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This commit is contained in:
Wesley Wiser 2021-05-17 11:09:13 -04:00
parent d650091117
commit d2d6fa852d
1 changed files with 33 additions and 3 deletions
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36
compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
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@ -1534,6 +1534,19 @@ impl EnumMemberDescriptionFactory<'ll, 'tcx> {
..
} => {
let tag_info = if fallback {
// For MSVC, we generate a union of structs for each variant with an explicit
// discriminant field roughly equivalent to the following C:
// ```c
// union _enum<{name}> {
// struct {variant 0 name} {
// tag$ variant$;
// <variant 0 fields>
// } Variant0;
// <other variant structs>
// }
// ```
// The natvis in `intrinsic.nativs` then matches on `this.Variant0.variant$` to
// determine which variant is active and then displays it.
Some(DirectTag {
tag_field: Field::from(tag_field),
tag_type_metadata: self.tag_type_metadata.unwrap(),
@ -1613,6 +1626,25 @@ impl EnumMemberDescriptionFactory<'ll, 'tcx> {
// For MSVC, we will generate a union of two structs, one for the dataful variant and one that just points to
// the discriminant field. We also create an enum that contains tag values for the non-dataful variants and
// make the discriminant field that type. We then use natvis to render the enum type correctly in Windbg/VS.
// This will generate debuginfo roughly equivalent to the following C:
// ```c
// union _enum<{name}, {min niche}, {max niche}, {dataful variant name} {
// struct dataful_variant {
// <fields in dataful variant>
// },
// struct discriminant$ {
// enum tag$ {
// <non-dataful variants>
// } discriminant;
// }
// }
// ```
// The natvis in `intrinsic.natvis` matches on the type name `_enum<*, *, *, *>`
// and evaluates `this.discriminant$.discriminant`. If the value is between
// the min niche and max niche, then the enum is in the dataful variant and
// `this.dataful_variant` is rendered. Otherwise, the enum is in one of the
// non-dataful variants. In that case, we just need to render the name of the
// `this.discriminant$.discriminant` enum.
if fallback {
let unique_type_id = debug_context(cx)
.type_map
@ -1938,9 +1970,7 @@ fn describe_enum_variant(
// We have the layout of an enum variant, we need the layout of the outer enum
let enum_layout = cx.layout_of(layout.ty);
let offset = enum_layout.fields.offset(tag_field.as_usize());
let tag_name =
if cx.tcx.sess.target.is_like_msvc { "variant$" } else { "RUST$ENUM$DISR" };
let args = (tag_name.to_owned(), enum_layout.field(cx, tag_field.as_usize()).ty);
let args = ("variant$".to_owned(), enum_layout.field(cx, tag_field.as_usize()).ty);
(Some(offset), Some(args))
}
_ => (None, None),