[llvm] [llvm] Replace unordered_{map,set} with Dense{Map,Set}/SmallPtrSet (PR #202222)

[Fangrui Song via llvm-commits]

================
@@ -2235,7 +2235,7 @@ Error Object::removeSections(
   // Now make sure there are no remaining references to the sections that will
   // be removed. Sometimes it is impossible to remove a reference so we emit
   // an error here instead.
-  std::unordered_set<const SectionBase *> RemoveSections;
+  SmallPtrSet<const SectionBase *, 0> RemoveSections;
----------------
MaskRay wrote:

For these cases that performance don't matter, I usually prefer 0 to generate smaller code. SmallPtrSet also generates smaller code than std::unordered_set.

https://github.com/llvm/llvm-project/pull/202222