[ruby/psych] Optimize cache with compare_by_identity

Using `compare_by_identity` gives a 4x performance boost on cache hits. Benchmark in fastruby/fast-ruby#189
marcandre · Dec 23, 2020 · 1976640 · 1976640
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commit 1976640
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Showing 2 changed files with 2 additions and 2 deletions.
diff --git a/ext/psych/lib/psych/visitors/visitor.rb b/ext/psych/lib/psych/visitors/visitor.rb
@@ -12,7 +12,7 @@ def accept target
       def self.dispatch_cache
         Hash.new do |hash, klass|
           hash[klass] = :"visit_#{klass.name.gsub('::', '_')}"
-        end
+        end.compare_by_identity
       end
 
       if defined?(Ractor)

diff --git a/ext/psych/lib/psych/visitors/yaml_tree.rb b/ext/psych/lib/psych/visitors/yaml_tree.rb
@@ -80,7 +80,7 @@ def initialize emitter, ss, options
           raise(TypeError, "Can't dump #{target.class}") unless method
 
           h[klass] = method
-        end
+        end.compare_by_identity
       end
 
       def start encoding = Nodes::Stream::UTF8