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interpret: refactor projection code to work on a common trait, and use that for visitors

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This commit is contained in:
Ralf Jung
2023-07-24 11:44:58 +02:00
parent a593de4fab
commit a2bcafa500
44 changed files with 863 additions and 1210 deletions
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28
compiler/rustc_const_eval/src/interpret/discriminant.rs
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@@ -22,7 +22,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
// When evaluating we will always error before even getting here, but ConstProp 'executes'
// dead code, so we cannot ICE here.
if dest.layout.for_variant(self, variant_index).abi.is_uninhabited() {
throw_ub!(UninhabitedEnumVariantWritten)
throw_ub!(UninhabitedEnumVariantWritten(variant_index))
}
match dest.layout.variants {
@@ -47,7 +47,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
let size = tag_layout.size(self);
let tag_val = size.truncate(discr_val);
let tag_dest = self.place_field(dest, tag_field)?;
let tag_dest = self.project_field(dest, tag_field)?;
self.write_scalar(Scalar::from_uint(tag_val, size), &tag_dest)?;
}
abi::Variants::Multiple {
@@ -78,7 +78,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
&niche_start_val,
)?;
// Write result.
let niche_dest = self.place_field(dest, tag_field)?;
let niche_dest = self.project_field(dest, tag_field)?;
self.write_immediate(*tag_val, &niche_dest)?;
}
}
@@ -106,6 +106,11 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
// straight-forward (`TagEncoding::Direct`) or with a niche (`TagEncoding::Niche`).
let (tag_scalar_layout, tag_encoding, tag_field) = match op.layout.variants {
Variants::Single { index } => {
// Hilariously, `Single` is used even for 0-variant enums.
// (See https://github.com/rust-lang/rust/issues/89765).
if matches!(op.layout.ty.kind(), ty::Adt(def, ..) if def.variants().is_empty()) {
throw_ub!(UninhabitedEnumVariantRead(index))
}
let discr = match op.layout.ty.discriminant_for_variant(*self.tcx, index) {
Some(discr) => {
// This type actually has discriminants.
@@ -118,6 +123,12 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
Scalar::from_uint(index.as_u32(), discr_layout.size)
}
};
// For consisteny with `write_discriminant`, and to make sure that
// `project_downcast` cannot fail due to strange layouts, we declare immediate UB
// for uninhabited variants.
if op.layout.ty.is_enum() && op.layout.for_variant(self, index).abi.is_uninhabited() {
throw_ub!(UninhabitedEnumVariantRead(index))
}
return Ok((discr, index));
}
Variants::Multiple { tag, ref tag_encoding, tag_field, .. } => {
@@ -138,13 +149,13 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
let tag_layout = self.layout_of(tag_scalar_layout.primitive().to_int_ty(*self.tcx))?;
// Read tag and sanity-check `tag_layout`.
let tag_val = self.read_immediate(&self.operand_field(op, tag_field)?)?;
let tag_val = self.read_immediate(&self.project_field(op, tag_field)?)?;
assert_eq!(tag_layout.size, tag_val.layout.size);
assert_eq!(tag_layout.abi.is_signed(), tag_val.layout.abi.is_signed());
trace!("tag value: {}", tag_val);
// Figure out which discriminant and variant this corresponds to.
Ok(match *tag_encoding {
let (discr, index) = match *tag_encoding {
TagEncoding::Direct => {
let scalar = tag_val.to_scalar();
// Generate a specific error if `tag_val` is not an integer.
@@ -232,6 +243,11 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
// encoded in the tag.
(Scalar::from_uint(variant.as_u32(), discr_layout.size), variant)
}
})
};
// For consisteny with `write_discriminant`, and to make sure that `project_downcast` cannot fail due to strange layouts, we declare immediate UB for uninhabited variants.
if op.layout.for_variant(self, index).abi.is_uninhabited() {
throw_ub!(UninhabitedEnumVariantRead(index))
}
Ok((discr, index))
}
}