Introduce disposable call-cache.

This patch contains several ideas:

(1) Disposable inline method cache (IMC) for race-free inline method cache
    * Making call-cache (CC) as a RVALUE (GC target object) and allocate new
      CC on cache miss.
    * This technique allows race-free access from parallel processing
      elements like RCU.
(2) Introduce per-Class method cache (pCMC)
    * Instead of fixed-size global method cache (GMC), pCMC allows flexible
      cache size.
    * Caching CCs reduces CC allocation and allow sharing CC's fast-path
      between same call-info (CI) call-sites.
(3) Invalidate an inline method cache by invalidating corresponding method
    entries (MEs)
    * Instead of using class serials, we set "invalidated" flag for method
      entry itself to represent cache invalidation.
    * Compare with using class serials, the impact of method modification
      (add/overwrite/delete) is small.
    * Updating class serials invalidate all method caches of the class and
      sub-classes.
    * Proposed approach only invalidate the method cache of only one ME.

See [Feature #16614] for more details.

1 files changed, 29 insertions, 0 deletions

diff --git a/mjit.h b/mjit.h
index bdc186f788..15be560786 100644
--- a/mjit.h
+++ b/mjit.h
@@ -70,6 +70,35 @@ struct rb_mjit_compile_info {
     bool disable_inlining;
 };
 
+// The unit structure that holds metadata of ISeq for MJIT.
+struct rb_mjit_unit {
+    // Unique order number of unit.
+    int id;
+    // Dlopen handle of the loaded object file.
+    void *handle;
+    rb_iseq_t *iseq;
+#ifndef _MSC_VER
+    // This value is always set for `compact_all_jit_code`. Also used for lazy deletion.
+    char *o_file;
+    // true if it's inherited from parent Ruby process and lazy deletion should be skipped.
+    // `o_file = NULL` can't be used to skip lazy deletion because `o_file` could be used
+    // by child for `compact_all_jit_code`.
+    bool o_file_inherited_p;
+#endif
+#if defined(_WIN32)
+    // DLL cannot be removed while loaded on Windows. If this is set, it'll be lazily deleted.
+    char *so_file;
+#endif
+    // Only used by unload_units. Flag to check this unit is currently on stack or not.
+    char used_code_p;
+    struct list_node unode;
+    // mjit_compile's optimization switches
+    struct rb_mjit_compile_info compile_info;
+
+    // captured CC values, they should be marked with iseq.
+    const struct rb_callcache **cc_entries; // size: iseq->body->ci_size
+};
+
 typedef VALUE (*mjit_func_t)(rb_execution_context_t *, rb_control_frame_t *);
 
 RUBY_SYMBOL_EXPORT_BEGIN