8367689: Revert removal of several compilation-related vmStructs fields

Reviewed-by: aturbanov, shade
Backport-of: 4c5e901c96dee3885e1b29a53d3400174f9bba09

Author: fandreuz

src/hotspot/share/ci/ciClassList.hpp

@@ -80,6 +80,7 @@ friend class ciObjectFactory; \
 // Any more access must be given explicitly.
 #define CI_PACKAGE_ACCESS_TO           \
 friend class ciObjectFactory;          \
+friend class VMStructs;                \
 friend class ciCallSite;               \
 friend class ciConstantPoolCache;      \
 friend class ciField;                  \

src/hotspot/share/runtime/vmStructs.cpp

@@ -667,6 +667,14 @@
      static_field(VMRegImpl,                   regName[0],                                    const char*)                           \
      static_field(VMRegImpl,                   stack0,                                        VMReg)                                 \
                                                                                                                                      \
+  /******************************************************************************************/                                       \
+  /* CI (NOTE: these CI fields are retained in VMStructs for the benefit of external tools, */                                       \
+  /* to ease their migration to a future alternative.)                                      */                                       \
+  /******************************************************************************************/                                       \
+                                                                                                                                     \
+  nonstatic_field(CompilerThread,              _env,                                          ciEnv*)                                \
+  nonstatic_field(ciEnv,                       _task,                                         CompileTask*)                          \
+                                                                                                                                     \
   /************/                                                                                                                     \
   /* Monitors */                                                                                                                     \
   /************/                                                                                                                     \
@@ -1150,6 +1158,12 @@
   declare_toplevel_type(BasicLock)                                        \
   declare_toplevel_type(BasicObjectLock)                                  \
                                                                           \
+  /*********************/                                                 \
+  /* CI */                                                                \
+  /*********************/                                                 \
+                                                                          \
+  declare_toplevel_type(ciEnv)                                            \
+                                                                          \
   /********************/                                                  \
   /* -XX flags        */                                                  \
   /********************/                                                  \