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layout: Factor out a utility function. #63899

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layout: Factor out a utility function. #63899

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60 changes: 20 additions & 40 deletions src/librustc/ty/layout.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -267,24 +267,27 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
}
}

fn align_and_pack(&self, repr: &ReprOptions) -> (AbiAndPrefAlign, Option<Align>) {
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What if you added a pack: Option<Align> field to ReprOptions?
The Align encoding is logarithmic so it would occupy less space and not need further conversion.

cc @oli-obk @nagisa @rkruppe (curious what other people think)

let dl = self.data_layout();
if repr.packed() {
let pack = Align::from_bytes(repr.pack as u64).unwrap();
if repr.align > 0 {
bug!("adt cannot be packed and aligned");
}
(dl.i8_align, Some(pack))
} else {
let align = Align::from_bytes(repr.align as u64).unwrap();
(dl.aggregate_align.max(AbiAndPrefAlign::new(align)), None)
}
}

fn univariant_uninterned(&self,
ty: Ty<'tcx>,
fields: &[TyLayout<'_>],
repr: &ReprOptions,
kind: StructKind) -> Result<LayoutDetails, LayoutError<'tcx>> {
let dl = self.data_layout();
let packed = repr.packed();
if packed && repr.align > 0 {
bug!("struct cannot be packed and aligned");
}

let pack = Align::from_bytes(repr.pack as u64).unwrap();

let mut align = if packed {
dl.i8_align
} else {
dl.aggregate_align
};
let (mut align, pack) = self.align_and_pack(repr);

let mut sized = true;
let mut offsets = vec![Size::ZERO; fields.len()];
Expand All @@ -303,7 +306,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
};
let optimizing = &mut inverse_memory_index[..end];
let field_align = |f: &TyLayout<'_>| {
if packed { f.align.abi.min(pack) } else { f.align.abi }
if let Some(pack) = pack { f.align.abi.min(pack) } else { f.align.abi }
};
match kind {
StructKind::AlwaysSized |
Expand Down Expand Up @@ -334,7 +337,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
let mut largest_niche_available = 0;

if let StructKind::Prefixed(prefix_size, prefix_align) = kind {
let prefix_align = if packed {
let prefix_align = if let Some(pack) = pack {
prefix_align.min(pack)
} else {
prefix_align
Expand All @@ -355,7 +358,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
}

// Invariant: offset < dl.obj_size_bound() <= 1<<61
let field_align = if packed {
let field_align = if let Some(pack) = pack {
field.align.min(AbiAndPrefAlign::new(pack))
} else {
field.align
Expand All @@ -379,12 +382,6 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
.ok_or(LayoutError::SizeOverflow(ty))?;
}

if repr.align > 0 {
let repr_align = repr.align as u64;
align = align.max(AbiAndPrefAlign::new(Align::from_bytes(repr_align).unwrap()));
debug!("univariant repr_align: {:?}", repr_align);
}

debug!("univariant min_size: {:?}", offset);
let min_size = offset;

Expand Down Expand Up @@ -730,24 +727,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
}).collect::<Result<IndexVec<VariantIdx, _>, _>>()?;

if def.is_union() {
let packed = def.repr.packed();
if packed && def.repr.align > 0 {
bug!("Union cannot be packed and aligned");
}

let pack = Align::from_bytes(def.repr.pack as u64).unwrap();

let mut align = if packed {
dl.i8_align
} else {
dl.aggregate_align
};

if def.repr.align > 0 {
let repr_align = def.repr.align as u64;
align = align.max(
AbiAndPrefAlign::new(Align::from_bytes(repr_align).unwrap()));
}
let (mut align, pack) = self.align_and_pack(&def.repr);

let optimize = !def.repr.inhibit_union_abi_opt();
let mut size = Size::ZERO;
Expand All @@ -756,7 +736,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
for field in &variants[index] {
assert!(!field.is_unsized());

let field_align = if packed {
let field_align = if let Some(pack) = pack {
field.align.min(AbiAndPrefAlign::new(pack))
} else {
field.align
Expand Down