mark payload fields of ScalarPair enums as Scalar::Union when they're not always initialized

This commit is contained in:
Erik Desjardins 2022-04-18 21:28:53 -04:00
parent 311e2683e1
commit 1bbae507d4
3 changed files with 828 additions and 16 deletions

View File

@ -1120,21 +1120,12 @@ fn layout_of_uncached(&self, ty: Ty<'tcx>) -> Result<Layout<'tcx>, LayoutError<'
match st[i].abi() {
Abi::Scalar(_) => Abi::Scalar(niche_scalar),
Abi::ScalarPair(first, second) => {
// We need to use scalar_unit to reset the
// valid range to the maximal one for that
// primitive, because only the niche is
// guaranteed to be initialised, not the
// other primitive.
// Only the niche is guaranteed to be initialised,
// so use union layout for the other primitive.
if offset.bytes() == 0 {
Abi::ScalarPair(
niche_scalar,
scalar_unit(second.primitive()),
)
Abi::ScalarPair(niche_scalar, second.to_union())
} else {
Abi::ScalarPair(
scalar_unit(first.primitive()),
niche_scalar,
)
Abi::ScalarPair(first.to_union(), niche_scalar)
}
}
_ => Abi::Aggregate { sized: true },
@ -1329,6 +1320,7 @@ fn layout_of_uncached(&self, ty: Ty<'tcx>) -> Result<Layout<'tcx>, LayoutError<'
} else {
// Try to use a ScalarPair for all tagged enums.
let mut common_prim = None;
let mut common_prim_initialized_in_all_variants = true;
for (field_layouts, layout_variant) in iter::zip(&variants, &layout_variants) {
let FieldsShape::Arbitrary { ref offsets, .. } = layout_variant.fields else {
bug!();
@ -1336,7 +1328,10 @@ fn layout_of_uncached(&self, ty: Ty<'tcx>) -> Result<Layout<'tcx>, LayoutError<'
let mut fields =
iter::zip(field_layouts, offsets).filter(|p| !p.0.is_zst());
let (field, offset) = match (fields.next(), fields.next()) {
(None, None) => continue,
(None, None) => {
common_prim_initialized_in_all_variants = false;
continue;
}
(Some(pair), None) => pair,
_ => {
common_prim = None;
@ -1344,7 +1339,11 @@ fn layout_of_uncached(&self, ty: Ty<'tcx>) -> Result<Layout<'tcx>, LayoutError<'
}
};
let prim = match field.abi {
Abi::Scalar(scalar) => scalar.primitive(),
Abi::Scalar(scalar) => {
common_prim_initialized_in_all_variants &=
matches!(scalar, Scalar::Initialized { .. });
scalar.primitive()
}
_ => {
common_prim = None;
break;
@ -1364,7 +1363,13 @@ fn layout_of_uncached(&self, ty: Ty<'tcx>) -> Result<Layout<'tcx>, LayoutError<'
}
}
if let Some((prim, offset)) = common_prim {
let pair = self.scalar_pair(tag, scalar_unit(prim));
let prim_scalar = if common_prim_initialized_in_all_variants {
scalar_unit(prim)
} else {
// Common prim might be uninit.
Scalar::Union { value: prim }
};
let pair = self.scalar_pair(tag, prim_scalar);
let pair_offsets = match pair.fields {
FieldsShape::Arbitrary { ref offsets, ref memory_index } => {
assert_eq!(memory_index, &[0, 1]);

View File

@ -0,0 +1,53 @@
#![crate_type = "lib"]
#![feature(rustc_attrs)]
use std::mem::MaybeUninit;
enum HasNiche {
A,
B,
C,
}
// This should result in ScalarPair(Initialized, Union),
// since the u8 payload will be uninit for `None`.
#[rustc_layout(debug)]
pub enum MissingPayloadField { //~ ERROR: layout_of
Some(u8),
None
}
// This should result in ScalarPair(Initialized, Initialized),
// since the u8 field is present in all variants,
// and hence will always be initialized.
#[rustc_layout(debug)]
pub enum CommonPayloadField { //~ ERROR: layout_of
A(u8),
B(u8),
}
// This should result in ScalarPair(Initialized, Union),
// since, though a u8-sized field is present in all variants, it might be uninit.
#[rustc_layout(debug)]
pub enum CommonPayloadFieldIsMaybeUninit { //~ ERROR: layout_of
A(u8),
B(MaybeUninit<u8>),
}
// This should result in ScalarPair(Initialized, Union),
// since only the niche field (used for the tag) is guaranteed to be initialized.
#[rustc_layout(debug)]
pub enum NicheFirst { //~ ERROR: layout_of
A(HasNiche, u8),
B,
C
}
// This should result in ScalarPair(Union, Initialized),
// since only the niche field (used for the tag) is guaranteed to be initialized.
#[rustc_layout(debug)]
pub enum NicheSecond { //~ ERROR: layout_of
A(u8, HasNiche),
B,
C,
}

View File

@ -0,0 +1,754 @@
error: layout_of(MissingPayloadField) = Layout {
fields: Arbitrary {
offsets: [
Size {
raw: 0,
},
],
memory_index: [
0,
],
},
variants: Multiple {
tag: Initialized {
value: Int(
I8,
false,
),
valid_range: 0..=1,
},
tag_encoding: Direct,
tag_field: 0,
variants: [
Layout {
fields: Arbitrary {
offsets: [
Size {
raw: 1,
},
],
memory_index: [
0,
],
},
variants: Single {
index: 0,
},
abi: Aggregate {
sized: true,
},
largest_niche: None,
align: AbiAndPrefAlign {
abi: Align {
pow2: 0,
},
pref: Align {
pow2: 3,
},
},
size: Size {
raw: 2,
},
},
Layout {
fields: Arbitrary {
offsets: [],
memory_index: [],
},
variants: Single {
index: 1,
},
abi: Aggregate {
sized: true,
},
largest_niche: None,
align: AbiAndPrefAlign {
abi: Align {
pow2: 0,
},
pref: Align {
pow2: 3,
},
},
size: Size {
raw: 1,
},
},
],
},
abi: ScalarPair(
Initialized {
value: Int(
I8,
false,
),
valid_range: 0..=1,
},
Union {
value: Int(
I8,
false,
),
},
),
largest_niche: Some(
Niche {
offset: Size {
raw: 0,
},
value: Int(
I8,
false,
),
valid_range: 0..=1,
},
),
align: AbiAndPrefAlign {
abi: Align {
pow2: 0,
},
pref: Align {
pow2: 3,
},
},
size: Size {
raw: 2,
},
}
--> $DIR/issue-96158-scalarpair-payload-might-be-uninit.rs:15:1
|
LL | / pub enum MissingPayloadField {
LL | | Some(u8),
LL | | None
LL | | }
| |_^
error: layout_of(CommonPayloadField) = Layout {
fields: Arbitrary {
offsets: [
Size {
raw: 0,
},
],
memory_index: [
0,
],
},
variants: Multiple {
tag: Initialized {
value: Int(
I8,
false,
),
valid_range: 0..=1,
},
tag_encoding: Direct,
tag_field: 0,
variants: [
Layout {
fields: Arbitrary {
offsets: [
Size {
raw: 1,
},
],
memory_index: [
0,
],
},
variants: Single {
index: 0,
},
abi: Aggregate {
sized: true,
},
largest_niche: None,
align: AbiAndPrefAlign {
abi: Align {
pow2: 0,
},
pref: Align {
pow2: 3,
},
},
size: Size {
raw: 2,
},
},
Layout {
fields: Arbitrary {
offsets: [
Size {
raw: 1,
},
],
memory_index: [
0,
],
},
variants: Single {
index: 1,
},
abi: Aggregate {
sized: true,
},
largest_niche: None,
align: AbiAndPrefAlign {
abi: Align {
pow2: 0,
},
pref: Align {
pow2: 3,
},
},
size: Size {
raw: 2,
},
},
],
},
abi: ScalarPair(
Initialized {
value: Int(
I8,
false,
),
valid_range: 0..=1,
},
Initialized {
value: Int(
I8,
false,
),
valid_range: 0..=255,
},
),
largest_niche: Some(
Niche {
offset: Size {
raw: 0,
},
value: Int(
I8,
false,
),
valid_range: 0..=1,
},
),
align: AbiAndPrefAlign {
abi: Align {
pow2: 0,
},
pref: Align {
pow2: 3,
},
},
size: Size {
raw: 2,
},
}
--> $DIR/issue-96158-scalarpair-payload-might-be-uninit.rs:24:1
|
LL | / pub enum CommonPayloadField {
LL | | A(u8),
LL | | B(u8),
LL | | }
| |_^
error: layout_of(CommonPayloadFieldIsMaybeUninit) = Layout {
fields: Arbitrary {
offsets: [
Size {
raw: 0,
},
],
memory_index: [
0,
],
},
variants: Multiple {
tag: Initialized {
value: Int(
I8,
false,
),
valid_range: 0..=1,
},
tag_encoding: Direct,
tag_field: 0,
variants: [
Layout {
fields: Arbitrary {
offsets: [
Size {
raw: 1,
},
],
memory_index: [
0,
],
},
variants: Single {
index: 0,
},
abi: Aggregate {
sized: true,
},
largest_niche: None,
align: AbiAndPrefAlign {
abi: Align {
pow2: 0,
},
pref: Align {
pow2: 3,
},
},
size: Size {
raw: 2,
},
},
Layout {
fields: Arbitrary {
offsets: [
Size {
raw: 1,
},
],
memory_index: [
0,
],
},
variants: Single {
index: 1,
},
abi: Aggregate {
sized: true,
},
largest_niche: None,
align: AbiAndPrefAlign {
abi: Align {
pow2: 0,
},
pref: Align {
pow2: 3,
},
},
size: Size {
raw: 2,
},
},
],
},
abi: ScalarPair(
Initialized {
value: Int(
I8,
false,
),
valid_range: 0..=1,
},
Union {
value: Int(
I8,
false,
),
},
),
largest_niche: Some(
Niche {
offset: Size {
raw: 0,
},
value: Int(
I8,
false,
),
valid_range: 0..=1,
},
),
align: AbiAndPrefAlign {
abi: Align {
pow2: 0,
},
pref: Align {
pow2: 3,
},
},
size: Size {
raw: 2,
},
}
--> $DIR/issue-96158-scalarpair-payload-might-be-uninit.rs:32:1
|
LL | / pub enum CommonPayloadFieldIsMaybeUninit {
LL | | A(u8),
LL | | B(MaybeUninit<u8>),
LL | | }
| |_^
error: layout_of(NicheFirst) = Layout {
fields: Arbitrary {
offsets: [
Size {
raw: 0,
},
],
memory_index: [
0,
],
},
variants: Multiple {
tag: Initialized {
value: Int(
I8,
false,
),
valid_range: 0..=4,
},
tag_encoding: Niche {
dataful_variant: 0,
niche_variants: 1..=2,
niche_start: 3,
},
tag_field: 0,
variants: [
Layout {
fields: Arbitrary {
offsets: [
Size {
raw: 0,
},
Size {
raw: 1,
},
],
memory_index: [
0,
1,
],
},
variants: Single {
index: 0,
},
abi: ScalarPair(
Initialized {
value: Int(
I8,
false,
),
valid_range: 0..=2,
},
Initialized {
value: Int(
I8,
false,
),
valid_range: 0..=255,
},
),
largest_niche: Some(
Niche {
offset: Size {
raw: 0,
},
value: Int(
I8,
false,
),
valid_range: 0..=2,
},
),
align: AbiAndPrefAlign {
abi: Align {
pow2: 0,
},
pref: Align {
pow2: 3,
},
},
size: Size {
raw: 2,
},
},
Layout {
fields: Arbitrary {
offsets: [],
memory_index: [],
},
variants: Single {
index: 1,
},
abi: Aggregate {
sized: true,
},
largest_niche: None,
align: AbiAndPrefAlign {
abi: Align {
pow2: 0,
},
pref: Align {
pow2: 3,
},
},
size: Size {
raw: 0,
},
},
Layout {
fields: Arbitrary {
offsets: [],
memory_index: [],
},
variants: Single {
index: 2,
},
abi: Aggregate {
sized: true,
},
largest_niche: None,
align: AbiAndPrefAlign {
abi: Align {
pow2: 0,
},
pref: Align {
pow2: 3,
},
},
size: Size {
raw: 0,
},
},
],
},
abi: ScalarPair(
Initialized {
value: Int(
I8,
false,
),
valid_range: 0..=4,
},
Union {
value: Int(
I8,
false,
),
},
),
largest_niche: Some(
Niche {
offset: Size {
raw: 0,
},
value: Int(
I8,
false,
),
valid_range: 0..=4,
},
),
align: AbiAndPrefAlign {
abi: Align {
pow2: 0,
},
pref: Align {
pow2: 3,
},
},
size: Size {
raw: 2,
},
}
--> $DIR/issue-96158-scalarpair-payload-might-be-uninit.rs:40:1
|
LL | / pub enum NicheFirst {
LL | | A(HasNiche, u8),
LL | | B,
LL | | C
LL | | }
| |_^
error: layout_of(NicheSecond) = Layout {
fields: Arbitrary {
offsets: [
Size {
raw: 1,
},
],
memory_index: [
0,
],
},
variants: Multiple {
tag: Initialized {
value: Int(
I8,
false,
),
valid_range: 0..=4,
},
tag_encoding: Niche {
dataful_variant: 0,
niche_variants: 1..=2,
niche_start: 3,
},
tag_field: 0,
variants: [
Layout {
fields: Arbitrary {
offsets: [
Size {
raw: 0,
},
Size {
raw: 1,
},
],
memory_index: [
0,
1,
],
},
variants: Single {
index: 0,
},
abi: ScalarPair(
Initialized {
value: Int(
I8,
false,
),
valid_range: 0..=255,
},
Initialized {
value: Int(
I8,
false,
),
valid_range: 0..=2,
},
),
largest_niche: Some(
Niche {
offset: Size {
raw: 1,
},
value: Int(
I8,
false,
),
valid_range: 0..=2,
},
),
align: AbiAndPrefAlign {
abi: Align {
pow2: 0,
},
pref: Align {
pow2: 3,
},
},
size: Size {
raw: 2,
},
},
Layout {
fields: Arbitrary {
offsets: [],
memory_index: [],
},
variants: Single {
index: 1,
},
abi: Aggregate {
sized: true,
},
largest_niche: None,
align: AbiAndPrefAlign {
abi: Align {
pow2: 0,
},
pref: Align {
pow2: 3,
},
},
size: Size {
raw: 0,
},
},
Layout {
fields: Arbitrary {
offsets: [],
memory_index: [],
},
variants: Single {
index: 2,
},
abi: Aggregate {
sized: true,
},
largest_niche: None,
align: AbiAndPrefAlign {
abi: Align {
pow2: 0,
},
pref: Align {
pow2: 3,
},
},
size: Size {
raw: 0,
},
},
],
},
abi: ScalarPair(
Union {
value: Int(
I8,
false,
),
},
Initialized {
value: Int(
I8,
false,
),
valid_range: 0..=4,
},
),
largest_niche: Some(
Niche {
offset: Size {
raw: 1,
},
value: Int(
I8,
false,
),
valid_range: 0..=4,
},
),
align: AbiAndPrefAlign {
abi: Align {
pow2: 0,
},
pref: Align {
pow2: 3,
},
},
size: Size {
raw: 2,
},
}
--> $DIR/issue-96158-scalarpair-payload-might-be-uninit.rs:49:1
|
LL | / pub enum NicheSecond {
LL | | A(u8, HasNiche),
LL | | B,
LL | | C,
LL | | }
| |_^
error: aborting due to 5 previous errors