RFR (XS) 8241545: Shenandoah: purge root work overwrites counters after JDK-8228818

[Aleksey Shipilev]

Bug:
  https://bugs.openjdk.java.net/browse/JDK-8241545

Fix:

diff -r 97a3e6ce2652 src/hotspot/share/gc/shenandoah/shenandoahPhaseTimings.hpp
--- a/src/hotspot/share/gc/shenandoah/shenandoahPhaseTimings.hpp        Tue Mar 24 18:46:48 2020 +0100
+++ b/src/hotspot/share/gc/shenandoah/shenandoahPhaseTimings.hpp        Tue Mar 24 20:02:16 2020 +0100
@@ -78,4 +78,5 @@
   f(purge_class_unload,                             "    Unload Classes")              \
   f(purge_par,                                      "    Parallel Cleanup")            \
+  SHENANDOAH_GC_PAR_PHASE_DO(purge_par_roots,       "      PC: ", f)                   \
   f(purge_cldg,                                     "    CLDG")                        \
   f(complete_liveness,                              "  Complete Liveness")             \
@@ -136,4 +137,5 @@
   f(full_gc_purge_class_unload,                     "      Unload Classes")            \
   f(full_gc_purge_par,                              "    Parallel Cleanup")            \
+  SHENANDOAH_GC_PAR_PHASE_DO(full_gc_purge_roots,   "      PC: ", f)                   \
   f(full_gc_purge_cldg,                             "    CLDG")                        \
   f(full_gc_calculate_addresses,                    "  Calculate Addresses")           \

Testing: eyeballing gc+stats logs

-- 
Thanks,
-Aleksey