120796 2013-09-05 14:19:37 -0700 REGRESSION(r155149): Fixing ToThis so that it is correct causes a 30% regression on LongSpider/3d-cube 2013-09-05 16:39:32 -0700 1 1 1 Unclassified WebKit JavaScriptCore 528+ (Nightly build) All All NEW P2 Normal --- 1 fpizlo ggaren barraclough ggaren mark.lam mhahnenberg msaboff oliver sam oldest_to_newest 925209 0 fpizlo 2013-09-05 14:19:37 -0700 We should fix it, and I'm not sure how - Geoff, do you have ideas since you introduced the new ToThis logic? 925279 1 ggaren 2013-09-05 16:39:32 -0700 Here’s a complete proposal: (*) If a simple structure check will do, use it. It’s good to check structures because our check will likely CSE with a property access. (*) If a simple array type check will do, use it. It’s good to check array types because our check will likely CSE with an indexed access. (*) Otherwise, check a bit in Structure that says “I don’t need ToThis conversion”. (*) For the global object: (*) The only example we have where this matters is a five-year-old typo, so we should probably just fix the typo. (*) But if we really care, we can add a specific check for global object => global this, and constant-fold it.