Auto merge of rust-lang#80122 - davidtwco:revert-76030, r=oli-obk

Revert "cg_llvm: `fewer_names` in `uncached_llvm_type`"

Fixes rust-lang#76213 and fixes rust-lang#79564.

This PR temporarily reverts commit fa01ce8 from rust-lang#76030 to until the root issue can be resolved. Requested [in t-compiler meeting](https://rust-lang.zulipchat.com/#narrow/stream/238009-t-compiler.2Fmeetings/topic/.5Bweekly.20meeting.5D.202020-12-17.20.2354818/near/220261541).

*Note*: I was seeing some failing debuginfo-gdb tests locally but I wasn't sure if they were spurious.

compiler/rustc_codegen_llvm/src/type_of.rs

@@ -40,9 +40,7 @@ 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
-            if !cx.sess().fewer_names() =>
-        {
+        ty::Adt(..) | ty::Closure(..) | ty::Foreign(..) | ty::Generator(..) | ty::Str => {
             let mut name = with_no_trimmed_paths(|| layout.ty.to_string());
             if let (&ty::Adt(def, _), &Variants::Single { index }) =
                 (layout.ty.kind(), &layout.variants)
@@ -58,12 +56,6 @@ fn uncached_llvm_type<'a, 'tcx>(
             }
             Some(name)
         }
-        ty::Adt(..) => {
-            // If `Some` is returned then a named struct is created in LLVM. Name collisions are
-            // avoided by LLVM (with increasing suffixes). If rustc doesn't generate names then that
-            // can improve perf.
-            Some(String::new())
-        }
         _ => None,
     };
 

src/test/ui/issues/issue-75763.rs

@@ -1,4 +1,5 @@
-// build-pass
+// ignore-test
+// FIXME(const_generics): This test causes an ICE after reverting #76030.
 
 #![allow(incomplete_features)]
 #![feature(const_generics)]