not match the `ScalarPair` components.
572 alloc.write_scalar(alloc_range(Size::ZERO, a_size), a_val)?;
573 alloc.write_scalar(alloc_range(b_offset, b_size), b_val)
575 Immediate::Uninit => alloc.write_uninit(),
579 pub fn write_uninit(&mut self, dest: &PlaceTy<'tcx, M::Provenance>) -> InterpResult<'tcx> {
580 let mplace = match dest.as_mplace_or_local() {
581 Left(mplace) => mplace,
582 Right((frame, local)) => {
583 match M::access_local_mut(self, frame, local)? {
584 Operand::Immediate(local) => {
585 *local = Immediate::Uninit;
588 Operand::Indirect(mplace) => {
589 // The local is in memory, go on below.
590 MPlaceTy { mplace: *mplace, layout: dest.layout, align: dest.align }
595 let Some(mut alloc) = self.get_place_alloc_mut(&mplace)? else {
599 alloc.write_uninit()?;
603 /// Copies the data from an operand to a place.
604 /// `allow_transmute` indicates whether the layouts may disagree.
606 #[instrument(skip(self), level = "debug")]
609 src: &OpTy<'tcx, M::Provenance>,
610 dest: &PlaceTy<'tcx, M::Provenance>,
611 allow_transmute: bool,
612 ) -> InterpResult<'tcx> {
613 self.copy_op_no_validate(src, dest, allow_transmute)?;
615 if M::enforce_validity(self) {
616 // Data got changed, better make sure it matches the type!
617 self.validate_operand(&self.place_to_op(dest)?)?;
623 /// Copies the data from an operand to a place.
624 /// `allow_transmute` indicates whether the layouts may disagree.
625 /// Also, if you use this you are responsible for validating that things get copied at the
627 #[instrument(skip(self), level = "debug")]
628 fn copy_op_no_validate(
630 src: &OpTy<'tcx, M::Provenance>,
631 dest: &PlaceTy<'tcx, M::Provenance>,
632 allow_transmute: bool,
633 ) -> InterpResult<'tcx> {
634 // We do NOT compare the types for equality, because well-typed code can
635 // actually "transmute" `&mut T` to `&T` in an assignment without a cast.
637 mir_assign_valid_types(*self.tcx, self.param_env, src.layout, dest.layout);
638 if !allow_transmute && !layout_compat {
641 "type mismatch when copying!\nsrc: {:?},\ndest: {:?}",
647 // Let us see if the layout is simple so we take a shortcut,
648 // avoid force_allocation.
649 let src = match self.read_immediate_raw(src)? {
651 // FIXME(const_prop): Const-prop can possibly evaluate an
652 // unsized copy operation when it thinks that the type is
653 // actually sized, due to a trivially false where-clause
654 // predicate like `where Self: Sized` with `Self = dyn Trait`.
655 // See #102553 for an example of such a predicate.
656 if src.layout.is_unsized() {
657 throw_inval!(SizeOfUnsizedType(src.layout.ty));
659 if dest.layout.is_unsized() {
660 throw_inval!(SizeOfUnsizedType(dest.layout.ty));
662 assert_eq!(src.layout.size, dest.layout.size);
663 // Yay, we got a value that we can write directly.
664 return if layout_compat {
665 self.write_immediate_no_validate(*src_val, dest)
667 // This is tricky. The problematic case is `ScalarPair`: the `src_val` was
668 // loaded using the offsets defined by `src.layout`. When we put this back into
669 // the destination, we have to use the same offsets! So (a) we make sure we
670 // write back to memory, and (b) we use `dest` *with the source layout*.
671 let dest_mem = self.force_allocation(dest)?;
672 self.write_immediate_to_mplace_no_validate(
680 Left(mplace) => mplace,
682 // Slow path, this does not fit into an immediate. Just memcpy.
683 trace!("copy_op: {:?} <- {:?}: {}", *dest, src, dest.layout.ty);
685 let dest = self.force_allocation(&dest)?;
686 let Some((dest_size, _)) = self.size_and_align_of_mplace(&dest)? else {
687 span_bug!(self.cur_span(), "copy_op needs (dynamically) sized values")
689 if cfg!(debug_assertions) {
690 let src_size = self.size_and_align_of_mplace(&src)?.unwrap().0;
691 assert_eq!(src_size, dest_size, "Cannot copy differently-sized data");
693 // As a cheap approximation, we compare the fixed parts of the size.
694 assert_eq!(src.layout.size, dest.layout.size);
698 src.ptr, src.align, dest.ptr, dest.align, dest_size, /*nonoverlapping*/ false,
702 /// Ensures that a place is in memory, and returns where it is.
703 /// If the place currently refers to a local that doesn't yet have a matching allocation,
704 /// create such an allocation.
705 /// This is essentially `force_to_memplace`.
706 #[instrument(skip(self), level = "debug")]
707 pub fn force_allocation(
709 place: &PlaceTy<'tcx, M::Provenance>,
710 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
711 let mplace = match place.place {
712 Place::Local { frame, local } => {
713 match M::access_local_mut(self, frame, local)? {
714 &mut Operand::Immediate(local_val) => {
715 // We need to make an allocation.
717 // We need the layout of the local. We can NOT use the layout we got,
718 // that might e.g., be an inner field of a struct with `Scalar` layout,
719 // that has different alignment than the outer field.
721 self.layout_of_local(&self.stack()[frame], local, None)?;
722 if local_layout.is_unsized() {
723 throw_unsup_format!("unsized locals are not supported");
725 let mplace = *self.allocate(local_layout, MemoryKind::Stack)?;
726 if !matches!(local_val, Immediate::Uninit) {
727 // Preserve old value. (As an optimization, we can skip this if it was uninit.)
728 // We don't have to validate as we can assume the local
729 // was already valid for its type.
730 self.write_immediate_to_mplace_no_validate(
733 local_layout.align.abi,
737 // Now we can call `access_mut` again, asserting it goes well,
738 // and actually overwrite things.
739 *M::access_local_mut(self, frame, local).unwrap() =
740 Operand::Indirect(mplace);
743 &mut Operand::Indirect(mplace) => mplace, // this already was an indirect local
746 Place::Ptr(mplace) => mplace,
748 // Return with the original layout, so that the caller can go on
749 Ok(MPlaceTy { mplace, layout: place.layout, align: place.align })
754 layout: TyAndLayout<'tcx>,
755 kind: MemoryKind<M::MemoryKind>,
756 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
757 assert!(layout.is_sized());
758 let ptr = self.allocate_ptr(layout.size, layout.align.abi, kind)?;
759 Ok(MPlaceTy::from_aligned_ptr(ptr.into(), layout))
762 /// Returns a wide MPlace of type `&'static [mut] str` to a new 1-aligned allocation.
766 kind: MemoryKind<M::MemoryKind>,
768 ) -> MPlaceTy<'tcx, M::Provenance> {
769 let ptr = self.allocate_bytes_ptr(str.as_bytes(), Align::ONE, kind, mutbl);
770 let meta = Scalar::from_machine_usize(u64::try_from(str.len()).unwrap(), self);
771 let mplace = MemPlace { ptr: ptr.into(), meta: MemPlaceMeta::Meta(meta) };
773 let ty = self.tcx.mk_ref(
774 self.tcx.lifetimes.re_static,
775 ty::TypeAndMut { ty: self.tcx.types.str_, mutbl },
777 let layout = self.layout_of(ty).unwrap();
778 MPlaceTy { mplace, layout, align: layout.align.abi }
781 /// Writes the discriminant of the given variant.
782 #[instrument(skip(self), level = "debug")]
783 pub fn write_discriminant(
785 variant_index: VariantIdx,
786 dest: &PlaceTy<'tcx, M::Provenance>,
787 ) -> InterpResult<'tcx> {
788 // This must be an enum or generator.
789 match dest.layout.ty.kind() {
790 ty::Adt(adt, _) => assert!(adt.is_enum()),
791 ty::Generator(..) => {}
794 "write_discriminant called on non-variant-type (neither enum nor generator)"
797 // Layout computation excludes uninhabited variants from consideration
798 // therefore there's no way to represent those variants in the given layout.
799 // Essentially, uninhabited variants do not have a tag that corresponds to their
800 // discriminant, so we cannot do anything here.
801 // When evaluating we will always error before even getting here, but ConstProp 'executes'
802 // dead code, so we cannot ICE here.
803 if dest.layout.for_variant(self, variant_index).abi.is_uninhabited() {
804 throw_ub!(UninhabitedEnumVariantWritten)
807 match dest.layout.variants {
808 abi::Variants::Single { index } => {
809 assert_eq!(index, variant_index);
811 abi::Variants::Multiple {
812 tag_encoding: TagEncoding::Direct,
817 // No need to validate that the discriminant here because the
818 // `TyAndLayout::for_variant()` call earlier already checks the variant is valid.
821 dest.layout.ty.discriminant_for_variant(*self.tcx, variant_index).unwrap().val;
823 // raw discriminants for enums are isize or bigger during
824 // their computation, but the in-memory tag is the smallest possible
826 let size = tag_layout.size(self);
827 let tag_val = size.truncate(discr_val);
829 let tag_dest = self.place_field(dest, tag_field)?;
830 self.write_scalar(Scalar::from_uint(tag_val, size), &tag_dest)?;
832 abi::Variants::Multiple {
834 TagEncoding::Niche { untagged_variant, ref niche_variants, niche_start },
839 // No need to validate that the discriminant here because the
840 // `TyAndLayout::for_variant()` call earlier already checks the variant is valid.
842 if variant_index != untagged_variant {
843 let variants_start = niche_variants.start().as_u32();
844 let variant_index_relative = variant_index
846 .checked_sub(variants_start)
847 .expect("overflow computing relative variant idx");
848 // We need to use machine arithmetic when taking into account `niche_start`:
849 // tag_val = variant_index_relative + niche_start_val
850 let tag_layout = self.layout_of(tag_layout.primitive().to_int_ty(*self.tcx))?;
851 let niche_start_val = ImmTy::from_uint(niche_start, tag_layout);
852 let variant_index_relative_val =
853 ImmTy::from_uint(variant_index_relative, tag_layout);
854 let tag_val = self.binary_op(
856 &variant_index_relative_val,
860 let niche_dest = self.place_field(dest, tag_field)?;
861 self.write_immediate(*tag_val, &niche_dest)?;
869 pub fn raw_const_to_mplace(
871 raw: ConstAlloc<'tcx>,
872 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
873 // This must be an allocation in `tcx`
874 let _ = self.tcx.global_alloc(raw.alloc_id);
875 let ptr = self.global_base_pointer(Pointer::from(raw.alloc_id))?;
876 let layout = self.layout_of(raw.ty)?;
877 Ok(MPlaceTy::from_aligned_ptr(ptr.into(), layout))
880 /// Turn a place with a `dyn Trait` type into a place with the actual dynamic type.
881 pub(super) fn unpack_dyn_trait(
883 mplace: &MPlaceTy<'tcx, M::Provenance>,
884 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
885 let vtable = mplace.vtable().to_pointer(self)?; // also sanity checks the type
886 let (ty, _) = self.get_ptr_vtable(vtable)?;
887 let layout = self.layout_of(ty)?;
889 let mplace = MPlaceTy {
890 mplace: MemPlace { meta: MemPlaceMeta::None, ..**mplace },
892 align: layout.align.abi,
898 // Some nodes are used a lot. Make sure they don't unintentionally get bigger.
899 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
902 use rustc_data_structures::static_assert_size;
903 // tidy-alphabetical-start
904 static_assert_size!(MemPlace, 40);
905 static_assert_size!(MemPlaceMeta, 24);
906 static_assert_size!(MPlaceTy<'_>, 64);
907 static_assert_size!(Place, 40);
908 static_assert_size!(PlaceTy<'_>, 64);
909 // tidy-alphabetical-end