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//! Computations on places -- field projections, going from mir::Place, and writing
//! into a place.
//! All high-level functions to write to memory work on places as destinations.
use std::assert_matches::assert_matches;
use either::{Either, Left, Right};
use rustc_ast::Mutability;
use rustc_index::IndexSlice;
use rustc_middle::mir;
use rustc_middle::ty;
use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
use rustc_middle::ty::Ty;
use rustc_target::abi::{Abi, Align, FieldIdx, HasDataLayout, Size, FIRST_VARIANT};
use super::{
alloc_range, mir_assign_valid_types, AllocId, AllocRef, AllocRefMut, CheckInAllocMsg, ImmTy,
Immediate, InterpCx, InterpResult, Machine, MemoryKind, OpTy, Operand, Pointer,
PointerArithmetic, Projectable, Provenance, Readable, Scalar,
};
#[derive(Copy, Clone, Hash, PartialEq, Eq, Debug)]
/// Information required for the sound usage of a `MemPlace`.
pub enum MemPlaceMeta<Prov: Provenance = AllocId> {
/// The unsized payload (e.g. length for slices or vtable pointer for trait objects).
Meta(Scalar<Prov>),
/// `Sized` types or unsized `extern type`
None,
}
impl<Prov: Provenance> MemPlaceMeta<Prov> {
#[cfg_attr(debug_assertions, track_caller)] // only in debug builds due to perf (see #98980)
pub fn unwrap_meta(self) -> Scalar<Prov> {
match self {
Self::Meta(s) => s,
Self::None => {
bug!("expected wide pointer extra data (e.g. slice length or trait object vtable)")
}
}
}
#[inline(always)]
pub fn has_meta(self) -> bool {
match self {
Self::Meta(_) => true,
Self::None => false,
}
}
}
#[derive(Copy, Clone, Hash, PartialEq, Eq, Debug)]
pub(super) struct MemPlace<Prov: Provenance = AllocId> {
/// The pointer can be a pure integer, with the `None` provenance.
pub ptr: Pointer<Option<Prov>>,
/// Metadata for unsized places. Interpretation is up to the type.
/// Must not be present for sized types, but can be missing for unsized types
/// (e.g., `extern type`).
pub meta: MemPlaceMeta<Prov>,
}
impl<Prov: Provenance> MemPlace<Prov> {
#[inline(always)]
pub fn from_ptr(ptr: Pointer<Option<Prov>>) -> Self {
MemPlace { ptr, meta: MemPlaceMeta::None }
}
#[inline(always)]
pub fn from_ptr_with_meta(ptr: Pointer<Option<Prov>>, meta: MemPlaceMeta<Prov>) -> Self {
MemPlace { ptr, meta }
}
/// Adjust the provenance of the main pointer (metadata is unaffected).
pub fn map_provenance(self, f: impl FnOnce(Option<Prov>) -> Option<Prov>) -> Self {
MemPlace { ptr: self.ptr.map_provenance(f), ..self }
}
/// Turn a mplace into a (thin or wide) pointer, as a reference, pointing to the same space.
#[inline]
pub fn to_ref(self, cx: &impl HasDataLayout) -> Immediate<Prov> {
match self.meta {
MemPlaceMeta::None => Immediate::from(Scalar::from_maybe_pointer(self.ptr, cx)),
MemPlaceMeta::Meta(meta) => {
Immediate::ScalarPair(Scalar::from_maybe_pointer(self.ptr, cx), meta)
}
}
}
#[inline]
// Not called `offset_with_meta` to avoid confusion with the trait method.
fn offset_with_meta_<'tcx>(
self,
offset: Size,
meta: MemPlaceMeta<Prov>,
cx: &impl HasDataLayout,
) -> InterpResult<'tcx, Self> {
debug_assert!(
!meta.has_meta() || self.meta.has_meta(),
"cannot use `offset_with_meta` to add metadata to a place"
);
Ok(MemPlace { ptr: self.ptr.offset(offset, cx)?, meta })
}
}
/// A MemPlace with its layout. Constructing it is only possible in this module.
#[derive(Clone, Hash, Eq, PartialEq)]
pub struct MPlaceTy<'tcx, Prov: Provenance = AllocId> {
mplace: MemPlace<Prov>,
pub layout: TyAndLayout<'tcx>,
/// rustc does not have a proper way to represent the type of a field of a `repr(packed)` struct:
/// it needs to have a different alignment than the field type would usually have.
/// So we represent this here with a separate field that "overwrites" `layout.align`.
/// This means `layout.align` should never be used for a `MPlaceTy`!
pub align: Align,
}
impl<Prov: Provenance> std::fmt::Debug for MPlaceTy<'_, Prov> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
// Printing `layout` results in too much noise; just print a nice version of the type.
f.debug_struct("MPlaceTy")
.field("mplace", &self.mplace)
.field("ty", &format_args!("{}", self.layout.ty))
.finish()
}
}
impl<'tcx, Prov: Provenance> MPlaceTy<'tcx, Prov> {
/// Produces a MemPlace that works for ZST but nothing else.
/// Conceptually this is a new allocation, but it doesn't actually create an allocation so you
/// don't need to worry about memory leaks.
#[inline]
pub fn fake_alloc_zst(layout: TyAndLayout<'tcx>) -> Self {
assert!(layout.is_zst());
let align = layout.align.abi;
let ptr = Pointer::from_addr_invalid(align.bytes()); // no provenance, absolute address
MPlaceTy { mplace: MemPlace { ptr, meta: MemPlaceMeta::None }, layout, align }
}
#[inline]
pub fn from_aligned_ptr(ptr: Pointer<Option<Prov>>, layout: TyAndLayout<'tcx>) -> Self {
MPlaceTy { mplace: MemPlace::from_ptr(ptr), layout, align: layout.align.abi }
}
#[inline]
pub fn from_aligned_ptr_with_meta(
ptr: Pointer<Option<Prov>>,
layout: TyAndLayout<'tcx>,
meta: MemPlaceMeta<Prov>,
) -> Self {
MPlaceTy {
mplace: MemPlace::from_ptr_with_meta(ptr, meta),
layout,
align: layout.align.abi,
}
}
/// Adjust the provenance of the main pointer (metadata is unaffected).
pub fn map_provenance(self, f: impl FnOnce(Option<Prov>) -> Option<Prov>) -> Self {
MPlaceTy { mplace: self.mplace.map_provenance(f), ..self }
}
#[inline(always)]
pub(super) fn mplace(&self) -> &MemPlace<Prov> {
&self.mplace
}
#[inline(always)]
pub fn ptr(&self) -> Pointer<Option<Prov>> {
self.mplace.ptr
}
#[inline(always)]
pub fn to_ref(&self, cx: &impl HasDataLayout) -> Immediate<Prov> {
self.mplace.to_ref(cx)
}
}
impl<'tcx, Prov: Provenance> Projectable<'tcx, Prov> for MPlaceTy<'tcx, Prov> {
#[inline(always)]
fn layout(&self) -> TyAndLayout<'tcx> {
self.layout
}
#[inline(always)]
fn meta(&self) -> MemPlaceMeta<Prov> {
self.mplace.meta
}
fn offset_with_meta<'mir, M: Machine<'mir, 'tcx, Provenance = Prov>>(
&self,
offset: Size,
meta: MemPlaceMeta<Prov>,
layout: TyAndLayout<'tcx>,
ecx: &InterpCx<'mir, 'tcx, M>,
) -> InterpResult<'tcx, Self> {
Ok(MPlaceTy {
mplace: self.mplace.offset_with_meta_(offset, meta, ecx)?,
align: self.align.restrict_for_offset(offset),
layout,
})
}
fn to_op<'mir, M: Machine<'mir, 'tcx, Provenance = Prov>>(
&self,
_ecx: &InterpCx<'mir, 'tcx, M>,
) -> InterpResult<'tcx, OpTy<'tcx, M::Provenance>> {
Ok(self.clone().into())
}
}
#[derive(Copy, Clone, Debug)]
pub(super) enum Place<Prov: Provenance = AllocId> {
/// A place referring to a value allocated in the `Memory` system.
Ptr(MemPlace<Prov>),
/// To support alloc-free locals, we are able to write directly to a local. The offset indicates
/// where in the local this place is located; if it is `None`, no projection has been applied.
/// Such projections are meaningful even if the offset is 0, since they can change layouts.
/// (Without that optimization, we'd just always be a `MemPlace`.)
/// Note that this only stores the frame index, not the thread this frame belongs to -- that is
/// implicit. This means a `Place` must never be moved across interpreter thread boundaries!
///
/// This variant shall not be used for unsized types -- those must always live in memory.
Local { frame: usize, local: mir::Local, offset: Option<Size> },
}
#[derive(Clone)]
pub struct PlaceTy<'tcx, Prov: Provenance = AllocId> {
place: Place<Prov>, // Keep this private; it helps enforce invariants.
pub layout: TyAndLayout<'tcx>,
/// rustc does not have a proper way to represent the type of a field of a `repr(packed)` struct:
/// it needs to have a different alignment than the field type would usually have.
/// So we represent this here with a separate field that "overwrites" `layout.align`.
/// This means `layout.align` should never be used for a `PlaceTy`!
pub align: Align,
}
impl<Prov: Provenance> std::fmt::Debug for PlaceTy<'_, Prov> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
// Printing `layout` results in too much noise; just print a nice version of the type.
f.debug_struct("PlaceTy")
.field("place", &self.place)
.field("ty", &format_args!("{}", self.layout.ty))
.finish()
}
}
impl<'tcx, Prov: Provenance> From<MPlaceTy<'tcx, Prov>> for PlaceTy<'tcx, Prov> {
#[inline(always)]
fn from(mplace: MPlaceTy<'tcx, Prov>) -> Self {
PlaceTy { place: Place::Ptr(mplace.mplace), layout: mplace.layout, align: mplace.align }
}
}
impl<'tcx, Prov: Provenance> PlaceTy<'tcx, Prov> {
#[inline(always)]
pub(super) fn place(&self) -> &Place<Prov> {
&self.place
}
/// A place is either an mplace or some local.
#[inline(always)]
pub fn as_mplace_or_local(
&self,
) -> Either<MPlaceTy<'tcx, Prov>, (usize, mir::Local, Option<Size>)> {
match self.place {
Place::Ptr(mplace) => Left(MPlaceTy { mplace, layout: self.layout, align: self.align }),
Place::Local { frame, local, offset } => Right((frame, local, offset)),
}
}
#[inline(always)]
#[cfg_attr(debug_assertions, track_caller)] // only in debug builds due to perf (see #98980)
pub fn assert_mem_place(&self) -> MPlaceTy<'tcx, Prov> {
self.as_mplace_or_local().left().unwrap_or_else(|| {
bug!(
"PlaceTy of type {} was a local when it was expected to be an MPlace",
self.layout.ty
)
})
}
}
impl<'tcx, Prov: Provenance> Projectable<'tcx, Prov> for PlaceTy<'tcx, Prov> {
#[inline(always)]
fn layout(&self) -> TyAndLayout<'tcx> {
self.layout
}
#[inline]
fn meta(&self) -> MemPlaceMeta<Prov> {
match self.as_mplace_or_local() {
Left(mplace) => mplace.meta(),
Right(_) => {
debug_assert!(self.layout.is_sized(), "unsized locals should live in memory");
MemPlaceMeta::None
}
}
}
fn offset_with_meta<'mir, M: Machine<'mir, 'tcx, Provenance = Prov>>(
&self,
offset: Size,
meta: MemPlaceMeta<Prov>,
layout: TyAndLayout<'tcx>,
ecx: &InterpCx<'mir, 'tcx, M>,
) -> InterpResult<'tcx, Self> {
Ok(match self.as_mplace_or_local() {
Left(mplace) => mplace.offset_with_meta(offset, meta, layout, ecx)?.into(),
Right((frame, local, old_offset)) => {
debug_assert!(layout.is_sized(), "unsized locals should live in memory");
assert_matches!(meta, MemPlaceMeta::None); // we couldn't store it anyway...
let new_offset = ecx
.data_layout()
.offset(old_offset.unwrap_or(Size::ZERO).bytes(), offset.bytes())?;
PlaceTy {
place: Place::Local {
frame,
local,
offset: Some(Size::from_bytes(new_offset)),
},
align: self.align.restrict_for_offset(offset),
layout,
}
}
})
}
fn to_op<'mir, M: Machine<'mir, 'tcx, Provenance = Prov>>(
&self,
ecx: &InterpCx<'mir, 'tcx, M>,
) -> InterpResult<'tcx, OpTy<'tcx, M::Provenance>> {
ecx.place_to_op(self)
}
}
// These are defined here because they produce a place.
impl<'tcx, Prov: Provenance> OpTy<'tcx, Prov> {
#[inline(always)]
pub fn as_mplace_or_imm(&self) -> Either<MPlaceTy<'tcx, Prov>, ImmTy<'tcx, Prov>> {
match self.op() {
Operand::Indirect(mplace) => {
Left(MPlaceTy { mplace: *mplace, layout: self.layout, align: self.align.unwrap() })
}
Operand::Immediate(imm) => Right(ImmTy::from_immediate(*imm, self.layout)),
}
}
#[inline(always)]
#[cfg_attr(debug_assertions, track_caller)] // only in debug builds due to perf (see #98980)
pub fn assert_mem_place(&self) -> MPlaceTy<'tcx, Prov> {
self.as_mplace_or_imm().left().unwrap_or_else(|| {
bug!(
"OpTy of type {} was immediate when it was expected to be an MPlace",
self.layout.ty
)
})
}
}
/// The `Weiteable` trait describes interpreter values that can be written to.
pub trait Writeable<'tcx, Prov: Provenance>: Projectable<'tcx, Prov> {
fn as_mplace_or_local(
&self,
) -> Either<MPlaceTy<'tcx, Prov>, (usize, mir::Local, Option<Size>, Align, TyAndLayout<'tcx>)>;
fn force_mplace<'mir, M: Machine<'mir, 'tcx, Provenance = Prov>>(
&self,
ecx: &mut InterpCx<'mir, 'tcx, M>,
) -> InterpResult<'tcx, MPlaceTy<'tcx, Prov>>;
}
impl<'tcx, Prov: Provenance> Writeable<'tcx, Prov> for PlaceTy<'tcx, Prov> {
#[inline(always)]
fn as_mplace_or_local(
&self,
) -> Either<MPlaceTy<'tcx, Prov>, (usize, mir::Local, Option<Size>, Align, TyAndLayout<'tcx>)>
{
self.as_mplace_or_local()
.map_right(|(frame, local, offset)| (frame, local, offset, self.align, self.layout))
}
#[inline(always)]
fn force_mplace<'mir, M: Machine<'mir, 'tcx, Provenance = Prov>>(
&self,
ecx: &mut InterpCx<'mir, 'tcx, M>,
) -> InterpResult<'tcx, MPlaceTy<'tcx, Prov>> {
ecx.force_allocation(self)
}
}
impl<'tcx, Prov: Provenance> Writeable<'tcx, Prov> for MPlaceTy<'tcx, Prov> {
#[inline(always)]
fn as_mplace_or_local(
&self,
) -> Either<MPlaceTy<'tcx, Prov>, (usize, mir::Local, Option<Size>, Align, TyAndLayout<'tcx>)>
{
Left(self.clone())
}
#[inline(always)]
fn force_mplace<'mir, M: Machine<'mir, 'tcx, Provenance = Prov>>(
&self,
_ecx: &mut InterpCx<'mir, 'tcx, M>,
) -> InterpResult<'tcx, MPlaceTy<'tcx, Prov>> {
Ok(self.clone())
}
}
// FIXME: Working around https://github.com/rust-lang/rust/issues/54385
impl<'mir, 'tcx: 'mir, Prov, M> InterpCx<'mir, 'tcx, M>
where
Prov: Provenance,
M: Machine<'mir, 'tcx, Provenance = Prov>,
{
/// Take a value, which represents a (thin or wide) reference, and make it a place.
/// Alignment is just based on the type. This is the inverse of `mplace_to_ref()`.
///
/// Only call this if you are sure the place is "valid" (aligned and inbounds), or do not
/// want to ever use the place for memory access!
/// Generally prefer `deref_pointer`.
pub fn ref_to_mplace(
&self,
val: &ImmTy<'tcx, M::Provenance>,
) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
let pointee_type =
val.layout.ty.builtin_deref(true).expect("`ref_to_mplace` called on non-ptr type").ty;
let layout = self.layout_of(pointee_type)?;
let (ptr, meta) = match **val {
Immediate::Scalar(ptr) => (ptr, MemPlaceMeta::None),
Immediate::ScalarPair(ptr, meta) => (ptr, MemPlaceMeta::Meta(meta)),
Immediate::Uninit => throw_ub!(InvalidUninitBytes(None)),
};
// `ref_to_mplace` is called on raw pointers even if they don't actually get dereferenced;
// we hence can't call `size_and_align_of` since that asserts more validity than we want.
Ok(MPlaceTy::from_aligned_ptr_with_meta(ptr.to_pointer(self)?, layout, meta))
}
/// Turn a mplace into a (thin or wide) mutable raw pointer, pointing to the same space.
/// `align` information is lost!
/// This is the inverse of `ref_to_mplace`.
pub fn mplace_to_ref(
&self,
mplace: &MPlaceTy<'tcx, M::Provenance>,
) -> InterpResult<'tcx, ImmTy<'tcx, M::Provenance>> {
let imm = mplace.mplace.to_ref(self);
let layout = self.layout_of(Ty::new_mut_ptr(self.tcx.tcx, mplace.layout.ty))?;
Ok(ImmTy::from_immediate(imm, layout))
}
/// Take an operand, representing a pointer, and dereference it to a place.
/// Corresponds to the `*` operator in Rust.
#[instrument(skip(self), level = "debug")]
pub fn deref_pointer(
&self,
src: &impl Readable<'tcx, M::Provenance>,
) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
let val = self.read_immediate(src)?;
trace!("deref to {} on {:?}", val.layout.ty, *val);
if val.layout.ty.is_box() {
bug!("dereferencing {}", val.layout.ty);
}
let mplace = self.ref_to_mplace(&val)?;
self.check_mplace(&mplace)?;
Ok(mplace)
}
#[inline]
pub(super) fn get_place_alloc(
&self,
mplace: &MPlaceTy<'tcx, M::Provenance>,
) -> InterpResult<'tcx, Option<AllocRef<'_, 'tcx, M::Provenance, M::AllocExtra, M::Bytes>>>
{
let (size, _align) = self
.size_and_align_of_mplace(&mplace)?
.unwrap_or((mplace.layout.size, mplace.layout.align.abi));
// Due to packed places, only `mplace.align` matters.
self.get_ptr_alloc(mplace.ptr(), size, mplace.align)
}
#[inline]
pub(super) fn get_place_alloc_mut(
&mut self,
mplace: &MPlaceTy<'tcx, M::Provenance>,
) -> InterpResult<'tcx, Option<AllocRefMut<'_, 'tcx, M::Provenance, M::AllocExtra, M::Bytes>>>
{
let (size, _align) = self
.size_and_align_of_mplace(&mplace)?
.unwrap_or((mplace.layout.size, mplace.layout.align.abi));
// Due to packed places, only `mplace.align` matters.
self.get_ptr_alloc_mut(mplace.ptr(), size, mplace.align)
}
/// Check if this mplace is dereferenceable and sufficiently aligned.
pub fn check_mplace(&self, mplace: &MPlaceTy<'tcx, M::Provenance>) -> InterpResult<'tcx> {
let (size, _align) = self
.size_and_align_of_mplace(&mplace)?
.unwrap_or((mplace.layout.size, mplace.layout.align.abi));
// Due to packed places, only `mplace.align` matters.
let align =
if M::enforce_alignment(self).should_check() { mplace.align } else { Align::ONE };
self.check_ptr_access_align(mplace.ptr(), size, align, CheckInAllocMsg::DerefTest)?;
Ok(())
}
/// Converts a repr(simd) place into a place where `place_index` accesses the SIMD elements.
/// Also returns the number of elements.
pub fn mplace_to_simd(
&self,
mplace: &MPlaceTy<'tcx, M::Provenance>,
) -> InterpResult<'tcx, (MPlaceTy<'tcx, M::Provenance>, u64)> {
// Basically we just transmute this place into an array following simd_size_and_type.
// (Transmuting is okay since this is an in-memory place. We also double-check the size
// stays the same.)
let (len, e_ty) = mplace.layout.ty.simd_size_and_type(*self.tcx);
let array = Ty::new_array(self.tcx.tcx, e_ty, len);
let layout = self.layout_of(array)?;
assert_eq!(layout.size, mplace.layout.size);
Ok((MPlaceTy { layout, ..*mplace }, len))
}
/// Converts a repr(simd) place into a place where `place_index` accesses the SIMD elements.
/// Also returns the number of elements.
pub fn place_to_simd(
&mut self,
place: &PlaceTy<'tcx, M::Provenance>,
) -> InterpResult<'tcx, (MPlaceTy<'tcx, M::Provenance>, u64)> {
let mplace = self.force_allocation(place)?;
self.mplace_to_simd(&mplace)
}
pub fn local_to_place(
&self,
frame: usize,
local: mir::Local,
) -> InterpResult<'tcx, PlaceTy<'tcx, M::Provenance>> {
// Other parts of the system rely on `Place::Local` never being unsized.
// So we eagerly check here if this local has an MPlace, and if yes we use it.
let frame_ref = &self.stack()[frame];
let layout = self.layout_of_local(frame_ref, local, None)?;
let place = if layout.is_sized() {
// We can just always use the `Local` for sized values.
Place::Local { frame, local, offset: None }
} else {
// Unsized `Local` isn't okay (we cannot store the metadata).
match frame_ref.locals[local].access()? {
Operand::Immediate(_) => {
// ConstProp marks *all* locals as `Immediate::Uninit` since it cannot
// efficiently check whether they are sized. We have to catch that case here.
throw_inval!(ConstPropNonsense);
}
Operand::Indirect(mplace) => Place::Ptr(*mplace),
}
};
Ok(PlaceTy { place, layout, align: layout.align.abi })
}
/// Computes a place. You should only use this if you intend to write into this
/// place; for reading, a more efficient alternative is `eval_place_to_op`.
#[instrument(skip(self), level = "debug")]
pub fn eval_place(
&self,
mir_place: mir::Place<'tcx>,
) -> InterpResult<'tcx, PlaceTy<'tcx, M::Provenance>> {
let mut place = self.local_to_place(self.frame_idx(), mir_place.local)?;
// Using `try_fold` turned out to be bad for performance, hence the loop.
for elem in mir_place.projection.iter() {
place = self.project(&place, elem)?
}
trace!("{:?}", self.dump_place(&place));
// Sanity-check the type we ended up with.
if cfg!(debug_assertions) {
let normalized_place_ty = self.subst_from_current_frame_and_normalize_erasing_regions(
mir_place.ty(&self.frame().body.local_decls, *self.tcx).ty,
)?;
if !mir_assign_valid_types(
*self.tcx,
self.param_env,
self.layout_of(normalized_place_ty)?,
place.layout,
) {
span_bug!(
self.cur_span(),
"eval_place of a MIR place with type {} produced an interpreter place with type {}",
normalized_place_ty,
place.layout.ty,
)
}
}
Ok(place)
}
/// Write an immediate to a place
#[inline(always)]
#[instrument(skip(self), level = "debug")]
pub fn write_immediate(
&mut self,
src: Immediate<M::Provenance>,
dest: &impl Writeable<'tcx, M::Provenance>,
) -> InterpResult<'tcx> {
self.write_immediate_no_validate(src, dest)?;
if M::enforce_validity(self, dest.layout()) {
// Data got changed, better make sure it matches the type!
self.validate_operand(&dest.to_op(self)?)?;
}
Ok(())
}
/// Write a scalar to a place
#[inline(always)]
pub fn write_scalar(
&mut self,
val: impl Into<Scalar<M::Provenance>>,
dest: &impl Writeable<'tcx, M::Provenance>,
) -> InterpResult<'tcx> {
self.write_immediate(Immediate::Scalar(val.into()), dest)
}
/// Write a pointer to a place
#[inline(always)]
pub fn write_pointer(
&mut self,
ptr: impl Into<Pointer<Option<M::Provenance>>>,
dest: &impl Writeable<'tcx, M::Provenance>,
) -> InterpResult<'tcx> {
self.write_scalar(Scalar::from_maybe_pointer(ptr.into(), self), dest)
}
/// Write an immediate to a place.
/// If you use this you are responsible for validating that things got copied at the
/// right type.
fn write_immediate_no_validate(
&mut self,
src: Immediate<M::Provenance>,
dest: &impl Writeable<'tcx, M::Provenance>,
) -> InterpResult<'tcx> {
assert!(dest.layout().is_sized(), "Cannot write unsized immediate data");
// See if we can avoid an allocation. This is the counterpart to `read_immediate_raw`,
// but not factored as a separate function.
let mplace = match dest.as_mplace_or_local() {
Right((frame, local, offset, align, layout)) => {
if offset.is_some() {
// This has been projected to a part of this local. We could have complicated
// logic to still keep this local as an `Operand`... but it's much easier to
// just fall back to the indirect path.
dest.force_mplace(self)?
} else {
M::before_access_local_mut(self, frame, local)?;
match self.stack_mut()[frame].locals[local].access_mut()? {
Operand::Immediate(local_val) => {
// Local can be updated in-place.
*local_val = src;
// Double-check that the value we are storing and the local fit to each other.
// (*After* doing the update for borrow checker reasons.)
if cfg!(debug_assertions) {
let local_layout =
self.layout_of_local(&self.stack()[frame], local, None)?;
match (src, local_layout.abi) {
(Immediate::Scalar(scalar), Abi::Scalar(s)) => {
assert_eq!(scalar.size(), s.size(self))
}
(
Immediate::ScalarPair(a_val, b_val),
Abi::ScalarPair(a, b),
) => {
assert_eq!(a_val.size(), a.size(self));
assert_eq!(b_val.size(), b.size(self));
}
(Immediate::Uninit, _) => {}
(src, abi) => {
bug!(
"value {src:?} cannot be written into local with type {} (ABI {abi:?})",
local_layout.ty
)
}
};
}
return Ok(());
}
Operand::Indirect(mplace) => {
// The local is in memory, go on below.
MPlaceTy { mplace: *mplace, align, layout }
}
}
}
}
Left(mplace) => mplace, // already referring to memory
};
// This is already in memory, write there.
self.write_immediate_to_mplace_no_validate(src, mplace.layout, mplace.align, mplace.mplace)
}
/// Write an immediate to memory.
/// If you use this you are responsible for validating that things got copied at the
/// right layout.
fn write_immediate_to_mplace_no_validate(
&mut self,
value: Immediate<M::Provenance>,
layout: TyAndLayout<'tcx>,
align: Align,
dest: MemPlace<M::Provenance>,
) -> InterpResult<'tcx> {
// Note that it is really important that the type here is the right one, and matches the
// type things are read at. In case `value` is a `ScalarPair`, we don't do any magic here
// to handle padding properly, which is only correct if we never look at this data with the
// wrong type.
let tcx = *self.tcx;
let Some(mut alloc) =
self.get_place_alloc_mut(&MPlaceTy { mplace: dest, layout, align })?
else {
// zero-sized access
return Ok(());
};
match value {
Immediate::Scalar(scalar) => {
let Abi::Scalar(s) = layout.abi else {
span_bug!(
self.cur_span(),
"write_immediate_to_mplace: invalid Scalar layout: {layout:#?}",
)
};
let size = s.size(&tcx);
assert_eq!(size, layout.size, "abi::Scalar size does not match layout size");
alloc.write_scalar(alloc_range(Size::ZERO, size), scalar)
}
Immediate::ScalarPair(a_val, b_val) => {
// We checked `ptr_align` above, so all fields will have the alignment they need.
// We would anyway check against `ptr_align.restrict_for_offset(b_offset)`,
// which `ptr.offset(b_offset)` cannot possibly fail to satisfy.
let Abi::ScalarPair(a, b) = layout.abi else {
span_bug!(
self.cur_span(),
"write_immediate_to_mplace: invalid ScalarPair layout: {:#?}",
layout
)
};
let (a_size, b_size) = (a.size(&tcx), b.size(&tcx));
let b_offset = a_size.align_to(b.align(&tcx).abi);
assert!(b_offset.bytes() > 0); // in `operand_field` we use the offset to tell apart the fields
// It is tempting to verify `b_offset` against `layout.fields.offset(1)`,
// but that does not work: We could be a newtype around a pair, then the
// fields do not match the `ScalarPair` components.
alloc.write_scalar(alloc_range(Size::ZERO, a_size), a_val)?;
alloc.write_scalar(alloc_range(b_offset, b_size), b_val)
}
Immediate::Uninit => alloc.write_uninit(),
}
}
pub fn write_uninit(
&mut self,
dest: &impl Writeable<'tcx, M::Provenance>,
) -> InterpResult<'tcx> {
let mplace = match dest.as_mplace_or_local() {
Left(mplace) => mplace,
Right((frame, local, offset, align, layout)) => {
if offset.is_some() {
// This has been projected to a part of this local. We could have complicated
// logic to still keep this local as an `Operand`... but it's much easier to
// just fall back to the indirect path.
// FIXME: share the logic with `write_immediate_no_validate`.
dest.force_mplace(self)?
} else {
M::before_access_local_mut(self, frame, local)?;
match self.stack_mut()[frame].locals[local].access_mut()? {
Operand::Immediate(local) => {
*local = Immediate::Uninit;
return Ok(());
}
Operand::Indirect(mplace) => {
// The local is in memory, go on below.
MPlaceTy { mplace: *mplace, layout, align }
}
}
}
}
};
let Some(mut alloc) = self.get_place_alloc_mut(&mplace)? else {
// Zero-sized access
return Ok(());
};
alloc.write_uninit()?;
Ok(())
}
/// Copies the data from an operand to a place.
/// `allow_transmute` indicates whether the layouts may disagree.
#[inline(always)]
#[instrument(skip(self), level = "debug")]
pub fn copy_op(
&mut self,
src: &impl Readable<'tcx, M::Provenance>,
dest: &impl Writeable<'tcx, M::Provenance>,
allow_transmute: bool,
) -> InterpResult<'tcx> {
// Generally for transmutation, data must be valid both at the old and new type.
// But if the types are the same, the 2nd validation below suffices.
if src.layout().ty != dest.layout().ty && M::enforce_validity(self, src.layout()) {
self.validate_operand(&src.to_op(self)?)?;
}
// Do the actual copy.
self.copy_op_no_validate(src, dest, allow_transmute)?;
if M::enforce_validity(self, dest.layout()) {
// Data got changed, better make sure it matches the type!
self.validate_operand(&dest.to_op(self)?)?;
}
Ok(())
}
/// Copies the data from an operand to a place.
/// `allow_transmute` indicates whether the layouts may disagree.
/// Also, if you use this you are responsible for validating that things get copied at the
/// right type.
#[instrument(skip(self), level = "debug")]
fn copy_op_no_validate(
&mut self,
src: &impl Readable<'tcx, M::Provenance>,
dest: &impl Writeable<'tcx, M::Provenance>,
allow_transmute: bool,
) -> InterpResult<'tcx> {
// We do NOT compare the types for equality, because well-typed code can
// actually "transmute" `&mut T` to `&T` in an assignment without a cast.
let layout_compat =
mir_assign_valid_types(*self.tcx, self.param_env, src.layout(), dest.layout());
if !allow_transmute && !layout_compat {
span_bug!(
self.cur_span(),
"type mismatch when copying!\nsrc: {},\ndest: {}",
src.layout().ty,
dest.layout().ty,
);
}
// Let us see if the layout is simple so we take a shortcut,
// avoid force_allocation.
let src = match self.read_immediate_raw(src)? {
Right(src_val) => {
// FIXME(const_prop): Const-prop can possibly evaluate an
// unsized copy operation when it thinks that the type is
// actually sized, due to a trivially false where-clause
// predicate like `where Self: Sized` with `Self = dyn Trait`.
// See #102553 for an example of such a predicate.
if src.layout().is_unsized() {
throw_inval!(ConstPropNonsense);
}
if dest.layout().is_unsized() {
throw_inval!(ConstPropNonsense);
}
assert_eq!(src.layout().size, dest.layout().size);
// Yay, we got a value that we can write directly.
return if layout_compat {
self.write_immediate_no_validate(*src_val, dest)
} else {
// This is tricky. The problematic case is `ScalarPair`: the `src_val` was
// loaded using the offsets defined by `src.layout`. When we put this back into
// the destination, we have to use the same offsets! So (a) we make sure we
// write back to memory, and (b) we use `dest` *with the source layout*.
let dest_mem = dest.force_mplace(self)?;
self.write_immediate_to_mplace_no_validate(
*src_val,
src.layout(),
dest_mem.align,
dest_mem.mplace,
)
};
}
Left(mplace) => mplace,
};
// Slow path, this does not fit into an immediate. Just memcpy.
trace!("copy_op: {:?} <- {:?}: {}", *dest, src, dest.layout().ty);
let dest = dest.force_mplace(self)?;
let Some((dest_size, _)) = self.size_and_align_of_mplace(&dest)? else {
span_bug!(self.cur_span(), "copy_op needs (dynamically) sized values")
};
if cfg!(debug_assertions) {
let src_size = self.size_and_align_of_mplace(&src)?.unwrap().0;
assert_eq!(src_size, dest_size, "Cannot copy differently-sized data");
} else {
// As a cheap approximation, we compare the fixed parts of the size.
assert_eq!(src.layout.size, dest.layout.size);
}
// Setting `nonoverlapping` here only has an effect when we don't hit the fast-path above,
// but that should at least match what LLVM does where `memcpy` is also only used when the
// type does not have Scalar/ScalarPair layout.
// (Or as the `Assign` docs put it, assignments "not producing primitives" must be
// non-overlapping.)
self.mem_copy(
src.ptr(),
src.align,
dest.ptr(),
dest.align,
dest_size,
/*nonoverlapping*/ true,
)
}
/// Ensures that a place is in memory, and returns where it is.
/// If the place currently refers to a local that doesn't yet have a matching allocation,
/// create such an allocation.
/// This is essentially `force_to_memplace`.
#[instrument(skip(self), level = "debug")]
pub fn force_allocation(
&mut self,
place: &PlaceTy<'tcx, M::Provenance>,
) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
let mplace = match place.place {
Place::Local { frame, local, offset } => {
M::before_access_local_mut(self, frame, local)?;
let whole_local = match self.stack_mut()[frame].locals[local].access_mut()? {
&mut Operand::Immediate(local_val) => {
// We need to make an allocation.
// We need the layout of the local. We can NOT use the layout we got,
// that might e.g., be an inner field of a struct with `Scalar` layout,
// that has different alignment than the outer field.
let local_layout =
self.layout_of_local(&self.stack()[frame], local, None)?;
assert!(local_layout.is_sized(), "unsized locals cannot be immediate");
let mplace = self.allocate(local_layout, MemoryKind::Stack)?;
// Preserve old value. (As an optimization, we can skip this if it was uninit.)
if !matches!(local_val, Immediate::Uninit) {
// We don't have to validate as we can assume the local was already
// valid for its type. We must not use any part of `place` here, that
// could be a projection to a part of the local!
self.write_immediate_to_mplace_no_validate(
local_val,
local_layout,
local_layout.align.abi,
mplace.mplace,
)?;
}
M::after_local_allocated(self, frame, local, &mplace)?;
// Now we can call `access_mut` again, asserting it goes well, and actually
// overwrite things. This points to the entire allocation, not just the part
// the place refers to, i.e. we do this before we apply `offset`.
*self.stack_mut()[frame].locals[local].access_mut().unwrap() =
Operand::Indirect(mplace.mplace);
mplace.mplace
}
&mut Operand::Indirect(mplace) => mplace, // this already was an indirect local
};
if let Some(offset) = offset {
whole_local.offset_with_meta_(offset, MemPlaceMeta::None, self)?
} else {
// Preserve wide place metadata, do not call `offset`.
whole_local
}
}
Place::Ptr(mplace) => mplace,
};
// Return with the original layout and align, so that the caller can go on
Ok(MPlaceTy { mplace, layout: place.layout, align: place.align })
}
pub fn allocate_dyn(
&mut self,
layout: TyAndLayout<'tcx>,
kind: MemoryKind<M::MemoryKind>,
meta: MemPlaceMeta<M::Provenance>,
) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
let Some((size, align)) = self.size_and_align_of(&meta, &layout)? else {
span_bug!(self.cur_span(), "cannot allocate space for `extern` type, size is not known")
};
let ptr = self.allocate_ptr(size, align, kind)?;
Ok(MPlaceTy::from_aligned_ptr_with_meta(ptr.into(), layout, meta))
}
pub fn allocate(
&mut self,
layout: TyAndLayout<'tcx>,
kind: MemoryKind<M::MemoryKind>,
) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
assert!(layout.is_sized());
self.allocate_dyn(layout, kind, MemPlaceMeta::None)
}
/// Returns a wide MPlace of type `&'static [mut] str` to a new 1-aligned allocation.
pub fn allocate_str(
&mut self,
str: &str,
kind: MemoryKind<M::MemoryKind>,
mutbl: Mutability,
) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
let ptr = self.allocate_bytes_ptr(str.as_bytes(), Align::ONE, kind, mutbl)?;
let meta = Scalar::from_target_usize(u64::try_from(str.len()).unwrap(), self);
let mplace = MemPlace { ptr: ptr.into(), meta: MemPlaceMeta::Meta(meta) };
let ty = Ty::new_ref(
self.tcx.tcx,
self.tcx.lifetimes.re_static,
ty::TypeAndMut { ty: self.tcx.types.str_, mutbl },
);
let layout = self.layout_of(ty).unwrap();
Ok(MPlaceTy { mplace, layout, align: layout.align.abi })
}
/// Writes the aggregate to the destination.
#[instrument(skip(self), level = "trace")]
pub fn write_aggregate(
&mut self,
kind: &mir::AggregateKind<'tcx>,
operands: &IndexSlice<FieldIdx, mir::Operand<'tcx>>,
dest: &PlaceTy<'tcx, M::Provenance>,
) -> InterpResult<'tcx> {
self.write_uninit(dest)?;
let (variant_index, variant_dest, active_field_index) = match *kind {
mir::AggregateKind::Adt(_, variant_index, _, _, active_field_index) => {
let variant_dest = self.project_downcast(dest, variant_index)?;
(variant_index, variant_dest, active_field_index)
}
_ => (FIRST_VARIANT, dest.clone(), None),
};
if active_field_index.is_some() {
assert_eq!(operands.len(), 1);
}
for (field_index, operand) in operands.iter_enumerated() {
let field_index = active_field_index.unwrap_or(field_index);
let field_dest = self.project_field(&variant_dest, field_index.as_usize())?;
let op = self.eval_operand(operand, Some(field_dest.layout))?;
self.copy_op(&op, &field_dest, /*allow_transmute*/ false)?;
}
self.write_discriminant(variant_index, dest)
}
pub fn raw_const_to_mplace(
&self,
raw: mir::ConstAlloc<'tcx>,
) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
// This must be an allocation in `tcx`
let _ = self.tcx.global_alloc(raw.alloc_id);
let ptr = self.global_base_pointer(Pointer::from(raw.alloc_id))?;
let layout = self.layout_of(raw.ty)?;
Ok(MPlaceTy::from_aligned_ptr(ptr.into(), layout))
}
/// Turn a place with a `dyn Trait` type into a place with the actual dynamic type.
/// Aso returns the vtable.
pub(super) fn unpack_dyn_trait(
&self,
mplace: &MPlaceTy<'tcx, M::Provenance>,
) -> InterpResult<'tcx, (MPlaceTy<'tcx, M::Provenance>, Pointer<Option<M::Provenance>>)> {
assert!(
matches!(mplace.layout.ty.kind(), ty::Dynamic(_, _, ty::Dyn)),
"`unpack_dyn_trait` only makes sense on `dyn*` types"
);
let vtable = mplace.meta().unwrap_meta().to_pointer(self)?;
let (ty, _) = self.get_ptr_vtable(vtable)?;
let layout = self.layout_of(ty)?;
let mplace = MPlaceTy {
mplace: MemPlace { meta: MemPlaceMeta::None, ..mplace.mplace },
layout,
align: layout.align.abi,
};
Ok((mplace, vtable))
}
/// Turn a `dyn* Trait` type into an value with the actual dynamic type.
/// Also returns the vtable.
pub(super) fn unpack_dyn_star<P: Projectable<'tcx, M::Provenance>>(
&self,
val: &P,
) -> InterpResult<'tcx, (P, Pointer<Option<M::Provenance>>)> {
assert!(
matches!(val.layout().ty.kind(), ty::Dynamic(_, _, ty::DynStar)),
"`unpack_dyn_star` only makes sense on `dyn*` types"
);
let data = self.project_field(val, 0)?;
let vtable = self.project_field(val, 1)?;
let vtable = self.read_pointer(&vtable.to_op(self)?)?;
let (ty, _) = self.get_ptr_vtable(vtable)?;
let layout = self.layout_of(ty)?;
// `data` is already the right thing but has the wrong type. So we transmute it, by
// projecting with offset 0.
let data = data.transmute(layout, self)?;
Ok((data, vtable))
}
}
// Some nodes are used a lot. Make sure they don't unintentionally get bigger.
#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
mod size_asserts {
use super::*;
use rustc_data_structures::static_assert_size;
// tidy-alphabetical-start
static_assert_size!(MemPlace, 40);
static_assert_size!(MemPlaceMeta, 24);
static_assert_size!(MPlaceTy<'_>, 64);
static_assert_size!(Place, 40);
static_assert_size!(PlaceTy<'_>, 64);
// tidy-alphabetical-end
}