Filling cache values on cvar write

Instead of on read. Once it's in the inline cache we never have to make
one again. We want to eventually put the value into the cache, and the
best opportunity to do that is when you write the value.

1 files changed, 19 insertions, 0 deletions

diff --git a/variable.c b/variable.c
index 82918037f9..8c29fbdf3b 100644
--- a/variable.c
+++ b/variable.c
@@ -40,6 +40,7 @@
 #include "vm_sync.h"
 
 RUBY_EXTERN rb_serial_t ruby_vm_global_cvar_state;
+#define GET_GLOBAL_CVAR_STATE() (ruby_vm_global_cvar_state)
 
 typedef void rb_gvar_compact_t(void *var);
 
@@ -3399,6 +3400,24 @@ rb_cvar_set(VALUE klass, ID id, VALUE val)
 
     int result = rb_class_ivar_set(target, id, val);
 
+    struct rb_id_table *rb_cvc_tbl = RCLASS_CVC_TBL(target);
+
+    if (!rb_cvc_tbl) {
+        rb_cvc_tbl = RCLASS_CVC_TBL(target) = rb_id_table_create(2);
+    }
+
+    struct rb_cvar_class_tbl_entry *ent;
+
+    if (!rb_id_table_lookup(rb_cvc_tbl, id, (VALUE*)&ent)) {
+        ent = ALLOC(struct rb_cvar_class_tbl_entry);
+        ent->class_value = target;
+        ent->global_cvar_state = GET_GLOBAL_CVAR_STATE();
+        rb_id_table_insert(rb_cvc_tbl, id, (VALUE)ent);
+        RB_DEBUG_COUNTER_INC(cvar_inline_miss);
+    } else {
+        ent->global_cvar_state = GET_GLOBAL_CVAR_STATE();
+    }
+
     // Break the cvar cache if this is a new class variable
     // and target is a module or a subclass with the same
     // cvar in this lookup.