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Diffstat (limited to 'compiler/rustc_abi/src/callconv.rs')
| -rw-r--r-- | compiler/rustc_abi/src/callconv.rs | 254 |
1 files changed, 254 insertions, 0 deletions
diff --git a/compiler/rustc_abi/src/callconv.rs b/compiler/rustc_abi/src/callconv.rs new file mode 100644 index 00000000000..2ecac8a9df1 --- /dev/null +++ b/compiler/rustc_abi/src/callconv.rs @@ -0,0 +1,254 @@ +mod abi { + pub(crate) use crate::Primitive::*; + pub(crate) use crate::Variants; +} + +use rustc_macros::HashStable_Generic; + +use crate::{Abi, Align, FieldsShape, HasDataLayout, Size, TyAbiInterface, TyAndLayout}; + +#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, HashStable_Generic)] +pub enum RegKind { + Integer, + Float, + Vector, +} + +#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, HashStable_Generic)] +pub struct Reg { + pub kind: RegKind, + pub size: Size, +} + +macro_rules! reg_ctor { + ($name:ident, $kind:ident, $bits:expr) => { + pub fn $name() -> Reg { + Reg { kind: RegKind::$kind, size: Size::from_bits($bits) } + } + }; +} + +impl Reg { + reg_ctor!(i8, Integer, 8); + reg_ctor!(i16, Integer, 16); + reg_ctor!(i32, Integer, 32); + reg_ctor!(i64, Integer, 64); + reg_ctor!(i128, Integer, 128); + + reg_ctor!(f32, Float, 32); + reg_ctor!(f64, Float, 64); +} + +impl Reg { + pub fn align<C: HasDataLayout>(&self, cx: &C) -> Align { + let dl = cx.data_layout(); + match self.kind { + RegKind::Integer => match self.size.bits() { + 1 => dl.i1_align.abi, + 2..=8 => dl.i8_align.abi, + 9..=16 => dl.i16_align.abi, + 17..=32 => dl.i32_align.abi, + 33..=64 => dl.i64_align.abi, + 65..=128 => dl.i128_align.abi, + _ => panic!("unsupported integer: {self:?}"), + }, + RegKind::Float => match self.size.bits() { + 16 => dl.f16_align.abi, + 32 => dl.f32_align.abi, + 64 => dl.f64_align.abi, + 128 => dl.f128_align.abi, + _ => panic!("unsupported float: {self:?}"), + }, + RegKind::Vector => dl.vector_align(self.size).abi, + } + } +} + +/// Return value from the `homogeneous_aggregate` test function. +#[derive(Copy, Clone, Debug)] +pub enum HomogeneousAggregate { + /// Yes, all the "leaf fields" of this struct are passed in the + /// same way (specified in the `Reg` value). + Homogeneous(Reg), + + /// There are no leaf fields at all. + NoData, +} + +/// Error from the `homogeneous_aggregate` test function, indicating +/// there are distinct leaf fields passed in different ways, +/// or this is uninhabited. +#[derive(Copy, Clone, Debug)] +pub struct Heterogeneous; + +impl HomogeneousAggregate { + /// If this is a homogeneous aggregate, returns the homogeneous + /// unit, else `None`. + pub fn unit(self) -> Option<Reg> { + match self { + HomogeneousAggregate::Homogeneous(reg) => Some(reg), + HomogeneousAggregate::NoData => None, + } + } + + /// Try to combine two `HomogeneousAggregate`s, e.g. from two fields in + /// the same `struct`. Only succeeds if only one of them has any data, + /// or both units are identical. + fn merge(self, other: HomogeneousAggregate) -> Result<HomogeneousAggregate, Heterogeneous> { + match (self, other) { + (x, HomogeneousAggregate::NoData) | (HomogeneousAggregate::NoData, x) => Ok(x), + + (HomogeneousAggregate::Homogeneous(a), HomogeneousAggregate::Homogeneous(b)) => { + if a != b { + return Err(Heterogeneous); + } + Ok(self) + } + } + } +} + +impl<'a, Ty> TyAndLayout<'a, Ty> { + /// Returns `true` if this is an aggregate type (including a ScalarPair!) + pub fn is_aggregate(&self) -> bool { + match self.abi { + Abi::Uninhabited | Abi::Scalar(_) | Abi::Vector { .. } => false, + Abi::ScalarPair(..) | Abi::Aggregate { .. } => true, + } + } + + /// Returns `Homogeneous` if this layout is an aggregate containing fields of + /// only a single type (e.g., `(u32, u32)`). Such aggregates are often + /// special-cased in ABIs. + /// + /// Note: We generally ignore 1-ZST fields when computing this value (see #56877). + /// + /// This is public so that it can be used in unit tests, but + /// should generally only be relevant to the ABI details of + /// specific targets. + pub fn homogeneous_aggregate<C>(&self, cx: &C) -> Result<HomogeneousAggregate, Heterogeneous> + where + Ty: TyAbiInterface<'a, C> + Copy, + { + match self.abi { + Abi::Uninhabited => Err(Heterogeneous), + + // The primitive for this algorithm. + Abi::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 { .. } => { + assert!(!self.is_zst()); + Ok(HomogeneousAggregate::Homogeneous(Reg { + kind: RegKind::Vector, + size: self.size, + })) + } + + Abi::ScalarPair(..) | Abi::Aggregate { sized: true } => { + // Helper for computing `homogeneous_aggregate`, allowing a custom + // starting offset (used below for handling variants). + let from_fields_at = + |layout: Self, + start: Size| + -> Result<(HomogeneousAggregate, Size), Heterogeneous> { + let is_union = match layout.fields { + FieldsShape::Primitive => { + unreachable!("aggregates can't have `FieldsShape::Primitive`") + } + FieldsShape::Array { count, .. } => { + assert_eq!(start, Size::ZERO); + + let result = if count > 0 { + layout.field(cx, 0).homogeneous_aggregate(cx)? + } else { + HomogeneousAggregate::NoData + }; + return Ok((result, layout.size)); + } + FieldsShape::Union(_) => true, + FieldsShape::Arbitrary { .. } => false, + }; + + let mut result = HomogeneousAggregate::NoData; + let mut total = start; + + for i in 0..layout.fields.count() { + let field = layout.field(cx, i); + if field.is_1zst() { + // No data here and no impact on layout, can be ignored. + // (We might be able to also ignore all aligned ZST but that's less clear.) + continue; + } + + if !is_union && total != layout.fields.offset(i) { + // This field isn't just after the previous one we considered, abort. + return Err(Heterogeneous); + } + + result = result.merge(field.homogeneous_aggregate(cx)?)?; + + // Keep track of the offset (without padding). + let size = field.size; + if is_union { + total = total.max(size); + } else { + total += size; + } + } + + Ok((result, total)) + }; + + let (mut result, mut total) = from_fields_at(*self, Size::ZERO)?; + + match &self.variants { + abi::Variants::Single { .. } => {} + abi::Variants::Multiple { variants, .. } => { + // Treat enum variants like union members. + // HACK(eddyb) pretend the `enum` field (discriminant) + // is at the start of every variant (otherwise the gap + // at the start of all variants would disqualify them). + // + // NB: for all tagged `enum`s (which include all non-C-like + // `enum`s with defined FFI representation), this will + // match the homogeneous computation on the equivalent + // `struct { tag; union { variant1; ... } }` and/or + // `union { struct { tag; variant1; } ... }` + // (the offsets of variant fields should be identical + // between the two for either to be a homogeneous aggregate). + let variant_start = total; + for variant_idx in variants.indices() { + let (variant_result, variant_total) = + from_fields_at(self.for_variant(cx, variant_idx), variant_start)?; + + result = result.merge(variant_result)?; + total = total.max(variant_total); + } + } + } + + // There needs to be no padding. + if total != self.size { + Err(Heterogeneous) + } else { + match result { + HomogeneousAggregate::Homogeneous(_) => { + assert_ne!(total, Size::ZERO); + } + HomogeneousAggregate::NoData => { + assert_eq!(total, Size::ZERO); + } + } + Ok(result) + } + } + Abi::Aggregate { sized: false } => Err(Heterogeneous), + } + } +} |