From 7ba3d7b54e7688f6f1a0fd22fe274ee7b06fea3e Mon Sep 17 00:00:00 2001 From: Zachary S Date: Sat, 25 Jan 2025 20:15:24 -0600 Subject: Remove `BackendRepr::Uninhabited`, replaced with an `uninhabited: bool` field in `LayoutData`. Also update comments that refered to BackendRepr::Uninhabited. --- compiler/rustc_abi/src/callconv.rs | 2 -- compiler/rustc_abi/src/layout.rs | 23 ++++++++++++----------- compiler/rustc_abi/src/lib.rs | 35 ++++++++++++++++------------------- 3 files changed, 28 insertions(+), 32 deletions(-) (limited to 'compiler/rustc_abi/src') diff --git a/compiler/rustc_abi/src/callconv.rs b/compiler/rustc_abi/src/callconv.rs index 9fb70b80c9e..4529ab8058e 100644 --- a/compiler/rustc_abi/src/callconv.rs +++ b/compiler/rustc_abi/src/callconv.rs @@ -65,8 +65,6 @@ impl<'a, Ty> TyAndLayout<'a, Ty> { Ty: TyAbiInterface<'a, C> + Copy, { match self.backend_repr { - BackendRepr::Uninhabited => Err(Heterogeneous), - // The primitive for this algorithm. BackendRepr::Scalar(scalar) => { let kind = match scalar.primitive() { diff --git a/compiler/rustc_abi/src/layout.rs b/compiler/rustc_abi/src/layout.rs index 45cd0b517f6..53243266f99 100644 --- a/compiler/rustc_abi/src/layout.rs +++ b/compiler/rustc_abi/src/layout.rs @@ -130,6 +130,7 @@ impl LayoutCalculator { }, backend_repr: BackendRepr::ScalarPair(a, b), largest_niche, + uninhabited: false, align, size, max_repr_align: None, @@ -221,8 +222,9 @@ impl LayoutCalculator { LayoutData { variants: Variants::Empty, fields: FieldsShape::Primitive, - backend_repr: BackendRepr::Uninhabited, + backend_repr: BackendRepr::Memory { sized: true }, largest_niche: None, + uninhabited: true, align: dl.i8_align, size: Size::ZERO, max_repr_align: None, @@ -400,6 +402,7 @@ impl LayoutCalculator { fields: FieldsShape::Union(union_field_count), backend_repr: abi, largest_niche: None, + uninhabited: false, align, size: size.align_to(align.abi), max_repr_align, @@ -447,7 +450,6 @@ impl LayoutCalculator { Scalar::Union { .. } => {} }; match &mut st.backend_repr { - BackendRepr::Uninhabited => {} BackendRepr::Scalar(scalar) => hide_niches(scalar), BackendRepr::ScalarPair(a, b) => { hide_niches(a); @@ -639,9 +641,8 @@ impl LayoutCalculator { let same_size = size == variant_layouts[largest_variant_index].size; let same_align = align == variant_layouts[largest_variant_index].align; - let abi = if variant_layouts.iter().all(|v| v.is_uninhabited()) { - BackendRepr::Uninhabited - } else if same_size && same_align && others_zst { + let uninhabited = variant_layouts.iter().all(|v| v.is_uninhabited()); + let abi = if same_size && same_align && others_zst { match variant_layouts[largest_variant_index].backend_repr { // When the total alignment and size match, we can use the // same ABI as the scalar variant with the reserved niche. @@ -683,6 +684,7 @@ impl LayoutCalculator { }, backend_repr: abi, largest_niche, + uninhabited, size, align, max_repr_align, @@ -853,9 +855,8 @@ impl LayoutCalculator { }; let mut abi = BackendRepr::Memory { sized: true }; - if layout_variants.iter().all(|v| v.is_uninhabited()) { - abi = BackendRepr::Uninhabited; - } else if tag.size(dl) == size { + let uninhabited = layout_variants.iter().all(|v| v.is_uninhabited()); + if tag.size(dl) == size { // Make sure we only use scalar layout when the enum is entirely its // own tag (i.e. it has no padding nor any non-ZST variant fields). abi = BackendRepr::Scalar(tag); @@ -995,6 +996,7 @@ impl LayoutCalculator { memory_index: [0].into(), }, largest_niche, + uninhabited, backend_repr: abi, align, size, @@ -1355,9 +1357,7 @@ impl LayoutCalculator { _ => {} } } - if fields.iter().any(|f| f.is_uninhabited()) { - abi = BackendRepr::Uninhabited; - } + let uninhabited = fields.iter().any(|f| f.is_uninhabited()); let unadjusted_abi_align = if repr.transparent() { match layout_of_single_non_zst_field { @@ -1378,6 +1378,7 @@ impl LayoutCalculator { fields: FieldsShape::Arbitrary { offsets, memory_index }, backend_repr: abi, largest_niche, + uninhabited, align, size, max_repr_align, diff --git a/compiler/rustc_abi/src/lib.rs b/compiler/rustc_abi/src/lib.rs index dbb4bed5cdd..14a8a579200 100644 --- a/compiler/rustc_abi/src/lib.rs +++ b/compiler/rustc_abi/src/lib.rs @@ -1404,7 +1404,6 @@ impl AddressSpace { #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)] #[cfg_attr(feature = "nightly", derive(HashStable_Generic))] pub enum BackendRepr { - Uninhabited, Scalar(Scalar), ScalarPair(Scalar, Scalar), Vector { @@ -1423,10 +1422,9 @@ impl BackendRepr { #[inline] pub fn is_unsized(&self) -> bool { match *self { - BackendRepr::Uninhabited - | BackendRepr::Scalar(_) - | BackendRepr::ScalarPair(..) - | BackendRepr::Vector { .. } => false, + BackendRepr::Scalar(_) | BackendRepr::ScalarPair(..) | BackendRepr::Vector { .. } => { + false + } BackendRepr::Memory { sized } => !sized, } } @@ -1445,12 +1443,6 @@ impl BackendRepr { } } - /// Returns `true` if this is an uninhabited type - #[inline] - pub fn is_uninhabited(&self) -> bool { - matches!(*self, BackendRepr::Uninhabited) - } - /// Returns `true` if this is a scalar type #[inline] pub fn is_scalar(&self) -> bool { @@ -1471,7 +1463,7 @@ impl BackendRepr { BackendRepr::Vector { element, count } => { cx.data_layout().vector_align(element.size(cx) * count) } - BackendRepr::Uninhabited | BackendRepr::Memory { .. } => return None, + BackendRepr::Memory { .. } => return None, }) } @@ -1492,7 +1484,7 @@ impl BackendRepr { // to make the size a multiple of align (e.g. for vectors of size 3). (element.size(cx) * count).align_to(self.inherent_align(cx)?.abi) } - BackendRepr::Uninhabited | BackendRepr::Memory { .. } => return None, + BackendRepr::Memory { .. } => return None, }) } @@ -1506,9 +1498,7 @@ impl BackendRepr { BackendRepr::Vector { element, count } => { BackendRepr::Vector { element: element.to_union(), count } } - BackendRepr::Uninhabited | BackendRepr::Memory { .. } => { - BackendRepr::Memory { sized: true } - } + BackendRepr::Memory { .. } => BackendRepr::Memory { sized: true }, } } @@ -1704,6 +1694,11 @@ pub struct LayoutData { /// The leaf scalar with the largest number of invalid values /// (i.e. outside of its `valid_range`), if it exists. pub largest_niche: Option, + /// Is this type known to be uninhabted? + /// + /// This is separate from BackendRepr, because an uninhabited return type may require special + /// consideration based on its size or other attributes. + pub uninhabited: bool, pub align: AbiAndPrefAlign, pub size: Size, @@ -1735,14 +1730,14 @@ impl LayoutData { /// Returns `true` if this is an aggregate type (including a ScalarPair!) pub fn is_aggregate(&self) -> bool { match self.backend_repr { - BackendRepr::Uninhabited | BackendRepr::Scalar(_) | BackendRepr::Vector { .. } => false, + BackendRepr::Scalar(_) | BackendRepr::Vector { .. } => false, BackendRepr::ScalarPair(..) | BackendRepr::Memory { .. } => true, } } /// Returns `true` if this is an uninhabited type pub fn is_uninhabited(&self) -> bool { - self.backend_repr.is_uninhabited() + self.uninhabited } pub fn scalar(cx: &C, scalar: Scalar) -> Self { @@ -1778,6 +1773,7 @@ impl LayoutData { fields: FieldsShape::Primitive, backend_repr: BackendRepr::Scalar(scalar), largest_niche, + uninhabited: false, size, align, max_repr_align: None, @@ -1802,6 +1798,7 @@ where backend_repr, fields, largest_niche, + uninhabited, variants, max_repr_align, unadjusted_abi_align, @@ -1813,6 +1810,7 @@ where .field("abi", backend_repr) .field("fields", fields) .field("largest_niche", largest_niche) + .field("uninhabited", uninhabited) .field("variants", variants) .field("max_repr_align", max_repr_align) .field("unadjusted_abi_align", unadjusted_abi_align) @@ -1877,7 +1875,6 @@ impl LayoutData { BackendRepr::Scalar(_) | BackendRepr::ScalarPair(..) | BackendRepr::Vector { .. } => { false } - BackendRepr::Uninhabited => self.size.bytes() == 0, BackendRepr::Memory { sized } => sized && self.size.bytes() == 0, } } -- cgit 1.4.1-3-g733a5 From 6493cd8699cc6d55a38b5187ff4cc731f969c483 Mon Sep 17 00:00:00 2001 From: zachs18 <8355914+zachs18@users.noreply.github.com> Date: Mon, 17 Feb 2025 18:49:18 -0600 Subject: Adjust LayoutData::uninhabited doc comment. Co-authored-by: Jubilee --- compiler/rustc_abi/src/lib.rs | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'compiler/rustc_abi/src') diff --git a/compiler/rustc_abi/src/lib.rs b/compiler/rustc_abi/src/lib.rs index 14a8a579200..098638b6bcf 100644 --- a/compiler/rustc_abi/src/lib.rs +++ b/compiler/rustc_abi/src/lib.rs @@ -1696,8 +1696,8 @@ pub struct LayoutData { pub largest_niche: Option, /// Is this type known to be uninhabted? /// - /// This is separate from BackendRepr, because an uninhabited return type may require special - /// consideration based on its size or other attributes. + /// This is separate from BackendRepr because uninhabited return types can affect ABI, + /// especially in the case of by-pointer struct returns, which allocate stack even when unused. pub uninhabited: bool, pub align: AbiAndPrefAlign, -- cgit 1.4.1-3-g733a5