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rustc_target: treat enum variants like union members, in call ABIs.

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This commit is contained in:
Eduard-Mihai Burtescu 2020-01-22 02:52:54 +02:00
parent 8f81593d6c
commit da33935c26
2 changed files with 44 additions and 10 deletions
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28
src/librustc_target/abi/call/mod.rs
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@ -308,7 +308,7 @@ impl<'a, Ty> TyLayout<'a, Ty> {
Abi::ScalarPair(..) | Abi::Aggregate { .. } => {
// Helper for computing `homogenous_aggregate`, allowing a custom
// starting offset (TODO(eddyb): use this to handle variants).
// starting offset (used below for handling variants).
let from_fields_at =
|layout: Self,
start: Size|
@ -354,6 +354,32 @@ impl<'a, Ty> TyLayout<'a, Ty> {
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 homogenous 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 homogenous 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)

26
src/librustc_target/abi/call/x86_64.rs
View File

@ -56,16 +56,24 @@ where
Abi::Vector { .. } => Class::Sse,
Abi::ScalarPair(..) | Abi::Aggregate { .. } => match layout.variants {
abi::Variants::Single { .. } => {
for i in 0..layout.fields.count() {
let field_off = off + layout.fields.offset(i);
classify(cx, layout.field(cx, i), cls, field_off)?;
}
return Ok(());
Abi::ScalarPair(..) | Abi::Aggregate { .. } => {
for i in 0..layout.fields.count() {
let field_off = off + layout.fields.offset(i);
classify(cx, layout.field(cx, i), cls, field_off)?;
}
abi::Variants::Multiple { .. } => return Err(Memory),
},
match &layout.variants {
abi::Variants::Single { .. } => {}
abi::Variants::Multiple { variants, .. } => {
// Treat enum variants like union members.
for variant_idx in variants.indices() {
classify(cx, layout.for_variant(cx, variant_idx), cls, off)?;
}
}
}
return Ok(());
}
};
// Fill in `cls` for scalars (Int/Sse) and vectors (Sse).