171421 2017-04-28 00:51:47 -0700 [JSC] Add @isUndefinedOrNullIgnoringMasquerade() 2021-01-04 11:01:14 -0800 1 1 1 Unclassified WebKit JavaScriptCore WebKit Nightly Build Unspecified Unspecified RESOLVED DUPLICATE 193127 P2 Normal --- 1 ysuzuki ysuzuki ashvayka fpizlo saam oldest_to_newest 1302518 0 ysuzuki 2017-04-28 00:51:47 -0700 In builtin JS, we have bunch of if (object === null || object === @undefined) thing. Previously, this is written as follows. if (object == null) However, the above one recognizes document.all as null/undefined due to its masquerade. So, they are rewritten. But the above thing is, 1. From JS developer, it looks very storange because it seems `== null` is better. 2. It bloats bytecodes, effectively prevents us from inlining. Keep builtin JS function small is a bit important in terms of inlining. So, to make the meaning explicit and tighten bytecode size, we would like to introduce a new bytecode, op_is_undefined_or_null_ignoring_masquerade. 1717168 1 ashvayka 2021-01-04 11:01:14 -0800 (In reply to Yusuke Suzuki from comment #0) > So, to make the meaning explicit and tighten bytecode size, we would like to > introduce a new bytecode, op_is_undefined_or_null_ignoring_masquerade. OpIsUndefinedOrNull was introduced in r239761. *** This bug has been marked as a duplicate of bug 193127 ***