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 rustc_ast
::Mutability
;
8 use rustc_middle
::ty
::layout
::{LayoutOf, PrimitiveExt, TyAndLayout}
;
9 use rustc_target
::abi
::{self, Abi, Align, HasDataLayout, Size, TagEncoding, VariantIdx}
;
12 alloc_range
, mir_assign_valid_types
, AllocId
, AllocRef
, AllocRefMut
, CheckInAllocMsg
,
13 ConstAlloc
, ImmTy
, Immediate
, InterpCx
, InterpResult
, Machine
, MemoryKind
, OpTy
, Operand
,
14 Pointer
, Provenance
, Scalar
,
17 #[derive(Copy, Clone, Hash, PartialEq, Eq, Debug)]
18 /// Information required for the sound usage of a `MemPlace`.
19 pub enum MemPlaceMeta
<Prov
: Provenance
= AllocId
> {
20 /// The unsized payload (e.g. length for slices or vtable pointer for trait objects).
22 /// `Sized` types or unsized `extern type`
26 impl<Prov
: Provenance
> MemPlaceMeta
<Prov
> {
27 pub fn unwrap_meta(self) -> Scalar
<Prov
> {
31 bug
!("expected wide pointer extra data (e.g. slice length or trait object vtable)")
36 pub fn has_meta(self) -> bool
{
38 Self::Meta(_
) => true,
44 #[derive(Copy, Clone, Hash, PartialEq, Eq, Debug)]
45 pub struct MemPlace
<Prov
: Provenance
= AllocId
> {
46 /// The pointer can be a pure integer, with the `None` provenance.
47 pub ptr
: Pointer
<Option
<Prov
>>,
48 /// Metadata for unsized places. Interpretation is up to the type.
49 /// Must not be present for sized types, but can be missing for unsized types
50 /// (e.g., `extern type`).
51 pub meta
: MemPlaceMeta
<Prov
>,
54 /// A MemPlace with its layout. Constructing it is only possible in this module.
55 #[derive(Copy, Clone, Hash, Eq, PartialEq, Debug)]
56 pub struct MPlaceTy
<'tcx
, Prov
: Provenance
= AllocId
> {
57 mplace
: MemPlace
<Prov
>,
58 pub layout
: TyAndLayout
<'tcx
>,
59 /// rustc does not have a proper way to represent the type of a field of a `repr(packed)` struct:
60 /// it needs to have a different alignment than the field type would usually have.
61 /// So we represent this here with a separate field that "overwrites" `layout.align`.
62 /// This means `layout.align` should never be used for a `MPlaceTy`!
66 #[derive(Copy, Clone, Debug)]
67 pub enum Place
<Prov
: Provenance
= AllocId
> {
68 /// A place referring to a value allocated in the `Memory` system.
71 /// To support alloc-free locals, we are able to write directly to a local.
72 /// (Without that optimization, we'd just always be a `MemPlace`.)
73 Local { frame: usize, local: mir::Local }
,
76 #[derive(Clone, Debug)]
77 pub struct PlaceTy
<'tcx
, Prov
: Provenance
= AllocId
> {
78 place
: Place
<Prov
>, // Keep this private; it helps enforce invariants.
79 pub layout
: TyAndLayout
<'tcx
>,
80 /// rustc does not have a proper way to represent the type of a field of a `repr(packed)` struct:
81 /// it needs to have a different alignment than the field type would usually have.
82 /// So we represent this here with a separate field that "overwrites" `layout.align`.
83 /// This means `layout.align` should never be used for a `PlaceTy`!
87 impl<'tcx
, Prov
: Provenance
> std
::ops
::Deref
for PlaceTy
<'tcx
, Prov
> {
88 type Target
= Place
<Prov
>;
90 fn deref(&self) -> &Place
<Prov
> {
95 impl<'tcx
, Prov
: Provenance
> std
::ops
::Deref
for MPlaceTy
<'tcx
, Prov
> {
96 type Target
= MemPlace
<Prov
>;
98 fn deref(&self) -> &MemPlace
<Prov
> {
103 impl<'tcx
, Prov
: Provenance
> From
<MPlaceTy
<'tcx
, Prov
>> for PlaceTy
<'tcx
, Prov
> {
105 fn from(mplace
: MPlaceTy
<'tcx
, Prov
>) -> Self {
106 PlaceTy { place: Place::Ptr(*mplace), layout: mplace.layout, align: mplace.align }
110 impl<'tcx
, Prov
: Provenance
> From
<&'_ MPlaceTy
<'tcx
, Prov
>> for PlaceTy
<'tcx
, Prov
> {
112 fn from(mplace
: &MPlaceTy
<'tcx
, Prov
>) -> Self {
113 PlaceTy { place: Place::Ptr(**mplace), layout: mplace.layout, align: mplace.align }
117 impl<'tcx
, Prov
: Provenance
> From
<&'_
mut MPlaceTy
<'tcx
, Prov
>> for PlaceTy
<'tcx
, Prov
> {
119 fn from(mplace
: &mut MPlaceTy
<'tcx
, Prov
>) -> Self {
120 PlaceTy { place: Place::Ptr(**mplace), layout: mplace.layout, align: mplace.align }
124 impl<Prov
: Provenance
> MemPlace
<Prov
> {
126 pub fn from_ptr(ptr
: Pointer
<Option
<Prov
>>) -> Self {
127 MemPlace { ptr, meta: MemPlaceMeta::None }
130 /// Adjust the provenance of the main pointer (metadata is unaffected).
131 pub fn map_provenance(self, f
: impl FnOnce(Option
<Prov
>) -> Option
<Prov
>) -> Self {
132 MemPlace { ptr: self.ptr.map_provenance(f), ..self }
135 /// Turn a mplace into a (thin or wide) pointer, as a reference, pointing to the same space.
136 /// This is the inverse of `ref_to_mplace`.
138 pub fn to_ref(self, cx
: &impl HasDataLayout
) -> Immediate
<Prov
> {
140 MemPlaceMeta
::None
=> Immediate
::from(Scalar
::from_maybe_pointer(self.ptr
, cx
)),
141 MemPlaceMeta
::Meta(meta
) => {
142 Immediate
::ScalarPair(Scalar
::from_maybe_pointer(self.ptr
, cx
).into(), meta
.into())
148 pub fn offset_with_meta
<'tcx
>(
151 meta
: MemPlaceMeta
<Prov
>,
152 cx
: &impl HasDataLayout
,
153 ) -> InterpResult
<'tcx
, Self> {
154 Ok(MemPlace { ptr: self.ptr.offset(offset, cx)?, meta }
)
158 impl<Prov
: Provenance
> Place
<Prov
> {
159 /// Asserts that this points to some local variable.
160 /// Returns the frame idx and the variable idx.
162 #[cfg_attr(debug_assertions, track_caller)] // only in debug builds due to perf (see #98980)
163 pub fn assert_local(&self) -> (usize, mir
::Local
) {
165 Place
::Local { frame, local }
=> (*frame
, *local
),
166 _
=> bug
!("assert_local: expected Place::Local, got {:?}", self),
171 impl<'tcx
, Prov
: Provenance
> MPlaceTy
<'tcx
, Prov
> {
172 /// Produces a MemPlace that works for ZST but nothing else.
173 /// Conceptually this is a new allocation, but it doesn't actually create an allocation so you
174 /// don't need to worry about memory leaks.
176 pub fn fake_alloc_zst(layout
: TyAndLayout
<'tcx
>) -> Self {
177 assert
!(layout
.is_zst());
178 let align
= layout
.align
.abi
;
179 let ptr
= Pointer
::from_addr(align
.bytes()); // no provenance, absolute address
180 MPlaceTy { mplace: MemPlace { ptr, meta: MemPlaceMeta::None }
, layout
, align
}
184 pub fn offset_with_meta(
187 meta
: MemPlaceMeta
<Prov
>,
188 layout
: TyAndLayout
<'tcx
>,
189 cx
: &impl HasDataLayout
,
190 ) -> InterpResult
<'tcx
, Self> {
192 mplace
: self.mplace
.offset_with_meta(offset
, meta
, cx
)?
,
193 align
: self.align
.restrict_for_offset(offset
),
201 layout
: TyAndLayout
<'tcx
>,
202 cx
: &impl HasDataLayout
,
203 ) -> InterpResult
<'tcx
, Self> {
204 assert
!(!layout
.is_unsized());
205 self.offset_with_meta(offset
, MemPlaceMeta
::None
, layout
, cx
)
209 pub fn from_aligned_ptr(ptr
: Pointer
<Option
<Prov
>>, layout
: TyAndLayout
<'tcx
>) -> Self {
210 MPlaceTy { mplace: MemPlace::from_ptr(ptr), layout, align: layout.align.abi }
214 pub fn from_aligned_ptr_with_meta(
215 ptr
: Pointer
<Option
<Prov
>>,
216 layout
: TyAndLayout
<'tcx
>,
217 meta
: MemPlaceMeta
<Prov
>,
219 let mut mplace
= MemPlace
::from_ptr(ptr
);
222 MPlaceTy { mplace, layout, align: layout.align.abi }
226 pub(crate) fn len(&self, cx
: &impl HasDataLayout
) -> InterpResult
<'tcx
, u64> {
227 if self.layout
.is_unsized() {
228 // We need to consult `meta` metadata
229 match self.layout
.ty
.kind() {
230 ty
::Slice(..) | ty
::Str
=> self.mplace
.meta
.unwrap_meta().to_machine_usize(cx
),
231 _
=> bug
!("len not supported on unsized type {:?}", self.layout
.ty
),
234 // Go through the layout. There are lots of types that support a length,
235 // e.g., SIMD types. (But not all repr(simd) types even have FieldsShape::Array!)
236 match self.layout
.fields
{
237 abi
::FieldsShape
::Array { count, .. }
=> Ok(count
),
238 _
=> bug
!("len not supported on sized type {:?}", self.layout
.ty
),
244 pub(super) fn vtable(&self) -> Scalar
<Prov
> {
245 match self.layout
.ty
.kind() {
246 ty
::Dynamic(..) => self.mplace
.meta
.unwrap_meta(),
247 _
=> bug
!("vtable not supported on type {:?}", self.layout
.ty
),
252 // These are defined here because they produce a place.
253 impl<'tcx
, Prov
: Provenance
> OpTy
<'tcx
, Prov
> {
255 pub fn try_as_mplace(&self) -> Result
<MPlaceTy
<'tcx
, Prov
>, ImmTy
<'tcx
, Prov
>> {
257 Operand
::Indirect(mplace
) => {
258 Ok(MPlaceTy { mplace, layout: self.layout, align: self.align.unwrap() }
)
260 Operand
::Immediate(imm
) => Err(ImmTy
::from_immediate(imm
, self.layout
)),
265 #[cfg_attr(debug_assertions, track_caller)] // only in debug builds due to perf (see #98980)
266 pub fn assert_mem_place(&self) -> MPlaceTy
<'tcx
, Prov
> {
267 self.try_as_mplace().unwrap()
271 impl<'tcx
, Prov
: Provenance
> PlaceTy
<'tcx
, Prov
> {
272 /// A place is either an mplace or some local.
274 pub fn try_as_mplace(&self) -> Result
<MPlaceTy
<'tcx
, Prov
>, (usize, mir
::Local
)> {
276 Place
::Ptr(mplace
) => Ok(MPlaceTy { mplace, layout: self.layout, align: self.align }
),
277 Place
::Local { frame, local }
=> Err((frame
, local
)),
282 #[cfg_attr(debug_assertions, track_caller)] // only in debug builds due to perf (see #98980)
283 pub fn assert_mem_place(&self) -> MPlaceTy
<'tcx
, Prov
> {
284 self.try_as_mplace().unwrap()
288 // FIXME: Working around https://github.com/rust-lang/rust/issues/54385
289 impl<'mir
, 'tcx
: 'mir
, Prov
, M
> InterpCx
<'mir
, 'tcx
, M
>
291 Prov
: Provenance
+ '
static,
292 M
: Machine
<'mir
, 'tcx
, Provenance
= Prov
>,
294 /// Take a value, which represents a (thin or wide) reference, and make it a place.
295 /// Alignment is just based on the type. This is the inverse of `MemPlace::to_ref()`.
297 /// Only call this if you are sure the place is "valid" (aligned and inbounds), or do not
298 /// want to ever use the place for memory access!
299 /// Generally prefer `deref_operand`.
300 pub fn ref_to_mplace(
302 val
: &ImmTy
<'tcx
, M
::Provenance
>,
303 ) -> InterpResult
<'tcx
, MPlaceTy
<'tcx
, M
::Provenance
>> {
305 val
.layout
.ty
.builtin_deref(true).expect("`ref_to_mplace` called on non-ptr type").ty
;
306 let layout
= self.layout_of(pointee_type
)?
;
307 let (ptr
, meta
) = match **val
{
308 Immediate
::Scalar(ptr
) => (ptr
, MemPlaceMeta
::None
),
309 Immediate
::ScalarPair(ptr
, meta
) => (ptr
, MemPlaceMeta
::Meta(meta
)),
310 Immediate
::Uninit
=> throw_ub
!(InvalidUninitBytes(None
)),
313 let mplace
= MemPlace { ptr: ptr.to_pointer(self)?, meta }
;
314 // When deref'ing a pointer, the *static* alignment given by the type is what matters.
315 let align
= layout
.align
.abi
;
316 Ok(MPlaceTy { mplace, layout, align }
)
319 /// Take an operand, representing a pointer, and dereference it to a place -- that
320 /// will always be a MemPlace. Lives in `place.rs` because it creates a place.
321 #[instrument(skip(self), level = "debug")]
322 pub fn deref_operand(
324 src
: &OpTy
<'tcx
, M
::Provenance
>,
325 ) -> InterpResult
<'tcx
, MPlaceTy
<'tcx
, M
::Provenance
>> {
326 let val
= self.read_immediate(src
)?
;
327 trace
!("deref to {} on {:?}", val
.layout
.ty
, *val
);
329 if val
.layout
.ty
.is_box() {
330 bug
!("dereferencing {:?}", val
.layout
.ty
);
333 let mplace
= self.ref_to_mplace(&val
)?
;
334 self.check_mplace_access(mplace
, CheckInAllocMsg
::DerefTest
)?
;
339 pub(super) fn get_place_alloc(
341 place
: &MPlaceTy
<'tcx
, M
::Provenance
>,
342 ) -> InterpResult
<'tcx
, Option
<AllocRef
<'_
, 'tcx
, M
::Provenance
, M
::AllocExtra
>>> {
343 assert
!(!place
.layout
.is_unsized());
344 assert
!(!place
.meta
.has_meta());
345 let size
= place
.layout
.size
;
346 self.get_ptr_alloc(place
.ptr
, size
, place
.align
)
350 pub(super) fn get_place_alloc_mut(
352 place
: &MPlaceTy
<'tcx
, M
::Provenance
>,
353 ) -> InterpResult
<'tcx
, Option
<AllocRefMut
<'_
, 'tcx
, M
::Provenance
, M
::AllocExtra
>>> {
354 assert
!(!place
.layout
.is_unsized());
355 assert
!(!place
.meta
.has_meta());
356 let size
= place
.layout
.size
;
357 self.get_ptr_alloc_mut(place
.ptr
, size
, place
.align
)
360 /// Check if this mplace is dereferenceable and sufficiently aligned.
361 fn check_mplace_access(
363 mplace
: MPlaceTy
<'tcx
, M
::Provenance
>,
364 msg
: CheckInAllocMsg
,
365 ) -> InterpResult
<'tcx
> {
366 let (size
, align
) = self
367 .size_and_align_of_mplace(&mplace
)?
368 .unwrap_or((mplace
.layout
.size
, mplace
.layout
.align
.abi
));
369 assert
!(mplace
.align
<= align
, "dynamic alignment less strict than static one?");
370 let align
= M
::enforce_alignment(self).then_some(align
);
371 self.check_ptr_access_align(mplace
.ptr
, size
, align
.unwrap_or(Align
::ONE
), msg
)?
;
375 /// Converts a repr(simd) place into a place where `place_index` accesses the SIMD elements.
376 /// Also returns the number of elements.
377 pub fn mplace_to_simd(
379 mplace
: &MPlaceTy
<'tcx
, M
::Provenance
>,
380 ) -> InterpResult
<'tcx
, (MPlaceTy
<'tcx
, M
::Provenance
>, u64)> {
381 // Basically we just transmute this place into an array following simd_size_and_type.
382 // (Transmuting is okay since this is an in-memory place. We also double-check the size
384 let (len
, e_ty
) = mplace
.layout
.ty
.simd_size_and_type(*self.tcx
);
385 let array
= self.tcx
.mk_array(e_ty
, len
);
386 let layout
= self.layout_of(array
)?
;
387 assert_eq
!(layout
.size
, mplace
.layout
.size
);
388 Ok((MPlaceTy { layout, ..*mplace }
, len
))
391 /// Converts a repr(simd) place into a place where `place_index` accesses the SIMD elements.
392 /// Also returns the number of elements.
393 pub fn place_to_simd(
395 place
: &PlaceTy
<'tcx
, M
::Provenance
>,
396 ) -> InterpResult
<'tcx
, (MPlaceTy
<'tcx
, M
::Provenance
>, u64)> {
397 let mplace
= self.force_allocation(place
)?
;
398 self.mplace_to_simd(&mplace
)
401 pub fn local_to_place(
405 ) -> InterpResult
<'tcx
, PlaceTy
<'tcx
, M
::Provenance
>> {
406 let layout
= self.layout_of_local(&self.stack()[frame
], local
, None
)?
;
407 let place
= Place
::Local { frame, local }
;
408 Ok(PlaceTy { place, layout, align: layout.align.abi }
)
411 /// Computes a place. You should only use this if you intend to write into this
412 /// place; for reading, a more efficient alternative is `eval_place_to_op`.
413 #[instrument(skip(self), level = "debug")]
416 mir_place
: mir
::Place
<'tcx
>,
417 ) -> InterpResult
<'tcx
, PlaceTy
<'tcx
, M
::Provenance
>> {
418 let mut place
= self.local_to_place(self.frame_idx(), mir_place
.local
)?
;
419 // Using `try_fold` turned out to be bad for performance, hence the loop.
420 for elem
in mir_place
.projection
.iter() {
421 place
= self.place_projection(&place
, elem
)?
424 trace
!("{:?}", self.dump_place(place
.place
));
425 // Sanity-check the type we ended up with.
427 mir_assign_valid_types(
430 self.layout_of(self.subst_from_current_frame_and_normalize_erasing_regions(
431 mir_place
.ty(&self.frame().body
.local_decls
, *self.tcx
).ty
435 "eval_place of a MIR place with type {:?} produced an interpreter place with type {:?}",
436 mir_place
.ty(&self.frame().body
.local_decls
, *self.tcx
).ty
,
442 /// Write an immediate to a place
444 #[instrument(skip(self), level = "debug")]
445 pub fn write_immediate(
447 src
: Immediate
<M
::Provenance
>,
448 dest
: &PlaceTy
<'tcx
, M
::Provenance
>,
449 ) -> InterpResult
<'tcx
> {
450 self.write_immediate_no_validate(src
, dest
)?
;
452 if M
::enforce_validity(self) {
453 // Data got changed, better make sure it matches the type!
454 self.validate_operand(&self.place_to_op(dest
)?
)?
;
460 /// Write a scalar to a place
464 val
: impl Into
<Scalar
<M
::Provenance
>>,
465 dest
: &PlaceTy
<'tcx
, M
::Provenance
>,
466 ) -> InterpResult
<'tcx
> {
467 self.write_immediate(Immediate
::Scalar(val
.into()), dest
)
470 /// Write a pointer to a place
472 pub fn write_pointer(
474 ptr
: impl Into
<Pointer
<Option
<M
::Provenance
>>>,
475 dest
: &PlaceTy
<'tcx
, M
::Provenance
>,
476 ) -> InterpResult
<'tcx
> {
477 self.write_scalar(Scalar
::from_maybe_pointer(ptr
.into(), self), dest
)
480 /// Write an immediate to a place.
481 /// If you use this you are responsible for validating that things got copied at the
483 fn write_immediate_no_validate(
485 src
: Immediate
<M
::Provenance
>,
486 dest
: &PlaceTy
<'tcx
, M
::Provenance
>,
487 ) -> InterpResult
<'tcx
> {
488 assert
!(!dest
.layout
.is_unsized(), "Cannot write unsized data");
489 trace
!("write_immediate: {:?} <- {:?}: {}", *dest
, src
, dest
.layout
.ty
);
491 // See if we can avoid an allocation. This is the counterpart to `read_immediate_raw`,
492 // but not factored as a separate function.
493 let mplace
= match dest
.place
{
494 Place
::Local { frame, local }
=> {
495 match M
::access_local_mut(self, frame
, local
)?
{
496 Operand
::Immediate(local
) => {
497 // Local can be updated in-place.
501 Operand
::Indirect(mplace
) => {
502 // The local is in memory, go on below.
507 Place
::Ptr(mplace
) => mplace
, // already referring to memory
510 // This is already in memory, write there.
511 self.write_immediate_to_mplace_no_validate(src
, dest
.layout
, dest
.align
, mplace
)
514 /// Write an immediate to memory.
515 /// If you use this you are responsible for validating that things got copied at the
517 fn write_immediate_to_mplace_no_validate(
519 value
: Immediate
<M
::Provenance
>,
520 layout
: TyAndLayout
<'tcx
>,
522 dest
: MemPlace
<M
::Provenance
>,
523 ) -> InterpResult
<'tcx
> {
524 // Note that it is really important that the type here is the right one, and matches the
525 // type things are read at. In case `value` is a `ScalarPair`, we don't do any magic here
526 // to handle padding properly, which is only correct if we never look at this data with the
530 let Some(mut alloc
) = self.get_place_alloc_mut(&MPlaceTy { mplace: dest, layout, align }
)?
else {
536 Immediate
::Scalar(scalar
) => {
537 let Abi
::Scalar(s
) = layout
.abi
else { span_bug
!(
539 "write_immediate_to_mplace: invalid Scalar layout: {layout:#?}",
542 let size
= s
.size(&tcx
);
543 assert_eq
!(size
, layout
.size
, "abi::Scalar size does not match layout size");
544 alloc
.write_scalar(alloc_range(Size
::ZERO
, size
), scalar
)
546 Immediate
::ScalarPair(a_val
, b_val
) => {
547 // We checked `ptr_align` above, so all fields will have the alignment they need.
548 // We would anyway check against `ptr_align.restrict_for_offset(b_offset)`,
549 // which `ptr.offset(b_offset)` cannot possibly fail to satisfy.
550 let Abi
::ScalarPair(a
, b
) = layout
.abi
else { span_bug
!(
552 "write_immediate_to_mplace: invalid ScalarPair layout: {:#?}",
556 let (a_size
, b_size
) = (a
.size(&tcx
), b
.size(&tcx
));
557 let b_offset
= a_size
.align_to(b
.align(&tcx
).abi
);
558 assert
!(b_offset
.bytes() > 0); // in `operand_field` we use the offset to tell apart the fields
560 // It is tempting to verify `b_offset` against `layout.fields.offset(1)`,
561 // but that does not work: We could be a newtype around a pair, then the
562 // fields do not match the `ScalarPair` components.
564 alloc
.write_scalar(alloc_range(Size
::ZERO
, a_size
), a_val
)?
;
565 alloc
.write_scalar(alloc_range(b_offset
, b_size
), b_val
)
567 Immediate
::Uninit
=> alloc
.write_uninit(),
571 pub fn write_uninit(&mut self, dest
: &PlaceTy
<'tcx
, M
::Provenance
>) -> InterpResult
<'tcx
> {
572 let mplace
= match dest
.try_as_mplace() {
573 Ok(mplace
) => mplace
,
574 Err((frame
, local
)) => {
575 match M
::access_local_mut(self, frame
, local
)?
{
576 Operand
::Immediate(local
) => {
577 *local
= Immediate
::Uninit
;
580 Operand
::Indirect(mplace
) => {
581 // The local is in memory, go on below.
582 MPlaceTy { mplace: *mplace, layout: dest.layout, align: dest.align }
587 let Some(mut alloc
) = self.get_place_alloc_mut(&mplace
)?
else {
591 alloc
.write_uninit()?
;
595 /// Copies the data from an operand to a place.
596 /// `allow_transmute` indicates whether the layouts may disagree.
598 #[instrument(skip(self), level = "debug")]
601 src
: &OpTy
<'tcx
, M
::Provenance
>,
602 dest
: &PlaceTy
<'tcx
, M
::Provenance
>,
603 allow_transmute
: bool
,
604 ) -> InterpResult
<'tcx
> {
605 self.copy_op_no_validate(src
, dest
, allow_transmute
)?
;
607 if M
::enforce_validity(self) {
608 // Data got changed, better make sure it matches the type!
609 self.validate_operand(&self.place_to_op(dest
)?
)?
;
615 /// Copies the data from an operand to a place.
616 /// `allow_transmute` indicates whether the layouts may disagree.
617 /// Also, if you use this you are responsible for validating that things get copied at the
619 #[instrument(skip(self), level = "debug")]
620 fn copy_op_no_validate(
622 src
: &OpTy
<'tcx
, M
::Provenance
>,
623 dest
: &PlaceTy
<'tcx
, M
::Provenance
>,
624 allow_transmute
: bool
,
625 ) -> InterpResult
<'tcx
> {
626 // We do NOT compare the types for equality, because well-typed code can
627 // actually "transmute" `&mut T` to `&T` in an assignment without a cast.
629 mir_assign_valid_types(*self.tcx
, self.param_env
, src
.layout
, dest
.layout
);
630 if !allow_transmute
&& !layout_compat
{
633 "type mismatch when copying!\nsrc: {:?},\ndest: {:?}",
639 // Let us see if the layout is simple so we take a shortcut,
640 // avoid force_allocation.
641 let src
= match self.read_immediate_raw(src
)?
{
643 // FIXME(const_prop): Const-prop can possibly evaluate an
644 // unsized copy operation when it thinks that the type is
645 // actually sized, due to a trivially false where-clause
646 // predicate like `where Self: Sized` with `Self = dyn Trait`.
647 // See #102553 for an example of such a predicate.
648 if src
.layout
.is_unsized() {
649 throw_inval
!(SizeOfUnsizedType(src
.layout
.ty
));
651 if dest
.layout
.is_unsized() {
652 throw_inval
!(SizeOfUnsizedType(dest
.layout
.ty
));
654 assert_eq
!(src
.layout
.size
, dest
.layout
.size
);
655 // Yay, we got a value that we can write directly.
656 return if layout_compat
{
657 self.write_immediate_no_validate(*src_val
, dest
)
659 // This is tricky. The problematic case is `ScalarPair`: the `src_val` was
660 // loaded using the offsets defined by `src.layout`. When we put this back into
661 // the destination, we have to use the same offsets! So (a) we make sure we
662 // write back to memory, and (b) we use `dest` *with the source layout*.
663 let dest_mem
= self.force_allocation(dest
)?
;
664 self.write_immediate_to_mplace_no_validate(
672 Err(mplace
) => mplace
,
674 // Slow path, this does not fit into an immediate. Just memcpy.
675 trace
!("copy_op: {:?} <- {:?}: {}", *dest
, src
, dest
.layout
.ty
);
677 let dest
= self.force_allocation(&dest
)?
;
678 let Some((dest_size
, _
)) = self.size_and_align_of_mplace(&dest
)?
else {
679 span_bug
!(self.cur_span(), "copy_op needs (dynamically) sized values")
681 if cfg
!(debug_assertions
) {
682 let src_size
= self.size_and_align_of_mplace(&src
)?
.unwrap().0;
683 assert_eq
!(src_size
, dest_size
, "Cannot copy differently-sized data");
685 // As a cheap approximation, we compare the fixed parts of the size.
686 assert_eq
!(src
.layout
.size
, dest
.layout
.size
);
690 src
.ptr
, src
.align
, dest
.ptr
, dest
.align
, dest_size
, /*nonoverlapping*/ false,
694 /// Ensures that a place is in memory, and returns where it is.
695 /// If the place currently refers to a local that doesn't yet have a matching allocation,
696 /// create such an allocation.
697 /// This is essentially `force_to_memplace`.
698 #[instrument(skip(self), level = "debug")]
699 pub fn force_allocation(
701 place
: &PlaceTy
<'tcx
, M
::Provenance
>,
702 ) -> InterpResult
<'tcx
, MPlaceTy
<'tcx
, M
::Provenance
>> {
703 let mplace
= match place
.place
{
704 Place
::Local { frame, local }
=> {
705 match M
::access_local_mut(self, frame
, local
)?
{
706 &mut Operand
::Immediate(local_val
) => {
707 // We need to make an allocation.
709 // We need the layout of the local. We can NOT use the layout we got,
710 // that might e.g., be an inner field of a struct with `Scalar` layout,
711 // that has different alignment than the outer field.
713 self.layout_of_local(&self.stack()[frame
], local
, None
)?
;
714 if local_layout
.is_unsized() {
715 throw_unsup_format
!("unsized locals are not supported");
717 let mplace
= *self.allocate(local_layout
, MemoryKind
::Stack
)?
;
718 if !matches
!(local_val
, Immediate
::Uninit
) {
719 // Preserve old value. (As an optimization, we can skip this if it was uninit.)
720 // We don't have to validate as we can assume the local
721 // was already valid for its type.
722 self.write_immediate_to_mplace_no_validate(
725 local_layout
.align
.abi
,
729 // Now we can call `access_mut` again, asserting it goes well,
730 // and actually overwrite things.
731 *M
::access_local_mut(self, frame
, local
).unwrap() =
732 Operand
::Indirect(mplace
);
735 &mut Operand
::Indirect(mplace
) => mplace
, // this already was an indirect local
738 Place
::Ptr(mplace
) => mplace
,
740 // Return with the original layout, so that the caller can go on
741 Ok(MPlaceTy { mplace, layout: place.layout, align: place.align }
)
746 layout
: TyAndLayout
<'tcx
>,
747 kind
: MemoryKind
<M
::MemoryKind
>,
748 ) -> InterpResult
<'tcx
, MPlaceTy
<'tcx
, M
::Provenance
>> {
749 assert
!(!layout
.is_unsized());
750 let ptr
= self.allocate_ptr(layout
.size
, layout
.align
.abi
, kind
)?
;
751 Ok(MPlaceTy
::from_aligned_ptr(ptr
.into(), layout
))
754 /// Returns a wide MPlace of type `&'static [mut] str` to a new 1-aligned allocation.
758 kind
: MemoryKind
<M
::MemoryKind
>,
760 ) -> MPlaceTy
<'tcx
, M
::Provenance
> {
761 let ptr
= self.allocate_bytes_ptr(str.as_bytes(), Align
::ONE
, kind
, mutbl
);
762 let meta
= Scalar
::from_machine_usize(u64::try_from(str.len()).unwrap(), self);
763 let mplace
= MemPlace { ptr: ptr.into(), meta: MemPlaceMeta::Meta(meta) }
;
765 let ty
= self.tcx
.mk_ref(
766 self.tcx
.lifetimes
.re_static
,
767 ty
::TypeAndMut { ty: self.tcx.types.str_, mutbl }
,
769 let layout
= self.layout_of(ty
).unwrap();
770 MPlaceTy { mplace, layout, align: layout.align.abi }
773 /// Writes the discriminant of the given variant.
774 #[instrument(skip(self), level = "debug")]
775 pub fn write_discriminant(
777 variant_index
: VariantIdx
,
778 dest
: &PlaceTy
<'tcx
, M
::Provenance
>,
779 ) -> InterpResult
<'tcx
> {
780 // This must be an enum or generator.
781 match dest
.layout
.ty
.kind() {
782 ty
::Adt(adt
, _
) => assert
!(adt
.is_enum()),
783 ty
::Generator(..) => {}
786 "write_discriminant called on non-variant-type (neither enum nor generator)"
789 // Layout computation excludes uninhabited variants from consideration
790 // therefore there's no way to represent those variants in the given layout.
791 // Essentially, uninhabited variants do not have a tag that corresponds to their
792 // discriminant, so we cannot do anything here.
793 // When evaluating we will always error before even getting here, but ConstProp 'executes'
794 // dead code, so we cannot ICE here.
795 if dest
.layout
.for_variant(self, variant_index
).abi
.is_uninhabited() {
796 throw_ub
!(UninhabitedEnumVariantWritten
)
799 match dest
.layout
.variants
{
800 abi
::Variants
::Single { index }
=> {
801 assert_eq
!(index
, variant_index
);
803 abi
::Variants
::Multiple
{
804 tag_encoding
: TagEncoding
::Direct
,
809 // No need to validate that the discriminant here because the
810 // `TyAndLayout::for_variant()` call earlier already checks the variant is valid.
813 dest
.layout
.ty
.discriminant_for_variant(*self.tcx
, variant_index
).unwrap().val
;
815 // raw discriminants for enums are isize or bigger during
816 // their computation, but the in-memory tag is the smallest possible
818 let size
= tag_layout
.size(self);
819 let tag_val
= size
.truncate(discr_val
);
821 let tag_dest
= self.place_field(dest
, tag_field
)?
;
822 self.write_scalar(Scalar
::from_uint(tag_val
, size
), &tag_dest
)?
;
824 abi
::Variants
::Multiple
{
826 TagEncoding
::Niche { untagged_variant, ref niche_variants, niche_start }
,
831 // No need to validate that the discriminant here because the
832 // `TyAndLayout::for_variant()` call earlier already checks the variant is valid.
834 if variant_index
!= untagged_variant
{
835 let variants_start
= niche_variants
.start().as_u32();
836 let variant_index_relative
= variant_index
838 .checked_sub(variants_start
)
839 .expect("overflow computing relative variant idx");
840 // We need to use machine arithmetic when taking into account `niche_start`:
841 // tag_val = variant_index_relative + niche_start_val
842 let tag_layout
= self.layout_of(tag_layout
.primitive().to_int_ty(*self.tcx
))?
;
843 let niche_start_val
= ImmTy
::from_uint(niche_start
, tag_layout
);
844 let variant_index_relative_val
=
845 ImmTy
::from_uint(variant_index_relative
, tag_layout
);
846 let tag_val
= self.binary_op(
848 &variant_index_relative_val
,
852 let niche_dest
= self.place_field(dest
, tag_field
)?
;
853 self.write_immediate(*tag_val
, &niche_dest
)?
;
861 pub fn raw_const_to_mplace(
863 raw
: ConstAlloc
<'tcx
>,
864 ) -> InterpResult
<'tcx
, MPlaceTy
<'tcx
, M
::Provenance
>> {
865 // This must be an allocation in `tcx`
866 let _
= self.tcx
.global_alloc(raw
.alloc_id
);
867 let ptr
= self.global_base_pointer(Pointer
::from(raw
.alloc_id
))?
;
868 let layout
= self.layout_of(raw
.ty
)?
;
869 Ok(MPlaceTy
::from_aligned_ptr(ptr
.into(), layout
))
872 /// Turn a place with a `dyn Trait` type into a place with the actual dynamic type.
873 pub(super) fn unpack_dyn_trait(
875 mplace
: &MPlaceTy
<'tcx
, M
::Provenance
>,
876 ) -> InterpResult
<'tcx
, MPlaceTy
<'tcx
, M
::Provenance
>> {
877 let vtable
= mplace
.vtable().to_pointer(self)?
; // also sanity checks the type
878 let (ty
, _
) = self.get_ptr_vtable(vtable
)?
;
879 let layout
= self.layout_of(ty
)?
;
881 let mplace
= MPlaceTy
{
882 mplace
: MemPlace { meta: MemPlaceMeta::None, ..**mplace }
,
884 align
: layout
.align
.abi
,
890 // Some nodes are used a lot. Make sure they don't unintentionally get bigger.
891 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
894 use rustc_data_structures
::static_assert_size
;
895 // tidy-alphabetical-start
896 static_assert_size
!(MemPlace
, 40);
897 static_assert_size
!(MemPlaceMeta
, 24);
898 static_assert_size
!(MPlaceTy
<'_
>, 64);
899 static_assert_size
!(Place
, 40);
900 static_assert_size
!(PlaceTy
<'_
>, 64);
901 // tidy-alphabetical-end