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rustc_target: factor out common fields of non-Single Variants. #59519

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Mar 31, 2019
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rustc_target: factor out common fields of non-Single Variants. #59519

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57 changes: 34 additions & 23 deletions src/librustc/ty/layout.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -913,11 +913,13 @@ impl<'a, 'tcx> LayoutCx<'tcx, TyCtxt<'a, 'tcx, 'tcx>> {
}

return Ok(tcx.intern_layout(LayoutDetails {
variants: Variants::NicheFilling {
dataful_variant: i,
niche_variants,
niche: niche_scalar,
niche_start,
variants: Variants::Multiple {
discr: niche_scalar,
discr_kind: DiscriminantKind::Niche {
dataful_variant: i,
niche_variants,
niche_start,
},
variants: st,
},
fields: FieldPlacement::Arbitrary {
Expand Down Expand Up @@ -1137,8 +1139,9 @@ impl<'a, 'tcx> LayoutCx<'tcx, TyCtxt<'a, 'tcx, 'tcx>> {
}

tcx.intern_layout(LayoutDetails {
variants: Variants::Tagged {
tag,
variants: Variants::Multiple {
discr: tag,
discr_kind: DiscriminantKind::Tag,
variants: layout_variants,
},
fields: FieldPlacement::Arbitrary {
Expand Down Expand Up @@ -1293,8 +1296,7 @@ impl<'a, 'tcx> LayoutCx<'tcx, TyCtxt<'a, 'tcx, 'tcx>> {
}
}

Variants::NicheFilling { .. } |
Variants::Tagged { .. } => {
Variants::Multiple { ref discr, ref discr_kind, .. } => {
debug!("print-type-size `{:#?}` adt general variants def {}",
layout.ty, adt_def.variants.len());
let variant_infos: Vec<_> =
Expand All @@ -1306,8 +1308,8 @@ impl<'a, 'tcx> LayoutCx<'tcx, TyCtxt<'a, 'tcx, 'tcx>> {
layout.for_variant(self, i))
})
.collect();
record(adt_kind.into(), adt_packed, match layout.variants {
Variants::Tagged { ref tag, .. } => Some(tag.value.size(self)),
record(adt_kind.into(), adt_packed, match discr_kind {
DiscriminantKind::Tag => Some(discr.value.size(self)),
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first occurrence here

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This whole thing needs to be rewritten to pretty-print layouts losslessly (or we can just use {:#?}, heh).

_ => None
}, variant_infos);
}
Expand Down Expand Up @@ -1627,8 +1629,7 @@ impl<'a, 'tcx, C> TyLayoutMethods<'tcx, C> for Ty<'tcx>
})
}

Variants::NicheFilling { ref variants, .. } |
Variants::Tagged { ref variants, .. } => {
Variants::Multiple { ref variants, .. } => {
&variants[variant_index]
}
};
Expand Down Expand Up @@ -1735,8 +1736,7 @@ impl<'a, 'tcx, C> TyLayoutMethods<'tcx, C> for Ty<'tcx>
}

// Discriminant field for enums (where applicable).
Variants::Tagged { tag: ref discr, .. } |
Variants::NicheFilling { niche: ref discr, .. } => {
Variants::Multiple { ref discr, .. } => {
assert_eq!(i, 0);
let layout = LayoutDetails::scalar(cx, discr.clone());
return MaybeResult::from_ok(TyLayout {
Expand Down Expand Up @@ -1881,26 +1881,37 @@ impl<'a> HashStable<StableHashingContext<'a>> for Variants {
Single { index } => {
index.hash_stable(hcx, hasher);
}
Tagged {
ref tag,
Multiple {
ref discr,
ref discr_kind,
ref variants,
} => {
tag.hash_stable(hcx, hasher);
discr.hash_stable(hcx, hasher);
discr_kind.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,
ref niche_variants,
ref niche,
niche_start,
ref variants,
} => {
dataful_variant.hash_stable(hcx, hasher);
niche_variants.start().hash_stable(hcx, hasher);
niche_variants.end().hash_stable(hcx, hasher);
niche.hash_stable(hcx, hasher);
niche_start.hash_stable(hcx, hasher);
variants.hash_stable(hcx, hasher);
}
}
}
Expand Down
68 changes: 48 additions & 20 deletions src/librustc_codegen_llvm/debuginfo/metadata.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -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 {
RegularDiscriminant(self.discriminant_type_metadata
.expect(""))
Expand Down Expand Up @@ -1277,12 +1281,14 @@ impl EnumMemberDescriptionFactory<'ll, 'tcx> {
}
}).collect()
}
layout::Variants::NicheFilling {
ref niche_variants,
niche_start,
layout::Variants::Multiple {
discr_kind: layout::DiscriminantKind::Niche {
ref niche_variants,
niche_start,
dataful_variant,
},
ref discr,
ref variants,
dataful_variant,
ref niche,
} => {
if fallback {
let variant = self.layout.for_variant(cx, dataful_variant);
Expand Down Expand Up @@ -1369,7 +1375,11 @@ impl EnumMemberDescriptionFactory<'ll, 'tcx> {
let value = (i.as_u32() as u128)
.wrapping_sub(niche_variants.start().as_u32() as u128)
.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)
};

Expand Down Expand Up @@ -1586,8 +1596,11 @@ fn prepare_enum_metadata(
let layout = cx.layout_of(enum_type);

match (&layout.abi, &layout.variants) {
(&layout::Abi::Scalar(_), &layout::Variants::Tagged {ref tag, .. }) =>
return FinalMetadata(discriminant_type_metadata(tag.value)),
(&layout::Abi::Scalar(_), &layout::Variants::Multiple {
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I've seen this code twice now (extracting the discr field if disc_kind is Tag. Pull it out into a method returning Option?

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I disagree, these are orthogonal. I didn't want to rewrite too much code, but arguably everything should match on Variants and then match on DiscriminantKind inside the Multiple case.

That way, code common to both niches and tags can be reused. Adding a .tag() method runs counter to that.

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I get that, but the three cases that I saw here all are very "tagged" special and can't share code with the niche part. Or do you see any additional refactorings that can be done here in the future?

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Ah this is the special case for C-like enums. Either way, I don't see a point in catering to this pattern, but I'll leave comments regarding the possibility of refactoring on the other 2 cases.

discr_kind: layout::DiscriminantKind::Tag,
ref discr,
..
}) => return FinalMetadata(discriminant_type_metadata(discr.value)),
_ => {}
}

Expand All @@ -1599,9 +1612,16 @@ fn prepare_enum_metadata(
if use_enum_fallback(cx) {
let discriminant_type_metadata = match layout.variants {
layout::Variants::Single { .. } |
layout::Variants::NicheFilling { .. } => None,
layout::Variants::Tagged { ref tag, .. } => {
Some(discriminant_type_metadata(tag.value))
layout::Variants::Multiple {
discr_kind: layout::DiscriminantKind::Niche { .. },
..
} => None,
layout::Variants::Multiple {
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thrice

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This is in if use_enum_fallback(cx) and will eventually be removed when we stop supporting LLVM versions that predate the addition of variant debuginfo.

discr_kind: layout::DiscriminantKind::Tag,
ref discr,
..
} => {
Some(discriminant_type_metadata(discr.value))
}
};

Expand Down Expand Up @@ -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.
&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.
let size = niche.value.size(cx);
let align = niche.value.align(cx);
let size = discr.value.size(cx);
let align = discr.value.align(cx);

let discr_type = match niche.value {
let discr_type = match discr.value {
layout::Int(t, _) => t,
layout::Float(layout::FloatTy::F32) => Integer::I32,
layout::Float(layout::FloatTy::F64) => Integer::I64,
Expand All @@ -1668,8 +1692,12 @@ fn prepare_enum_metadata(
}
},

&layout::Variants::Tagged { ref tag, .. } => {
let discr_type = tag.value.to_ty(cx.tcx);
layout::Variants::Multiple {
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 discr_metadata = basic_type_metadata(cx, discr_type);
Expand Down
8 changes: 7 additions & 1 deletion src/librustc_codegen_llvm/type_of.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -452,7 +452,13 @@ impl<'tcx> LayoutLlvmExt<'tcx> for TyLayout<'tcx> {

_ => {
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,
// so only check for a pointer at its offset.
//
Expand Down
36 changes: 20 additions & 16 deletions src/librustc_codegen_ssa/mir/place.rs
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Expand Up @@ -216,37 +216,36 @@ impl<'a, 'tcx: 'a, V: CodegenObject> PlaceRef<'tcx, V> {
if self.layout.abi.is_uninhabited() {
return bx.cx().const_undef(cast_to);
}
match self.layout.variants {
let (discr_scalar, discr_kind) = match self.layout.variants {
layout::Variants::Single { index } => {
let discr_val = self.layout.ty.ty_adt_def().map_or(
index.as_u32() as u128,
|def| def.discriminant_for_variant(bx.cx().tcx(), index).val);
return bx.cx().const_uint_big(cast_to, discr_val);
}
layout::Variants::Tagged { .. } |
layout::Variants::NicheFilling { .. } => {},
}
layout::Variants::Multiple { ref discr, ref discr_kind, .. } => {
(discr, discr_kind)
}
};

let discr = self.project_field(bx, 0);
let lldiscr = bx.load_operand(discr).immediate();
match self.layout.variants {
layout::Variants::Single { .. } => bug!(),
layout::Variants::Tagged { ref tag, .. } => {
let signed = match tag.value {
match *discr_kind {
layout::DiscriminantKind::Tag => {
let signed = match discr_scalar.value {
// We use `i1` for bytes that are always `0` or `1`,
// e.g., `#[repr(i8)] enum E { A, B }`, but we can't
// let LLVM interpret the `i1` as signed, because
// 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
};
bx.intcast(lldiscr, cast_to, signed)
}
layout::Variants::NicheFilling {
layout::DiscriminantKind::Niche {
dataful_variant,
ref niche_variants,
niche_start,
..
} => {
let niche_llty = bx.cx().immediate_backend_type(discr.layout);
if niche_variants.start() == niche_variants.end() {
Expand Down Expand Up @@ -291,7 +290,10 @@ impl<'a, 'tcx: 'a, V: CodegenObject> PlaceRef<'tcx, V> {
layout::Variants::Single { 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 to = self.layout.ty.ty_adt_def().unwrap()
.discriminant_for_variant(bx.tcx(), variant_index)
Expand All @@ -301,10 +303,12 @@ impl<'a, 'tcx: 'a, V: CodegenObject> PlaceRef<'tcx, V> {
ptr.llval,
ptr.align);
}
layout::Variants::NicheFilling {
dataful_variant,
ref niche_variants,
niche_start,
layout::Variants::Multiple {
discr_kind: layout::DiscriminantKind::Niche {
dataful_variant,
ref niche_variants,
niche_start,
},
..
} => {
if variant_index != dataful_variant {
Expand Down
3 changes: 1 addition & 2 deletions src/librustc_codegen_ssa/mir/rvalue.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -303,8 +303,7 @@ impl<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
});
}
}
layout::Variants::Tagged { .. } |
layout::Variants::NicheFilling { .. } => {},
layout::Variants::Multiple { .. } => {},
}
let llval = operand.immediate();

Expand Down
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