From f701de830557dac9f0005c129cab483c282a0124 Mon Sep 17 00:00:00 2001
From: Charles Oliver Nutter <headius@headius.com>
Date: Mon, 1 Apr 2024 15:51:25 -0500
Subject: [PATCH] Hook up to object-to-symbol paths to FString

This helps cases where an fstring (born frozen and dedup'ed) is
used in a symbol API where it must be interned. For example see
the benchmark and discussion in #3419.
---
 bench/bench_instance_variable_get.rb         | 66 ++++++++++++++++++++
 core/src/main/java/org/jruby/RubySymbol.java | 21 +++++--
 2 files changed, 81 insertions(+), 6 deletions(-)
 create mode 100644 bench/bench_instance_variable_get.rb

diff --git a/bench/bench_instance_variable_get.rb b/bench/bench_instance_variable_get.rb
new file mode 100644
index 00000000000..0df2343ab1e
--- /dev/null
+++ b/bench/bench_instance_variable_get.rb
@@ -0,0 +1,66 @@
+require 'benchmark/ips'
+
+# Modified version of benchmark from https://github.com/jruby/jruby/issues/3419
+
+class Test
+  def intitialize
+    @ivar = 'test'
+  end
+
+  def direct
+    @ivar
+  end
+
+  IVAR_NAME = "@ivar"
+  def hoist_ivar_name
+    instance_variable_get IVAR_NAME
+  end
+
+  def instance_variable_get_symbol
+    instance_variable_get :"@ivar"
+  end
+
+  def instance_variable_get_frozen
+    instance_variable_get('@ivar'.freeze)
+  end
+
+  def instance_variable_get_frozen_symbol
+    instance_variable_get('@ivar'.freeze.to_sym)
+  end
+end
+
+loop {
+Benchmark.ips do |benchmark|
+  instance = Test.new
+  benchmark.report("direct") {|i|
+    while i > 0
+      i-=1
+      instance.direct
+    end
+  }
+  benchmark.report("hoist_ivar_name") {|i|
+    while i > 0
+      i-=1
+      instance.hoist_ivar_name
+    end
+  }
+  benchmark.report("ivar get symbol") {|i|
+    while i > 0
+      i-=1
+      instance.instance_variable_get_symbol
+    end
+  }
+  benchmark.report("ivar get frozen") {|i|
+    while i > 0
+      i-=1
+      instance.instance_variable_get_frozen
+    end
+  }
+  benchmark.report("ivar get frozen sym") {|i|
+    while i > 0
+      i-=1
+      instance.instance_variable_get_frozen_symbol
+    end
+  }
+end
+}
\ No newline at end of file
diff --git a/core/src/main/java/org/jruby/RubySymbol.java b/core/src/main/java/org/jruby/RubySymbol.java
index 2d69584720b..1e125c8926d 100644
--- a/core/src/main/java/org/jruby/RubySymbol.java
+++ b/core/src/main/java/org/jruby/RubySymbol.java
@@ -227,20 +227,29 @@ public RubySymbol asInstanceVariable() {
      * @return the symbol table entry.
      */
     public static RubySymbol retrieveIDSymbol(IRubyObject name) {
-        return name instanceof RubySymbol ?
-                (RubySymbol) name : newIDSymbol(name.getRuntime(), name.convertToString().getByteList());
+        if (name instanceof RubySymbol sym) return sym;
+
+        if (name instanceof RubyString.FString fstring) {
+            return fstring.intern();
+        }
+
+        return newIDSymbol(name.getRuntime(), name.convertToString().getByteList());
     }
 
     /**
-     * Retrieve an ID symbol but call the handler before any new symbol is added to the symbol table.
-     * This can be used for verifying the symbol is valid.
+     * Retrieve an ID symbol but call the handler to verify the symbol is valid.
      *
      * @param name to get symbol table entry for (it may be a symbol already)
      * @return the symbol table entry.
      */
     public static RubySymbol retrieveIDSymbol(IRubyObject name, ObjBooleanConsumer<RubySymbol> handler) {
-        if (name instanceof RubySymbol) {
-            RubySymbol sym = (RubySymbol) name;
+        if (name instanceof RubySymbol sym) {
+            handler.accept(sym, false);
+            return sym;
+        }
+
+        if (name instanceof RubyString.FString fstring) {
+            RubySymbol sym = fstring.intern();
             handler.accept(sym, false);
             return sym;
         }