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use super::*;
use std::{
borrow::Borrow,
cmp,
fmt::Debug,
iter,
ops::{Bound, Deref},
};
#[cfg(feature = "randomize")]
use rand::{seq::SliceRandom, SeedableRng};
#[cfg(feature = "randomize")]
use rand_xoshiro::Xoshiro128StarStar;
use tracing::debug;
fn invert_mapping(map: &[u32]) -> Vec<u32> {
let mut inverse = vec![0; map.len()];
for i in 0..map.len() {
inverse[map[i] as usize] = i as u32;
}
inverse
}
pub trait LayoutCalculator {
type TargetDataLayoutRef: Borrow<TargetDataLayout>;
fn delay_bug(&self, txt: &str);
fn current_data_layout(&self) -> Self::TargetDataLayoutRef;
fn scalar_pair<V: Idx>(&self, a: Scalar, b: Scalar) -> LayoutS<V> {
let dl = self.current_data_layout();
let dl = dl.borrow();
let b_align = b.align(dl);
let align = a.align(dl).max(b_align).max(dl.aggregate_align);
let b_offset = a.size(dl).align_to(b_align.abi);
let size = (b_offset + b.size(dl)).align_to(align.abi);
let largest_niche = Niche::from_scalar(dl, b_offset, b)
.into_iter()
.chain(Niche::from_scalar(dl, Size::ZERO, a))
.max_by_key(|niche| niche.available(dl));
LayoutS {
variants: Variants::Single { index: V::new(0) },
fields: FieldsShape::Arbitrary {
offsets: vec![Size::ZERO, b_offset],
memory_index: vec![0, 1],
},
abi: Abi::ScalarPair(a, b),
largest_niche,
align,
size,
}
}
fn univariant<'a, V: Idx, F: Deref<Target = &'a LayoutS<V>> + Debug>(
&self,
dl: &TargetDataLayout,
fields: &[F],
repr: &ReprOptions,
kind: StructKind,
) -> Option<LayoutS<V>> {
let pack = repr.pack;
let mut align = if pack.is_some() { dl.i8_align } else { dl.aggregate_align };
let mut inverse_memory_index: Vec<u32> = (0..fields.len() as u32).collect();
let optimize = !repr.inhibit_struct_field_reordering_opt();
if optimize {
let end =
if let StructKind::MaybeUnsized = kind { fields.len() - 1 } else { fields.len() };
let optimizing = &mut inverse_memory_index[..end];
let effective_field_align = |f: &F| {
if let Some(pack) = pack {
f.align.abi.min(pack).bytes()
} else {
f.align.abi.bytes().max(f.size.bytes()).trailing_zeros() as u64
}
};
if repr.can_randomize_type_layout() && cfg!(feature = "randomize") {
#[cfg(feature = "randomize")]
{
let mut rng = Xoshiro128StarStar::seed_from_u64(repr.field_shuffle_seed);
optimizing.shuffle(&mut rng);
}
} else {
match kind {
StructKind::AlwaysSized | StructKind::MaybeUnsized => {
optimizing.sort_by_key(|&x| {
let f = &fields[x as usize];
let niche_size = f.largest_niche.map_or(0, |n| n.available(dl));
(!f.is_zst(), cmp::Reverse(effective_field_align(f)), niche_size)
});
}
StructKind::Prefixed(..) => {
optimizing.sort_by_key(|&x| {
let f = &fields[x as usize];
let niche_size = f.largest_niche.map_or(0, |n| n.available(dl));
(effective_field_align(f), niche_size)
});
}
}
}
}
let mut sized = true;
let mut offsets = vec![Size::ZERO; fields.len()];
let mut offset = Size::ZERO;
let mut largest_niche = None;
let mut largest_niche_available = 0;
if let StructKind::Prefixed(prefix_size, prefix_align) = kind {
let prefix_align =
if let Some(pack) = pack { prefix_align.min(pack) } else { prefix_align };
align = align.max(AbiAndPrefAlign::new(prefix_align));
offset = prefix_size.align_to(prefix_align);
}
for &i in &inverse_memory_index {
let field = &fields[i as usize];
if !sized {
self.delay_bug(&format!(
"univariant: field #{} comes after unsized field",
offsets.len(),
));
}
if field.is_unsized() {
sized = false;
}
let field_align = if let Some(pack) = pack {
field.align.min(AbiAndPrefAlign::new(pack))
} else {
field.align
};
offset = offset.align_to(field_align.abi);
align = align.max(field_align);
debug!("univariant offset: {:?} field: {:#?}", offset, field);
offsets[i as usize] = offset;
if let Some(mut niche) = field.largest_niche {
let available = niche.available(dl);
if available > largest_niche_available {
largest_niche_available = available;
niche.offset += offset;
largest_niche = Some(niche);
}
}
offset = offset.checked_add(field.size, dl)?;
}
if let Some(repr_align) = repr.align {
align = align.max(AbiAndPrefAlign::new(repr_align));
}
debug!("univariant min_size: {:?}", offset);
let min_size = offset;
let memory_index =
if optimize { invert_mapping(&inverse_memory_index) } else { inverse_memory_index };
let size = min_size.align_to(align.abi);
let mut abi = Abi::Aggregate { sized };
if sized && size.bytes() > 0 {
let mut non_zst_fields = fields.iter().enumerate().filter(|&(_, f)| !f.is_zst());
match (non_zst_fields.next(), non_zst_fields.next(), non_zst_fields.next()) {
(Some((i, field)), None, None) => {
if offsets[i].bytes() == 0 && align.abi == field.align.abi && size == field.size
{
match field.abi {
Abi::Scalar(_) | Abi::Vector { .. } if optimize => {
abi = field.abi;
}
Abi::ScalarPair(..) => {
abi = field.abi;
}
_ => {}
}
}
}
(Some((i, a)), Some((j, b)), None) => {
match (a.abi, b.abi) {
(Abi::Scalar(a), Abi::Scalar(b)) => {
let ((i, a), (j, b)) = if offsets[i] < offsets[j] {
((i, a), (j, b))
} else {
((j, b), (i, a))
};
let pair = self.scalar_pair::<V>(a, b);
let pair_offsets = match pair.fields {
FieldsShape::Arbitrary { ref offsets, ref memory_index } => {
assert_eq!(memory_index, &[0, 1]);
offsets
}
_ => panic!(),
};
if offsets[i] == pair_offsets[0]
&& offsets[j] == pair_offsets[1]
&& align == pair.align
&& size == pair.size
{
abi = pair.abi;
}
}
_ => {}
}
}
_ => {}
}
}
if fields.iter().any(|f| f.abi.is_uninhabited()) {
abi = Abi::Uninhabited;
}
Some(LayoutS {
variants: Variants::Single { index: V::new(0) },
fields: FieldsShape::Arbitrary { offsets, memory_index },
abi,
largest_niche,
align,
size,
})
}
fn layout_of_never_type<V: Idx>(&self) -> LayoutS<V> {
let dl = self.current_data_layout();
let dl = dl.borrow();
LayoutS {
variants: Variants::Single { index: V::new(0) },
fields: FieldsShape::Primitive,
abi: Abi::Uninhabited,
largest_niche: None,
align: dl.i8_align,
size: Size::ZERO,
}
}
fn layout_of_struct_or_enum<'a, V: Idx, F: Deref<Target = &'a LayoutS<V>> + Debug>(
&self,
repr: &ReprOptions,
variants: &IndexVec<V, Vec<F>>,
is_enum: bool,
is_unsafe_cell: bool,
scalar_valid_range: (Bound<u128>, Bound<u128>),
discr_range_of_repr: impl Fn(i128, i128) -> (Integer, bool),
discriminants: impl Iterator<Item = (V, i128)>,
niche_optimize_enum: bool,
always_sized: bool,
) -> Option<LayoutS<V>> {
let dl = self.current_data_layout();
let dl = dl.borrow();
let scalar_unit = |value: Primitive| {
let size = value.size(dl);
assert!(size.bits() <= 128);
Scalar::Initialized { value, valid_range: WrappingRange::full(size) }
};
let absent = |fields: &[F]| {
let uninhabited = fields.iter().any(|f| f.abi.is_uninhabited());
let is_zst = fields.iter().all(|f| f.is_zst());
uninhabited && is_zst
};
let (present_first, present_second) = {
let mut present_variants = variants
.iter_enumerated()
.filter_map(|(i, v)| if absent(v) { None } else { Some(i) });
(present_variants.next(), present_variants.next())
};
let present_first = match present_first {
Some(present_first) => present_first,
None if is_enum => {
return Some(self.layout_of_never_type());
}
None => V::new(0),
};
let is_struct = !is_enum ||
(present_second.is_none() &&
!repr.inhibit_enum_layout_opt());
if is_struct {
let v = present_first;
let kind = if is_enum || variants[v].is_empty() {
StructKind::AlwaysSized
} else {
if !always_sized { StructKind::MaybeUnsized } else { StructKind::AlwaysSized }
};
let mut st = self.univariant(dl, &variants[v], repr, kind)?;
st.variants = Variants::Single { index: v };
if is_unsafe_cell {
let hide_niches = |scalar: &mut _| match scalar {
Scalar::Initialized { value, valid_range } => {
*valid_range = WrappingRange::full(value.size(dl))
}
Scalar::Union { .. } => {}
};
match &mut st.abi {
Abi::Uninhabited => {}
Abi::Scalar(scalar) => hide_niches(scalar),
Abi::ScalarPair(a, b) => {
hide_niches(a);
hide_niches(b);
}
Abi::Vector { element, count: _ } => hide_niches(element),
Abi::Aggregate { sized: _ } => {}
}
st.largest_niche = None;
return Some(st);
}
let (start, end) = scalar_valid_range;
match st.abi {
Abi::Scalar(ref mut scalar) | Abi::ScalarPair(ref mut scalar, _) => {
let max_value = scalar.size(dl).unsigned_int_max();
if let Bound::Included(start) = start {
assert!(start <= max_value, "{start} > {max_value}");
scalar.valid_range_mut().start = start;
}
if let Bound::Included(end) = end {
assert!(end <= max_value, "{end} > {max_value}");
scalar.valid_range_mut().end = end;
}
let niche = Niche::from_scalar(dl, Size::ZERO, *scalar);
if let Some(niche) = niche {
match st.largest_niche {
Some(largest_niche) => {
if largest_niche.available(dl) <= niche.available(dl) {
st.largest_niche = Some(niche);
}
}
None => st.largest_niche = Some(niche),
}
}
}
_ => assert!(
start == Bound::Unbounded && end == Bound::Unbounded,
"nonscalar layout for layout_scalar_valid_range type: {:#?}",
st,
),
}
return Some(st);
}
assert!(is_enum);
struct TmpLayout<V: Idx> {
layout: LayoutS<V>,
variants: IndexVec<V, LayoutS<V>>,
}
let calculate_niche_filling_layout = || -> Option<TmpLayout<V>> {
if niche_optimize_enum {
return None;
}
if variants.len() < 2 {
return None;
}
let mut align = dl.aggregate_align;
let mut variant_layouts = variants
.iter_enumerated()
.map(|(j, v)| {
let mut st = self.univariant(dl, v, repr, StructKind::AlwaysSized)?;
st.variants = Variants::Single { index: j };
align = align.max(st.align);
Some(st)
})
.collect::<Option<IndexVec<V, _>>>()?;
let largest_variant_index = variant_layouts
.iter_enumerated()
.max_by_key(|(_i, layout)| layout.size.bytes())
.map(|(i, _layout)| i)?;
let all_indices = (0..=variants.len() - 1).map(V::new);
let needs_disc = |index: V| index != largest_variant_index && !absent(&variants[index]);
let niche_variants = all_indices.clone().find(|v| needs_disc(*v)).unwrap().index()
..=all_indices.rev().find(|v| needs_disc(*v)).unwrap().index();
let count = niche_variants.size_hint().1.unwrap() as u128;
let (field_index, niche, (niche_start, niche_scalar)) = variants[largest_variant_index]
.iter()
.enumerate()
.filter_map(|(j, field)| Some((j, field.largest_niche?)))
.max_by_key(|(_, niche)| niche.available(dl))
.and_then(|(j, niche)| Some((j, niche, niche.reserve(dl, count)?)))?;
let niche_offset =
niche.offset + variant_layouts[largest_variant_index].fields.offset(field_index);
let niche_size = niche.value.size(dl);
let size = variant_layouts[largest_variant_index].size.align_to(align.abi);
let all_variants_fit = variant_layouts.iter_enumerated_mut().all(|(i, layout)| {
if i == largest_variant_index {
return true;
}
layout.largest_niche = None;
if layout.size <= niche_offset {
return true;
}
let this_align = layout.align.abi;
let this_offset = (niche_offset + niche_size).align_to(this_align);
if this_offset + layout.size > size {
return false;
}
match layout.fields {
FieldsShape::Arbitrary { ref mut offsets, .. } => {
for (j, offset) in offsets.iter_mut().enumerate() {
if !variants[i][j].is_zst() {
*offset += this_offset;
}
}
}
_ => {
panic!("Layout of fields should be Arbitrary for variants")
}
}
if !layout.abi.is_uninhabited() {
layout.abi = Abi::Aggregate { sized: true };
}
layout.size += this_offset;
true
});
if !all_variants_fit {
return None;
}
let largest_niche = Niche::from_scalar(dl, niche_offset, niche_scalar);
let others_zst = variant_layouts
.iter_enumerated()
.all(|(i, layout)| i == largest_variant_index || layout.size == Size::ZERO);
let same_size = size == variant_layouts[largest_variant_index].size;
let same_align = align == variant_layouts[largest_variant_index].align;
let abi = if variant_layouts.iter().all(|v| v.abi.is_uninhabited()) {
Abi::Uninhabited
} else if same_size && same_align && others_zst {
match variant_layouts[largest_variant_index].abi {
Abi::Scalar(_) => Abi::Scalar(niche_scalar),
Abi::ScalarPair(first, second) => {
if niche_offset == Size::ZERO {
Abi::ScalarPair(niche_scalar, second.to_union())
} else {
Abi::ScalarPair(first.to_union(), niche_scalar)
}
}
_ => Abi::Aggregate { sized: true },
}
} else {
Abi::Aggregate { sized: true }
};
let layout = LayoutS {
variants: Variants::Multiple {
tag: niche_scalar,
tag_encoding: TagEncoding::Niche {
untagged_variant: largest_variant_index,
niche_variants: (V::new(*niche_variants.start())
..=V::new(*niche_variants.end())),
niche_start,
},
tag_field: 0,
variants: IndexVec::new(),
},
fields: FieldsShape::Arbitrary {
offsets: vec![niche_offset],
memory_index: vec![0],
},
abi,
largest_niche,
size,
align,
};
Some(TmpLayout { layout, variants: variant_layouts })
};
let niche_filling_layout = calculate_niche_filling_layout();
let (mut min, mut max) = (i128::MAX, i128::MIN);
let discr_type = repr.discr_type();
let bits = Integer::from_attr(dl, discr_type).size().bits();
for (i, mut val) in discriminants {
if variants[i].iter().any(|f| f.abi.is_uninhabited()) {
continue;
}
if discr_type.is_signed() {
val = (val << (128 - bits)) >> (128 - bits);
}
if val < min {
min = val;
}
if val > max {
max = val;
}
}
if (min, max) == (i128::MAX, i128::MIN) {
min = 0;
max = 0;
}
assert!(min <= max, "discriminant range is {}...{}", min, max);
let (min_ity, signed) = discr_range_of_repr(min, max); let mut align = dl.aggregate_align;
let mut size = Size::ZERO;
let mut start_align = Align::from_bytes(256).unwrap();
assert_eq!(Integer::for_align(dl, start_align), None);
let mut prefix_align = min_ity.align(dl).abi;
if repr.c() {
for fields in variants {
for field in fields {
prefix_align = prefix_align.max(field.align.abi);
}
}
}
let mut layout_variants = variants
.iter_enumerated()
.map(|(i, field_layouts)| {
let mut st = self.univariant(
dl,
field_layouts,
repr,
StructKind::Prefixed(min_ity.size(), prefix_align),
)?;
st.variants = Variants::Single { index: i };
for field in st.fields.index_by_increasing_offset().map(|j| &field_layouts[j]) {
if !field.is_zst() || field.align.abi.bytes() != 1 {
start_align = start_align.min(field.align.abi);
break;
}
}
size = cmp::max(size, st.size);
align = align.max(st.align);
Some(st)
})
.collect::<Option<IndexVec<V, _>>>()?;
size = size.align_to(align.abi);
if size.bytes() >= dl.obj_size_bound() {
return None;
}
let typeck_ity = Integer::from_attr(dl, repr.discr_type());
if typeck_ity < min_ity {
panic!(
"layout decided on a larger discriminant type ({:?}) than typeck ({:?})",
min_ity, typeck_ity
);
}
let mut ity = if repr.c() || repr.int.is_some() {
min_ity
} else {
Integer::for_align(dl, start_align).unwrap_or(min_ity)
};
if ity <= min_ity {
ity = min_ity;
} else {
let old_ity_size = min_ity.size();
let new_ity_size = ity.size();
for variant in &mut layout_variants {
match variant.fields {
FieldsShape::Arbitrary { ref mut offsets, .. } => {
for i in offsets {
if *i <= old_ity_size {
assert_eq!(*i, old_ity_size);
*i = new_ity_size;
}
}
if variant.size <= old_ity_size {
variant.size = new_ity_size;
}
}
_ => panic!(),
}
}
}
let tag_mask = ity.size().unsigned_int_max();
let tag = Scalar::Initialized {
value: Int(ity, signed),
valid_range: WrappingRange {
start: (min as u128 & tag_mask),
end: (max as u128 & tag_mask),
},
};
let mut abi = Abi::Aggregate { sized: true };
if layout_variants.iter().all(|v| v.abi.is_uninhabited()) {
abi = Abi::Uninhabited;
} else if tag.size(dl) == size {
abi = Abi::Scalar(tag);
} else {
let mut common_prim = None;
let mut common_prim_initialized_in_all_variants = true;
for (field_layouts, layout_variant) in iter::zip(variants, &layout_variants) {
let FieldsShape::Arbitrary { ref offsets, .. } = layout_variant.fields else {
panic!();
};
let mut fields = iter::zip(field_layouts, offsets).filter(|p| !p.0.is_zst());
let (field, offset) = match (fields.next(), fields.next()) {
(None, None) => {
common_prim_initialized_in_all_variants = false;
continue;
}
(Some(pair), None) => pair,
_ => {
common_prim = None;
break;
}
};
let prim = match field.abi {
Abi::Scalar(scalar) => {
common_prim_initialized_in_all_variants &=
matches!(scalar, Scalar::Initialized { .. });
scalar.primitive()
}
_ => {
common_prim = None;
break;
}
};
if let Some(pair) = common_prim {
if pair != (prim, offset) {
common_prim = None;
break;
}
} else {
common_prim = Some((prim, offset));
}
}
if let Some((prim, offset)) = common_prim {
let prim_scalar = if common_prim_initialized_in_all_variants {
scalar_unit(prim)
} else {
Scalar::Union { value: prim }
};
let pair = self.scalar_pair::<V>(tag, prim_scalar);
let pair_offsets = match pair.fields {
FieldsShape::Arbitrary { ref offsets, ref memory_index } => {
assert_eq!(memory_index, &[0, 1]);
offsets
}
_ => panic!(),
};
if pair_offsets[0] == Size::ZERO
&& pair_offsets[1] == *offset
&& align == pair.align
&& size == pair.size
{
abi = pair.abi;
}
}
}
if matches!(abi, Abi::Scalar(..) | Abi::ScalarPair(..)) {
for variant in &mut layout_variants {
if variant.fields.count() > 0 && matches!(variant.abi, Abi::Aggregate { .. }) {
variant.abi = abi;
variant.size = cmp::max(variant.size, size);
variant.align.abi = cmp::max(variant.align.abi, align.abi);
}
}
}
let largest_niche = Niche::from_scalar(dl, Size::ZERO, tag);
let tagged_layout = LayoutS {
variants: Variants::Multiple {
tag,
tag_encoding: TagEncoding::Direct,
tag_field: 0,
variants: IndexVec::new(),
},
fields: FieldsShape::Arbitrary { offsets: vec![Size::ZERO], memory_index: vec![0] },
largest_niche,
abi,
align,
size,
};
let tagged_layout = TmpLayout { layout: tagged_layout, variants: layout_variants };
let mut best_layout = match (tagged_layout, niche_filling_layout) {
(tl, Some(nl)) => {
use cmp::Ordering::*;
let niche_size = |tmp_l: &TmpLayout<V>| {
tmp_l.layout.largest_niche.map_or(0, |n| n.available(dl))
};
match (tl.layout.size.cmp(&nl.layout.size), niche_size(&tl).cmp(&niche_size(&nl))) {
(Greater, _) => nl,
(Equal, Less) => nl,
_ => tl,
}
}
(tl, None) => tl,
};
best_layout.layout.variants = match best_layout.layout.variants {
Variants::Multiple { tag, tag_encoding, tag_field, .. } => {
Variants::Multiple { tag, tag_encoding, tag_field, variants: best_layout.variants }
}
_ => panic!(),
};
Some(best_layout.layout)
}
fn layout_of_union<'a, V: Idx, F: Deref<Target = &'a LayoutS<V>> + Debug>(
&self,
repr: &ReprOptions,
variants: &IndexVec<V, Vec<F>>,
) -> Option<LayoutS<V>> {
let dl = self.current_data_layout();
let dl = dl.borrow();
let mut align = if repr.pack.is_some() { dl.i8_align } else { dl.aggregate_align };
if let Some(repr_align) = repr.align {
align = align.max(AbiAndPrefAlign::new(repr_align));
}
let optimize = !repr.inhibit_union_abi_opt();
let mut size = Size::ZERO;
let mut abi = Abi::Aggregate { sized: true };
let index = V::new(0);
for field in &variants[index] {
assert!(field.is_sized());
align = align.max(field.align);
if optimize && !field.is_zst() {
let field_abi = match field.abi {
Abi::Scalar(x) => Abi::Scalar(x.to_union()),
Abi::ScalarPair(x, y) => Abi::ScalarPair(x.to_union(), y.to_union()),
Abi::Vector { element: x, count } => {
Abi::Vector { element: x.to_union(), count }
}
Abi::Uninhabited | Abi::Aggregate { .. } => Abi::Aggregate { sized: true },
};
if size == Size::ZERO {
abi = field_abi;
} else if abi != field_abi {
abi = Abi::Aggregate { sized: true };
}
}
size = cmp::max(size, field.size);
}
if let Some(pack) = repr.pack {
align = align.min(AbiAndPrefAlign::new(pack));
}
Some(LayoutS {
variants: Variants::Single { index },
fields: FieldsShape::Union(NonZeroUsize::new(variants[index].len())?),
abi,
largest_niche: None,
align,
size: size.align_to(align.abi),
})
}
}