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rustc_target: factor out common fields of non-Single Variants.

This commit is contained in:
Eduard-Mihai Burtescu 2019-03-29 07:44:54 +02:00
parent 70a497a437
commit 5b7f4e9e21
12 changed files with 193 additions and 134 deletions
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51
src/librustc/ty/layout.rs
View File

@ -913,11 +913,13 @@ impl<'a, 'tcx> LayoutCx<'tcx, TyCtxt<'a, 'tcx, 'tcx>> {
} }
return Ok(tcx.intern_layout(LayoutDetails { return Ok(tcx.intern_layout(LayoutDetails {
variants: Variants::NicheFilling { variants: Variants::Multiple {
discr: niche_scalar,
discr_kind: DiscriminantKind::Niche {
dataful_variant: i, dataful_variant: i,
niche_variants, niche_variants,
niche: niche_scalar,
niche_start, niche_start,
},
variants: st, variants: st,
}, },
fields: FieldPlacement::Arbitrary { fields: FieldPlacement::Arbitrary {
@ -1137,8 +1139,9 @@ impl<'a, 'tcx> LayoutCx<'tcx, TyCtxt<'a, 'tcx, 'tcx>> {
} }
tcx.intern_layout(LayoutDetails { tcx.intern_layout(LayoutDetails {
variants: Variants::Tagged { variants: Variants::Multiple {
tag, discr: tag,
discr_kind: DiscriminantKind::Tag,
variants: layout_variants, variants: layout_variants,
}, },
fields: FieldPlacement::Arbitrary { fields: FieldPlacement::Arbitrary {
@ -1293,8 +1296,7 @@ impl<'a, 'tcx> LayoutCx<'tcx, TyCtxt<'a, 'tcx, 'tcx>> {
} }
} }
Variants::NicheFilling { .. } | Variants::Multiple { ref discr, ref discr_kind, .. } => {
Variants::Tagged { .. } => {
debug!("print-type-size `{:#?}` adt general variants def {}", debug!("print-type-size `{:#?}` adt general variants def {}",
layout.ty, adt_def.variants.len()); layout.ty, adt_def.variants.len());
let variant_infos: Vec<_> = let variant_infos: Vec<_> =
@ -1306,8 +1308,8 @@ impl<'a, 'tcx> LayoutCx<'tcx, TyCtxt<'a, 'tcx, 'tcx>> {
layout.for_variant(self, i)) layout.for_variant(self, i))
}) })
.collect(); .collect();
record(adt_kind.into(), adt_packed, match layout.variants { record(adt_kind.into(), adt_packed, match discr_kind {
Variants::Tagged { ref tag, .. } => Some(tag.value.size(self)), DiscriminantKind::Tag => Some(discr.value.size(self)),
_ => None _ => None
}, variant_infos); }, variant_infos);
} }
@ -1627,8 +1629,7 @@ impl<'a, 'tcx, C> TyLayoutMethods<'tcx, C> for Ty<'tcx>
}) })
} }
Variants::NicheFilling { ref variants, .. } | Variants::Multiple { ref variants, .. } => {
Variants::Tagged { ref variants, .. } => {
&variants[variant_index] &variants[variant_index]
} }
}; };
@ -1735,8 +1736,7 @@ impl<'a, 'tcx, C> TyLayoutMethods<'tcx, C> for Ty<'tcx>
} }
// Discriminant field for enums (where applicable). // Discriminant field for enums (where applicable).
Variants::Tagged { tag: ref discr, .. } | Variants::Multiple { ref discr, .. } => {
Variants::NicheFilling { niche: ref discr, .. } => {
assert_eq!(i, 0); assert_eq!(i, 0);
let layout = LayoutDetails::scalar(cx, discr.clone()); let layout = LayoutDetails::scalar(cx, discr.clone());
return MaybeResult::from_ok(TyLayout { return MaybeResult::from_ok(TyLayout {
@ -1881,26 +1881,37 @@ impl<'a> HashStable<StableHashingContext<'a>> for Variants {
Single { index } => { Single { index } => {
index.hash_stable(hcx, hasher); index.hash_stable(hcx, hasher);
} }
Tagged { Multiple {
ref tag, ref discr,
ref discr_kind,
ref variants, ref variants,
} => { } => {
tag.hash_stable(hcx, hasher); discr.hash_stable(hcx, hasher);
discr_kind.hash_stable(hcx, hasher);
variants.hash_stable(hcx, hasher); variants.hash_stable(hcx, hasher);
} }
NicheFilling { }
}
}
impl<'a> HashStable<StableHashingContext<'a>> for DiscriminantKind {
fn hash_stable<W: StableHasherResult>(&self,
hcx: &mut StableHashingContext<'a>,
hasher: &mut StableHasher<W>) {
use crate::ty::layout::DiscriminantKind::*;
mem::discriminant(self).hash_stable(hcx, hasher);
match *self {
Tag => {}
Niche {
dataful_variant, dataful_variant,
ref niche_variants, ref niche_variants,
ref niche,
niche_start, niche_start,
ref variants,
} => { } => {
dataful_variant.hash_stable(hcx, hasher); dataful_variant.hash_stable(hcx, hasher);
niche_variants.start().hash_stable(hcx, hasher); niche_variants.start().hash_stable(hcx, hasher);
niche_variants.end().hash_stable(hcx, hasher); niche_variants.end().hash_stable(hcx, hasher);
niche.hash_stable(hcx, hasher);
niche_start.hash_stable(hcx, hasher); niche_start.hash_stable(hcx, hasher);
variants.hash_stable(hcx, hasher);
} }
} }
} }

64
src/librustc_codegen_llvm/debuginfo/metadata.rs
View File

@ -1235,7 +1235,11 @@ impl EnumMemberDescriptionFactory<'ll, 'tcx> {
} }
] ]
} }
layout::Variants::Tagged { ref variants, .. } => { layout::Variants::Multiple {
discr_kind: layout::DiscriminantKind::Tag,
ref variants,
..
} => {
let discriminant_info = if fallback { let discriminant_info = if fallback {
RegularDiscriminant(self.discriminant_type_metadata RegularDiscriminant(self.discriminant_type_metadata
.expect("")) .expect(""))
@ -1277,12 +1281,14 @@ impl EnumMemberDescriptionFactory<'ll, 'tcx> {
} }
}).collect() }).collect()
} }
layout::Variants::NicheFilling { layout::Variants::Multiple {
discr_kind: layout::DiscriminantKind::Niche {
ref niche_variants, ref niche_variants,
niche_start, niche_start,
ref variants,
dataful_variant, dataful_variant,
ref niche, },
ref discr,
ref variants,
} => { } => {
if fallback { if fallback {
let variant = self.layout.for_variant(cx, dataful_variant); let variant = self.layout.for_variant(cx, dataful_variant);
@ -1369,7 +1375,11 @@ impl EnumMemberDescriptionFactory<'ll, 'tcx> {
let value = (i.as_u32() as u128) let value = (i.as_u32() as u128)
.wrapping_sub(niche_variants.start().as_u32() as u128) .wrapping_sub(niche_variants.start().as_u32() as u128)
.wrapping_add(niche_start); .wrapping_add(niche_start);
let value = truncate(value, niche.value.size(cx)); let value = truncate(value, discr.value.size(cx));
// NOTE(eddyb) do *NOT* remove this assert, until
// we pass the full 128-bit value to LLVM, otherwise
// truncation will be silent and remain undetected.
assert_eq!(value as u64 as u128, value);
Some(value as u64) Some(value as u64)
}; };
@ -1586,8 +1596,11 @@ fn prepare_enum_metadata(
let layout = cx.layout_of(enum_type); let layout = cx.layout_of(enum_type);
match (&layout.abi, &layout.variants) { match (&layout.abi, &layout.variants) {
(&layout::Abi::Scalar(_), &layout::Variants::Tagged {ref tag, .. }) => (&layout::Abi::Scalar(_), &layout::Variants::Multiple {
return FinalMetadata(discriminant_type_metadata(tag.value)), discr_kind: layout::DiscriminantKind::Tag,
ref discr,
..
}) => return FinalMetadata(discriminant_type_metadata(discr.value)),
_ => {} _ => {}
} }
@ -1599,9 +1612,16 @@ fn prepare_enum_metadata(
if use_enum_fallback(cx) { if use_enum_fallback(cx) {
let discriminant_type_metadata = match layout.variants { let discriminant_type_metadata = match layout.variants {
layout::Variants::Single { .. } | layout::Variants::Single { .. } |
layout::Variants::NicheFilling { .. } => None, layout::Variants::Multiple {
layout::Variants::Tagged { ref tag, .. } => { discr_kind: layout::DiscriminantKind::Niche { .. },
Some(discriminant_type_metadata(tag.value)) ..
} => None,
layout::Variants::Multiple {
discr_kind: layout::DiscriminantKind::Tag,
ref discr,
..
} => {
Some(discriminant_type_metadata(discr.value))
} }
}; };
@ -1636,16 +1656,20 @@ fn prepare_enum_metadata(
); );
} }
let discriminator_metadata = match &layout.variants { let discriminator_metadata = match layout.variants {
// A single-variant enum has no discriminant. // A single-variant enum has no discriminant.
&layout::Variants::Single { .. } => None, layout::Variants::Single { .. } => None,
&layout::Variants::NicheFilling { ref niche, .. } => { layout::Variants::Multiple {
discr_kind: layout::DiscriminantKind::Niche { .. },
ref discr,
..
} => {
// Find the integer type of the correct size. // Find the integer type of the correct size.
let size = niche.value.size(cx); let size = discr.value.size(cx);
let align = niche.value.align(cx); let align = discr.value.align(cx);
let discr_type = match niche.value { let discr_type = match discr.value {
layout::Int(t, _) => t, layout::Int(t, _) => t,
layout::Float(layout::FloatTy::F32) => Integer::I32, layout::Float(layout::FloatTy::F32) => Integer::I32,
layout::Float(layout::FloatTy::F64) => Integer::I64, layout::Float(layout::FloatTy::F64) => Integer::I64,
@ -1668,8 +1692,12 @@ fn prepare_enum_metadata(
} }
}, },
&layout::Variants::Tagged { ref tag, .. } => { layout::Variants::Multiple {
let discr_type = tag.value.to_ty(cx.tcx); discr_kind: layout::DiscriminantKind::Tag,
ref discr,
..
} => {
let discr_type = discr.value.to_ty(cx.tcx);
let (size, align) = cx.size_and_align_of(discr_type); let (size, align) = cx.size_and_align_of(discr_type);
let discr_metadata = basic_type_metadata(cx, discr_type); let discr_metadata = basic_type_metadata(cx, discr_type);

8
src/librustc_codegen_llvm/type_of.rs
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@ -452,7 +452,13 @@ impl<'tcx> LayoutLlvmExt<'tcx> for TyLayout<'tcx> {
_ => { _ => {
let mut data_variant = match self.variants { let mut data_variant = match self.variants {
layout::Variants::NicheFilling { dataful_variant, .. } => { layout::Variants::Multiple {
discr_kind: layout::DiscriminantKind::Niche {
dataful_variant,
..
},
..
} => {
// Only the niche itself is always initialized, // Only the niche itself is always initialized,
// so only check for a pointer at its offset. // so only check for a pointer at its offset.
// //

28
src/librustc_codegen_ssa/mir/place.rs
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@ -216,37 +216,36 @@ impl<'a, 'tcx: 'a, V: CodegenObject> PlaceRef<'tcx, V> {
if self.layout.abi.is_uninhabited() { if self.layout.abi.is_uninhabited() {
return bx.cx().const_undef(cast_to); return bx.cx().const_undef(cast_to);
} }
match self.layout.variants { let (discr_scalar, discr_kind) = match self.layout.variants {
layout::Variants::Single { index } => { layout::Variants::Single { index } => {
let discr_val = self.layout.ty.ty_adt_def().map_or( let discr_val = self.layout.ty.ty_adt_def().map_or(
index.as_u32() as u128, index.as_u32() as u128,
|def| def.discriminant_for_variant(bx.cx().tcx(), index).val); |def| def.discriminant_for_variant(bx.cx().tcx(), index).val);
return bx.cx().const_uint_big(cast_to, discr_val); return bx.cx().const_uint_big(cast_to, discr_val);
} }
layout::Variants::Tagged { .. } | layout::Variants::Multiple { ref discr, ref discr_kind, .. } => {
layout::Variants::NicheFilling { .. } => {}, (discr, discr_kind)
} }
};
let discr = self.project_field(bx, 0); let discr = self.project_field(bx, 0);
let lldiscr = bx.load_operand(discr).immediate(); let lldiscr = bx.load_operand(discr).immediate();
match self.layout.variants { match *discr_kind {
layout::Variants::Single { .. } => bug!(), layout::DiscriminantKind::Tag => {
layout::Variants::Tagged { ref tag, .. } => { let signed = match discr_scalar.value {
let signed = match tag.value {
// We use `i1` for bytes that are always `0` or `1`, // We use `i1` for bytes that are always `0` or `1`,
// e.g., `#[repr(i8)] enum E { A, B }`, but we can't // e.g., `#[repr(i8)] enum E { A, B }`, but we can't
// let LLVM interpret the `i1` as signed, because // let LLVM interpret the `i1` as signed, because
// then `i1 1` (i.e., E::B) is effectively `i8 -1`. // then `i1 1` (i.e., E::B) is effectively `i8 -1`.
layout::Int(_, signed) => !tag.is_bool() && signed, layout::Int(_, signed) => !discr_scalar.is_bool() && signed,
_ => false _ => false
}; };
bx.intcast(lldiscr, cast_to, signed) bx.intcast(lldiscr, cast_to, signed)
} }
layout::Variants::NicheFilling { layout::DiscriminantKind::Niche {
dataful_variant, dataful_variant,
ref niche_variants, ref niche_variants,
niche_start, niche_start,
..
} => { } => {
let niche_llty = bx.cx().immediate_backend_type(discr.layout); let niche_llty = bx.cx().immediate_backend_type(discr.layout);
if niche_variants.start() == niche_variants.end() { if niche_variants.start() == niche_variants.end() {
@ -291,7 +290,10 @@ impl<'a, 'tcx: 'a, V: CodegenObject> PlaceRef<'tcx, V> {
layout::Variants::Single { index } => { layout::Variants::Single { index } => {
assert_eq!(index, variant_index); assert_eq!(index, variant_index);
} }
layout::Variants::Tagged { .. } => { layout::Variants::Multiple {
discr_kind: layout::DiscriminantKind::Tag,
..
} => {
let ptr = self.project_field(bx, 0); let ptr = self.project_field(bx, 0);
let to = self.layout.ty.ty_adt_def().unwrap() let to = self.layout.ty.ty_adt_def().unwrap()
.discriminant_for_variant(bx.tcx(), variant_index) .discriminant_for_variant(bx.tcx(), variant_index)
@ -301,10 +303,12 @@ impl<'a, 'tcx: 'a, V: CodegenObject> PlaceRef<'tcx, V> {
ptr.llval, ptr.llval,
ptr.align); ptr.align);
} }
layout::Variants::NicheFilling { layout::Variants::Multiple {
discr_kind: layout::DiscriminantKind::Niche {
dataful_variant, dataful_variant,
ref niche_variants, ref niche_variants,
niche_start, niche_start,
},
.. ..
} => { } => {
if variant_index != dataful_variant { if variant_index != dataful_variant {

3
src/librustc_codegen_ssa/mir/rvalue.rs
View File

@ -303,8 +303,7 @@ impl<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
}); });
} }
} }
layout::Variants::Tagged { .. } | layout::Variants::Multiple { .. } => {},
layout::Variants::NicheFilling { .. } => {},
} }
let llval = operand.immediate(); let llval = operand.immediate();

27
src/librustc_lint/types.rs
View File

@ -842,10 +842,22 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for VariantSizeDifferences {
let item_def_id = cx.tcx.hir().local_def_id_from_hir_id(it.hir_id); let item_def_id = cx.tcx.hir().local_def_id_from_hir_id(it.hir_id);
let t = cx.tcx.type_of(item_def_id); let t = cx.tcx.type_of(item_def_id);
let ty = cx.tcx.erase_regions(&t); let ty = cx.tcx.erase_regions(&t);
match cx.layout_of(ty) { let layout = match cx.layout_of(ty) {
Ok(layout) => { Ok(layout) => layout,
let variants = &layout.variants; Err(ty::layout::LayoutError::Unknown(_)) => return,
if let layout::Variants::Tagged { ref variants, ref tag, .. } = variants { Err(err @ ty::layout::LayoutError::SizeOverflow(_)) => {
bug!("failed to get layout for `{}`: {}", t, err);
}
};
let (variants, tag) = match layout.variants {
layout::Variants::Multiple {
discr_kind: layout::DiscriminantKind::Tag,
ref discr,
ref variants,
} => (variants, discr),
_ => return,
};
let discr_size = tag.value.size(&cx.tcx).bytes(); let discr_size = tag.value.size(&cx.tcx).bytes();
debug!("enum `{}` is {} bytes large with layout:\n{:#?}", debug!("enum `{}` is {} bytes large with layout:\n{:#?}",
@ -883,11 +895,4 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for VariantSizeDifferences {
} }
} }
} }
Err(ty::layout::LayoutError::Unknown(_)) => return,
Err(err @ ty::layout::LayoutError::SizeOverflow(_)) => {
bug!("failed to get layout for `{}`: {}", t, err);
}
}
}
}
} }

3
src/librustc_mir/interpret/cast.rs
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@ -64,8 +64,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> InterpretCx<'a, 'mir, 'tcx, M>
dest); dest);
} }
} }
layout::Variants::Tagged { .. } | layout::Variants::Multiple { .. } => {},
layout::Variants::NicheFilling { .. } => {},
} }
let dest_val = self.cast_scalar(src.to_scalar()?, src.layout, dest.layout)?; let dest_val = self.cast_scalar(src.to_scalar()?, src.layout, dest.layout)?;

16
src/librustc_mir/interpret/operand.rs
View File

@ -610,25 +610,24 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> InterpretCx<'a, 'mir, 'tcx, M>
) -> EvalResult<'tcx, (u128, VariantIdx)> { ) -> EvalResult<'tcx, (u128, VariantIdx)> {
trace!("read_discriminant_value {:#?}", rval.layout); trace!("read_discriminant_value {:#?}", rval.layout);
match rval.layout.variants { let discr_kind = match rval.layout.variants {
layout::Variants::Single { index } => { layout::Variants::Single { index } => {
let discr_val = rval.layout.ty.ty_adt_def().map_or( let discr_val = rval.layout.ty.ty_adt_def().map_or(
index.as_u32() as u128, index.as_u32() as u128,
|def| def.discriminant_for_variant(*self.tcx, index).val); |def| def.discriminant_for_variant(*self.tcx, index).val);
return Ok((discr_val, index)); return Ok((discr_val, index));
} }
layout::Variants::Tagged { .. } | layout::Variants::Multiple { ref discr_kind, .. } => discr_kind,
layout::Variants::NicheFilling { .. } => {}, };
}
// read raw discriminant value // read raw discriminant value
let discr_op = self.operand_field(rval, 0)?; let discr_op = self.operand_field(rval, 0)?;
let discr_val = self.read_immediate(discr_op)?; let discr_val = self.read_immediate(discr_op)?;
let raw_discr = discr_val.to_scalar_or_undef(); let raw_discr = discr_val.to_scalar_or_undef();
trace!("discr value: {:?}", raw_discr); trace!("discr value: {:?}", raw_discr);
// post-process // post-process
Ok(match rval.layout.variants { Ok(match *discr_kind {
layout::Variants::Single { .. } => bug!(), layout::DiscriminantKind::Tag => {
layout::Variants::Tagged { .. } => {
let bits_discr = match raw_discr.to_bits(discr_val.layout.size) { let bits_discr = match raw_discr.to_bits(discr_val.layout.size) {
Ok(raw_discr) => raw_discr, Ok(raw_discr) => raw_discr,
Err(_) => return err!(InvalidDiscriminant(raw_discr.erase_tag())), Err(_) => return err!(InvalidDiscriminant(raw_discr.erase_tag())),
@ -657,11 +656,10 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> InterpretCx<'a, 'mir, 'tcx, M>
.ok_or_else(|| EvalErrorKind::InvalidDiscriminant(raw_discr.erase_tag()))?; .ok_or_else(|| EvalErrorKind::InvalidDiscriminant(raw_discr.erase_tag()))?;
(real_discr, index.0) (real_discr, index.0)
}, },
layout::Variants::NicheFilling { layout::DiscriminantKind::Niche {
dataful_variant, dataful_variant,
ref niche_variants, ref niche_variants,
niche_start, niche_start,
..
} => { } => {
let variants_start = niche_variants.start().as_u32() as u128; let variants_start = niche_variants.start().as_u32() as u128;
let variants_end = niche_variants.end().as_u32() as u128; let variants_end = niche_variants.end().as_u32() as u128;

12
src/librustc_mir/interpret/place.rs
View File

@ -958,7 +958,11 @@ where
layout::Variants::Single { index } => { layout::Variants::Single { index } => {
assert_eq!(index, variant_index); assert_eq!(index, variant_index);
} }
layout::Variants::Tagged { ref tag, .. } => { layout::Variants::Multiple {
discr_kind: layout::DiscriminantKind::Tag,
ref discr,
..
} => {
let adt_def = dest.layout.ty.ty_adt_def().unwrap(); let adt_def = dest.layout.ty.ty_adt_def().unwrap();
assert!(variant_index.as_usize() < adt_def.variants.len()); assert!(variant_index.as_usize() < adt_def.variants.len());
let discr_val = adt_def let discr_val = adt_def
@ -968,16 +972,18 @@ where
// raw discriminants for enums are isize or bigger during // raw discriminants for enums are isize or bigger during
// their computation, but the in-memory tag is the smallest possible // their computation, but the in-memory tag is the smallest possible
// representation // representation
let size = tag.value.size(self); let size = discr.value.size(self);
let discr_val = truncate(discr_val, size); let discr_val = truncate(discr_val, size);
let discr_dest = self.place_field(dest, 0)?; let discr_dest = self.place_field(dest, 0)?;
self.write_scalar(Scalar::from_uint(discr_val, size), discr_dest)?; self.write_scalar(Scalar::from_uint(discr_val, size), discr_dest)?;
} }
layout::Variants::NicheFilling { layout::Variants::Multiple {
discr_kind: layout::DiscriminantKind::Niche {
dataful_variant, dataful_variant,
ref niche_variants, ref niche_variants,
niche_start, niche_start,
},
.. ..
} => { } => {
assert!( assert!(

3
src/librustc_mir/interpret/visitor.rs
View File

@ -241,8 +241,7 @@ macro_rules! make_value_visitor {
// If this is a multi-variant layout, we have find the right one and proceed with // If this is a multi-variant layout, we have find the right one and proceed with
// that. // that.
match v.layout().variants { match v.layout().variants {
layout::Variants::NicheFilling { .. } | layout::Variants::Multiple { .. } => {
layout::Variants::Tagged { .. } => {
let op = v.to_op(self.ecx())?; let op = v.to_op(self.ecx())?;
let idx = self.ecx().read_discriminant(op)?.1; let idx = self.ecx().read_discriminant(op)?.1;
let inner = v.project_downcast(self.ecx(), idx)?; let inner = v.project_downcast(self.ecx(), idx)?;

3
src/librustc_target/abi/call/x86_64.rs
View File

@ -61,8 +61,7 @@ fn classify_arg<'a, Ty, C>(cx: &C, arg: &ArgType<'a, Ty>)
} }
return Ok(()); return Ok(());
} }
abi::Variants::Tagged { .. } | abi::Variants::Multiple { .. } => return Err(Memory),
abi::Variants::NicheFilling { .. } => return Err(Memory),
} }
} }

25
src/librustc_target/abi/mod.rs
View File

@ -828,15 +828,22 @@ pub enum Variants {
index: VariantIdx, index: VariantIdx,
}, },
/// General-case enums: for each case there is a struct, and they all have /// Enums with more than one inhabited variant: for each case there is
/// all space reserved for the tag, and their first field starts /// a struct, and they all have space reserved for the discriminant,
/// at a non-0 offset, after where the tag would go. /// which is the sole field of the enum layout.
Tagged { Multiple {
tag: Scalar, discr: Scalar,
discr_kind: DiscriminantKind,
variants: IndexVec<VariantIdx, LayoutDetails>, variants: IndexVec<VariantIdx, LayoutDetails>,
}, },
}
/// Multiple cases distinguished by a niche (values invalid for a type): #[derive(PartialEq, Eq, Hash, Debug)]
pub enum DiscriminantKind {
/// Integer tag holding the discriminant value itself.
Tag,
/// Niche (values invalid for a type) encoding the discriminant:
/// the variant `dataful_variant` contains a niche at an arbitrary /// the variant `dataful_variant` contains a niche at an arbitrary
/// offset (field 0 of the enum), which for a variant with discriminant /// offset (field 0 of the enum), which for a variant with discriminant
/// `d` is set to `(d - niche_variants.start).wrapping_add(niche_start)`. /// `d` is set to `(d - niche_variants.start).wrapping_add(niche_start)`.
@ -844,13 +851,11 @@ pub enum Variants {
/// For example, `Option<(usize, &T)>` is represented such that /// For example, `Option<(usize, &T)>` is represented such that
/// `None` has a null pointer for the second tuple field, and /// `None` has a null pointer for the second tuple field, and
/// `Some` is the identity function (with a non-null reference). /// `Some` is the identity function (with a non-null reference).
NicheFilling { Niche {
dataful_variant: VariantIdx, dataful_variant: VariantIdx,
niche_variants: RangeInclusive<VariantIdx>, niche_variants: RangeInclusive<VariantIdx>,
niche: Scalar,
niche_start: u128, niche_start: u128,
variants: IndexVec<VariantIdx, LayoutDetails>, },
}
} }
#[derive(PartialEq, Eq, Hash, Debug)] #[derive(PartialEq, Eq, Hash, Debug)]