Finer-grained constant cache invalidation (take 2)

This commit reintroduces finer-grained constant cache invalidation.
After 8008fb7 got merged, it was causing issues on token-threaded
builds (such as on Windows).

The issue was that when you're iterating through instruction sequences
and using the translator functions to get back the instruction structs,
you're either using `rb_vm_insn_null_translator` or
`rb_vm_insn_addr2insn2` depending if it's a direct-threading build.
`rb_vm_insn_addr2insn2` does some normalization to always return to
you the non-trace version of whatever instruction you're looking at.
`rb_vm_insn_null_translator` does not do that normalization.

This means that when you're looping through the instructions if you're
trying to do an opcode comparison, it can change depending on the type
of threading that you're using. This can be very confusing. So, this
commit creates a new translator function
`rb_vm_insn_normalizing_translator` to always return the non-trace
version so that opcode comparisons don't have to worry about different
configurations.

[Feature #18589]

1 files changed, 187 insertions, 0 deletions

diff --git a/bootstraptest/test_constant_cache.rb b/bootstraptest/test_constant_cache.rb
new file mode 100644
index 0000000000..1fa83256ed
--- /dev/null
+++ b/bootstraptest/test_constant_cache.rb
@@ -0,0 +1,187 @@
+# Constant lookup is cached.
+assert_equal '1', %q{
+  CONST = 1
+
+  def const
+    CONST
+  end
+
+  const
+  const
+}
+
+# Invalidate when a constant is set.
+assert_equal '2', %q{
+  CONST = 1
+
+  def const
+    CONST
+  end
+
+  const
+
+  CONST = 2
+
+  const
+}
+
+# Invalidate when a constant of the same name is set.
+assert_equal '1', %q{
+  CONST = 1
+
+  def const
+    CONST
+  end
+
+  const
+
+  class Container
+    CONST = 2
+  end
+
+  const
+}
+
+# Invalidate when a constant is removed.
+assert_equal 'missing', %q{
+  class Container
+    CONST = 1
+
+    def const
+      CONST
+    end
+
+    def self.const_missing(name)
+      'missing'
+    end
+
+    new.const
+    remove_const :CONST
+  end
+
+  Container.new.const
+}
+
+# Invalidate when a constant's visibility changes.
+assert_equal 'missing', %q{
+  class Container
+    CONST = 1
+
+    def self.const_missing(name)
+      'missing'
+    end
+  end
+
+  def const
+    Container::CONST
+  end
+
+  const
+
+  Container.private_constant :CONST
+
+  const
+}
+
+# Invalidate when a constant's visibility changes even if the call to the
+# visibility change method fails.
+assert_equal 'missing', %q{
+  class Container
+    CONST1 = 1
+
+    def self.const_missing(name)
+      'missing'
+    end
+  end
+
+  def const1
+    Container::CONST1
+  end
+
+  const1
+
+  begin
+    Container.private_constant :CONST1, :CONST2
+  rescue NameError
+  end
+
+  const1
+}
+
+# Invalidate when a module is included.
+assert_equal 'INCLUDE', %q{
+  module Include
+    CONST = :INCLUDE
+  end
+
+  class Parent
+    CONST = :PARENT
+  end
+
+  class Child < Parent
+    def const
+      CONST
+    end
+
+    new.const
+
+    include Include
+  end
+
+  Child.new.const
+}
+
+# Invalidate when const_missing is hit.
+assert_equal '2', %q{
+  module Container
+    Foo = 1
+    Bar = 2
+
+    class << self
+      attr_accessor :count
+
+      def const_missing(name)
+        @count += 1
+        @count == 1 ? Foo : Bar
+      end
+    end
+
+    @count = 0
+  end
+
+  def const
+    Container::Baz
+  end
+
+  const
+  const
+}
+
+# Invalidate when the iseq gets cleaned up.
+assert_equal '2', %q{
+  CONSTANT = 1
+
+  iseq = RubyVM::InstructionSequence.compile(<<~RUBY)
+    CONSTANT
+  RUBY
+
+  iseq.eval
+  iseq = nil
+
+  GC.start
+  CONSTANT = 2
+}
+
+# Invalidate when the iseq gets cleaned up even if it was never in the cache.
+assert_equal '2', %q{
+  CONSTANT = 1
+
+  iseq = RubyVM::InstructionSequence.compile(<<~RUBY)
+    CONSTANT
+  RUBY
+
+  iseq = nil
+
+  GC.start
+  CONSTANT = 2
+}