ZJIT: Skip defined? codegen on x86_64 for now

Author: st0012

zjit/src/codegen.rs

@@ -456,14 +456,20 @@ fn gen_defined(jit: &JITState, asm: &mut Assembler, op_type: usize, obj: VALUE,
             }
         }
         _ => {
-            // Save the PC and SP because the callee may allocate or call #respond_to?
-            gen_prepare_non_leaf_call(jit, asm, state)?;
+            // Skip on x86_64 due to index out of bounds on live ranges
+            // May be related to https://github.com/Shopify/ruby/issues/646
+            if cfg!(target_arch = "x86_64") {
+                None
+            } else {
+                // Save the PC and SP because the callee may allocate or call #respond_to?
+                gen_prepare_non_leaf_call(jit, asm, state)?;
 
-            // Call vm_defined(ec, reg_cfp, op_type, obj, v)
-            let def_result = asm.ccall(rb_vm_defined as *const u8, vec![EC, CFP, op_type.into(), obj.into(), tested_value]);
+                // Call vm_defined(ec, reg_cfp, op_type, obj, v)
+                let def_result = asm.ccall(rb_vm_defined as *const u8, vec![EC, CFP, op_type.into(), obj.into(), tested_value]);
 
-            asm.test(def_result, Opnd::UImm(255));
-            Some(asm.csel_nz(pushval.into(), Qnil.into()))
+                asm.test(def_result, Opnd::UImm(255));
+                Some(asm.csel_nz(pushval.into(), Qnil.into()))
+            }
         }
     }
 }