8035828: Turn on @Stable support in VM

Reviewed-by: jrose, twisti

src/share/vm/opto/c2_globals.hpp

@@ -458,7 +458,7 @@
   product(bool, EliminateAutoBox, false,                                    \
           "Control optimizations for autobox elimination")                  \
                                                                             \
-  experimental(bool, UseImplicitStableValues, false,                        \
+  diagnostic(bool, UseImplicitStableValues, true,                           \
           "Mark well-known stable fields as such (e.g. String.value)")      \
                                                                             \
   product(intx, AutoBoxCacheMax, 128,                                       \

src/share/vm/runtime/globals.hpp

@@ -3798,8 +3798,8 @@ class CommandLineFlags {
   experimental(bool, TrustFinalNonStaticFields, false,                      \
           "trust final non-static declarations for constant folding")       \
                                                                             \
-  experimental(bool, FoldStableValues, false,                               \
-          "Private flag to control optimizations for stable variables")     \
+  diagnostic(bool, FoldStableValues, true,                                  \
+          "Optimize loads from stable fields (marked w/ @Stable)")          \
                                                                             \
   develop(bool, TraceInvokeDynamic, false,                                  \
           "trace internal invoke dynamic operations")                       \