Auto merge of #128037 - beetrees:repr128-c-style-use-natvis, r=michaelwoerister

Use the `enum2$` Natvis visualiser for repr128 C-style enums

Use the preexisting `enum2$` Natvis visualiser to allow PDB debuggers to display fieldless `#[repr(u128)]]`/`#[repr(i128)]]` enums correctly.

Tracking issue: #56071

try-job: x86_64-msvc

compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/cpp_like.rs

@@ -2,7 +2,7 @@
 
 use libc::c_uint;
 use rustc_codegen_ssa::debuginfo::type_names::compute_debuginfo_type_name;
-use rustc_codegen_ssa::debuginfo::wants_c_like_enum_debuginfo;
+use rustc_codegen_ssa::debuginfo::{tag_base_type, wants_c_like_enum_debuginfo};
 use rustc_codegen_ssa::traits::ConstMethods;
 use rustc_index::IndexVec;
 use rustc_middle::bug;
@@ -12,7 +12,7 @@
 use smallvec::smallvec;
 
 use crate::common::CodegenCx;
-use crate::debuginfo::metadata::enums::{tag_base_type, DiscrResult};
+use crate::debuginfo::metadata::enums::DiscrResult;
 use crate::debuginfo::metadata::type_map::{self, Stub, UniqueTypeId};
 use crate::debuginfo::metadata::{
     build_field_di_node, file_metadata, size_and_align_of, type_di_node, unknown_file_metadata,
@@ -190,7 +190,7 @@ pub(super) fn build_enum_type_di_node<'ll, 'tcx>(
     let enum_type_and_layout = cx.layout_of(enum_type);
     let enum_type_name = compute_debuginfo_type_name(cx.tcx, enum_type, false);
 
-    assert!(!wants_c_like_enum_debuginfo(enum_type_and_layout));
+    assert!(!wants_c_like_enum_debuginfo(cx.tcx, enum_type_and_layout));
 
     type_map::build_type_with_children(
         cx,
@@ -265,7 +265,7 @@ pub(super) fn build_coroutine_di_node<'ll, 'tcx>(
     let coroutine_type_and_layout = cx.layout_of(coroutine_type);
     let coroutine_type_name = compute_debuginfo_type_name(cx.tcx, coroutine_type, false);
 
-    assert!(!wants_c_like_enum_debuginfo(coroutine_type_and_layout));
+    assert!(!wants_c_like_enum_debuginfo(cx.tcx, coroutine_type_and_layout));
 
     type_map::build_type_with_children(
         cx,
@@ -381,7 +381,7 @@ fn build_union_fields_for_enum<'ll, 'tcx>(
     tag_field: usize,
     untagged_variant_index: Option<VariantIdx>,
 ) -> SmallVec<&'ll DIType> {
-    let tag_base_type = super::tag_base_type(cx, enum_type_and_layout);
+    let tag_base_type = tag_base_type(cx.tcx, enum_type_and_layout);
 
     let variant_names_type_di_node = build_variant_names_type_di_node(
         cx,
@@ -676,7 +676,7 @@ fn build_union_fields_for_direct_tag_coroutine<'ll, 'tcx>(
     let variant_range = coroutine_args.variant_range(coroutine_def_id, cx.tcx);
     let variant_count = (variant_range.start.as_u32()..variant_range.end.as_u32()).len();
 
-    let tag_base_type = tag_base_type(cx, coroutine_type_and_layout);
+    let tag_base_type = tag_base_type(cx.tcx, coroutine_type_and_layout);
 
     let variant_names_type_di_node = build_variant_names_type_di_node(
         cx,
@@ -803,7 +803,7 @@ fn build_union_fields_for_direct_tag_enum_or_coroutine<'ll, 'tcx>(
 
     assert_eq!(
         cx.size_and_align_of(enum_type_and_layout.field(cx, tag_field).ty),
-        cx.size_and_align_of(super::tag_base_type(cx, enum_type_and_layout))
+        cx.size_and_align_of(self::tag_base_type(cx.tcx, enum_type_and_layout))
     );
 
     // ... and a field for the tag. If the tag is 128 bits wide, this will actually

compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/mod.rs

@@ -1,17 +1,15 @@
 use std::borrow::Cow;
 
 use rustc_codegen_ssa::debuginfo::type_names::{compute_debuginfo_type_name, cpp_like_debuginfo};
-use rustc_codegen_ssa::debuginfo::wants_c_like_enum_debuginfo;
+use rustc_codegen_ssa::debuginfo::{tag_base_type, wants_c_like_enum_debuginfo};
 use rustc_hir::def::CtorKind;
 use rustc_index::IndexSlice;
 use rustc_middle::bug;
 use rustc_middle::mir::CoroutineLayout;
-use rustc_middle::ty::layout::{IntegerExt, LayoutOf, PrimitiveExt, TyAndLayout};
+use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
 use rustc_middle::ty::{self, AdtDef, CoroutineArgs, CoroutineArgsExt, Ty, VariantDef};
 use rustc_span::Symbol;
-use rustc_target::abi::{
+use rustc_target::abi::{FieldIdx, TagEncoding, VariantIdx, Variants};
-    FieldIdx, HasDataLayout, Integer, Primitive, TagEncoding, VariantIdx, Variants,
-};
 
 use super::type_map::{DINodeCreationResult, UniqueTypeId};
 use super::{size_and_align_of, SmallVec};
@@ -39,7 +37,7 @@ pub(super) fn build_enum_type_di_node<'ll, 'tcx>(
 
     let enum_type_and_layout = cx.layout_of(enum_type);
 
-    if wants_c_like_enum_debuginfo(enum_type_and_layout) {
+    if wants_c_like_enum_debuginfo(cx.tcx, enum_type_and_layout) {
         return build_c_style_enum_di_node(cx, enum_adt_def, enum_type_and_layout);
     }
 
@@ -74,7 +72,7 @@ fn build_c_style_enum_di_node<'ll, 'tcx>(
         di_node: build_enumeration_type_di_node(
             cx,
             &compute_debuginfo_type_name(cx.tcx, enum_type_and_layout.ty, false),
-            tag_base_type(cx, enum_type_and_layout),
+            tag_base_type(cx.tcx, enum_type_and_layout),
             enum_adt_def.discriminants(cx.tcx).map(|(variant_index, discr)| {
                 let name = Cow::from(enum_adt_def.variant(variant_index).name.as_str());
                 (name, discr.val)
@@ -85,48 +83,6 @@ fn build_c_style_enum_di_node<'ll, 'tcx>(
     }
 }
 
-/// Extract the type with which we want to describe the tag of the given enum or coroutine.
-fn tag_base_type<'ll, 'tcx>(
-    cx: &CodegenCx<'ll, 'tcx>,
-    enum_type_and_layout: TyAndLayout<'tcx>,
-) -> Ty<'tcx> {
-    assert!(match enum_type_and_layout.ty.kind() {
-        ty::Coroutine(..) => true,
-        ty::Adt(adt_def, _) => adt_def.is_enum(),
-        _ => false,
-    });
-
-    match enum_type_and_layout.layout.variants() {
-        // A single-variant enum has no discriminant.
-        Variants::Single { .. } => {
-            bug!("tag_base_type() called for enum without tag: {:?}", enum_type_and_layout)
-        }
-
-        Variants::Multiple { tag_encoding: TagEncoding::Niche { .. }, tag, .. } => {
-            // Niche tags are always normalized to unsized integers of the correct size.
-            match tag.primitive() {
-                Primitive::Int(t, _) => t,
-                Primitive::Float(f) => Integer::from_size(f.size()).unwrap(),
-                // FIXME(erikdesjardins): handle non-default addrspace ptr sizes
-                Primitive::Pointer(_) => {
-                    // If the niche is the NULL value of a reference, then `discr_enum_ty` will be
-                    // a RawPtr. CodeView doesn't know what to do with enums whose base type is a
-                    // pointer so we fix this up to just be `usize`.
-                    // DWARF might be able to deal with this but with an integer type we are on
-                    // the safe side there too.
-                    cx.data_layout().ptr_sized_integer()
-                }
-            }
-            .to_ty(cx.tcx, false)
-        }
-
-        Variants::Multiple { tag_encoding: TagEncoding::Direct, tag, .. } => {
-            // Direct tags preserve the sign.
-            tag.primitive().to_ty(cx.tcx)
-        }
-    }
-}
-
 /// Build a DW_TAG_enumeration_type debuginfo node, with the given base type and variants.
 /// This is a helper function and does not register anything in the type map by itself.
 ///

compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/native.rs

@@ -2,7 +2,7 @@
 
 use libc::c_uint;
 use rustc_codegen_ssa::debuginfo::type_names::compute_debuginfo_type_name;
-use rustc_codegen_ssa::debuginfo::wants_c_like_enum_debuginfo;
+use rustc_codegen_ssa::debuginfo::{tag_base_type, wants_c_like_enum_debuginfo};
 use rustc_codegen_ssa::traits::ConstMethods;
 use rustc_middle::bug;
 use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
@@ -11,7 +11,6 @@
 use smallvec::smallvec;
 
 use crate::common::CodegenCx;
-use crate::debuginfo::metadata::enums::tag_base_type;
 use crate::debuginfo::metadata::type_map::{self, Stub, StubInfo, UniqueTypeId};
 use crate::debuginfo::metadata::{
     file_metadata, size_and_align_of, type_di_node, unknown_file_metadata, visibility_di_flags,
@@ -54,7 +53,7 @@ pub(super) fn build_enum_type_di_node<'ll, 'tcx>(
 
     let visibility_flags = visibility_di_flags(cx, enum_adt_def.did(), enum_adt_def.did());
 
-    assert!(!wants_c_like_enum_debuginfo(enum_type_and_layout));
+    assert!(!wants_c_like_enum_debuginfo(cx.tcx, enum_type_and_layout));
 
     type_map::build_type_with_children(
         cx,
@@ -131,7 +130,7 @@ pub(super) fn build_coroutine_di_node<'ll, 'tcx>(
     let containing_scope = get_namespace_for_item(cx, coroutine_def_id);
     let coroutine_type_and_layout = cx.layout_of(coroutine_type);
 
-    assert!(!wants_c_like_enum_debuginfo(coroutine_type_and_layout));
+    assert!(!wants_c_like_enum_debuginfo(cx.tcx, coroutine_type_and_layout));
 
     let coroutine_type_name = compute_debuginfo_type_name(cx.tcx, coroutine_type, false);
 
@@ -321,7 +320,7 @@ fn build_discr_member_di_node<'ll, 'tcx>(
         &Variants::Single { .. } => None,
 
         &Variants::Multiple { tag_field, .. } => {
-            let tag_base_type = tag_base_type(cx, enum_or_coroutine_type_and_layout);
+            let tag_base_type = tag_base_type(cx.tcx, enum_or_coroutine_type_and_layout);
             let (size, align) = cx.size_and_align_of(tag_base_type);
 
             unsafe {

compiler/rustc_codegen_ssa/src/debuginfo/mod.rs

@@ -1,6 +1,7 @@
-use rustc_middle::ty::layout::TyAndLayout;
+use rustc_middle::bug;
-use rustc_middle::ty::{self};
+use rustc_middle::ty::layout::{IntegerExt, PrimitiveExt, TyAndLayout};
-use rustc_target::abi::Size;
+use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_target::abi::{Integer, Primitive, Size, TagEncoding, Variants};
 
 // FIXME(eddyb) find a place for this (or a way to replace it).
 pub mod type_names;
@@ -11,13 +12,25 @@
 /// NOTE: This is somewhat inconsistent right now: For empty enums and enums with a single
 ///       fieldless variant, we generate DW_TAG_struct_type, although a
 ///       DW_TAG_enumeration_type would be a better fit.
-pub fn wants_c_like_enum_debuginfo(enum_type_and_layout: TyAndLayout<'_>) -> bool {
+pub fn wants_c_like_enum_debuginfo<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    enum_type_and_layout: TyAndLayout<'tcx>,
+) -> bool {
     match enum_type_and_layout.ty.kind() {
         ty::Adt(adt_def, _) => {
             if !adt_def.is_enum() {
                 return false;
             }
 
+            if type_names::cpp_like_debuginfo(tcx)
+                && tag_base_type_opt(tcx, enum_type_and_layout)
+                    .map(|ty| ty.primitive_size(tcx).bits())
+                    == Some(128)
+            {
+                // C++-like debuginfo never uses the C-like representation for 128-bit enums.
+                return false;
+            }
+
             match adt_def.variants().len() {
                 0 => false,
                 1 => {
@@ -33,3 +46,51 @@ pub fn wants_c_like_enum_debuginfo(enum_type_and_layout: TyAndLayout<'_>) -> boo
         _ => false,
     }
 }
+
+/// Extract the type with which we want to describe the tag of the given enum or coroutine.
+pub fn tag_base_type<'tcx>(tcx: TyCtxt<'tcx>, enum_type_and_layout: TyAndLayout<'tcx>) -> Ty<'tcx> {
+    tag_base_type_opt(tcx, enum_type_and_layout).unwrap_or_else(|| {
+        bug!("tag_base_type() called for enum without tag: {:?}", enum_type_and_layout)
+    })
+}
+
+pub fn tag_base_type_opt<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    enum_type_and_layout: TyAndLayout<'tcx>,
+) -> Option<Ty<'tcx>> {
+    assert!(match enum_type_and_layout.ty.kind() {
+        ty::Coroutine(..) => true,
+        ty::Adt(adt_def, _) => adt_def.is_enum(),
+        _ => false,
+    });
+
+    match enum_type_and_layout.layout.variants() {
+        // A single-variant enum has no discriminant.
+        Variants::Single { .. } => None,
+
+        Variants::Multiple { tag_encoding: TagEncoding::Niche { .. }, tag, .. } => {
+            // Niche tags are always normalized to unsized integers of the correct size.
+            Some(
+                match tag.primitive() {
+                    Primitive::Int(t, _) => t,
+                    Primitive::Float(f) => Integer::from_size(f.size()).unwrap(),
+                    // FIXME(erikdesjardins): handle non-default addrspace ptr sizes
+                    Primitive::Pointer(_) => {
+                        // If the niche is the NULL value of a reference, then `discr_enum_ty` will be
+                        // a RawPtr. CodeView doesn't know what to do with enums whose base type is a
+                        // pointer so we fix this up to just be `usize`.
+                        // DWARF might be able to deal with this but with an integer type we are on
+                        // the safe side there too.
+                        tcx.data_layout.ptr_sized_integer()
+                    }
+                }
+                .to_ty(tcx, false),
+            )
+        }
+
+        Variants::Multiple { tag_encoding: TagEncoding::Direct, tag, .. } => {
+            // Direct tags preserve the sign.
+            Some(tag.primitive().to_ty(tcx))
+        }
+    }
+}

compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs

@@ -85,7 +85,7 @@ fn push_debuginfo_type_name<'tcx>(
             let layout_for_cpp_like_fallback = if cpp_like_debuginfo && def.is_enum() {
                 match tcx.layout_of(ParamEnv::reveal_all().and(t)) {
                     Ok(layout) => {
-                        if !wants_c_like_enum_debuginfo(layout) {
+                        if !wants_c_like_enum_debuginfo(tcx, layout) {
                             Some(layout)
                         } else {
                             // This is a C-like enum so we don't want to use the fallback encoding
@@ -106,6 +106,7 @@ fn push_debuginfo_type_name<'tcx>(
 
             if let Some(ty_and_layout) = layout_for_cpp_like_fallback {
                 msvc_enum_fallback(
+                    tcx,
                     ty_and_layout,
                     &|output, visited| {
                         push_item_name(tcx, def.did(), true, output);
@@ -421,6 +422,7 @@ fn push_debuginfo_type_name<'tcx>(
             if cpp_like_debuginfo && t.is_coroutine() {
                 let ty_and_layout = tcx.layout_of(ParamEnv::reveal_all().and(t)).unwrap();
                 msvc_enum_fallback(
+                    tcx,
                     ty_and_layout,
                     &|output, visited| {
                         push_closure_or_coroutine_name(tcx, def_id, args, true, output, visited);
@@ -455,12 +457,13 @@ fn push_debuginfo_type_name<'tcx>(
     // debugger. For more information, look in
     // rustc_codegen_llvm/src/debuginfo/metadata/enums/cpp_like.rs.
     fn msvc_enum_fallback<'tcx>(
+        tcx: TyCtxt<'tcx>,
         ty_and_layout: TyAndLayout<'tcx>,
         push_inner: &dyn Fn(/*output*/ &mut String, /*visited*/ &mut FxHashSet<Ty<'tcx>>),
         output: &mut String,
         visited: &mut FxHashSet<Ty<'tcx>>,
     ) {
-        assert!(!wants_c_like_enum_debuginfo(ty_and_layout));
+        assert!(!wants_c_like_enum_debuginfo(tcx, ty_and_layout));
         output.push_str("enum2$<");
         push_inner(output, visited);
         push_close_angle_bracket(true, output);

tests/debuginfo/msvc-pretty-enums.rs

@@ -206,6 +206,30 @@
 // cdb-command: dx -r2 arbitrary_discr2,d
 // cdb-check: arbitrary_discr2,d : Def [Type: enum2$<msvc_pretty_enums::ArbitraryDiscr>]
 // cdb-check:     [+0x[...]] __0              : 5678 [Type: unsigned int]
+//
+// cdb-command: dx c_style_u128_a
+// cdb-check: c_style_u128_a   : A [Type: enum2$<msvc_pretty_enums::CStyleU128>]
+//
+// cdb-command: dx c_style_u128_b
+// cdb-check: c_style_u128_b   : B [Type: enum2$<msvc_pretty_enums::CStyleU128>]
+//
+// cdb-command: dx c_style_u128_c
+// cdb-check: c_style_u128_c   : C [Type: enum2$<msvc_pretty_enums::CStyleU128>]
+//
+// cdb-command: dx c_style_u128_d
+// cdb-check: c_style_u128_d   : D [Type: enum2$<msvc_pretty_enums::CStyleU128>]
+//
+// cdb-command: dx c_style_i128_a
+// cdb-check: c_style_i128_a   : A [Type: enum2$<msvc_pretty_enums::CStyleI128>]
+//
+// cdb-command: dx c_style_i128_b
+// cdb-check: c_style_i128_b   : B [Type: enum2$<msvc_pretty_enums::CStyleI128>]
+//
+// cdb-command: dx c_style_i128_c
+// cdb-check: c_style_i128_c   : C [Type: enum2$<msvc_pretty_enums::CStyleI128>]
+//
+// cdb-command: dx c_style_i128_d
+// cdb-check: c_style_i128_d   : D [Type: enum2$<msvc_pretty_enums::CStyleI128>]
 #![feature(rustc_attrs)]
 #![feature(repr128)]
 #![feature(arbitrary_enum_discriminant)]
@@ -270,6 +294,22 @@ enum ArbitraryDiscr {
     Def(u32) = 5000_000,
 }
 
+#[repr(u128)]
+pub enum CStyleU128 {
+    A = 0_u128,
+    B = 1_u128,
+    C = u64::MAX as u128 + 1,
+    D = u128::MAX,
+}
+
+#[repr(i128)]
+pub enum CStyleI128 {
+    A = 0_i128,
+    B = -1_i128,
+    C = i128::MIN,
+    D = i128::MAX,
+}
+
 fn main() {
     let a = Some(CStyleEnum::Low);
     let b = Option::<CStyleEnum>::None;
@@ -313,6 +353,16 @@ fn main() {
     let arbitrary_discr1 = ArbitraryDiscr::Abc(1234);
     let arbitrary_discr2 = ArbitraryDiscr::Def(5678);
 
+    let c_style_u128_a = CStyleU128::A;
+    let c_style_u128_b = CStyleU128::B;
+    let c_style_u128_c = CStyleU128::C;
+    let c_style_u128_d = CStyleU128::D;
+
+    let c_style_i128_a = CStyleI128::A;
+    let c_style_i128_b = CStyleI128::B;
+    let c_style_i128_c = CStyleI128::C;
+    let c_style_i128_d = CStyleI128::D;
+
     zzz(); // #break
 }