Auto merge of #17581 - lnicola:sync-from-rust, r=lnicola

minor: Sync from rust

1 files changed, 47 insertions, 10 deletions

diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
index 8de4e0effad..851a4c42e99 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
@@ -705,10 +705,12 @@ impl MsvcBasicName for ty::UintTy {
 
 impl MsvcBasicName for ty::FloatTy {
     fn msvc_basic_name(self) -> &'static str {
-        // FIXME: f16 and f128 have no MSVC representation. We could improve the debuginfo.
-        // See: <https://github.com/rust-lang/rust/pull/114607/files#r1454683264>
+        // FIXME(f16_f128): `f16` and `f128` have no MSVC representation. We could improve the
+        // debuginfo. See: <https://github.com/rust-lang/rust/issues/121837>
         match self {
-            ty::FloatTy::F16 => "half",
+            ty::FloatTy::F16 => {
+                bug!("`f16` should have been handled in `build_basic_type_di_node`")
+            }
             ty::FloatTy::F32 => "float",
             ty::FloatTy::F64 => "double",
             ty::FloatTy::F128 => "fp128",
@@ -716,6 +718,38 @@ impl MsvcBasicName for ty::FloatTy {
     }
 }
 
+fn build_cpp_f16_di_node<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>) -> DINodeCreationResult<'ll> {
+    // MSVC has no native support for `f16`. Instead, emit `struct f16 { bits: u16 }` to allow the
+    // `f16`'s value to be displayed using a Natvis visualiser in `intrinsic.natvis`.
+    let float_ty = cx.tcx.types.f16;
+    let bits_ty = cx.tcx.types.u16;
+    type_map::build_type_with_children(
+        cx,
+        type_map::stub(
+            cx,
+            Stub::Struct,
+            UniqueTypeId::for_ty(cx.tcx, float_ty),
+            "f16",
+            cx.size_and_align_of(float_ty),
+            NO_SCOPE_METADATA,
+            DIFlags::FlagZero,
+        ),
+        // Fields:
+        |cx, float_di_node| {
+            smallvec![build_field_di_node(
+                cx,
+                float_di_node,
+                "bits",
+                cx.size_and_align_of(bits_ty),
+                Size::ZERO,
+                DIFlags::FlagZero,
+                type_di_node(cx, bits_ty),
+            )]
+        },
+        NO_GENERICS,
+    )
+}
+
 fn build_basic_type_di_node<'ll, 'tcx>(
     cx: &CodegenCx<'ll, 'tcx>,
     t: Ty<'tcx>,
@@ -739,6 +773,9 @@ fn build_basic_type_di_node<'ll, 'tcx>(
         ty::Char => ("char", DW_ATE_UTF),
         ty::Int(int_ty) if cpp_like_debuginfo => (int_ty.msvc_basic_name(), DW_ATE_signed),
         ty::Uint(uint_ty) if cpp_like_debuginfo => (uint_ty.msvc_basic_name(), DW_ATE_unsigned),
+        ty::Float(ty::FloatTy::F16) if cpp_like_debuginfo => {
+            return build_cpp_f16_di_node(cx);
+        }
         ty::Float(float_ty) if cpp_like_debuginfo => (float_ty.msvc_basic_name(), DW_ATE_float),
         ty::Int(int_ty) => (int_ty.name_str(), DW_ATE_signed),
         ty::Uint(uint_ty) => (uint_ty.name_str(), DW_ATE_unsigned),
@@ -1449,12 +1486,18 @@ fn build_vtable_type_di_node<'ll, 'tcx>(
     .di_node
 }
 
-fn vcall_visibility_metadata<'ll, 'tcx>(
+pub(crate) fn apply_vcall_visibility_metadata<'ll, 'tcx>(
     cx: &CodegenCx<'ll, 'tcx>,
     ty: Ty<'tcx>,
     trait_ref: Option<PolyExistentialTraitRef<'tcx>>,
     vtable: &'ll Value,
 ) {
+    // FIXME(flip1995): The virtual function elimination optimization only works with full LTO in
+    // LLVM at the moment.
+    if !cx.sess().opts.unstable_opts.virtual_function_elimination || cx.sess().lto() != Lto::Fat {
+        return;
+    }
+
     enum VCallVisibility {
         Public = 0,
         LinkageUnit = 1,
@@ -1531,12 +1574,6 @@ pub fn create_vtable_di_node<'ll, 'tcx>(
     poly_trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
     vtable: &'ll Value,
 ) {
-    // FIXME(flip1995): The virtual function elimination optimization only works with full LTO in
-    // LLVM at the moment.
-    if cx.sess().opts.unstable_opts.virtual_function_elimination && cx.sess().lto() == Lto::Fat {
-        vcall_visibility_metadata(cx, ty, poly_trait_ref, vtable);
-    }
-
     if cx.dbg_cx.is_none() {
         return;
     }