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Not all evaluated MIR constants are byte strings #1318

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merged 3 commits into from
Feb 20, 2025
Merged

Not all evaluated MIR constants are byte strings #1318

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08c98b7
Fix formatting
Nadrieril Feb 18, 2025
0923906
Not all evaluated MIR constants are byte strings
Nadrieril Feb 18, 2025
2046c22
The style of string literals is semantically irrelevant
Nadrieril Feb 19, 2025
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9 changes: 5 additions & 4 deletions engine/lib/import_thir.ml
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Original file line number Diff line number Diff line change
Expand Up @@ -852,9 +852,10 @@ end) : EXPR = struct
| Borrow arg ->
Borrow { arg = constant_expr_to_expr arg; borrow_kind = Thir.Shared }
| ConstRef { id } -> ConstRef { id }
| Cast _ | RawBorrow _ | TraitConst _ | FnPtr _ ->
| Cast _ | RawBorrow _ | TraitConst _ | FnPtr _ | Memory _ ->
assertion_failure [ span ]
"constant_lit_to_lit: TraitConst | FnPtr | MutPtr"
"constant_lit_to_lit: TraitConst | FnPtr | RawBorrow | Cast | \
Memory"
| Todo _ -> assertion_failure [ span ] "ConstantExpr::Todo"
and constant_lit_to_lit (l : Thir.constant_literal) _span :
Thir.lit_kind * bool =
Expand All @@ -870,8 +871,8 @@ end) : EXPR = struct
match String.chop_prefix v ~prefix:"-" with
| Some v -> (Float (v, Suffixed ty), true)
| None -> (Float (v, Suffixed ty), false))
| Str (v, style) -> (Str (v, style), false)
| ByteStr (v, style) -> (ByteStr (v, style), false)
| Str v -> (Str (v, Cooked), false)
| ByteStr v -> (ByteStr (v, Cooked), false)
and constant_field_expr ({ field; value } : Thir.constant_field_expr) :
Thir.field_expr =
{ field; value = constant_expr_to_expr value }
Expand Down
94 changes: 53 additions & 41 deletions frontend/exporter/src/constant_utils.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -24,8 +24,8 @@ pub enum ConstantLiteral {
Char(char),
Float(String, FloatTy),
Int(ConstantInt),
Str(String, StrStyle),
ByteStr(Vec<u8>, StrStyle),
Str(String),
ByteStr(Vec<u8>),
}

/// The subset of [Expr] that corresponds to constants.
Expand Down Expand Up @@ -104,6 +104,10 @@ pub enum ConstantExprKind {
/// is an implementation of `Foo`
method_impl: Option<ImplExpr>,
},
/// A blob of memory containing the byte representation of the value. This can occur when
/// evaluating MIR constants. Interpreting this back to a structured value is left as an
/// exercice to the consumer.
Memory(Vec<u8>),
Todo(String),
}

Expand Down Expand Up @@ -143,10 +147,10 @@ mod rustc {
/// Rustc always represents string constants as `&[u8]`, but this
/// is not nice to consume. This associated function interpret
/// bytes as an unicode string, and as a byte string otherwise.
fn byte_str(bytes: Vec<u8>, style: StrStyle) -> Self {
fn byte_str(bytes: Vec<u8>) -> Self {
match String::from_utf8(bytes.clone()) {
Ok(s) => Self::Str(s, style),
Err(_) => Self::ByteStr(bytes, style),
Ok(s) => Self::Str(s),
Err(_) => Self::ByteStr(bytes),
}
}
}
Expand All @@ -172,8 +176,8 @@ mod rustc {
}
}
Float(f, ty) => LitKind::Float(f, LitFloatType::Suffixed(ty)),
ByteStr(raw, str_style) => LitKind::ByteStr(raw, str_style),
Str(raw, str_style) => LitKind::Str(raw, str_style),
ByteStr(raw) => LitKind::ByteStr(raw, StrStyle::Cooked),
Str(raw) => LitKind::Str(raw, StrStyle::Cooked),
};
let span = c.span.clone();
let lit = Spanned { span, node };
Expand Down Expand Up @@ -213,9 +217,9 @@ mod rustc {
Cast { source } => ExprKind::Cast {
source: source.into(),
},
kind @ (FnPtr { .. } | TraitConst { .. }) => {
kind @ (FnPtr { .. } | TraitConst { .. } | Memory { .. }) => {
// SH: I see the `Closure` kind, but it's not the same as function pointer?
ExprKind::Todo(format!("FnPtr or TraitConst. kind={:#?}", kind))
ExprKind::Todo(format!("FnPtr or TraitConst or Memory. kind={:#?}", kind))
}
Todo(msg) => ExprKind::Todo(msg),
};
Expand Down Expand Up @@ -327,16 +331,21 @@ mod rustc {
variant_information: None,
},
GlobalAlloc::Memory(alloc) => {
let values = alloc.inner().get_bytes_unchecked(
rustc_middle::mir::interpret::AllocRange {
let bytes = alloc
.inner()
.get_bytes_unchecked(rustc_middle::mir::interpret::AllocRange {
start: rustc_abi::Size::ZERO,
size: alloc.inner().size(),
},
);
ConstantExprKind::Literal(ConstantLiteral::ByteStr(
values.to_vec(),
StrStyle::Cooked,
))
})
.to_vec();
match inner_ty.kind() {
ty::Slice(slice_ty) | ty::Array(slice_ty, _)
if matches!(slice_ty.kind(), ty::Uint(ty::UintTy::U8)) =>
{
ConstantExprKind::Literal(ConstantLiteral::ByteStr(bytes))
}
_ => ConstantExprKind::Memory(bytes),
}
}
provenance => fatal!(
s[span],
Expand Down Expand Up @@ -562,37 +571,43 @@ mod rustc {
(_, ty::Ref(_, inner_ty, _)) => {
ConstantExprKind::Borrow(valtree_to_constant_expr(s, valtree, *inner_ty, span))
}
(ty::ValTree::Branch(valtrees), ty::Str) => ConstantExprKind::Literal(
ConstantLiteral::byte_str(valtrees.iter().map(|x| match x {
ty::ValTree::Leaf(leaf) => leaf.to_u8(),
_ => fatal!(s[span], "Expected a flat list of leaves while translating a str literal, got a arbitrary valtree.")
}).collect(), StrStyle::Cooked))
,
(ty::ValTree::Branch(valtrees), ty::Str) => {
let bytes = valtrees
.iter()
.map(|x| match x {
ty::ValTree::Leaf(leaf) => leaf.to_u8(),
_ => fatal!(
s[span],
"Expected a flat list of leaves while translating \
a str literal, got a arbitrary valtree."
),
})
.collect();
ConstantExprKind::Literal(ConstantLiteral::byte_str(bytes))
}
(ty::ValTree::Branch(_), ty::Array(..) | ty::Tuple(..) | ty::Adt(..)) => {
let contents: rustc_middle::ty::DestructuredConst = s
.base().tcx
.base()
.tcx
.destructure_const(ty::Const::new_value(s.base().tcx, valtree, ty));
let fields = contents.fields.iter().copied();
match ty.kind() {
ty::Array(_, _) => ConstantExprKind::Array {
fields: fields
.map(|field| field.sinto(s))
.collect(),
fields: fields.map(|field| field.sinto(s)).collect(),
},
ty::Tuple(_) => ConstantExprKind::Tuple {
fields: fields
.map(|field| field.sinto(s))
.collect(),
fields: fields.map(|field| field.sinto(s)).collect(),
},
ty::Adt(def, _) => {
let variant_idx = contents
.variant
.s_expect(s, "destructed const of adt without variant idx");
let variant_def = &def.variant(variant_idx);

ConstantExprKind::Adt{
ConstantExprKind::Adt {
info: get_variant_information(def, variant_idx, s),
fields: fields.into_iter()
fields: fields
.into_iter()
.zip(&variant_def.fields)
.map(|(value, field)| ConstantFieldExpr {
field: field.did.sinto(s),
Expand All @@ -611,12 +626,12 @@ mod rustc {
let usize_ty = rustc_middle::ty::Ty::new_usize(s.base().tcx).sinto(s);
let lit = ConstantLiteral::Int(ConstantInt::Uint(raw_address, uint_ty));
ConstantExprKind::Cast {
source: ConstantExprKind::Literal(lit).decorate(usize_ty, span.sinto(s))
source: ConstantExprKind::Literal(lit).decorate(usize_ty, span.sinto(s)),
}
}
(ty::ValTree::Leaf(x), _) => ConstantExprKind::Literal (
scalar_int_to_constant_literal(s, x, ty)
),
(ty::ValTree::Leaf(x), _) => {
ConstantExprKind::Literal(scalar_int_to_constant_literal(s, x, ty))
}
_ => supposely_unreachable_fatal!(
s[span], "valtree_to_expr";
{valtree, ty}
Expand Down Expand Up @@ -697,11 +712,8 @@ mod rustc {
let slice: &[u8] = data
.inner()
.inspect_with_uninit_and_ptr_outside_interpreter(0..end);
ConstantExprKind::Literal(ConstantLiteral::byte_str(
slice.to_vec(),
StrStyle::Cooked,
))
.decorate(ty.sinto(s), span.sinto(s))
ConstantExprKind::Literal(ConstantLiteral::byte_str(slice.to_vec()))
.decorate(ty.sinto(s), span.sinto(s))
}
ConstValue::ZeroSized { .. } => {
// Should be unit
Expand Down
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