172458 2017-05-22 11:44:54 -0700 for-in bytecode generation is exponential 2021-07-23 16:55:05 -0700 1 1 1 Unclassified WebKit JavaScriptCore WebKit Nightly Build Unspecified Unspecified RESOLVED DUPLICATE 227989 P2 Normal --- 1 saam webkit-unassigned ashvayka benjamin fpizlo ggaren gskachkov jfbastien keith_miller mark.lam msaboff oliver ticaiolima ysuzuki oldest_to_newest 1311465 0 saam 2017-05-22 11:44:54 -0700 we emit the loop 3 times. If we start nesting for-in loops, this is exponential. I'll verify this is indeed the case. 1311467 1 saam 2017-05-22 11:46:41 -0700 Yup. We emit 1072675 instruction words for this function: ``` function foo(o) { for (let i in o) { for (let i in o) { for (let i in o) { for (let i in o) { for (let i in o) { for (let i in o) { for (let i in o) { for (let i in o) { for (let i in o) { 2+2; } } } } } } } } } } ``` 1779247 2 ashvayka 2021-07-23 16:55:05 -0700 Keith is fixing for / in to emit only one loop in https://bugs.webkit.org/show_bug.cgi?id=227989. *** This bug has been marked as a duplicate of bug 227989 ***