Optimized instruction for Array#freeze

If an Array which is empty or only using literals is frozen, we detect
this as a peephole optimization and change the instructions to be
`opt_ary_freeze`.

[Feature #20684]

Co-authored-by: Jean Boussier <byroot@ruby-lang.org>

1 files changed, 46 insertions, 0 deletions

diff --git a/test/ruby/test_optimization.rb b/test/ruby/test_optimization.rb
index a7a0582dbb..671f7d7ed5 100644
--- a/test/ruby/test_optimization.rb
+++ b/test/ruby/test_optimization.rb
@@ -749,6 +749,52 @@ class TestRubyOptimization < Test::Unit::TestCase
     end
   end
 
+  def test_peephole_array_freeze
+    code = "#{<<~'begin;'}\n#{<<~'end;'}"
+    begin;
+      [1].freeze
+    end;
+    iseq = RubyVM::InstructionSequence.compile(code)
+    insn = iseq.disasm
+    assert_match(/opt_ary_freeze/, insn)
+    assert_no_match(/duparray/, insn)
+    assert_no_match(/send/, insn)
+    assert_predicate([1].freeze, :frozen?)
+    assert_in_out_err([], <<~RUBY, [":ok"])
+      class Array
+        prepend Module.new {
+          def freeze
+            :ok
+          end
+        }
+      end
+      p [1].freeze
+    RUBY
+  end
+
+  def test_peephole_array_freeze_empty
+    code = "#{<<~'begin;'}\n#{<<~'end;'}"
+    begin;
+      [].freeze
+    end;
+    iseq = RubyVM::InstructionSequence.compile(code)
+    insn = iseq.disasm
+    assert_match(/opt_ary_freeze/, insn)
+    assert_no_match(/duparray/, insn)
+    assert_no_match(/send/, insn)
+    assert_predicate([].freeze, :frozen?)
+    assert_in_out_err([], <<~RUBY, [":ok"])
+      class Array
+        prepend Module.new {
+          def freeze
+            :ok
+          end
+        }
+      end
+      p [].freeze
+    RUBY
+  end
+
   def test_branch_condition_backquote
     bug = '[ruby-core:80740] [Bug #13444] redefined backquote should be called'
     class << self