Reapply cg_llvm: fewer_names in uncached_llvm_type

Co-authored-by: Erik Desjardins <erikdesjardins@users.noreply.github.com>
Co-authored-by: Tomasz Miąsko <tomasz.miasko@gmail.com>

compiler/rustc_codegen_llvm/src/type_of.rs

@@ -1,5 +1,6 @@
 use crate::common::*;
 use crate::context::TypeLowering;
+use crate::llvm_util::get_version;
 use crate::type_::Type;
 use rustc_codegen_ssa::traits::*;
 use rustc_middle::bug;
@@ -42,7 +43,12 @@ fn uncached_llvm_type<'a, 'tcx>(
         // FIXME(eddyb) producing readable type names for trait objects can result
         // in problematically distinct types due to HRTB and subtyping (see #47638).
         // ty::Dynamic(..) |
-        ty::Adt(..) | ty::Closure(..) | ty::Foreign(..) | ty::Generator(..) | ty::Str => {
+        ty::Adt(..) | ty::Closure(..) | ty::Foreign(..) | ty::Generator(..) | ty::Str
+            // For performance reasons we use names only when emitting LLVM IR. Unless we are on
+            // LLVM < 14, where the use of unnamed types resulted in various issues, e.g., #76213,
+            // #79564, and #79246.
+            if get_version() < (14, 0, 0) || !cx.sess().fewer_names() =>
+        {
             let mut name = with_no_visible_paths!(with_no_trimmed_paths!(layout.ty.to_string()));
             if let (&ty::Adt(def, _), &Variants::Single { index }) =
                 (layout.ty.kind(), &layout.variants)
@@ -58,6 +64,9 @@ fn uncached_llvm_type<'a, 'tcx>(
             }
             Some(name)
         }
+        // Use identified structure types for ADT. Due to pointee types in LLVM IR their definition
+        // might be recursive. Other cases are non-recursive and we can use literal structure types.
+        ty::Adt(..) => Some(String::new()),
         _ => None,
     };