Finer-grained inline constant cache invalidation

Current behavior - caches depend on a global counter. All constant mutations cause caches to be invalidated.

```ruby
class A
  B = 1
end

def foo
  A::B # inline cache depends on global counter
end

foo # populate inline cache
foo # hit inline cache

C = 1 # global counter increments, all caches are invalidated

foo # misses inline cache due to `C = 1`
```

Proposed behavior - caches depend on name components. Only constant mutations with corresponding names will invalidate the cache.

```ruby
class A
  B = 1
end

def foo
  A::B # inline cache depends constants named "A" and "B"
end

foo # populate inline cache
foo # hit inline cache

C = 1 # caches that depend on the name "C" are invalidated

foo # hits inline cache because IC only depends on "A" and "B"
```

Examples of breaking the new cache:

```ruby
module C
  # Breaks `foo` cache because "A" constant is set and the cache in foo depends
  # on "A" and "B"
  class A; end
end

B = 1
```

We expect the new cache scheme to be invalidated less often because names aren't frequently reused. With the cache being invalidated less, we can rely on its stability more to keep our constant references fast and reduce the need to throw away generated code in YJIT.

1 files changed, 0 insertions, 3 deletions

diff --git a/vm_insnhelper.h b/vm_insnhelper.h
index 459f567106..e26ecfa77c 100644
--- a/vm_insnhelper.h
+++ b/vm_insnhelper.h
@@ -14,7 +14,6 @@
 MJIT_SYMBOL_EXPORT_BEGIN
 
 RUBY_EXTERN VALUE ruby_vm_const_missing_count;
-RUBY_EXTERN rb_serial_t ruby_vm_global_constant_state;
 RUBY_EXTERN rb_serial_t ruby_vm_class_serial;
 RUBY_EXTERN rb_serial_t ruby_vm_global_cvar_state;
 
@@ -183,8 +182,6 @@ CC_SET_FASTPATH(const struct rb_callcache *cc, vm_call_handler func, bool enable
 
 #define PREV_CLASS_SERIAL() (ruby_vm_class_serial)
 #define NEXT_CLASS_SERIAL() (++ruby_vm_class_serial)
-#define GET_GLOBAL_CONSTANT_STATE() (ruby_vm_global_constant_state)
-#define INC_GLOBAL_CONSTANT_STATE() (++ruby_vm_global_constant_state)
 #define GET_GLOBAL_CVAR_STATE() (ruby_vm_global_cvar_state)
 #define INC_GLOBAL_CVAR_STATE() (++ruby_vm_global_cvar_state)