tighter checks for (some) ScalarPair layouts
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@ -240,7 +240,11 @@ fn sanity_check_layout<'tcx>(cx: &LayoutCx<'tcx, TyCtxt<'tcx>>, layout: &TyAndLa
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) -> impl Iterator<Item = (Size, TyAndLayout<'tcx>)> + 'a {
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(0..layout.layout.fields().count()).filter_map(|i| {
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let field = layout.field(cx, i);
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let zst = field.is_zst() && field.align.abi.bytes() == 1;
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// Also checking `align == 1` here leads to test failures in
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// `layout/zero-sized-array-union.rs`, where a type has a zero-size field with
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// alignment 4 that still gets ignored during layout computation (which is okay
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// since other fields already force alignment 4).
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let zst = field.is_zst();
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(!zst).then(|| (layout.fields.offset(i), field))
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})
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}
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@ -327,12 +331,110 @@ fn sanity_check_layout<'tcx>(cx: &LayoutCx<'tcx, TyCtxt<'tcx>>, layout: &TyAndLa
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field.align.abi, align,
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"`Scalar` field with bad align in {inner:#?}",
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);
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assert!(
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matches!(field.abi, Abi::Scalar(_)),
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"`Scalar` field with bad ABI in {inner:#?}",
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);
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}
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_ => {
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panic!("`Scalar` layout for non-primitive non-enum type {}", inner.ty);
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}
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}
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}
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Abi::ScalarPair(scalar1, scalar2) => {
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// Sanity-check scalar pairs. These are a bit more flexible and support
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// padding, but we can at least ensure both fields actually fit into the layout
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// and the alignment requirement has not been weakened.
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let size1 = scalar1.size(cx);
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let align1 = scalar1.align(cx).abi;
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let size2 = scalar2.size(cx);
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let align2 = scalar2.align(cx).abi;
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assert!(
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layout.layout.align().abi >= cmp::max(align1, align2),
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"alignment mismatch between ABI and layout in {layout:#?}",
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);
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let field2_offset = size1.align_to(align2);
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assert!(
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layout.layout.size() >= field2_offset + size2,
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"size mismatch between ABI and layout in {layout:#?}"
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);
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// Check that the underlying pair of fields matches.
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let inner = skip_newtypes(cx, layout);
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assert!(
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matches!(inner.layout.abi(), Abi::ScalarPair(..)),
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"`ScalarPair` type {} is newtype around non-`ScalarPair` type {}",
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layout.ty,
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inner.ty
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);
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if matches!(inner.layout.variants(), Variants::Multiple { .. }) {
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// FIXME: ScalarPair for enums is enormously complicated and it is very hard
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// to check anything about them.
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return;
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}
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match inner.layout.fields() {
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FieldsShape::Arbitrary { .. } => {
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// Checked below.
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}
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FieldsShape::Union(..) => {
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// FIXME: I guess we could also check something here? Like, look at all fields?
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return;
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}
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_ => {
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panic!("`ScalarPair` layout with unexpected field shape in {inner:#?}");
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}
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}
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let mut fields = non_zst_fields(cx, &inner);
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let (offset1, field1) = fields.next().unwrap_or_else(|| {
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panic!("`ScalarPair` layout for type with not even one non-ZST field: {inner:#?}")
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});
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let (offset2, field2) = fields.next().unwrap_or_else(|| {
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panic!("`ScalarPair` layout for type with less than two non-ZST fields: {inner:#?}")
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});
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assert!(
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fields.next().is_none(),
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"`ScalarPair` layout for type with at least three non-ZST fields: {inner:#?}"
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);
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// The fields might be in opposite order.
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let (offset1, field1, offset2, field2) = if offset1 <= offset2 {
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(offset1, field1, offset2, field2)
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} else {
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(offset2, field2, offset1, field1)
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};
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// The fields should be at the right offset, and match the `scalar` layout.
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assert_eq!(
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offset1,
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Size::ZERO,
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"`ScalarPair` first field at non-0 offset in {inner:#?}",
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);
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assert_eq!(
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field1.size, size1,
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"`ScalarPair` first field with bad size in {inner:#?}",
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);
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assert_eq!(
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field1.align.abi, align1,
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"`ScalarPair` first field with bad align in {inner:#?}",
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);
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assert!(
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matches!(field1.abi, Abi::Scalar(_)),
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"`ScalarPair` first field with bad ABI in {inner:#?}",
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);
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assert_eq!(
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offset2, field2_offset,
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"`ScalarPair` second field at bad offset in {inner:#?}",
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);
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assert_eq!(
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field2.size, size2,
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"`ScalarPair` second field with bad size in {inner:#?}",
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);
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assert_eq!(
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field2.align.abi, align2,
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"`ScalarPair` second field with bad align in {inner:#?}",
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);
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assert!(
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matches!(field2.abi, Abi::Scalar(_)),
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"`ScalarPair` second field with bad ABI in {inner:#?}",
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);
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}
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Abi::Vector { count, element } => {
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// No padding in vectors. Alignment can be strengthened, though.
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assert!(
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@ -346,22 +448,6 @@ fn sanity_check_layout<'tcx>(cx: &LayoutCx<'tcx, TyCtxt<'tcx>>, layout: &TyAndLa
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"size mismatch between ABI and layout in {layout:#?}"
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);
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}
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Abi::ScalarPair(scalar1, scalar2) => {
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// Sanity-check scalar pairs. These are a bit more flexible and support
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// padding, but we can at least ensure both fields actually fit into the layout
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// and the alignment requirement has not been weakened.
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let align1 = scalar1.align(cx).abi;
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let align2 = scalar2.align(cx).abi;
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assert!(
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layout.layout.align().abi >= cmp::max(align1, align2),
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"alignment mismatch between ABI and layout in {layout:#?}",
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);
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let field2_offset = scalar1.size(cx).align_to(align2);
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assert!(
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layout.layout.size() >= field2_offset + scalar2.size(cx),
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"size mismatch between ABI and layout in {layout:#?}"
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);
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}
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Abi::Uninhabited | Abi::Aggregate { .. } => {} // Nothing to check.
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}
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}
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