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Hoist fn absent

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This commit is contained in:
Jubilee Young 2023-12-16 01:37:00 -08:00
parent 1c6a06183a
commit 6959818ec2
1 changed files with 18 additions and 12 deletions
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30
compiler/rustc_abi/src/layout.rs
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@ -11,6 +11,24 @@ use crate::{
Variants, WrappingRange,
};
// A variant is absent if it's uninhabited and only has ZST fields.
// Present uninhabited variants only require space for their fields,
// but *not* an encoding of the discriminant (e.g., a tag value).
// See issue #49298 for more details on the need to leave space
// for non-ZST uninhabited data (mostly partial initialization).
fn absent<'a, FieldIdx, VariantIdx, F>(fields: &IndexSlice<FieldIdx, F>) -> bool
where
FieldIdx: Idx,
VariantIdx: Idx,
F: Deref<Target = &'a LayoutS<FieldIdx, VariantIdx>> + fmt::Debug,
{
let uninhabited = fields.iter().any(|f| f.abi.is_uninhabited());
// We cannot ignore alignment; that might lead us to entirely discard a variant and
// produce an enum that is less aligned than it should be!
let is_1zst = fields.iter().all(|f| f.is_1zst());
uninhabited && is_1zst
}
pub trait LayoutCalculator {
type TargetDataLayoutRef: Borrow<TargetDataLayout>;
@ -168,18 +186,6 @@ pub trait LayoutCalculator {
Scalar::Initialized { value, valid_range: WrappingRange::full(size) }
};
// A variant is absent if it's uninhabited and only has ZST fields.
// Present uninhabited variants only require space for their fields,
// but *not* an encoding of the discriminant (e.g., a tag value).
// See issue #49298 for more details on the need to leave space
// for non-ZST uninhabited data (mostly partial initialization).
let absent = |fields: &IndexSlice<FieldIdx, F>| {
let uninhabited = fields.iter().any(|f| f.abi.is_uninhabited());
// We cannot ignore alignment; that might lead us to entirely discard a variant and
// produce an enum that is less aligned than it should be!
let is_1zst = fields.iter().all(|f| f.is_1zst());
uninhabited && is_1zst
};
let (present_first, present_second) = {
let mut present_variants = variants
.iter_enumerated()