rustc_codegen_ssa/debuginfo/
mod.rs

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1use rustc_abi::{Integer, Primitive, Size, TagEncoding, Variants};
2use rustc_middle::bug;
3use rustc_middle::ty::layout::{IntegerExt, PrimitiveExt, TyAndLayout};
4use rustc_middle::ty::{self, Ty, TyCtxt};
5
6// FIXME(eddyb) find a place for this (or a way to replace it).
7pub mod type_names;
8
9/// Returns true if we want to generate a DW_TAG_enumeration_type description for
10/// this instead of a DW_TAG_struct_type with DW_TAG_variant_part.
11///
12/// NOTE: This is somewhat inconsistent right now: For empty enums and enums with a single
13///       fieldless variant, we generate DW_TAG_struct_type, although a
14///       DW_TAG_enumeration_type would be a better fit.
15pub fn wants_c_like_enum_debuginfo<'tcx>(
16    tcx: TyCtxt<'tcx>,
17    enum_type_and_layout: TyAndLayout<'tcx>,
18) -> bool {
19    match enum_type_and_layout.ty.kind() {
20        ty::Adt(adt_def, _) => {
21            if !adt_def.is_enum() {
22                return false;
23            }
24
25            if type_names::cpp_like_debuginfo(tcx)
26                && tag_base_type_opt(tcx, enum_type_and_layout)
27                    .map(|ty| ty.primitive_size(tcx).bits())
28                    == Some(128)
29            {
30                // C++-like debuginfo never uses the C-like representation for 128-bit enums.
31                return false;
32            }
33
34            match adt_def.variants().len() {
35                0 => false,
36                1 => {
37                    // Univariant enums unless they are zero-sized
38                    enum_type_and_layout.size != Size::ZERO && adt_def.all_fields().count() == 0
39                }
40                _ => {
41                    // Enums with more than one variant if they have no fields
42                    adt_def.all_fields().count() == 0
43                }
44            }
45        }
46        _ => false,
47    }
48}
49
50/// Extract the type with which we want to describe the tag of the given enum or coroutine.
51pub fn tag_base_type<'tcx>(tcx: TyCtxt<'tcx>, enum_type_and_layout: TyAndLayout<'tcx>) -> Ty<'tcx> {
52    tag_base_type_opt(tcx, enum_type_and_layout).unwrap_or_else(|| {
53        bug!("tag_base_type() called for enum without tag: {:?}", enum_type_and_layout)
54    })
55}
56
57fn tag_base_type_opt<'tcx>(
58    tcx: TyCtxt<'tcx>,
59    enum_type_and_layout: TyAndLayout<'tcx>,
60) -> Option<Ty<'tcx>> {
61    assert!(match enum_type_and_layout.ty.kind() {
62        ty::Coroutine(..) => true,
63        ty::Adt(adt_def, _) => adt_def.is_enum(),
64        _ => false,
65    });
66
67    match enum_type_and_layout.layout.variants() {
68        // A single-variant or no-variant enum has no discriminant.
69        Variants::Single { .. } | Variants::Empty => None,
70
71        Variants::Multiple { tag_encoding: TagEncoding::Niche { .. }, tag, .. } => {
72            // Niche tags are always normalized to unsized integers of the correct size.
73            Some(
74                match tag.primitive() {
75                    Primitive::Int(t, _) => t,
76                    Primitive::Float(f) => Integer::from_size(f.size()).unwrap(),
77                    // FIXME(erikdesjardins): handle non-default addrspace ptr sizes
78                    Primitive::Pointer(_) => {
79                        // If the niche is the NULL value of a reference, then `discr_enum_ty` will
80                        // be a RawPtr. CodeView doesn't know what to do with enums whose base type
81                        // is a pointer so we fix this up to just be `usize`.
82                        // DWARF might be able to deal with this but with an integer type we are on
83                        // the safe side there too.
84                        tcx.data_layout.ptr_sized_integer()
85                    }
86                }
87                .to_ty(tcx, false),
88            )
89        }
90
91        Variants::Multiple { tag_encoding: TagEncoding::Direct, tag, .. } => {
92            // Direct tags preserve the sign.
93            Some(tag.primitive().to_ty(tcx))
94        }
95    }
96}
rustc_codegen_ssa/debuginfo/mod.rs

rustc_codegen_ssa/debuginfo/
mod.rs
