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};
24 GlobalId, AllocId, Allocation, Scalar, EvalResult, Pointer, PointerArithmetic,
25 EvalContext, Machine, AllocMap, AllocationExtra,
26 RawConst, Immediate, ImmTy, ScalarMaybeUndef, Operand, OpTy, MemoryKind
29 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
30 pub struct MemPlace<Tag=(), Id=AllocId> {
31 /// A place may have an integral pointer for ZSTs, and since it might
32 /// be turned back into a reference before ever being dereferenced.
33 /// However, it may never be undef.
34 pub ptr: Scalar<Tag, Id>,
36 /// Metadata for unsized places. Interpretation is up to the type.
37 /// Must not be present for sized types, but can be missing for unsized types
38 /// (e.g., `extern type`).
39 pub meta: Option<Scalar<Tag, Id>>,
42 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
43 pub enum Place<Tag=(), Id=AllocId> {
44 /// A place referring to a value allocated in the `Memory` system.
45 Ptr(MemPlace<Tag, Id>),
47 /// To support alloc-free locals, we are able to write directly to a local.
48 /// (Without that optimization, we'd just always be a `MemPlace`.)
55 #[derive(Copy, Clone, Debug)]
56 pub struct PlaceTy<'tcx, Tag=()> {
58 pub layout: TyLayout<'tcx>,
61 impl<'tcx, Tag> ::std::ops::Deref for PlaceTy<'tcx, Tag> {
62 type Target = Place<Tag>;
64 fn deref(&self) -> &Place<Tag> {
69 /// A MemPlace with its layout. Constructing it is only possible in this module.
70 #[derive(Copy, Clone, Debug)]
71 pub struct MPlaceTy<'tcx, Tag=()> {
72 mplace: MemPlace<Tag>,
73 pub layout: TyLayout<'tcx>,
76 impl<'tcx, Tag> ::std::ops::Deref for MPlaceTy<'tcx, Tag> {
77 type Target = MemPlace<Tag>;
79 fn deref(&self) -> &MemPlace<Tag> {
84 impl<'tcx, Tag> From<MPlaceTy<'tcx, Tag>> for PlaceTy<'tcx, Tag> {
86 fn from(mplace: MPlaceTy<'tcx, Tag>) -> Self {
88 place: Place::Ptr(mplace.mplace),
96 pub fn with_default_tag<Tag>(self) -> MemPlace<Tag>
100 ptr: self.ptr.with_default_tag(),
102 meta: self.meta.map(Scalar::with_default_tag),
107 impl<Tag> MemPlace<Tag> {
109 pub fn erase_tag(self) -> MemPlace
112 ptr: self.ptr.erase_tag(),
114 meta: self.meta.map(Scalar::erase_tag),
119 pub fn with_tag(self, new_tag: Tag) -> Self
122 ptr: self.ptr.with_tag(new_tag),
129 pub fn from_scalar_ptr(ptr: Scalar<Tag>, align: Align) -> Self {
137 /// Produces a Place that will error if attempted to be read from or written to
139 pub fn null(cx: &impl HasDataLayout) -> Self {
140 Self::from_scalar_ptr(Scalar::ptr_null(cx), Align::from_bytes(1).unwrap())
144 pub fn from_ptr(ptr: Pointer<Tag>, align: Align) -> Self {
145 Self::from_scalar_ptr(ptr.into(), align)
149 pub fn to_scalar_ptr_align(self) -> (Scalar<Tag>, Align) {
150 assert!(self.meta.is_none());
151 (self.ptr, self.align)
154 /// metact the ptr part of the mplace
156 pub fn to_ptr(self) -> EvalResult<'tcx, Pointer<Tag>> {
157 // At this point, we forget about the alignment information --
158 // the place has been turned into a reference, and no matter where it came from,
159 // it now must be aligned.
160 self.to_scalar_ptr_align().0.to_ptr()
163 /// Turn a mplace into a (thin or fat) pointer, as a reference, pointing to the same space.
164 /// This is the inverse of `ref_to_mplace`.
166 pub fn to_ref(self) -> Immediate<Tag> {
168 None => Immediate::Scalar(self.ptr.into()),
169 Some(meta) => Immediate::ScalarPair(self.ptr.into(), meta.into()),
176 meta: Option<Scalar<Tag>>,
177 cx: &impl HasDataLayout,
178 ) -> EvalResult<'tcx, Self> {
180 ptr: self.ptr.ptr_offset(offset, cx)?,
181 align: self.align.restrict_for_offset(offset),
187 impl<'tcx, Tag> MPlaceTy<'tcx, Tag> {
188 /// Produces a MemPlace that works for ZST but nothing else
190 pub fn dangling(layout: TyLayout<'tcx>, cx: &impl HasDataLayout) -> Self {
192 mplace: MemPlace::from_scalar_ptr(
193 Scalar::from_uint(layout.align.abi.bytes(), cx.pointer_size()),
201 pub fn with_tag(self, new_tag: Tag) -> Self
204 mplace: self.mplace.with_tag(new_tag),
213 meta: Option<Scalar<Tag>>,
214 layout: TyLayout<'tcx>,
215 cx: &impl HasDataLayout,
216 ) -> EvalResult<'tcx, Self> {
218 mplace: self.mplace.offset(offset, meta, cx)?,
224 fn from_aligned_ptr(ptr: Pointer<Tag>, layout: TyLayout<'tcx>) -> Self {
225 MPlaceTy { mplace: MemPlace::from_ptr(ptr, layout.align.abi), layout }
229 pub(super) fn len(self, cx: &impl HasDataLayout) -> EvalResult<'tcx, u64> {
230 if self.layout.is_unsized() {
231 // We need to consult `meta` metadata
232 match self.layout.ty.sty {
233 ty::Slice(..) | ty::Str =>
234 return self.mplace.meta.unwrap().to_usize(cx),
235 _ => bug!("len not supported on unsized type {:?}", self.layout.ty),
238 // Go through the layout. There are lots of types that support a length,
240 match self.layout.fields {
241 layout::FieldPlacement::Array { count, .. } => Ok(count),
242 _ => bug!("len not supported on sized type {:?}", self.layout.ty),
248 pub(super) fn vtable(self) -> EvalResult<'tcx, Pointer<Tag>> {
249 match self.layout.ty.sty {
250 ty::Dynamic(..) => self.mplace.meta.unwrap().to_ptr(),
251 _ => bug!("vtable not supported on type {:?}", self.layout.ty),
256 impl<'tcx, Tag: ::std::fmt::Debug> OpTy<'tcx, Tag> {
258 pub fn try_as_mplace(self) -> Result<MPlaceTy<'tcx, Tag>, Immediate<Tag>> {
260 Operand::Indirect(mplace) => Ok(MPlaceTy { mplace, layout: self.layout }),
261 Operand::Immediate(imm) => Err(imm),
266 pub fn to_mem_place(self) -> MPlaceTy<'tcx, Tag> {
267 self.try_as_mplace().unwrap()
271 impl<'tcx, Tag: ::std::fmt::Debug> Place<Tag> {
272 /// Produces a Place that will error if attempted to be read from or written to
274 pub fn null(cx: &impl HasDataLayout) -> Self {
275 Place::Ptr(MemPlace::null(cx))
279 pub fn from_scalar_ptr(ptr: Scalar<Tag>, align: Align) -> Self {
280 Place::Ptr(MemPlace::from_scalar_ptr(ptr, align))
284 pub fn from_ptr(ptr: Pointer<Tag>, align: Align) -> Self {
285 Place::Ptr(MemPlace::from_ptr(ptr, align))
289 pub fn to_mem_place(self) -> MemPlace<Tag> {
291 Place::Ptr(mplace) => mplace,
292 _ => bug!("to_mem_place: expected Place::Ptr, got {:?}", self),
298 pub fn to_scalar_ptr_align(self) -> (Scalar<Tag>, Align) {
299 self.to_mem_place().to_scalar_ptr_align()
303 pub fn to_ptr(self) -> EvalResult<'tcx, Pointer<Tag>> {
304 self.to_mem_place().to_ptr()
308 impl<'tcx, Tag: ::std::fmt::Debug> PlaceTy<'tcx, Tag> {
310 pub fn to_mem_place(self) -> MPlaceTy<'tcx, Tag> {
311 MPlaceTy { mplace: self.place.to_mem_place(), layout: self.layout }
315 // separating the pointer tag for `impl Trait`, see https://github.com/rust-lang/rust/issues/54385
316 impl<'a, 'mir, 'tcx, Tag, M> EvalContext<'a, 'mir, 'tcx, M>
318 // FIXME: Working around https://github.com/rust-lang/rust/issues/54385
319 Tag: ::std::fmt::Debug+Default+Copy+Eq+Hash+'static,
320 M: Machine<'a, 'mir, 'tcx, PointerTag=Tag>,
321 // FIXME: Working around https://github.com/rust-lang/rust/issues/24159
322 M::MemoryMap: AllocMap<AllocId, (MemoryKind<M::MemoryKinds>, Allocation<Tag, M::AllocExtra>)>,
323 M::AllocExtra: AllocationExtra<Tag, M::MemoryExtra>,
325 /// Take a value, which represents a (thin or fat) reference, and make it a place.
326 /// Alignment is just based on the type. This is the inverse of `MemPlace::to_ref()`.
327 /// This does NOT call the "deref" machine hook, so it does NOT count as a
328 /// deref as far as Stacked Borrows is concerned. Use `deref_operand` for that!
329 pub fn ref_to_mplace(
331 val: ImmTy<'tcx, M::PointerTag>,
332 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
333 let pointee_type = val.layout.ty.builtin_deref(true).unwrap().ty;
334 let layout = self.layout_of(pointee_type)?;
336 let mplace = MemPlace {
337 ptr: val.to_scalar_ptr()?,
338 align: layout.align.abi,
339 meta: val.to_meta()?,
341 Ok(MPlaceTy { mplace, layout })
344 // Take an operand, representing a pointer, and dereference it to a place -- that
345 // will always be a MemPlace. Lives in `place.rs` because it creates a place.
346 // This calls the "deref" machine hook, and counts as a deref as far as
347 // Stacked Borrows is concerned.
348 pub fn deref_operand(
350 src: OpTy<'tcx, M::PointerTag>,
351 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
352 let val = self.read_immediate(src)?;
353 trace!("deref to {} on {:?}", val.layout.ty, *val);
354 let mut place = self.ref_to_mplace(val)?;
355 // Pointer tag tracking might want to adjust the tag.
356 let mutbl = match val.layout.ty.sty {
357 // `builtin_deref` considers boxes immutable, that's useless for our purposes
358 ty::Ref(_, _, mutbl) => Some(mutbl),
359 ty::Adt(def, _) if def.is_box() => Some(hir::MutMutable),
360 ty::RawPtr(_) => None,
361 _ => bug!("Unexpected pointer type {}", val.layout.ty.sty),
363 place.mplace.ptr = M::tag_dereference(self, place, mutbl)?;
367 /// Offset a pointer to project to a field. Unlike place_field, this is always
368 /// possible without allocating, so it can take &self. Also return the field's layout.
369 /// This supports both struct and array fields.
373 base: MPlaceTy<'tcx, M::PointerTag>,
375 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
376 // Not using the layout method because we want to compute on u64
377 let offset = match base.layout.fields {
378 layout::FieldPlacement::Arbitrary { ref offsets, .. } =>
379 offsets[usize::try_from(field).unwrap()],
380 layout::FieldPlacement::Array { stride, .. } => {
381 let len = base.len(self)?;
382 assert!(field < len, "Tried to access element {} of array/slice with length {}",
386 layout::FieldPlacement::Union(count) => {
387 assert!(field < count as u64,
388 "Tried to access field {} of union with {} fields", field, count);
389 // Offset is always 0
393 // the only way conversion can fail if is this is an array (otherwise we already panicked
394 // above). In that case, all fields are equal.
395 let field_layout = base.layout.field(self, usize::try_from(field).unwrap_or(0))?;
397 // Offset may need adjustment for unsized fields
398 let (meta, offset) = if field_layout.is_unsized() {
399 // re-use parent metadata to determine dynamic field layout
400 let align = match self.size_and_align_of(base.meta, field_layout)? {
401 Some((_, align)) => align,
402 None if offset == Size::ZERO =>
403 // An extern type at offset 0, we fall back to its static alignment.
404 // FIXME: Once we have made decisions for how to handle size and alignment
405 // of `extern type`, this should be adapted. It is just a temporary hack
406 // to get some code to work that probably ought to work.
407 field_layout.align.abi,
409 bug!("Cannot compute offset for extern type field at non-0 offset"),
411 (base.meta, offset.align_to(align))
413 // base.meta could be present; we might be accessing a sized field of an unsized
418 // We do not look at `base.layout.align` nor `field_layout.align`, unlike
419 // codegen -- mostly to see if we can get away with that
420 base.offset(offset, meta, field_layout, self)
423 // Iterates over all fields of an array. Much more efficient than doing the
424 // same by repeatedly calling `mplace_array`.
425 pub fn mplace_array_fields(
427 base: MPlaceTy<'tcx, Tag>,
429 EvalResult<'tcx, impl Iterator<Item=EvalResult<'tcx, MPlaceTy<'tcx, Tag>>> + 'a>
431 let len = base.len(self)?; // also asserts that we have a type where this makes sense
432 let stride = match base.layout.fields {
433 layout::FieldPlacement::Array { stride, .. } => stride,
434 _ => bug!("mplace_array_fields: expected an array layout"),
436 let layout = base.layout.field(self, 0)?;
437 let dl = &self.tcx.data_layout;
438 Ok((0..len).map(move |i| base.offset(i * stride, None, layout, dl)))
441 pub fn mplace_subslice(
443 base: MPlaceTy<'tcx, M::PointerTag>,
446 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
447 let len = base.len(self)?; // also asserts that we have a type where this makes sense
448 assert!(from <= len - to);
450 // Not using layout method because that works with usize, and does not work with slices
451 // (that have count 0 in their layout).
452 let from_offset = match base.layout.fields {
453 layout::FieldPlacement::Array { stride, .. } =>
455 _ => bug!("Unexpected layout of index access: {:#?}", base.layout),
458 // Compute meta and new layout
459 let inner_len = len - to - from;
460 let (meta, ty) = match base.layout.ty.sty {
461 // It is not nice to match on the type, but that seems to be the only way to
463 ty::Array(inner, _) =>
464 (None, self.tcx.mk_array(inner, inner_len)),
466 let len = Scalar::from_uint(inner_len, self.pointer_size());
467 (Some(len), base.layout.ty)
470 bug!("cannot subslice non-array type: `{:?}`", base.layout.ty),
472 let layout = self.layout_of(ty)?;
473 base.offset(from_offset, meta, layout, self)
476 pub fn mplace_downcast(
478 base: MPlaceTy<'tcx, M::PointerTag>,
480 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
481 // Downcasts only change the layout
482 assert!(base.meta.is_none());
483 Ok(MPlaceTy { layout: base.layout.for_variant(self, variant), ..base })
486 /// Project into an mplace
487 pub fn mplace_projection(
489 base: MPlaceTy<'tcx, M::PointerTag>,
490 proj_elem: &mir::PlaceElem<'tcx>,
491 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
492 use rustc::mir::ProjectionElem::*;
493 Ok(match *proj_elem {
494 Field(field, _) => self.mplace_field(base, field.index() as u64)?,
495 Downcast(_, variant) => self.mplace_downcast(base, variant)?,
496 Deref => self.deref_operand(base.into())?,
499 let n = *self.frame().locals[local].access()?;
500 let n_layout = self.layout_of(self.tcx.types.usize)?;
501 let n = self.read_scalar(OpTy { op: n, layout: n_layout })?;
502 let n = n.to_bits(self.tcx.data_layout.pointer_size)?;
503 self.mplace_field(base, u64::try_from(n).unwrap())?
511 let n = base.len(self)?;
512 assert!(n >= min_length as u64);
514 let index = if from_end {
515 n - u64::from(offset)
520 self.mplace_field(base, index)?
523 Subslice { from, to } =>
524 self.mplace_subslice(base, u64::from(from), u64::from(to))?,
528 /// Get the place of a field inside the place, and also the field's type.
529 /// Just a convenience function, but used quite a bit.
530 /// This is the only projection that might have a side-effect: We cannot project
531 /// into the field of a local `ScalarPair`, we have to first allocate it.
534 base: PlaceTy<'tcx, M::PointerTag>,
536 ) -> EvalResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
537 // FIXME: We could try to be smarter and avoid allocation for fields that span the
539 let mplace = self.force_allocation(base)?;
540 Ok(self.mplace_field(mplace, field)?.into())
543 pub fn place_downcast(
545 base: PlaceTy<'tcx, M::PointerTag>,
547 ) -> EvalResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
548 // Downcast just changes the layout
549 Ok(match base.place {
550 Place::Ptr(mplace) =>
551 self.mplace_downcast(MPlaceTy { mplace, layout: base.layout }, variant)?.into(),
552 Place::Local { .. } => {
553 let layout = base.layout.for_variant(self, variant);
554 PlaceTy { layout, ..base }
559 /// Project into a place
560 pub fn place_projection(
562 base: PlaceTy<'tcx, M::PointerTag>,
563 proj_elem: &mir::ProjectionElem<'tcx, mir::Local, Ty<'tcx>>,
564 ) -> EvalResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
565 use rustc::mir::ProjectionElem::*;
566 Ok(match *proj_elem {
567 Field(field, _) => self.place_field(base, field.index() as u64)?,
568 Downcast(_, variant) => self.place_downcast(base, variant)?,
569 Deref => self.deref_operand(self.place_to_op(base)?)?.into(),
570 // For the other variants, we have to force an allocation.
571 // This matches `operand_projection`.
572 Subslice { .. } | ConstantIndex { .. } | Index(_) => {
573 let mplace = self.force_allocation(base)?;
574 self.mplace_projection(mplace, proj_elem)?.into()
579 /// Evaluate statics and promoteds to an `MPlace`. Used to share some code between
580 /// `eval_place` and `eval_place_to_op`.
581 pub(super) fn eval_place_to_mplace(
583 mir_place: &mir::Place<'tcx>
584 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
585 use rustc::mir::Place::*;
586 Ok(match *mir_place {
587 Promoted(ref promoted) => {
588 let instance = self.frame().instance;
589 self.const_eval_raw(GlobalId {
591 promoted: Some(promoted.0),
595 Static(ref static_) => {
596 let ty = self.monomorphize(static_.ty, self.substs());
597 let layout = self.layout_of(ty)?;
598 let instance = ty::Instance::mono(*self.tcx, static_.def_id);
603 // Just create a lazy reference, so we can support recursive statics.
604 // tcx takes are of assigning every static one and only one unique AllocId.
605 // When the data here is ever actually used, memory will notice,
606 // and it knows how to deal with alloc_id that are present in the
607 // global table but not in its local memory: It calls back into tcx through
608 // a query, triggering the CTFE machinery to actually turn this lazy reference
609 // into a bunch of bytes. IOW, statics are evaluated with CTFE even when
610 // this EvalContext uses another Machine (e.g., in miri). This is what we
611 // want! This way, computing statics works concistently between codegen
612 // and miri: They use the same query to eventually obtain a `ty::Const`
613 // and use that for further computation.
614 let alloc = self.tcx.alloc_map.lock().intern_static(cid.instance.def_id());
615 MPlaceTy::from_aligned_ptr(Pointer::from(alloc).with_default_tag(), layout)
618 _ => bug!("eval_place_to_mplace called on {:?}", mir_place),
622 /// Compute a place. You should only use this if you intend to write into this
623 /// place; for reading, a more efficient alternative is `eval_place_for_read`.
626 mir_place: &mir::Place<'tcx>
627 ) -> EvalResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
628 use rustc::mir::Place::*;
629 let place = match *mir_place {
630 Local(mir::RETURN_PLACE) => match self.frame().return_place {
631 Some(return_place) =>
632 // We use our layout to verify our assumption; caller will validate
633 // their layout on return.
635 place: *return_place,
636 layout: self.layout_of_local(self.frame(), mir::RETURN_PLACE)?,
638 None => return err!(InvalidNullPointerUsage),
640 Local(local) => PlaceTy {
641 place: Place::Local {
642 frame: self.cur_frame(),
645 layout: self.layout_of_local(self.frame(), local)?,
648 Projection(ref proj) => {
649 let place = self.eval_place(&proj.base)?;
650 self.place_projection(place, &proj.elem)?
653 _ => self.eval_place_to_mplace(mir_place)?.into(),
656 self.dump_place(place.place);
660 /// Write a scalar to a place
663 val: impl Into<ScalarMaybeUndef<M::PointerTag>>,
664 dest: PlaceTy<'tcx, M::PointerTag>,
665 ) -> EvalResult<'tcx> {
666 self.write_immediate(Immediate::Scalar(val.into()), dest)
669 /// Write an immediate to a place
671 pub fn write_immediate(
673 src: Immediate<M::PointerTag>,
674 dest: PlaceTy<'tcx, M::PointerTag>,
675 ) -> EvalResult<'tcx> {
676 self.write_immediate_no_validate(src, dest)?;
678 if M::enforce_validity(self) {
679 // Data got changed, better make sure it matches the type!
680 self.validate_operand(self.place_to_op(dest)?, vec![], None, /*const_mode*/false)?;
686 /// Write an immediate to a place.
687 /// If you use this you are responsible for validating that things got copied at the
689 fn write_immediate_no_validate(
691 src: Immediate<M::PointerTag>,
692 dest: PlaceTy<'tcx, M::PointerTag>,
693 ) -> EvalResult<'tcx> {
694 if cfg!(debug_assertions) {
695 // This is a very common path, avoid some checks in release mode
696 assert!(!dest.layout.is_unsized(), "Cannot write unsized data");
698 Immediate::Scalar(ScalarMaybeUndef::Scalar(Scalar::Ptr(_))) =>
699 assert_eq!(self.pointer_size(), dest.layout.size,
700 "Size mismatch when writing pointer"),
701 Immediate::Scalar(ScalarMaybeUndef::Scalar(Scalar::Bits { size, .. })) =>
702 assert_eq!(Size::from_bytes(size.into()), dest.layout.size,
703 "Size mismatch when writing bits"),
704 Immediate::Scalar(ScalarMaybeUndef::Undef) => {}, // undef can have any size
705 Immediate::ScalarPair(_, _) => {
706 // FIXME: Can we check anything here?
710 trace!("write_immediate: {:?} <- {:?}: {}", *dest, src, dest.layout.ty);
712 // See if we can avoid an allocation. This is the counterpart to `try_read_immediate`,
713 // but not factored as a separate function.
714 let mplace = match dest.place {
715 Place::Local { frame, local } => {
716 match *self.stack[frame].locals[local].access_mut()? {
717 Operand::Immediate(ref mut dest_val) => {
718 // Yay, we can just change the local directly.
722 Operand::Indirect(mplace) => mplace, // already in memory
725 Place::Ptr(mplace) => mplace, // already in memory
727 let dest = MPlaceTy { mplace, layout: dest.layout };
729 // This is already in memory, write there.
730 self.write_immediate_to_mplace_no_validate(src, dest)
733 /// Write an immediate to memory.
734 /// If you use this you are responsible for validating that things git copied at the
736 fn write_immediate_to_mplace_no_validate(
738 value: Immediate<M::PointerTag>,
739 dest: MPlaceTy<'tcx, M::PointerTag>,
740 ) -> EvalResult<'tcx> {
741 let (ptr, ptr_align) = dest.to_scalar_ptr_align();
742 // Note that it is really important that the type here is the right one, and matches the
743 // type things are read at. In case `src_val` is a `ScalarPair`, we don't do any magic here
744 // to handle padding properly, which is only correct if we never look at this data with the
747 // Nothing to do for ZSTs, other than checking alignment
748 if dest.layout.is_zst() {
749 return self.memory.check_align(ptr, ptr_align);
752 // check for integer pointers before alignment to report better errors
753 let ptr = ptr.to_ptr()?;
754 self.memory.check_align(ptr.into(), ptr_align)?;
755 let tcx = &*self.tcx;
756 // FIXME: We should check that there are dest.layout.size many bytes available in
757 // memory. The code below is not sufficient, with enough padding it might not
758 // cover all the bytes!
760 Immediate::Scalar(scalar) => {
761 match dest.layout.abi {
762 layout::Abi::Scalar(_) => {}, // fine
763 _ => bug!("write_immediate_to_mplace: invalid Scalar layout: {:#?}",
766 self.memory.get_mut(ptr.alloc_id)?.write_scalar(
767 tcx, ptr, scalar, dest.layout.size
770 Immediate::ScalarPair(a_val, b_val) => {
771 let (a, b) = match dest.layout.abi {
772 layout::Abi::ScalarPair(ref a, ref b) => (&a.value, &b.value),
773 _ => bug!("write_immediate_to_mplace: invalid ScalarPair layout: {:#?}",
776 let (a_size, b_size) = (a.size(self), b.size(self));
777 let b_offset = a_size.align_to(b.align(self).abi);
778 let b_align = ptr_align.restrict_for_offset(b_offset);
779 let b_ptr = ptr.offset(b_offset, self)?;
781 self.memory.check_align(b_ptr.into(), b_align)?;
783 // It is tempting to verify `b_offset` against `layout.fields.offset(1)`,
784 // but that does not work: We could be a newtype around a pair, then the
785 // fields do not match the `ScalarPair` components.
788 .get_mut(ptr.alloc_id)?
789 .write_scalar(tcx, ptr, a_val, a_size)?;
791 .get_mut(b_ptr.alloc_id)?
792 .write_scalar(tcx, b_ptr, b_val, b_size)
797 /// Copy the data from an operand to a place. This does not support transmuting!
798 /// Use `copy_op_transmute` if the layouts could disagree.
802 src: OpTy<'tcx, M::PointerTag>,
803 dest: PlaceTy<'tcx, M::PointerTag>,
804 ) -> EvalResult<'tcx> {
805 self.copy_op_no_validate(src, dest)?;
807 if M::enforce_validity(self) {
808 // Data got changed, better make sure it matches the type!
809 self.validate_operand(self.place_to_op(dest)?, vec![], None, /*const_mode*/false)?;
815 /// Copy the data from an operand to a place. This does not support transmuting!
816 /// Use `copy_op_transmute` if the layouts could disagree.
817 /// Also, if you use this you are responsible for validating that things git copied at the
819 fn copy_op_no_validate(
821 src: OpTy<'tcx, M::PointerTag>,
822 dest: PlaceTy<'tcx, M::PointerTag>,
823 ) -> EvalResult<'tcx> {
824 debug_assert!(!src.layout.is_unsized() && !dest.layout.is_unsized(),
825 "Cannot copy unsized data");
826 // We do NOT compare the types for equality, because well-typed code can
827 // actually "transmute" `&mut T` to `&T` in an assignment without a cast.
828 assert!(src.layout.details == dest.layout.details,
829 "Layout mismatch when copying!\nsrc: {:#?}\ndest: {:#?}", src, dest);
831 // Let us see if the layout is simple so we take a shortcut, avoid force_allocation.
832 let src = match self.try_read_immediate(src)? {
834 // Yay, we got a value that we can write directly.
835 return self.write_immediate_no_validate(src_val, dest);
837 Err(mplace) => mplace,
839 // Slow path, this does not fit into an immediate. Just memcpy.
840 trace!("copy_op: {:?} <- {:?}: {}", *dest, src, dest.layout.ty);
842 let dest = self.force_allocation(dest)?;
843 let (src_ptr, src_align) = src.to_scalar_ptr_align();
844 let (dest_ptr, dest_align) = dest.to_scalar_ptr_align();
847 dest_ptr, dest_align,
848 dest.layout.size, false
854 /// Copy the data from an operand to a place. The layouts may disagree, but they must
855 /// have the same size.
856 pub fn copy_op_transmute(
858 src: OpTy<'tcx, M::PointerTag>,
859 dest: PlaceTy<'tcx, M::PointerTag>,
860 ) -> EvalResult<'tcx> {
861 if src.layout.details == dest.layout.details {
862 // Fast path: Just use normal `copy_op`
863 return self.copy_op(src, dest);
865 // We still require the sizes to match
866 debug_assert!(!src.layout.is_unsized() && !dest.layout.is_unsized(),
867 "Cannot copy unsized data");
868 assert!(src.layout.size == dest.layout.size,
869 "Size mismatch when transmuting!\nsrc: {:#?}\ndest: {:#?}", src, dest);
871 // The hard case is `ScalarPair`. `src` is already read from memory in this case,
872 // using `src.layout` to figure out which bytes to use for the 1st and 2nd field.
873 // We have to write them to `dest` at the offsets they were *read at*, which is
874 // not necessarily the same as the offsets in `dest.layout`!
875 // Hence we do the copy with the source layout on both sides. We also make sure to write
876 // into memory, because if `dest` is a local we would not even have a way to write
877 // at the `src` offsets; the fact that we came from a different layout would
879 let dest = self.force_allocation(dest)?;
880 self.copy_op_no_validate(
882 PlaceTy::from(MPlaceTy { mplace: *dest, layout: src.layout }),
885 if M::enforce_validity(self) {
886 // Data got changed, better make sure it matches the type!
887 self.validate_operand(dest.into(), vec![], None, /*const_mode*/false)?;
893 /// Make sure that a place is in memory, and return where it is.
894 /// If the place currently refers to a local that doesn't yet have a matching allocation,
895 /// create such an allocation.
896 /// This is essentially `force_to_memplace`.
897 pub fn force_allocation(
899 place: PlaceTy<'tcx, M::PointerTag>,
900 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
901 let mplace = match place.place {
902 Place::Local { frame, local } => {
903 match *self.stack[frame].locals[local].access()? {
904 Operand::Indirect(mplace) => mplace,
905 Operand::Immediate(value) => {
906 // We need to make an allocation.
907 // FIXME: Consider not doing anything for a ZST, and just returning
908 // a fake pointer? Are we even called for ZST?
910 // We need the layout of the local. We can NOT use the layout we got,
911 // that might e.g., be an inner field of a struct with `Scalar` layout,
912 // that has different alignment than the outer field.
913 let local_layout = self.layout_of_local(&self.stack[frame], local)?;
914 let ptr = self.allocate(local_layout, MemoryKind::Stack)?;
915 // We don't have to validate as we can assume the local
916 // was already valid for its type.
917 self.write_immediate_to_mplace_no_validate(value, ptr)?;
918 let mplace = ptr.mplace;
920 *self.stack[frame].locals[local].access_mut()? =
921 Operand::Indirect(mplace);
926 Place::Ptr(mplace) => mplace
928 // Return with the original layout, so that the caller can go on
929 Ok(MPlaceTy { mplace, layout: place.layout })
934 layout: TyLayout<'tcx>,
935 kind: MemoryKind<M::MemoryKinds>,
936 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
937 if layout.is_unsized() {
938 assert!(self.tcx.features().unsized_locals, "cannot alloc memory for unsized type");
939 // FIXME: What should we do here? We should definitely also tag!
940 Ok(MPlaceTy::dangling(layout, self))
942 let ptr = self.memory.allocate(layout.size, layout.align.abi, kind)?;
943 let ptr = M::tag_new_allocation(self, ptr, kind)?;
944 Ok(MPlaceTy::from_aligned_ptr(ptr, layout))
948 pub fn write_discriminant_index(
950 variant_index: VariantIdx,
951 dest: PlaceTy<'tcx, M::PointerTag>,
952 ) -> EvalResult<'tcx> {
953 match dest.layout.variants {
954 layout::Variants::Single { index } => {
955 assert_eq!(index, variant_index);
957 layout::Variants::Tagged { ref tag, .. } => {
958 let adt_def = dest.layout.ty.ty_adt_def().unwrap();
959 assert!(variant_index.as_usize() < adt_def.variants.len());
960 let discr_val = adt_def
961 .discriminant_for_variant(*self.tcx, variant_index)
964 // raw discriminants for enums are isize or bigger during
965 // their computation, but the in-memory tag is the smallest possible
967 let size = tag.value.size(self);
968 let shift = 128 - size.bits();
969 let discr_val = (discr_val << shift) >> shift;
971 let discr_dest = self.place_field(dest, 0)?;
972 self.write_scalar(Scalar::from_uint(discr_val, size), discr_dest)?;
974 layout::Variants::NicheFilling {
981 variant_index.as_usize() < dest.layout.ty.ty_adt_def().unwrap().variants.len(),
983 if variant_index != dataful_variant {
985 self.place_field(dest, 0)?;
986 let niche_value = variant_index.as_u32() - niche_variants.start().as_u32();
987 let niche_value = (niche_value as u128)
988 .wrapping_add(niche_start);
990 Scalar::from_uint(niche_value, niche_dest.layout.size),
1000 /// Every place can be read from, so we can turm them into an operand
1004 place: PlaceTy<'tcx, M::PointerTag>
1005 ) -> EvalResult<'tcx, OpTy<'tcx, M::PointerTag>> {
1006 let op = match place.place {
1007 Place::Ptr(mplace) => {
1008 Operand::Indirect(mplace)
1010 Place::Local { frame, local } =>
1011 *self.stack[frame].locals[local].access()?
1013 Ok(OpTy { op, layout: place.layout })
1016 pub fn raw_const_to_mplace(
1018 raw: RawConst<'tcx>,
1019 ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
1020 // This must be an allocation in `tcx`
1021 assert!(self.tcx.alloc_map.lock().get(raw.alloc_id).is_some());
1022 let layout = self.layout_of(raw.ty)?;
1023 Ok(MPlaceTy::from_aligned_ptr(
1024 Pointer::new(raw.alloc_id, Size::ZERO).with_default_tag(),
1029 /// Turn a place with a `dyn Trait` type into a place with the actual dynamic type.
1030 /// Also return some more information so drop doesn't have to run the same code twice.
1031 pub(super) fn unpack_dyn_trait(&self, mplace: MPlaceTy<'tcx, M::PointerTag>)
1032 -> EvalResult<'tcx, (ty::Instance<'tcx>, MPlaceTy<'tcx, M::PointerTag>)> {
1033 let vtable = mplace.vtable()?; // also sanity checks the type
1034 let (instance, ty) = self.read_drop_type_from_vtable(vtable)?;
1035 let layout = self.layout_of(ty)?;
1037 // More sanity checks
1038 if cfg!(debug_assertions) {
1039 let (size, align) = self.read_size_and_align_from_vtable(vtable)?;
1040 assert_eq!(size, layout.size);
1041 // only ABI alignment is preserved
1042 assert_eq!(align, layout.align.abi);
1045 let mplace = MPlaceTy {
1046 mplace: MemPlace { meta: None, ..*mplace },
1049 Ok((instance, mplace))