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Fix having multiple reprs on the same type.
This bug has applied to master for an indefinite period of time and is orthogonal to univariant layout optimization.
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@ -416,7 +416,7 @@ impl Integer {
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/// signed discriminant range and #[repr] attribute.
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/// N.B.: u64 values above i64::MAX will be treated as signed, but
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/// that shouldn't affect anything, other than maybe debuginfo.
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pub fn repr_discr(tcx: TyCtxt, ty: Ty, hint: attr::ReprAttr, min: i64, max: i64)
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fn repr_discr(tcx: TyCtxt, ty: Ty, hints: &[attr::ReprAttr], min: i64, max: i64)
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-> (Integer, bool) {
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// Theoretically, negative values could be larger in unsigned representation
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// than the unsigned representation of the signed minimum. However, if there
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@ -425,33 +425,44 @@ impl Integer {
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let unsigned_fit = Integer::fit_unsigned(cmp::max(min as u64, max as u64));
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let signed_fit = cmp::max(Integer::fit_signed(min), Integer::fit_signed(max));
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let at_least = match hint {
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attr::ReprInt(ity) => {
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let discr = Integer::from_attr(&tcx.data_layout, ity);
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let fit = if ity.is_signed() { signed_fit } else { unsigned_fit };
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if discr < fit {
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bug!("Integer::repr_discr: `#[repr]` hint too small for \
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discriminant range of enum `{}", ty)
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let mut min_from_extern = None;
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let min_default = I8;
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for &r in hints.iter() {
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match r {
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attr::ReprInt(ity) => {
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let discr = Integer::from_attr(&tcx.data_layout, ity);
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let fit = if ity.is_signed() { signed_fit } else { unsigned_fit };
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if discr < fit {
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bug!("Integer::repr_discr: `#[repr]` hint too small for \
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discriminant range of enum `{}", ty)
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}
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return (discr, ity.is_signed());
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}
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return (discr, ity.is_signed());
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}
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attr::ReprExtern => {
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match &tcx.sess.target.target.arch[..] {
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// WARNING: the ARM EABI has two variants; the one corresponding
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// to `at_least == I32` appears to be used on Linux and NetBSD,
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// but some systems may use the variant corresponding to no
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// lower bound. However, we don't run on those yet...?
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"arm" => I32,
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_ => I32,
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attr::ReprExtern => {
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match &tcx.sess.target.target.arch[..] {
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// WARNING: the ARM EABI has two variants; the one corresponding
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// to `at_least == I32` appears to be used on Linux and NetBSD,
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// but some systems may use the variant corresponding to no
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// lower bound. However, we don't run on those yet...?
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"arm" => min_from_extern = Some(I32),
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_ => min_from_extern = Some(I32),
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}
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}
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attr::ReprAny => {},
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attr::ReprPacked => {
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bug!("Integer::repr_discr: found #[repr(packed)] on enum `{}", ty);
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}
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attr::ReprSimd => {
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bug!("Integer::repr_discr: found #[repr(simd)] on enum `{}", ty);
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}
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}
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attr::ReprAny => I8,
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attr::ReprPacked => {
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bug!("Integer::repr_discr: found #[repr(packed)] on enum `{}", ty);
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}
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attr::ReprSimd => {
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bug!("Integer::repr_discr: found #[repr(simd)] on enum `{}", ty);
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}
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}
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let at_least = if let Some(i) = min_from_extern {
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i
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} else {
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min_default
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};
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// If there are no negative values, we can use the unsigned fit.
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@ -536,10 +547,11 @@ enum StructKind {
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}
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impl<'a, 'gcx, 'tcx> Struct {
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// FIXME(camlorn): reprs need a better representation to deal with multiple reprs on one type.
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fn new(dl: &TargetDataLayout, fields: &Vec<&'a Layout>,
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repr: attr::ReprAttr, kind: StructKind,
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reprs: &[attr::ReprAttr], kind: StructKind,
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scapegoat: Ty<'gcx>) -> Result<Struct, LayoutError<'gcx>> {
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let packed = repr == attr::ReprPacked;
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let packed = reprs.contains(&attr::ReprPacked);
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let mut ret = Struct {
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align: if packed { dl.i8_align } else { dl.aggregate_align },
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packed: packed,
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@ -549,23 +561,37 @@ impl<'a, 'gcx, 'tcx> Struct {
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min_size: Size::from_bytes(0),
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};
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// 1-member and 2-member structs don't optimize.
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if fields.len() == 0 {return Ok(ret)};
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// Anything with ReprExtern or ReprPacked doesn't optimize.
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// Neither do 1-member and 2-member structs.
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// In addition, code in trans assume that 2-element structs can become pairs.
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// It's easier to just short-circuit here.
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let can_optimize_struct = fields.len() > 2;
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let mut can_optimize = fields.len() > 2 || StructKind::EnumVariant == kind;
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if can_optimize {
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// This exhaustive match makes new reprs force the adder to modify this function.
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// Otherwise, things can silently break.
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// Note the inversion, return true to stop matching.
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can_optimize = !reprs.iter().any(|r| {
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match *r {
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attr::ReprAny => false,
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attr::ReprInt(_) => false,
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attr::ReprExtern => true,
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attr::ReprPacked => true,
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attr::ReprSimd => bug!("Simd vectors should be represented as a layout::Vector")
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}
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});
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}
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let (optimize, sort_ascending) = match (repr, kind) {
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(attr::ReprAny, StructKind::AlwaysSizedUnivariant) => (can_optimize_struct, false),
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(attr::ReprAny, StructKind::MaybeUnsizedUnivariant) => (can_optimize_struct, true),
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(attr::ReprAny, StructKind::EnumVariant) => {
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let (optimize, sort_ascending) = match kind {
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StructKind::AlwaysSizedUnivariant => (can_optimize, false),
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StructKind::MaybeUnsizedUnivariant => (can_optimize, true),
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StructKind::EnumVariant => {
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assert!(fields.len() >= 1, "Enum variants must have discriminants.");
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(true, fields[0].size(dl).bytes() == 1)
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(can_optimize, fields[0].size(dl).bytes() == 1)
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}
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_ => (false, false)
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};
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if fields.len() == 0 {return Ok(ret)};
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ret.offsets = vec![Size::from_bytes(0); fields.len()];
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let mut inverse_memory_index: Vec<u32> = (0..fields.len() as u32).collect();
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@ -590,6 +616,7 @@ impl<'a, 'gcx, 'tcx> Struct {
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}
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}
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// inverse_memory_index holds field indices by increasing memory offset.
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// That is, if field 5 has offset 0, the first element of inverse_memory_index is 5.
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// We now write field offsets to the corresponding offset slot;
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// field 5 with offset 0 puts 0 in offsets[5].
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@ -1021,7 +1048,7 @@ impl<'a, 'gcx, 'tcx> Layout {
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// The never type.
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ty::TyNever => Univariant {
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variant: Struct::new(dl, &vec![], attr::ReprAny,
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variant: Struct::new(dl, &vec![], &[],
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StructKind::AlwaysSizedUnivariant, ty)?,
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non_zero: false
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},
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@ -1076,12 +1103,12 @@ impl<'a, 'gcx, 'tcx> Layout {
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ty::TyFnDef(..) => {
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Univariant {
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variant: Struct::new(dl, &vec![],
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attr::ReprAny, StructKind::AlwaysSizedUnivariant, ty)?,
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&[], StructKind::AlwaysSizedUnivariant, ty)?,
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non_zero: false
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}
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}
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ty::TyDynamic(_) => {
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let mut unit = Struct::new(dl, &vec![], attr::ReprAny,
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let mut unit = Struct::new(dl, &vec![], &[],
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StructKind::AlwaysSizedUnivariant, ty)?;
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unit.sized = false;
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Univariant { variant: unit, non_zero: false }
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@ -1093,7 +1120,7 @@ impl<'a, 'gcx, 'tcx> Layout {
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let st = Struct::new(dl,
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&tys.map(|ty| ty.layout(infcx))
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.collect::<Result<Vec<_>, _>>()?,
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attr::ReprAny,
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&[],
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StructKind::AlwaysSizedUnivariant, ty)?;
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Univariant { variant: st, non_zero: false }
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}
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@ -1104,7 +1131,7 @@ impl<'a, 'gcx, 'tcx> Layout {
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let st = Struct::new(dl,
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&tys.iter().map(|ty| ty.layout(infcx))
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.collect::<Result<Vec<_>, _>>()?,
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attr::ReprAny, StructKind::AlwaysSizedUnivariant, ty)?;
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&[], StructKind::AlwaysSizedUnivariant, ty)?;
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Univariant { variant: st, non_zero: false }
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}
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@ -1128,17 +1155,16 @@ impl<'a, 'gcx, 'tcx> Layout {
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// ADTs.
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ty::TyAdt(def, substs) => {
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let hint = *tcx.lookup_repr_hints(def.did).get(0)
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.unwrap_or(&attr::ReprAny);
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let hints = &tcx.lookup_repr_hints(def.did)[..];
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if def.variants.is_empty() {
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// Uninhabitable; represent as unit
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// (Typechecking will reject discriminant-sizing attrs.)
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assert_eq!(hint, attr::ReprAny);
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assert_eq!(hints.len(), 0);
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return success(Univariant {
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variant: Struct::new(dl, &vec![],
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hint, StructKind::AlwaysSizedUnivariant, ty)?,
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&hints[..], StructKind::AlwaysSizedUnivariant, ty)?,
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non_zero: false
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});
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}
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@ -1153,7 +1179,7 @@ impl<'a, 'gcx, 'tcx> Layout {
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if x > max { max = x; }
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}
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let (discr, signed) = Integer::repr_discr(tcx, ty, hint, min, max);
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let (discr, signed) = Integer::repr_discr(tcx, ty, &hints[..], min, max);
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return success(CEnum {
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discr: discr,
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signed: signed,
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@ -1163,7 +1189,7 @@ impl<'a, 'gcx, 'tcx> Layout {
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});
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}
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if !def.is_enum() || def.variants.len() == 1 && hint == attr::ReprAny {
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if !def.is_enum() || def.variants.len() == 1 && hints.len() == 0 {
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// Struct, or union, or univariant enum equivalent to a struct.
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// (Typechecking will reject discriminant-sizing attrs.)
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@ -1190,7 +1216,7 @@ impl<'a, 'gcx, 'tcx> Layout {
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un.extend(dl, fields.iter().map(|&f| Ok(f)), ty)?;
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UntaggedUnion { variants: un }
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} else {
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let st = Struct::new(dl, &fields, hint,
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let st = Struct::new(dl, &fields, &hints[..],
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kind, ty)?;
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let non_zero = Some(def.did) == tcx.lang_items.non_zero();
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Univariant { variant: st, non_zero: non_zero }
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@ -1213,7 +1239,7 @@ impl<'a, 'gcx, 'tcx> Layout {
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v.fields.iter().map(|field| field.ty(tcx, substs)).collect::<Vec<_>>()
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}).collect::<Vec<_>>();
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if variants.len() == 2 && hint == attr::ReprAny {
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if variants.len() == 2 && hints.len() == 0 {
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// Nullable pointer optimization
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for discr in 0..2 {
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let other_fields = variants[1 - discr].iter().map(|ty| {
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@ -1245,7 +1271,7 @@ impl<'a, 'gcx, 'tcx> Layout {
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let st = Struct::new(dl,
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&variants[discr].iter().map(|ty| ty.layout(infcx))
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.collect::<Result<Vec<_>, _>>()?,
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hint, StructKind::AlwaysSizedUnivariant, ty)?;
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&hints[..], StructKind::AlwaysSizedUnivariant, ty)?;
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// We have to fix the last element of path here.
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let mut i = *path.last().unwrap();
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@ -1265,7 +1291,7 @@ impl<'a, 'gcx, 'tcx> Layout {
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// The general case.
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let discr_max = (variants.len() - 1) as i64;
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assert!(discr_max >= 0);
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let (min_ity, _) = Integer::repr_discr(tcx, ty, hint, 0, discr_max);
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let (min_ity, _) = Integer::repr_discr(tcx, ty, &hints[..], 0, discr_max);
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let mut align = dl.aggregate_align;
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let mut size = Size::from_bytes(0);
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@ -1283,7 +1309,7 @@ impl<'a, 'gcx, 'tcx> Layout {
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fields.insert(0, &discr);
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let st = Struct::new(dl,
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&fields,
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hint, StructKind::EnumVariant, ty)?;
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&hints[..], StructKind::EnumVariant, ty)?;
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// Find the first field we can't move later
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// to make room for a larger discriminant.
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// It is important to skip the first field.
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44
src/test/run-pass/multiple-reprs.rs
Normal file
44
src/test/run-pass/multiple-reprs.rs
Normal file
@ -0,0 +1,44 @@
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// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use std::mem::size_of;
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// The two enums that follow are designed so that bugs trigger layout optimization.
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// Specifically, if either of the following reprs used here is not detected by the compiler,
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// then the sizes will be wrong.
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#[repr(C, u8)]
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enum E1 {
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A(u8, u16, u8),
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B(u8, u16, u8)
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}
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#[repr(u8, C)]
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enum E2 {
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A(u8, u16, u8),
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B(u8, u16, u8)
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}
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// From pr 37429
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pub const SIZEOF_QUERY: usize = 21;
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#[repr(C,packed)]
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pub struct p0f_api_query {
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pub magic: u32,
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pub addr_type: u8,
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pub addr: [u8; 16],
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}
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pub fn main() {
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assert_eq!(size_of::<E1>(), 6);
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assert_eq!(size_of::<E2>(), 6);
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assert_eq!(size_of::<p0f_api_query>(), 21);
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}
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@ -26,7 +26,7 @@ enum e2 {
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a(u32), b
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}
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#[repr(u8)]
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#[repr(C, u8)]
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enum e3 {
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a([u16; 0], u8), b
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}
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