Add `String#getbyte` YJIT implementation (#8397)

* Add getbyte JIT implementation

Adds an implementation for String#getbyte for YJIT, along with a
bootstrap test. This should be helpful for pure Ruby implementations
and to avoid unneeded allocations.

Co-authored-by: John Hawthorn <jhawthorn@github.com>

* Skip the getbyte test for RJIT for now

---------

Co-authored-by: John Hawthorn <jhawthorn@github.com>
Co-authored-by: Takashi Kokubun <takashikkbn@gmail.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/bootstraptest/test_yjit.rb b/bootstraptest/test_yjit.rb
index 3c53641f91..82fd1e1376 100644
--- a/bootstraptest/test_yjit.rb
+++ b/bootstraptest/test_yjit.rb
@@ -1832,6 +1832,24 @@ assert_equal 'true', %q{
   jittable_method
 }
 
+# test getbyte on string class
+assert_equal '[97, :nil, 97, :nil, :raised]', %q{
+  def getbyte(s, i)
+   byte = begin
+    s.getbyte(i)
+   rescue TypeError
+    :raised
+   end
+
+   byte || :nil
+  end
+
+  getbyte("a", 0)
+  getbyte("a", 0)
+
+  [getbyte("a", 0), getbyte("a", 1), getbyte("a", -1), getbyte("a", -2), getbyte("a", "a")]
+} unless defined?(RubyVM::RJIT) && RubyVM::RJIT.enabled? # Not yet working on RJIT
+
 # Test << operator on string subclass
 assert_equal 'abab', %q{
   class MyString < String; end