Add defined_ivar instruction

This is a variation of the `defined` instruction, for use when we
are checking for an instance variable. Splitting this out as a
separate instruction lets us skip some checks, and it also allows
us to use an instance variable cache, letting shape analysis
speed up the operation further.

1 files changed, 14 insertions, 0 deletions

diff --git a/insns.def b/insns.def
index c6284ee444..b98e44bc01 100644
--- a/insns.def
+++ b/insns.def
@@ -701,6 +701,20 @@ defined
     }
 }
 
+/* defined?(@foo) */
+DEFINE_INSN
+defined_ivar
+(ID id, IVC ic, VALUE pushval)
+()
+(VALUE val)
+// attr bool leaf  = false;
+{
+    val = Qnil;
+    if (vm_getivar(GET_SELF(), id, GET_ISEQ(), ic, NULL, FALSE, Qundef) != Qundef) {
+        val = pushval;
+    }
+}
+
 /* check `target' matches `pattern'.
      `flag & VM_CHECKMATCH_TYPE_MASK' describe how to check pattern.
       VM_CHECKMATCH_TYPE_WHEN: ignore target and check pattern is truthy.