ignore zst offsets instead
This commit is contained in:
Erik Desjardins
parent
e9bc3ddb07
commit
68217c9e0f
@ -93,15 +93,29 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
|
||||
let effective_field_align = self.align.restrict_for_offset(offset);
|
||||
|
||||
let mut simple = || {
|
||||
// Unions and newtypes only use an offset of 0.
|
||||
let llval = if offset.bytes() == 0 {
|
||||
self.llval
|
||||
} else if let Abi::ScalarPair(ref a, ref b) = self.layout.abi {
|
||||
// Offsets have to match either first or second field.
|
||||
assert_eq!(offset, a.value.size(bx.cx()).align_to(b.value.align(bx.cx()).abi));
|
||||
bx.struct_gep(self.llval, 1)
|
||||
} else {
|
||||
bx.struct_gep(self.llval, bx.cx().backend_field_index(self.layout, ix))
|
||||
let llval = match self.layout.abi {
|
||||
_ if offset.bytes() == 0 => {
|
||||
// Unions and newtypes only use an offset of 0.
|
||||
// Also handles the first field of Scalar and ScalarPair layouts.
|
||||
self.llval
|
||||
}
|
||||
Abi::ScalarPair(ref a, ref b)
|
||||
if offset == a.value.size(bx.cx()).align_to(b.value.align(bx.cx()).abi) =>
|
||||
{
|
||||
// Offset matches second field.
|
||||
bx.struct_gep(self.llval, 1)
|
||||
}
|
||||
Abi::ScalarPair(..) | Abi::Scalar(_) => {
|
||||
// ZST fields are not included in Scalar and ScalarPair layouts, so manually offset the pointer.
|
||||
assert!(
|
||||
field.is_zst(),
|
||||
"non-ZST field offset does not match layout: {:?}",
|
||||
field
|
||||
);
|
||||
let byte_ptr = bx.pointercast(self.llval, bx.cx().type_i8p());
|
||||
bx.gep(byte_ptr, &[bx.const_usize(offset.bytes())])
|
||||
}
|
||||
_ => bx.struct_gep(self.llval, bx.cx().backend_field_index(self.layout, ix)),
|
||||
};
|
||||
PlaceRef {
|
||||
// HACK(eddyb): have to bitcast pointers until LLVM removes pointee types.
|
||||
|
||||
@ -289,32 +289,25 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
|
||||
|
||||
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 field_align = |f: &TyAndLayout<'_>| {
|
||||
if let Some(pack) = pack { f.align.abi.min(pack) } else { f.align.abi }
|
||||
};
|
||||
match kind {
|
||||
StructKind::AlwaysSized => {
|
||||
inverse_memory_index.sort_by_key(|&x| {
|
||||
StructKind::AlwaysSized | StructKind::MaybeUnsized => {
|
||||
optimizing.sort_by_key(|&x| {
|
||||
// Place ZSTs first to avoid "interesting offsets",
|
||||
// especially with only one or two non-ZST fields.
|
||||
let f = &fields[x as usize];
|
||||
(!f.is_zst(), cmp::Reverse(field_align(f)))
|
||||
});
|
||||
}
|
||||
StructKind::MaybeUnsized => {
|
||||
// Sort in descending alignment, except for the last field,
|
||||
// which may be accessed through an unsized type.
|
||||
inverse_memory_index[..fields.len() - 1]
|
||||
.sort_by_key(|&x| cmp::Reverse(field_align(&fields[x as usize])));
|
||||
// Place ZSTs first to avoid "interesting offsets".
|
||||
// This will reorder the last field if it is a ZST, which is okay because
|
||||
// there's nothing in memory that could be accessed through an unsized type.
|
||||
inverse_memory_index.sort_by_key(|&x| !fields[x as usize].is_zst());
|
||||
}
|
||||
StructKind::Prefixed(..) => {
|
||||
// Sort in ascending alignment so that the layout stay optimal
|
||||
// regardless of the prefix
|
||||
inverse_memory_index.sort_by_key(|&x| field_align(&fields[x as usize]));
|
||||
optimizing.sort_by_key(|&x| field_align(&fields[x as usize]));
|
||||
}
|
||||
}
|
||||
}
|
||||
@ -397,78 +390,60 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
|
||||
|
||||
// Unpack newtype ABIs and find scalar pairs.
|
||||
if sized && size.bytes() > 0 {
|
||||
// All other fields must be ZSTs, and we need them to all start at 0.
|
||||
let mut zst_offsets = offsets.iter().enumerate().filter(|&(i, _)| fields[i].is_zst());
|
||||
if zst_offsets.all(|(_, o)| o.bytes() == 0) {
|
||||
let mut non_zst_fields = fields.iter().enumerate().filter(|&(_, f)| !f.is_zst());
|
||||
// All other fields must be ZSTs.
|
||||
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()) {
|
||||
// We have exactly one non-ZST field.
|
||||
(Some((i, field)), None, None) => {
|
||||
// Field fills the struct and it has a scalar or scalar pair ABI.
|
||||
if offsets[i].bytes() == 0
|
||||
&& align.abi == field.align.abi
|
||||
&& size == field.size
|
||||
{
|
||||
match field.abi {
|
||||
// For plain scalars, or vectors of them, we can't unpack
|
||||
// newtypes for `#[repr(C)]`, as that affects C ABIs.
|
||||
Abi::Scalar(_) | Abi::Vector { .. } if optimize => {
|
||||
abi = field.abi.clone();
|
||||
}
|
||||
// But scalar pairs are Rust-specific and get
|
||||
// treated as aggregates by C ABIs anyway.
|
||||
Abi::ScalarPair(..) => {
|
||||
abi = field.abi.clone();
|
||||
}
|
||||
_ => {}
|
||||
match (non_zst_fields.next(), non_zst_fields.next(), non_zst_fields.next()) {
|
||||
// We have exactly one non-ZST field.
|
||||
(Some((i, field)), None, None) => {
|
||||
// Field fills the struct and it has a scalar or scalar pair ABI.
|
||||
if offsets[i].bytes() == 0 && align.abi == field.align.abi && size == field.size
|
||||
{
|
||||
match field.abi {
|
||||
// For plain scalars, or vectors of them, we can't unpack
|
||||
// newtypes for `#[repr(C)]`, as that affects C ABIs.
|
||||
Abi::Scalar(_) | Abi::Vector { .. } if optimize => {
|
||||
abi = field.abi.clone();
|
||||
}
|
||||
// But scalar pairs are Rust-specific and get
|
||||
// treated as aggregates by C ABIs anyway.
|
||||
Abi::ScalarPair(..) => {
|
||||
abi = field.abi.clone();
|
||||
}
|
||||
_ => {}
|
||||
}
|
||||
}
|
||||
|
||||
// Two non-ZST fields, and they're both scalars.
|
||||
(
|
||||
Some((
|
||||
i,
|
||||
&TyAndLayout {
|
||||
layout: &Layout { abi: Abi::Scalar(ref a), .. }, ..
|
||||
},
|
||||
)),
|
||||
Some((
|
||||
j,
|
||||
&TyAndLayout {
|
||||
layout: &Layout { abi: Abi::Scalar(ref b), .. }, ..
|
||||
},
|
||||
)),
|
||||
None,
|
||||
) => {
|
||||
// Order by the memory placement, not source order.
|
||||
let ((i, a), (j, b)) = if offsets[i] < offsets[j] {
|
||||
((i, a), (j, b))
|
||||
} else {
|
||||
((j, b), (i, a))
|
||||
};
|
||||
let pair = self.scalar_pair(a.clone(), b.clone());
|
||||
let pair_offsets = match pair.fields {
|
||||
FieldsShape::Arbitrary { ref offsets, ref memory_index } => {
|
||||
assert_eq!(memory_index, &[0, 1]);
|
||||
offsets
|
||||
}
|
||||
_ => bug!(),
|
||||
};
|
||||
if offsets[i] == pair_offsets[0]
|
||||
&& offsets[j] == pair_offsets[1]
|
||||
&& align == pair.align
|
||||
&& size == pair.size
|
||||
{
|
||||
// We can use `ScalarPair` only when it matches our
|
||||
// already computed layout (including `#[repr(C)]`).
|
||||
abi = pair.abi;
|
||||
}
|
||||
}
|
||||
|
||||
_ => {}
|
||||
}
|
||||
|
||||
// Two non-ZST fields, and they're both scalars.
|
||||
(
|
||||
Some((i, &TyAndLayout { layout: &Layout { abi: Abi::Scalar(ref a), .. }, .. })),
|
||||
Some((j, &TyAndLayout { layout: &Layout { abi: Abi::Scalar(ref b), .. }, .. })),
|
||||
None,
|
||||
) => {
|
||||
// Order by the memory placement, not source order.
|
||||
let ((i, a), (j, b)) =
|
||||
if offsets[i] < offsets[j] { ((i, a), (j, b)) } else { ((j, b), (i, a)) };
|
||||
let pair = self.scalar_pair(a.clone(), b.clone());
|
||||
let pair_offsets = match pair.fields {
|
||||
FieldsShape::Arbitrary { ref offsets, ref memory_index } => {
|
||||
assert_eq!(memory_index, &[0, 1]);
|
||||
offsets
|
||||
}
|
||||
_ => bug!(),
|
||||
};
|
||||
if offsets[i] == pair_offsets[0]
|
||||
&& offsets[j] == pair_offsets[1]
|
||||
&& align == pair.align
|
||||
&& size == pair.size
|
||||
{
|
||||
// We can use `ScalarPair` only when it matches our
|
||||
// already computed layout (including `#[repr(C)]`).
|
||||
abi = pair.abi;
|
||||
}
|
||||
}
|
||||
|
||||
_ => {}
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
Loading…
Reference in New Issue
Block a user