8341992: GenShen: Fix formatting, remove unreachable code, unused imp…

…orts and unnecessary comments

Backport-of: bb7938446b3b6d6729df627cd580957f4a3a2116

src/hotspot/share/gc/shenandoah/shenandoahAffiliation.hpp

@@ -41,7 +41,6 @@ inline const char* shenandoah_affiliation_code(ShenandoahAffiliation type) {
       return "O";
     default:
       ShouldNotReachHere();
-      return "?";
   }
 }
 
@@ -55,7 +54,6 @@ inline const char* shenandoah_affiliation_name(ShenandoahAffiliation type) {
       return "OLD";
     default:
       ShouldNotReachHere();
-      return "?";
   }
 }
 

src/hotspot/share/gc/shenandoah/shenandoahHeap.hpp

@@ -532,9 +532,9 @@ class ShenandoahHeap : public CollectedHeap {
   ShenandoahFreeSet*         free_set()          const { return _free_set;          }
   ShenandoahPacer*           pacer()             const { return _pacer;             }
 
-  ShenandoahPhaseTimings*      phase_timings()   const { return _phase_timings;     }
+  ShenandoahPhaseTimings*    phase_timings()     const { return _phase_timings;     }
 
-  ShenandoahEvacOOMHandler* oom_evac_handler() { return &_oom_evac_handler; }
+  ShenandoahEvacOOMHandler*  oom_evac_handler()        { return &_oom_evac_handler; }
 
   void on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation);
   void on_cycle_end(ShenandoahGeneration* generation);

src/hotspot/share/gc/shenandoah/shenandoahHeap.inline.hpp

@@ -331,8 +331,6 @@ void ShenandoahHeap::increase_object_age(oop obj, uint additional_age) {
 // necessarily be determined because of concurrent locking by the
 // mutator
 uint ShenandoahHeap::get_object_age(oop obj) {
-  // This is impossible to do unless we "freeze" ABA-type oscillations
-  // With Lilliput, we can do this more easily.
   markWord w = obj->mark();
   assert(!w.is_marked(), "must not be forwarded");
   if (w.has_monitor()) {

src/hotspot/share/gc/shenandoah/shenandoahMmuTracker.hpp

@@ -25,7 +25,6 @@
 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHMMUTRACKER_HPP
 #define SHARE_GC_SHENANDOAH_SHENANDOAHMMUTRACKER_HPP
 
-#include "runtime/mutex.hpp"
 #include "utilities/numberSeq.hpp"
 
 class ShenandoahGeneration;