1 // Copyright 2018 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! Computations on places -- field projections, going from mir::Place, and writing
13 //! All high-level functions to write to memory work on places as destinations.
15 use std::convert::TryFrom;
20 use rustc::ty::{self, Ty};
21 use rustc::ty::layout::{self, Size, Align, LayoutOf, TyLayout, HasDataLayout, VariantIdx};
23 use rustc::mir::interpret::{
24 GlobalId, AllocId, Allocation, Scalar, EvalResult, Pointer, PointerArithmetic
27 EvalContext, Machine, AllocMap, AllocationExtra,
28 Immediate, ImmTy, ScalarMaybeUndef, Operand, OpTy, MemoryKind
31 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
32 pub struct MemPlace<Tag=(), Id=AllocId> {
33 /// A place may have an integral pointer for ZSTs, and since it might
34 /// be turned back into a reference before ever being dereferenced.
35 /// However, it may never be undef.
36 pub ptr: Scalar<Tag, Id>,
38 /// Metadata for unsized places. Interpretation is up to the type.
39 /// Must not be present for sized types, but can be missing for unsized types
40 /// (e.g. `extern type`).
41 pub meta: Option<Scalar<Tag, Id>>,
44 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
45 pub enum Place<Tag=(), Id=AllocId> {
46 /// A place referring to a value allocated in the `Memory` system.
47 Ptr(MemPlace<Tag, Id>),
49 /// To support alloc-free locals, we are able to write directly to a local.
50 /// (Without that optimization, we'd just always be a `MemPlace`.)
57 #[derive(Copy, Clone, Debug)]
58 pub struct PlaceTy<'tcx, Tag=()> {
60 pub layout: TyLayout<'tcx>,
63 impl<'tcx, Tag> ::std::ops::Deref for PlaceTy<'tcx, Tag> {
64 type Target = Place<Tag>;
66 fn deref(&self) -> &Place<Tag> {
71 /// A MemPlace with its layout. Constructing it is only possible in this module.
72 #[derive(Copy, Clone, Debug)]
73 pub struct MPlaceTy<'tcx, Tag=()> {
74 mplace: MemPlace<Tag>,
75 pub layout: TyLayout<'tcx>,
78 impl<'tcx, Tag> ::std::ops::Deref for MPlaceTy<'tcx, Tag> {
79 type Target = MemPlace<Tag>;
81 fn deref(&self) -> &MemPlace<Tag> {
86 impl<'tcx, Tag> From<MPlaceTy<'tcx, Tag>> for PlaceTy<'tcx, Tag> {
88 fn from(mplace: MPlaceTy<'tcx, Tag>) -> Self {
90 place: Place::Ptr(mplace.mplace),
98 pub fn with_default_tag<Tag>(self) -> MemPlace<Tag>
102 ptr: self.ptr.with_default_tag(),
104 meta: self.meta.map(Scalar::with_default_tag),
109 impl<Tag> MemPlace<Tag> {
111 pub fn erase_tag(self) -> MemPlace
114 ptr: self.ptr.erase_tag(),
116 meta: self.meta.map(Scalar::erase_tag),
121 pub fn from_scalar_ptr(ptr: Scalar<Tag>, align: Align) -> Self {
129 /// Produces a Place that will error if attempted to be read from or written to
131 pub fn null(cx: &impl HasDataLayout) -> Self {
132 Self::from_scalar_ptr(Scalar::ptr_null(cx), Align::from_bytes(1, 1).unwrap())
136 pub fn from_ptr(ptr: Pointer<Tag>, align: Align) -> Self {
137 Self::from_scalar_ptr(ptr.into(), align)
141 pub fn to_scalar_ptr_align(self) -> (Scalar<Tag>, Align) {
142 assert!(self.meta.is_none());
143 (self.ptr, self.align)
146 /// metact the ptr part of the mplace
148 pub fn to_ptr(self) -> EvalResult<'tcx, Pointer<Tag>> {
149 // At this point, we forget about the alignment information --
150 // the place has been turned into a reference, and no matter where it came from,
151 // it now must be aligned.
152 self.to_scalar_ptr_align().0.to_ptr()
155 /// Turn a mplace into a (thin or fat) pointer, as a reference, pointing to the same space.
156 /// This is the inverse of `ref_to_mplace`.
158 pub fn to_ref(self) -> Immediate<Tag> {
160 None => Immediate::Scalar(self.ptr.into()),
161 Some(meta) => Immediate::ScalarPair(self.ptr.into(), meta.into()),
166 impl<'tcx, Tag> MPlaceTy<'tcx, Tag> {
167 /// Produces a MemPlace that works for ZST but nothing else
169 pub fn dangling(layout: TyLayout<'tcx>, cx: &impl HasDataLayout) -> Self {
171 mplace: MemPlace::from_scalar_ptr(
172 Scalar::from_uint(layout.align.abi(), cx.pointer_size()),
180 fn from_aligned_ptr(ptr: Pointer<Tag>, layout: TyLayout<'tcx>) -> Self {
181 MPlaceTy { mplace: MemPlace::from_ptr(ptr, layout.align), layout }
185 pub(super) fn len(self, cx: &impl HasDataLayout) -> EvalResult<'tcx, u64> {
186 if self.layout.is_unsized() {
187 // We need to consult `meta` metadata
188 match self.layout.ty.sty {
189 ty::Slice(..) | ty::Str =>
190 return self.mplace.meta.unwrap().to_usize(cx),
191 _ => bug!("len not supported on unsized type {:?}", self.layout.ty),
194 // Go through the layout. There are lots of types that support a length,
196 match self.layout.fields {
197 layout::FieldPlacement::Array { count, .. } => Ok(count),
198 _ => bug!("len not supported on sized type {:?}", self.layout.ty),
204 pub(super) fn vtable(self) -> EvalResult<'tcx, Pointer<Tag>> {
205 match self.layout.ty.sty {
206 ty::Dynamic(..) => self.mplace.meta.unwrap().to_ptr(),
207 _ => bug!("vtable not supported on type {:?}", self.layout.ty),
212 impl<'tcx, Tag: ::std::fmt::Debug> OpTy<'tcx, Tag> {
214 pub fn try_as_mplace(self) -> Result<MPlaceTy<'tcx, Tag>, Immediate<Tag>> {
216 Operand::Indirect(mplace) => Ok(MPlaceTy { mplace, layout: self.layout }),
217 Operand::Immediate(imm) => Err(imm),
222 pub fn to_mem_place(self) -> MPlaceTy<'tcx, Tag> {
223 self.try_as_mplace().unwrap()
227 impl<'tcx, Tag: ::std::fmt::Debug> Place<Tag> {
228 /// Produces a Place that will error if attempted to be read from or written to
230 pub fn null(cx: &impl HasDataLayout) -> Self {
231 Place::Ptr(MemPlace::null(cx))
235 pub fn from_scalar_ptr(ptr: Scalar<Tag>, align: Align) -> Self {
236 Place::Ptr(MemPlace::from_scalar_ptr(ptr, align))
240 pub fn from_ptr(ptr: Pointer<Tag>, align: Align) -> Self {
241 Place::Ptr(MemPlace::from_ptr(ptr, align))
245 pub fn to_mem_place(self) -> MemPlace<Tag> {
247 Place::Ptr(mplace) => mplace,
248 _ => bug!("to_mem_place: expected Place::Ptr, got {:?}", self),
254 pub fn to_scalar_ptr_align(self) -> (Scalar<Tag>, Align) {
255 self.to_mem_place().to_scalar_ptr_align()
259 pub fn to_ptr(self) -> EvalResult<'tcx, Pointer<Tag>> {
260 self.to_mem_place().to_ptr()
264 impl<'tcx, Tag: ::std::fmt::Debug> PlaceTy<'tcx, Tag> {
266 pub fn to_mem_place(self) -> MPlaceTy<'tcx, Tag> {
267 MPlaceTy { mplace: self.place.to_mem_place(), layout: self.layout }
271 // separating the pointer tag for `impl Trait`, see https://github.com/rust-lang/rust/issues/54385
272 impl<'a, 'mir, 'tcx, Tag, M> EvalContext<'a, 'mir, 'tcx, M>
274 Tag: ::std::fmt::Debug+Default+Copy+Eq+Hash+'static,
275 M: Machine<'a, 'mir, 'tcx, PointerTag=Tag>,
276 M::MemoryMap: AllocMap<AllocId, (MemoryKind<M::MemoryKinds>, Allocation<Tag, M::AllocExtra>)>,
277 M::AllocExtra: AllocationExtra<Tag>,
279 /// Take a value, which represents a (thin or fat) reference, and make it a place.
280 /// Alignment is just based on the type. This is the inverse of `MemPlace::to_ref()`.
281 /// This does NOT call the "deref" machine hook, so it does NOT count as a
282 /// deref as far as Stacked Borrows is concerned. Use `deref_operand` for that!
283 pub fn ref_to_mplace(
285 val: ImmTy<'tcx, M::PointerTag>,
286 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
287 let pointee_type = val.layout.ty.builtin_deref(true).unwrap().ty;
288 let layout = self.layout_of(pointee_type)?;
290 let mplace = MemPlace {
291 ptr: val.to_scalar_ptr()?,
293 meta: val.to_meta()?,
295 Ok(MPlaceTy { mplace, layout })
298 // Take an operand, representing a pointer, and dereference it to a place -- that
299 // will always be a MemPlace. Lives in `place.rs` because it creates a place.
300 // This calls the "deref" machine hook, and counts as a deref as far as
301 // Stacked Borrows is concerned.
302 pub fn deref_operand(
304 src: OpTy<'tcx, M::PointerTag>,
305 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
306 let val = self.read_immediate(src)?;
307 trace!("deref to {} on {:?}", val.layout.ty, *val);
308 let mut place = self.ref_to_mplace(val)?;
309 // Pointer tag tracking might want to adjust the tag.
310 let mutbl = match val.layout.ty.sty {
311 // `builtin_deref` considers boxes immutable, that's useless for our purposes
312 ty::Ref(_, _, mutbl) => Some(mutbl),
313 ty::Adt(def, _) if def.is_box() => Some(hir::MutMutable),
314 ty::RawPtr(_) => None,
315 _ => bug!("Unexpected pointer type {}", val.layout.ty.sty),
317 place.mplace.ptr = M::tag_dereference(self, place, mutbl)?;
321 /// Offset a pointer to project to a field. Unlike place_field, this is always
322 /// possible without allocating, so it can take &self. Also return the field's layout.
323 /// This supports both struct and array fields.
327 base: MPlaceTy<'tcx, M::PointerTag>,
329 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
330 // Not using the layout method because we want to compute on u64
331 let offset = match base.layout.fields {
332 layout::FieldPlacement::Arbitrary { ref offsets, .. } =>
333 offsets[usize::try_from(field).unwrap()],
334 layout::FieldPlacement::Array { stride, .. } => {
335 let len = base.len(self)?;
336 assert!(field < len, "Tried to access element {} of array/slice with length {}",
340 layout::FieldPlacement::Union(count) => {
341 assert!(field < count as u64,
342 "Tried to access field {} of union with {} fields", field, count);
343 // Offset is always 0
347 // the only way conversion can fail if is this is an array (otherwise we already panicked
348 // above). In that case, all fields are equal.
349 let field_layout = base.layout.field(self, usize::try_from(field).unwrap_or(0))?;
351 // Offset may need adjustment for unsized fields
352 let (meta, offset) = if field_layout.is_unsized() {
353 // re-use parent metadata to determine dynamic field layout
354 let align = match self.size_and_align_of(base.meta, field_layout)? {
355 Some((_, align)) => align,
356 None if offset == Size::ZERO =>
357 // An extern type at offset 0, we fall back to its static alignment.
358 // FIXME: Once we have made decisions for how to handle size and alignment
359 // of `extern type`, this should be adapted. It is just a temporary hack
360 // to get some code to work that probably ought to work.
363 bug!("Cannot compute offset for extern type field at non-0 offset"),
365 (base.meta, offset.abi_align(align))
367 // base.meta could be present; we might be accessing a sized field of an unsized
372 let ptr = base.ptr.ptr_offset(offset, self)?;
373 let align = base.align
374 // We do not look at `base.layout.align` nor `field_layout.align`, unlike
375 // codegen -- mostly to see if we can get away with that
376 .restrict_for_offset(offset); // must be last thing that happens
378 Ok(MPlaceTy { mplace: MemPlace { ptr, align, meta }, layout: field_layout })
381 // Iterates over all fields of an array. Much more efficient than doing the
382 // same by repeatedly calling `mplace_array`.
383 pub fn mplace_array_fields(
385 base: MPlaceTy<'tcx, Tag>,
387 EvalResult<'tcx, impl Iterator<Item=EvalResult<'tcx, MPlaceTy<'tcx, Tag>>> + 'a>
389 let len = base.len(self)?; // also asserts that we have a type where this makes sense
390 let stride = match base.layout.fields {
391 layout::FieldPlacement::Array { stride, .. } => stride,
392 _ => bug!("mplace_array_fields: expected an array layout"),
394 let layout = base.layout.field(self, 0)?;
395 let dl = &self.tcx.data_layout;
396 Ok((0..len).map(move |i| {
397 let ptr = base.ptr.ptr_offset(i * stride, dl)?;
399 mplace: MemPlace { ptr, align: base.align, meta: None },
405 pub fn mplace_subslice(
407 base: MPlaceTy<'tcx, M::PointerTag>,
410 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
411 let len = base.len(self)?; // also asserts that we have a type where this makes sense
412 assert!(from <= len - to);
414 // Not using layout method because that works with usize, and does not work with slices
415 // (that have count 0 in their layout).
416 let from_offset = match base.layout.fields {
417 layout::FieldPlacement::Array { stride, .. } =>
419 _ => bug!("Unexpected layout of index access: {:#?}", base.layout),
421 let ptr = base.ptr.ptr_offset(from_offset, self)?;
423 // Compute meta and new layout
424 let inner_len = len - to - from;
425 let (meta, ty) = match base.layout.ty.sty {
426 // It is not nice to match on the type, but that seems to be the only way to
428 ty::Array(inner, _) =>
429 (None, self.tcx.mk_array(inner, inner_len)),
431 let len = Scalar::from_uint(inner_len, self.pointer_size());
432 (Some(len), base.layout.ty)
435 bug!("cannot subslice non-array type: `{:?}`", base.layout.ty),
437 let layout = self.layout_of(ty)?;
440 mplace: MemPlace { ptr, align: base.align, meta },
445 pub fn mplace_downcast(
447 base: MPlaceTy<'tcx, M::PointerTag>,
449 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
450 // Downcasts only change the layout
451 assert!(base.meta.is_none());
452 Ok(MPlaceTy { layout: base.layout.for_variant(self, variant), ..base })
455 /// Project into an mplace
456 pub fn mplace_projection(
458 base: MPlaceTy<'tcx, M::PointerTag>,
459 proj_elem: &mir::PlaceElem<'tcx>,
460 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
461 use rustc::mir::ProjectionElem::*;
462 Ok(match *proj_elem {
463 Field(field, _) => self.mplace_field(base, field.index() as u64)?,
464 Downcast(_, variant) => self.mplace_downcast(base, variant)?,
465 Deref => self.deref_operand(base.into())?,
468 let n = *self.frame().locals[local].access()?;
469 let n_layout = self.layout_of(self.tcx.types.usize)?;
470 let n = self.read_scalar(OpTy { op: n, layout: n_layout })?;
471 let n = n.to_bits(self.tcx.data_layout.pointer_size)?;
472 self.mplace_field(base, u64::try_from(n).unwrap())?
480 let n = base.len(self)?;
481 assert!(n >= min_length as u64);
483 let index = if from_end {
484 n - u64::from(offset)
489 self.mplace_field(base, index)?
492 Subslice { from, to } =>
493 self.mplace_subslice(base, u64::from(from), u64::from(to))?,
497 /// Get the place of a field inside the place, and also the field's type.
498 /// Just a convenience function, but used quite a bit.
499 /// This is the only projection that might have a side-effect: We cannot project
500 /// into the field of a local `ScalarPair`, we have to first allocate it.
503 base: PlaceTy<'tcx, M::PointerTag>,
505 ) -> EvalResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
506 // FIXME: We could try to be smarter and avoid allocation for fields that span the
508 let mplace = self.force_allocation(base)?;
509 Ok(self.mplace_field(mplace, field)?.into())
512 pub fn place_downcast(
514 base: PlaceTy<'tcx, M::PointerTag>,
516 ) -> EvalResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
517 // Downcast just changes the layout
518 Ok(match base.place {
519 Place::Ptr(mplace) =>
520 self.mplace_downcast(MPlaceTy { mplace, layout: base.layout }, variant)?.into(),
521 Place::Local { .. } => {
522 let layout = base.layout.for_variant(self, variant);
523 PlaceTy { layout, ..base }
528 /// Project into a place
529 pub fn place_projection(
531 base: PlaceTy<'tcx, M::PointerTag>,
532 proj_elem: &mir::ProjectionElem<'tcx, mir::Local, Ty<'tcx>>,
533 ) -> EvalResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
534 use rustc::mir::ProjectionElem::*;
535 Ok(match *proj_elem {
536 Field(field, _) => self.place_field(base, field.index() as u64)?,
537 Downcast(_, variant) => self.place_downcast(base, variant)?,
538 Deref => self.deref_operand(self.place_to_op(base)?)?.into(),
539 // For the other variants, we have to force an allocation.
540 // This matches `operand_projection`.
541 Subslice { .. } | ConstantIndex { .. } | Index(_) => {
542 let mplace = self.force_allocation(base)?;
543 self.mplace_projection(mplace, proj_elem)?.into()
548 /// Evaluate statics and promoteds to an `MPlace`. Used to share some code between
549 /// `eval_place` and `eval_place_to_op`.
550 pub(super) fn eval_place_to_mplace(
552 mir_place: &mir::Place<'tcx>
553 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
554 use rustc::mir::Place::*;
555 Ok(match *mir_place {
556 Promoted(ref promoted) => {
557 let instance = self.frame().instance;
558 let op = self.global_to_op(GlobalId {
560 promoted: Some(promoted.0),
562 let mplace = op.to_mem_place(); // these are always in memory
563 let ty = self.monomorphize(promoted.1, self.substs());
566 layout: self.layout_of(ty)?,
570 Static(ref static_) => {
571 let ty = self.monomorphize(static_.ty, self.substs());
572 let layout = self.layout_of(ty)?;
573 let instance = ty::Instance::mono(*self.tcx, static_.def_id);
578 // Just create a lazy reference, so we can support recursive statics.
579 // tcx takes are of assigning every static one and only one unique AllocId.
580 // When the data here is ever actually used, memory will notice,
581 // and it knows how to deal with alloc_id that are present in the
582 // global table but not in its local memory: It calls back into tcx through
583 // a query, triggering the CTFE machinery to actually turn this lazy reference
584 // into a bunch of bytes. IOW, statics are evaluated with CTFE even when
585 // this EvalContext uses another Machine (e.g., in miri). This is what we
586 // want! This way, computing statics works concistently between codegen
587 // and miri: They use the same query to eventually obtain a `ty::Const`
588 // and use that for further computation.
589 let alloc = self.tcx.alloc_map.lock().intern_static(cid.instance.def_id());
590 MPlaceTy::from_aligned_ptr(Pointer::from(alloc).with_default_tag(), layout)
593 _ => bug!("eval_place_to_mplace called on {:?}", mir_place),
597 /// Compute a place. You should only use this if you intend to write into this
598 /// place; for reading, a more efficient alternative is `eval_place_for_read`.
601 mir_place: &mir::Place<'tcx>
602 ) -> EvalResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
603 use rustc::mir::Place::*;
604 let place = match *mir_place {
605 Local(mir::RETURN_PLACE) => match self.frame().return_place {
606 Some(return_place) =>
607 // We use our layout to verify our assumption; caller will validate
608 // their layout on return.
610 place: *return_place,
611 layout: self.layout_of_local(self.frame(), mir::RETURN_PLACE)?,
613 None => return err!(InvalidNullPointerUsage),
615 Local(local) => PlaceTy {
616 place: Place::Local {
617 frame: self.cur_frame(),
620 layout: self.layout_of_local(self.frame(), local)?,
623 Projection(ref proj) => {
624 let place = self.eval_place(&proj.base)?;
625 self.place_projection(place, &proj.elem)?
628 _ => self.eval_place_to_mplace(mir_place)?.into(),
631 self.dump_place(place.place);
635 /// Write a scalar to a place
638 val: impl Into<ScalarMaybeUndef<M::PointerTag>>,
639 dest: PlaceTy<'tcx, M::PointerTag>,
640 ) -> EvalResult<'tcx> {
641 self.write_immediate(Immediate::Scalar(val.into()), dest)
644 /// Write an immediate to a place
646 pub fn write_immediate(
648 src: Immediate<M::PointerTag>,
649 dest: PlaceTy<'tcx, M::PointerTag>,
650 ) -> EvalResult<'tcx> {
651 self.write_immediate_no_validate(src, dest)?;
653 if M::enforce_validity(self) {
654 // Data got changed, better make sure it matches the type!
655 self.validate_operand(self.place_to_op(dest)?, vec![], None, /*const_mode*/false)?;
661 /// Write an immediate to a place.
662 /// If you use this you are responsible for validating that things got copied at the
664 fn write_immediate_no_validate(
666 src: Immediate<M::PointerTag>,
667 dest: PlaceTy<'tcx, M::PointerTag>,
668 ) -> EvalResult<'tcx> {
669 if cfg!(debug_assertions) {
670 // This is a very common path, avoid some checks in release mode
671 assert!(!dest.layout.is_unsized(), "Cannot write unsized data");
673 Immediate::Scalar(ScalarMaybeUndef::Scalar(Scalar::Ptr(_))) =>
674 assert_eq!(self.pointer_size(), dest.layout.size,
675 "Size mismatch when writing pointer"),
676 Immediate::Scalar(ScalarMaybeUndef::Scalar(Scalar::Bits { size, .. })) =>
677 assert_eq!(Size::from_bytes(size.into()), dest.layout.size,
678 "Size mismatch when writing bits"),
679 Immediate::Scalar(ScalarMaybeUndef::Undef) => {}, // undef can have any size
680 Immediate::ScalarPair(_, _) => {
681 // FIXME: Can we check anything here?
685 trace!("write_immediate: {:?} <- {:?}: {}", *dest, src, dest.layout.ty);
687 // See if we can avoid an allocation. This is the counterpart to `try_read_immediate`,
688 // but not factored as a separate function.
689 let mplace = match dest.place {
690 Place::Local { frame, local } => {
691 match *self.stack[frame].locals[local].access_mut()? {
692 Operand::Immediate(ref mut dest_val) => {
693 // Yay, we can just change the local directly.
697 Operand::Indirect(mplace) => mplace, // already in memory
700 Place::Ptr(mplace) => mplace, // already in memory
702 let dest = MPlaceTy { mplace, layout: dest.layout };
704 // This is already in memory, write there.
705 self.write_immediate_to_mplace_no_validate(src, dest)
708 /// Write an immediate to memory.
709 /// If you use this you are responsible for validating that things git copied at the
711 fn write_immediate_to_mplace_no_validate(
713 value: Immediate<M::PointerTag>,
714 dest: MPlaceTy<'tcx, M::PointerTag>,
715 ) -> EvalResult<'tcx> {
716 let (ptr, ptr_align) = dest.to_scalar_ptr_align();
717 // Note that it is really important that the type here is the right one, and matches the
718 // type things are read at. In case `src_val` is a `ScalarPair`, we don't do any magic here
719 // to handle padding properly, which is only correct if we never look at this data with the
722 // Nothing to do for ZSTs, other than checking alignment
723 if dest.layout.is_zst() {
724 self.memory.check_align(ptr, ptr_align)?;
728 let ptr = ptr.to_ptr()?;
729 // FIXME: We should check that there are dest.layout.size many bytes available in
730 // memory. The code below is not sufficient, with enough padding it might not
731 // cover all the bytes!
733 Immediate::Scalar(scalar) => {
734 match dest.layout.abi {
735 layout::Abi::Scalar(_) => {}, // fine
736 _ => bug!("write_immediate_to_mplace: invalid Scalar layout: {:#?}",
740 self.memory.write_scalar(
741 ptr, ptr_align.min(dest.layout.align), scalar, dest.layout.size
744 Immediate::ScalarPair(a_val, b_val) => {
745 let (a, b) = match dest.layout.abi {
746 layout::Abi::ScalarPair(ref a, ref b) => (&a.value, &b.value),
747 _ => bug!("write_immediate_to_mplace: invalid ScalarPair layout: {:#?}",
750 let (a_size, b_size) = (a.size(self), b.size(self));
751 let (a_align, b_align) = (a.align(self), b.align(self));
752 let b_offset = a_size.abi_align(b_align);
753 let b_ptr = ptr.offset(b_offset, self)?.into();
755 // It is tempting to verify `b_offset` against `layout.fields.offset(1)`,
756 // but that does not work: We could be a newtype around a pair, then the
757 // fields do not match the `ScalarPair` components.
759 self.memory.write_scalar(ptr, ptr_align.min(a_align), a_val, a_size)?;
760 self.memory.write_scalar(b_ptr, ptr_align.min(b_align), b_val, b_size)
765 /// Copy the data from an operand to a place. This does not support transmuting!
766 /// Use `copy_op_transmute` if the layouts could disagree.
770 src: OpTy<'tcx, M::PointerTag>,
771 dest: PlaceTy<'tcx, M::PointerTag>,
772 ) -> EvalResult<'tcx> {
773 self.copy_op_no_validate(src, dest)?;
775 if M::enforce_validity(self) {
776 // Data got changed, better make sure it matches the type!
777 self.validate_operand(self.place_to_op(dest)?, vec![], None, /*const_mode*/false)?;
783 /// Copy the data from an operand to a place. This does not support transmuting!
784 /// Use `copy_op_transmute` if the layouts could disagree.
785 /// Also, if you use this you are responsible for validating that things git copied at the
787 fn copy_op_no_validate(
789 src: OpTy<'tcx, M::PointerTag>,
790 dest: PlaceTy<'tcx, M::PointerTag>,
791 ) -> EvalResult<'tcx> {
792 debug_assert!(!src.layout.is_unsized() && !dest.layout.is_unsized(),
793 "Cannot copy unsized data");
794 // We do NOT compare the types for equality, because well-typed code can
795 // actually "transmute" `&mut T` to `&T` in an assignment without a cast.
796 assert!(src.layout.details == dest.layout.details,
797 "Layout mismatch when copying!\nsrc: {:#?}\ndest: {:#?}", src, dest);
799 // Let us see if the layout is simple so we take a shortcut, avoid force_allocation.
800 let src = match self.try_read_immediate(src)? {
802 // Yay, we got a value that we can write directly.
803 return self.write_immediate_no_validate(src_val, dest);
805 Err(mplace) => mplace,
807 // Slow path, this does not fit into an immediate. Just memcpy.
808 trace!("copy_op: {:?} <- {:?}: {}", *dest, src, dest.layout.ty);
810 let dest = self.force_allocation(dest)?;
811 let (src_ptr, src_align) = src.to_scalar_ptr_align();
812 let (dest_ptr, dest_align) = dest.to_scalar_ptr_align();
815 dest_ptr, dest_align,
816 dest.layout.size, false
822 /// Copy the data from an operand to a place. The layouts may disagree, but they must
823 /// have the same size.
824 pub fn copy_op_transmute(
826 src: OpTy<'tcx, M::PointerTag>,
827 dest: PlaceTy<'tcx, M::PointerTag>,
828 ) -> EvalResult<'tcx> {
829 if src.layout.details == dest.layout.details {
830 // Fast path: Just use normal `copy_op`
831 return self.copy_op(src, dest);
833 // We still require the sizes to match
834 debug_assert!(!src.layout.is_unsized() && !dest.layout.is_unsized(),
835 "Cannot copy unsized data");
836 assert!(src.layout.size == dest.layout.size,
837 "Size mismatch when transmuting!\nsrc: {:#?}\ndest: {:#?}", src, dest);
839 // The hard case is `ScalarPair`. `src` is already read from memory in this case,
840 // using `src.layout` to figure out which bytes to use for the 1st and 2nd field.
841 // We have to write them to `dest` at the offsets they were *read at*, which is
842 // not necessarily the same as the offsets in `dest.layout`!
843 // Hence we do the copy with the source layout on both sides. We also make sure to write
844 // into memory, because if `dest` is a local we would not even have a way to write
845 // at the `src` offsets; the fact that we came from a different layout would
847 let dest = self.force_allocation(dest)?;
848 self.copy_op_no_validate(
850 PlaceTy::from(MPlaceTy { mplace: *dest, layout: src.layout }),
853 if M::enforce_validity(self) {
854 // Data got changed, better make sure it matches the type!
855 self.validate_operand(dest.into(), vec![], None, /*const_mode*/false)?;
861 /// Make sure that a place is in memory, and return where it is.
862 /// If the place currently refers to a local that doesn't yet have a matching allocation,
863 /// create such an allocation.
864 /// This is essentially `force_to_memplace`.
865 pub fn force_allocation(
867 place: PlaceTy<'tcx, M::PointerTag>,
868 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
869 let mplace = match place.place {
870 Place::Local { frame, local } => {
871 match *self.stack[frame].locals[local].access()? {
872 Operand::Indirect(mplace) => mplace,
873 Operand::Immediate(value) => {
874 // We need to make an allocation.
875 // FIXME: Consider not doing anything for a ZST, and just returning
876 // a fake pointer? Are we even called for ZST?
878 // We need the layout of the local. We can NOT use the layout we got,
879 // that might e.g. be an inner field of a struct with `Scalar` layout,
880 // that has different alignment than the outer field.
881 let local_layout = self.layout_of_local(&self.stack[frame], local)?;
882 let ptr = self.allocate(local_layout, MemoryKind::Stack)?;
883 // We don't have to validate as we can assume the local
884 // was already valid for its type.
885 self.write_immediate_to_mplace_no_validate(value, ptr)?;
886 let mplace = ptr.mplace;
888 *self.stack[frame].locals[local].access_mut()? =
889 Operand::Indirect(mplace);
894 Place::Ptr(mplace) => mplace
896 // Return with the original layout, so that the caller can go on
897 Ok(MPlaceTy { mplace, layout: place.layout })
902 layout: TyLayout<'tcx>,
903 kind: MemoryKind<M::MemoryKinds>,
904 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
905 if layout.is_unsized() {
906 assert!(self.tcx.features().unsized_locals, "cannot alloc memory for unsized type");
907 // FIXME: What should we do here? We should definitely also tag!
908 Ok(MPlaceTy::dangling(layout, self))
910 let ptr = self.memory.allocate(layout.size, layout.align, kind)?;
911 let ptr = M::tag_new_allocation(self, ptr, kind)?;
912 Ok(MPlaceTy::from_aligned_ptr(ptr, layout))
916 pub fn write_discriminant_index(
918 variant_index: VariantIdx,
919 dest: PlaceTy<'tcx, M::PointerTag>,
920 ) -> EvalResult<'tcx> {
921 match dest.layout.variants {
922 layout::Variants::Single { index } => {
923 assert_eq!(index, variant_index);
925 layout::Variants::Tagged { ref tag, .. } => {
926 let adt_def = dest.layout.ty.ty_adt_def().unwrap();
927 assert!(variant_index.as_usize() < adt_def.variants.len());
928 let discr_val = adt_def
929 .discriminant_for_variant(*self.tcx, variant_index)
932 // raw discriminants for enums are isize or bigger during
933 // their computation, but the in-memory tag is the smallest possible
935 let size = tag.value.size(self);
936 let shift = 128 - size.bits();
937 let discr_val = (discr_val << shift) >> shift;
939 let discr_dest = self.place_field(dest, 0)?;
940 self.write_scalar(Scalar::from_uint(discr_val, size), discr_dest)?;
942 layout::Variants::NicheFilling {
949 variant_index.as_usize() < dest.layout.ty.ty_adt_def().unwrap().variants.len(),
951 if variant_index != dataful_variant {
953 self.place_field(dest, 0)?;
954 let niche_value = variant_index.as_u32() - niche_variants.start().as_u32();
955 let niche_value = (niche_value as u128)
956 .wrapping_add(niche_start);
958 Scalar::from_uint(niche_value, niche_dest.layout.size),
968 /// Every place can be read from, so we can turm them into an operand
972 place: PlaceTy<'tcx, M::PointerTag>
973 ) -> EvalResult<'tcx, OpTy<'tcx, M::PointerTag>> {
974 let op = match place.place {
975 Place::Ptr(mplace) => {
976 Operand::Indirect(mplace)
978 Place::Local { frame, local } =>
979 *self.stack[frame].locals[local].access()?
981 Ok(OpTy { op, layout: place.layout })
984 /// Turn a place with a `dyn Trait` type into a place with the actual dynamic type.
985 /// Also return some more information so drop doesn't have to run the same code twice.
986 pub(super) fn unpack_dyn_trait(&self, mplace: MPlaceTy<'tcx, M::PointerTag>)
987 -> EvalResult<'tcx, (ty::Instance<'tcx>, MPlaceTy<'tcx, M::PointerTag>)> {
988 let vtable = mplace.vtable()?; // also sanity checks the type
989 let (instance, ty) = self.read_drop_type_from_vtable(vtable)?;
990 let layout = self.layout_of(ty)?;
992 // More sanity checks
993 if cfg!(debug_assertions) {
994 let (size, align) = self.read_size_and_align_from_vtable(vtable)?;
995 assert_eq!(size, layout.size);
996 assert_eq!(align.abi(), layout.align.abi()); // only ABI alignment is preserved
999 let mplace = MPlaceTy {
1000 mplace: MemPlace { meta: None, ..*mplace },
1003 Ok((instance, mplace))