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properly handle arrays and wide pointers in naive_layout_of

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This commit is contained in:
Moulins 2023-06-19 19:26:53 +02:00
parent cb8b1d1bc9
commit 30ae640a3c
2 changed files with 116 additions and 81 deletions
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195
compiler/rustc_ty_utils/src/layout.rs
View File

@ -154,9 +154,19 @@ fn naive_layout_of_uncached<'tcx>(
ty::Never => NaiveLayout::EMPTY,
// Potentially-wide pointers.
ty::Ref(_, _, _) | ty::RawPtr(_) => {
// TODO(reference_niches): handle wide pointers
scalar(Pointer(AddressSpace::DATA))
ty::Ref(_, pointee, _) | ty::RawPtr(ty::TypeAndMut { ty: pointee, .. }) => {
let data_ptr = scalar(Pointer(AddressSpace::DATA));
if let Some(metadata) = ptr_metadata_scalar(cx, pointee)? {
// Effectively a (ptr, meta) tuple.
data_ptr
.concat(&scalar(metadata.primitive()), cx)
.ok_or_else(|| error(cx, LayoutError::SizeOverflow(ty)))?
.pad_to_align()
} else {
// No metadata, this is a thin pointer.
data_ptr
}
}
ty::Dynamic(_, _, ty::DynStar) => {
@ -165,10 +175,15 @@ fn naive_layout_of_uncached<'tcx>(
}
// Arrays and slices.
ty::Array(element, _count) => {
ty::Array(element, count) => {
let count = compute_array_count(cx, count)
.ok_or_else(|| error(cx, LayoutError::Unknown(ty)))?;
let element = cx.naive_layout_of(element)?;
NaiveLayout {
min_size: Size::ZERO, // TODO(reference_niches): proper array size
min_size: element
.min_size
.checked_mul(count, cx)
.ok_or_else(|| error(cx, LayoutError::SizeOverflow(ty)))?,
min_align: element.min_align,
}
}
@ -311,72 +326,13 @@ fn layout_of_uncached<'tcx>(
data_ptr.valid_range_mut().start = 1;
}
let pointee = tcx.normalize_erasing_regions(param_env, pointee);
if pointee.is_sized(tcx, param_env) {
return Ok(tcx.mk_layout(LayoutS::scalar(cx, data_ptr)));
}
let metadata = if let Some(metadata_def_id) = tcx.lang_items().metadata_type()
// Projection eagerly bails out when the pointee references errors,
// fall back to structurally deducing metadata.
&& !pointee.references_error()
{
let pointee_metadata = Ty::new_projection(tcx,metadata_def_id, [pointee]);
let metadata_ty = match tcx.try_normalize_erasing_regions(
param_env,
pointee_metadata,
) {
Ok(metadata_ty) => metadata_ty,
Err(mut err) => {
// Usually `<Ty as Pointee>::Metadata` can't be normalized because
// its struct tail cannot be normalized either, so try to get a
// more descriptive layout error here, which will lead to less confusing
// diagnostics.
match tcx.try_normalize_erasing_regions(
param_env,
tcx.struct_tail_without_normalization(pointee),
) {
Ok(_) => {},
Err(better_err) => {
err = better_err;
}
}
return Err(error(cx, LayoutError::NormalizationFailure(pointee, err)));
},
};
let metadata_layout = cx.layout_of(metadata_ty)?;
// If the metadata is a 1-zst, then the pointer is thin.
if metadata_layout.is_zst() && metadata_layout.align.abi.bytes() == 1 {
return Ok(tcx.mk_layout(LayoutS::scalar(cx, data_ptr)));
}
let Abi::Scalar(metadata) = metadata_layout.abi else {
return Err(error(cx, LayoutError::Unknown(pointee)));
};
metadata
if let Some(metadata) = ptr_metadata_scalar(cx, pointee)? {
// Effectively a (ptr, meta) tuple.
tcx.mk_layout(cx.scalar_pair(data_ptr, metadata))
} else {
let unsized_part = tcx.struct_tail_erasing_lifetimes(pointee, param_env);
match unsized_part.kind() {
ty::Foreign(..) => {
return Ok(tcx.mk_layout(LayoutS::scalar(cx, data_ptr)));
}
ty::Slice(_) | ty::Str => scalar_unit(Int(dl.ptr_sized_integer(), false)),
ty::Dynamic(..) => {
let mut vtable = scalar_unit(Pointer(AddressSpace::DATA));
vtable.valid_range_mut().start = 1;
vtable
}
_ => {
return Err(error(cx, LayoutError::Unknown(pointee)));
}
}
};
// Effectively a (ptr, meta) tuple.
tcx.mk_layout(cx.scalar_pair(data_ptr, metadata))
// No metadata, this is a thin pointer.
tcx.mk_layout(LayoutS::scalar(cx, data_ptr))
}
}
ty::Dynamic(_, _, ty::DynStar) => {
@ -388,16 +344,8 @@ fn layout_of_uncached<'tcx>(
}
// Arrays and slices.
ty::Array(element, mut count) => {
if count.has_projections() {
count = tcx.normalize_erasing_regions(param_env, count);
if count.has_projections() {
return Err(error(cx, LayoutError::Unknown(ty)));
}
}
let count = count
.try_eval_target_usize(tcx, param_env)
ty::Array(element, count) => {
let count = compute_array_count(cx, count)
.ok_or_else(|| error(cx, LayoutError::Unknown(ty)))?;
let element = cx.layout_of(element)?;
let size = element
@ -733,6 +681,93 @@ fn layout_of_uncached<'tcx>(
})
}
fn compute_array_count<'tcx>(
cx: &LayoutCx<'tcx, TyCtxt<'tcx>>,
mut count: ty::Const<'tcx>,
) -> Option<u64> {
let LayoutCx { tcx, param_env } = *cx;
if count.has_projections() {
count = tcx.normalize_erasing_regions(param_env, count);
if count.has_projections() {
return None;
}
}
count.try_eval_target_usize(tcx, param_env)
}
fn ptr_metadata_scalar<'tcx>(
cx: &LayoutCx<'tcx, TyCtxt<'tcx>>,
pointee: Ty<'tcx>,
) -> Result<Option<Scalar>, &'tcx LayoutError<'tcx>> {
let dl = cx.data_layout();
let scalar_unit = |value: Primitive| {
let size = value.size(dl);
assert!(size.bits() <= 128);
Scalar::Initialized { value, valid_range: WrappingRange::full(size) }
};
let LayoutCx { tcx, param_env } = *cx;
let pointee = tcx.normalize_erasing_regions(param_env, pointee);
if pointee.is_sized(tcx, param_env) {
return Ok(None);
}
if let Some(metadata_def_id) = tcx.lang_items().metadata_type()
// Projection eagerly bails out when the pointee references errors,
// fall back to structurally deducing metadata.
&& !pointee.references_error()
{
let pointee_metadata = Ty::new_projection(tcx,metadata_def_id, [pointee]);
let metadata_ty = match tcx.try_normalize_erasing_regions(
param_env,
pointee_metadata,
) {
Ok(metadata_ty) => metadata_ty,
Err(mut err) => {
// Usually `<Ty as Pointee>::Metadata` can't be normalized because
// its struct tail cannot be normalized either, so try to get a
// more descriptive layout error here, which will lead to less confusing
// diagnostics.
match tcx.try_normalize_erasing_regions(
param_env,
tcx.struct_tail_without_normalization(pointee),
) {
Ok(_) => {},
Err(better_err) => {
err = better_err;
}
}
return Err(error(cx, LayoutError::NormalizationFailure(pointee, err)));
},
};
let metadata_layout = cx.layout_of(metadata_ty)?;
if metadata_layout.is_zst() && metadata_layout.align.abi.bytes() == 1 {
Ok(None) // If the metadata is a 1-zst, then the pointer is thin.
} else if let Abi::Scalar(metadata) = metadata_layout.abi {
Ok(Some(metadata))
} else {
Err(error(cx, LayoutError::Unknown(pointee)))
}
} else {
let unsized_part = tcx.struct_tail_erasing_lifetimes(pointee, param_env);
match unsized_part.kind() {
ty::Foreign(..) => Ok(None),
ty::Slice(_) | ty::Str => Ok(Some(scalar_unit(Int(dl.ptr_sized_integer(), false)))),
ty::Dynamic(..) => {
let mut vtable = scalar_unit(Pointer(AddressSpace::DATA));
vtable.valid_range_mut().start = 1;
Ok(Some(vtable))
}
_ => Err(error(cx, LayoutError::Unknown(pointee))),
}
}
}
/// Overlap eligibility and variant assignment for each GeneratorSavedLocal.
#[derive(Clone, Debug, PartialEq)]
enum SavedLocalEligibility {

2
tests/ui/layout/cannot-transmute-unnormalizable-type.stderr
View File

@ -11,7 +11,7 @@ LL | std::mem::transmute::<Option<()>, Option<&Other>>(None);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: source type: `Option<()>` (8 bits)
= note: target type: `Option<&Other>` (unable to determine layout for `<() as Trait>::RefTarget` because `<() as Trait>::RefTarget` cannot be normalized)
= note: target type: `Option<&Other>` (unable to determine layout for `Other` because `<() as Trait>::RefTarget` cannot be normalized)
error: aborting due to 2 previous errors