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Rollup merge of #132246 - workingjubilee:campaign-on-irform, r=compil…
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…er-errors

Rename `rustc_abi::Abi` to `BackendRepr`

Remove the confabulation of `rustc_abi::Abi` with what "ABI" actually means by renaming it to `BackendRepr`, and rename `Abi::Aggregate` to `BackendRepr::Memory`. The type never actually represented how things are passed, as that has to have `PassMode` considered, at minimum, but rather it just is how we represented some things to the backend. This conflation arose because LLVM, the primary backend at the time, would lower certain IR forms using certain ABIs. Even that only somewhat was true, as it broke down when one ventured significantly afield of what is described by the System V AMD64 ABI either by using different architectures, ABI-modifying IR annotations, the same architecture **with different ISA extensions enabled**, or other... unexpected delights.

Unfortunately both names are still somewhat of a misnomer right now, as people have written code for years based on this misunderstanding. Still, their original names are even moreso, and for better or worse, this backend code hasn't received as much maintenance as the rest of the compiler, lately. Actually arriving at a correct end-state will simply require us to disentangle a lot of code in order to fix, much of it pointlessly repeated in several places. Thus this is not an "actual fix", just a way to deflect further misunderstandings.
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@workingjubilee
workingjubilee authored Oct 30, 2024
2 parents 62ba25d + 083a362 commit 847b6fe
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Showing 98 changed files with 876 additions and 646 deletions.
16 changes: 8 additions & 8 deletions compiler/rustc_abi/src/callconv.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -6,9 +6,9 @@ mod abi {
#[cfg(feature = "nightly")]
use rustc_macros::HashStable_Generic;

#[cfg(feature = "nightly")]
use crate::{Abi, FieldsShape, TyAbiInterface, TyAndLayout};
use crate::{Align, HasDataLayout, Size};
#[cfg(feature = "nightly")]
use crate::{BackendRepr, FieldsShape, TyAbiInterface, TyAndLayout};

#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
Expand Down Expand Up @@ -128,27 +128,27 @@ impl<'a, Ty> TyAndLayout<'a, Ty> {
where
Ty: TyAbiInterface<'a, C> + Copy,
{
match self.abi {
Abi::Uninhabited => Err(Heterogeneous),
match self.backend_repr {
BackendRepr::Uninhabited => Err(Heterogeneous),

// The primitive for this algorithm.
Abi::Scalar(scalar) => {
BackendRepr::Scalar(scalar) => {
let kind = match scalar.primitive() {
abi::Int(..) | abi::Pointer(_) => RegKind::Integer,
abi::Float(_) => RegKind::Float,
};
Ok(HomogeneousAggregate::Homogeneous(Reg { kind, size: self.size }))
}

Abi::Vector { .. } => {
BackendRepr::Vector { .. } => {
assert!(!self.is_zst());
Ok(HomogeneousAggregate::Homogeneous(Reg {
kind: RegKind::Vector,
size: self.size,
}))
}

Abi::ScalarPair(..) | Abi::Aggregate { sized: true } => {
BackendRepr::ScalarPair(..) | BackendRepr::Memory { sized: true } => {
// Helper for computing `homogeneous_aggregate`, allowing a custom
// starting offset (used below for handling variants).
let from_fields_at =
Expand Down Expand Up @@ -246,7 +246,7 @@ impl<'a, Ty> TyAndLayout<'a, Ty> {
Ok(result)
}
}
Abi::Aggregate { sized: false } => Err(Heterogeneous),
BackendRepr::Memory { sized: false } => Err(Heterogeneous),
}
}
}
104 changes: 53 additions & 51 deletions compiler/rustc_abi/src/layout.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ use rustc_index::Idx;
use tracing::debug;

use crate::{
Abi, AbiAndPrefAlign, Align, FieldsShape, HasDataLayout, IndexSlice, IndexVec, Integer,
AbiAndPrefAlign, Align, BackendRepr, FieldsShape, HasDataLayout, IndexSlice, IndexVec, Integer,
LayoutData, Niche, NonZeroUsize, Primitive, ReprOptions, Scalar, Size, StructKind, TagEncoding,
Variants, WrappingRange,
};
Expand Down Expand Up @@ -125,7 +125,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
offsets: [Size::ZERO, b_offset].into(),
memory_index: [0, 1].into(),
},
abi: Abi::ScalarPair(a, b),
backend_repr: BackendRepr::ScalarPair(a, b),
largest_niche,
align,
size,
Expand Down Expand Up @@ -216,7 +216,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
LayoutData {
variants: Variants::Single { index: VariantIdx::new(0) },
fields: FieldsShape::Primitive,
abi: Abi::Uninhabited,
backend_repr: BackendRepr::Uninhabited,
largest_niche: None,
align: dl.i8_align,
size: Size::ZERO,
Expand Down Expand Up @@ -331,7 +331,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {

if let Ok(common) = common_non_zst_abi_and_align {
// Discard valid range information and allow undef
let field_abi = field.abi.to_union();
let field_abi = field.backend_repr.to_union();

if let Some((common_abi, common_align)) = common {
if common_abi != field_abi {
Expand All @@ -340,7 +340,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
} else {
// Fields with the same non-Aggregate ABI should also
// have the same alignment
if !matches!(common_abi, Abi::Aggregate { .. }) {
if !matches!(common_abi, BackendRepr::Memory { .. }) {
assert_eq!(
common_align, field.align.abi,
"non-Aggregate field with matching ABI but differing alignment"
Expand Down Expand Up @@ -369,11 +369,11 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
// If all non-ZST fields have the same ABI, we may forward that ABI
// for the union as a whole, unless otherwise inhibited.
let abi = match common_non_zst_abi_and_align {
Err(AbiMismatch) | Ok(None) => Abi::Aggregate { sized: true },
Err(AbiMismatch) | Ok(None) => BackendRepr::Memory { sized: true },
Ok(Some((abi, _))) => {
if abi.inherent_align(dl).map(|a| a.abi) != Some(align.abi) {
// Mismatched alignment (e.g. union is #[repr(packed)]): disable opt
Abi::Aggregate { sized: true }
BackendRepr::Memory { sized: true }
} else {
abi
}
Expand All @@ -387,7 +387,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
Ok(LayoutData {
variants: Variants::Single { index: only_variant_idx },
fields: FieldsShape::Union(union_field_count),
abi,
backend_repr: abi,
largest_niche: None,
align,
size: size.align_to(align.abi),
Expand Down Expand Up @@ -434,23 +434,23 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
// Already doesn't have any niches
Scalar::Union { .. } => {}
};
match &mut st.abi {
Abi::Uninhabited => {}
Abi::Scalar(scalar) => hide_niches(scalar),
Abi::ScalarPair(a, b) => {
match &mut st.backend_repr {
BackendRepr::Uninhabited => {}
BackendRepr::Scalar(scalar) => hide_niches(scalar),
BackendRepr::ScalarPair(a, b) => {
hide_niches(a);
hide_niches(b);
}
Abi::Vector { element, count: _ } => hide_niches(element),
Abi::Aggregate { sized: _ } => {}
BackendRepr::Vector { element, count: _ } => hide_niches(element),
BackendRepr::Memory { sized: _ } => {}
}
st.largest_niche = None;
return Ok(st);
}

let (start, end) = scalar_valid_range;
match st.abi {
Abi::Scalar(ref mut scalar) | Abi::ScalarPair(ref mut scalar, _) => {
match st.backend_repr {
BackendRepr::Scalar(ref mut scalar) | BackendRepr::ScalarPair(ref mut scalar, _) => {
// Enlarging validity ranges would result in missed
// optimizations, *not* wrongly assuming the inner
// value is valid. e.g. unions already enlarge validity ranges,
Expand Down Expand Up @@ -607,8 +607,8 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
}

// It can't be a Scalar or ScalarPair because the offset isn't 0.
if !layout.abi.is_uninhabited() {
layout.abi = Abi::Aggregate { sized: true };
if !layout.is_uninhabited() {
layout.backend_repr = BackendRepr::Memory { sized: true };
}
layout.size += this_offset;

Expand All @@ -627,26 +627,26 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
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.abi.is_uninhabited()) {
Abi::Uninhabited
let abi = if variant_layouts.iter().all(|v| v.is_uninhabited()) {
BackendRepr::Uninhabited
} else if same_size && same_align && others_zst {
match variant_layouts[largest_variant_index].abi {
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.
Abi::Scalar(_) => Abi::Scalar(niche_scalar),
Abi::ScalarPair(first, second) => {
BackendRepr::Scalar(_) => BackendRepr::Scalar(niche_scalar),
BackendRepr::ScalarPair(first, second) => {
// Only the niche is guaranteed to be initialised,
// so use union layouts for the other primitive.
if niche_offset == Size::ZERO {
Abi::ScalarPair(niche_scalar, second.to_union())
BackendRepr::ScalarPair(niche_scalar, second.to_union())
} else {
Abi::ScalarPair(first.to_union(), niche_scalar)
BackendRepr::ScalarPair(first.to_union(), niche_scalar)
}
}
_ => Abi::Aggregate { sized: true },
_ => BackendRepr::Memory { sized: true },
}
} else {
Abi::Aggregate { sized: true }
BackendRepr::Memory { sized: true }
};

let layout = LayoutData {
Expand All @@ -664,7 +664,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
offsets: [niche_offset].into(),
memory_index: [0].into(),
},
abi,
backend_repr: abi,
largest_niche,
size,
align,
Expand Down Expand Up @@ -833,14 +833,14 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
end: (max as u128 & tag_mask),
},
};
let mut abi = Abi::Aggregate { sized: true };
let mut abi = BackendRepr::Memory { sized: true };

if layout_variants.iter().all(|v| v.abi.is_uninhabited()) {
abi = Abi::Uninhabited;
if layout_variants.iter().all(|v| v.is_uninhabited()) {
abi = BackendRepr::Uninhabited;
} else 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 = Abi::Scalar(tag);
abi = BackendRepr::Scalar(tag);
} else {
// Try to use a ScalarPair for all tagged enums.
// That's possible only if we can find a common primitive type for all variants.
Expand All @@ -864,8 +864,8 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
break;
}
};
let prim = match field.abi {
Abi::Scalar(scalar) => {
let prim = match field.backend_repr {
BackendRepr::Scalar(scalar) => {
common_prim_initialized_in_all_variants &=
matches!(scalar, Scalar::Initialized { .. });
scalar.primitive()
Expand Down Expand Up @@ -934,20 +934,22 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
{
// We can use `ScalarPair` only when it matches our
// already computed layout (including `#[repr(C)]`).
abi = pair.abi;
abi = pair.backend_repr;
}
}
}

// If we pick a "clever" (by-value) ABI, we might have to adjust the ABI of the
// variants to ensure they are consistent. This is because a downcast is
// semantically a NOP, and thus should not affect layout.
if matches!(abi, Abi::Scalar(..) | Abi::ScalarPair(..)) {
if matches!(abi, BackendRepr::Scalar(..) | BackendRepr::ScalarPair(..)) {
for variant in &mut layout_variants {
// We only do this for variants with fields; the others are not accessed anyway.
// Also do not overwrite any already existing "clever" ABIs.
if variant.fields.count() > 0 && matches!(variant.abi, Abi::Aggregate { .. }) {
variant.abi = abi;
if variant.fields.count() > 0
&& matches!(variant.backend_repr, BackendRepr::Memory { .. })
{
variant.backend_repr = abi;
// Also need to bump up the size and alignment, so that the entire value fits
// in here.
variant.size = cmp::max(variant.size, size);
Expand All @@ -970,7 +972,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
memory_index: [0].into(),
},
largest_niche,
abi,
backend_repr: abi,
align,
size,
max_repr_align,
Expand Down Expand Up @@ -1252,7 +1254,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
}
let mut layout_of_single_non_zst_field = None;
let sized = unsized_field.is_none();
let mut abi = Abi::Aggregate { sized };
let mut abi = BackendRepr::Memory { sized };

let optimize_abi = !repr.inhibit_newtype_abi_optimization();

Expand All @@ -1270,16 +1272,16 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
// Field fills the struct and it has a scalar or scalar pair ABI.
if offsets[i].bytes() == 0 && align.abi == field.align.abi && size == field.size
{
match field.abi {
match field.backend_repr {
// For plain scalars, or vectors of them, we can't unpack
// newtypes for `#[repr(C)]`, as that affects C ABIs.
Abi::Scalar(_) | Abi::Vector { .. } if optimize_abi => {
abi = field.abi;
BackendRepr::Scalar(_) | BackendRepr::Vector { .. } if optimize_abi => {
abi = field.backend_repr;
}
// But scalar pairs are Rust-specific and get
// treated as aggregates by C ABIs anyway.
Abi::ScalarPair(..) => {
abi = field.abi;
BackendRepr::ScalarPair(..) => {
abi = field.backend_repr;
}
_ => {}
}
Expand All @@ -1288,8 +1290,8 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {

// Two non-ZST fields, and they're both scalars.
(Some((i, a)), Some((j, b)), None) => {
match (a.abi, b.abi) {
(Abi::Scalar(a), Abi::Scalar(b)) => {
match (a.backend_repr, b.backend_repr) {
(BackendRepr::Scalar(a), BackendRepr::Scalar(b)) => {
// Order by the memory placement, not source order.
let ((i, a), (j, b)) = if offsets[i] < offsets[j] {
((i, a), (j, b))
Expand All @@ -1315,7 +1317,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
{
// We can use `ScalarPair` only when it matches our
// already computed layout (including `#[repr(C)]`).
abi = pair.abi;
abi = pair.backend_repr;
}
}
_ => {}
Expand All @@ -1325,8 +1327,8 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
_ => {}
}
}
if fields.iter().any(|f| f.abi.is_uninhabited()) {
abi = Abi::Uninhabited;
if fields.iter().any(|f| f.is_uninhabited()) {
abi = BackendRepr::Uninhabited;
}

let unadjusted_abi_align = if repr.transparent() {
Expand All @@ -1344,7 +1346,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
Ok(LayoutData {
variants: Variants::Single { index: VariantIdx::new(0) },
fields: FieldsShape::Arbitrary { offsets, memory_index },
abi,
backend_repr: abi,
largest_niche,
align,
size,
Expand Down
12 changes: 6 additions & 6 deletions compiler/rustc_abi/src/layout/ty.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -83,8 +83,8 @@ impl<'a> Layout<'a> {
&self.0.0.variants
}

pub fn abi(self) -> Abi {
self.0.0.abi
pub fn backend_repr(self) -> BackendRepr {
self.0.0.backend_repr
}

pub fn largest_niche(self) -> Option<Niche> {
Expand Down Expand Up @@ -114,7 +114,7 @@ impl<'a> Layout<'a> {
pub fn is_pointer_like(self, data_layout: &TargetDataLayout) -> bool {
self.size() == data_layout.pointer_size
&& self.align().abi == data_layout.pointer_align.abi
&& matches!(self.abi(), Abi::Scalar(Scalar::Initialized { .. }))
&& matches!(self.backend_repr(), BackendRepr::Scalar(Scalar::Initialized { .. }))
}
}

Expand Down Expand Up @@ -196,9 +196,9 @@ impl<'a, Ty> TyAndLayout<'a, Ty> {
Ty: TyAbiInterface<'a, C>,
C: HasDataLayout,
{
match self.abi {
Abi::Scalar(scalar) => matches!(scalar.primitive(), Float(F32 | F64)),
Abi::Aggregate { .. } => {
match self.backend_repr {
BackendRepr::Scalar(scalar) => matches!(scalar.primitive(), Float(F32 | F64)),
BackendRepr::Memory { .. } => {
if self.fields.count() == 1 && self.fields.offset(0).bytes() == 0 {
self.field(cx, 0).is_single_fp_element(cx)
} else {
Expand Down
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