Bug 68677

Summary: The DFG should not attempt to guess types in the absence of value profiles
Product: WebKit Reporter: Filip Pizlo <fpizlo>
Component: JavaScriptCoreAssignee: Nobody <webkit-unassigned>
Severity: Normal CC: fpizlo, oliver
Priority: P2    
Version: 528+ (Nightly build)   
Hardware: All   
OS: All   
Bug Depends on: 68676, 68723, 68763    
Bug Blocks: 68593    
Description Flags
the patch oliver: review+

Description Filip Pizlo 2011-09-22 20:30:13 PDT
The DFG still has a bunch of code to try to guess the types of variables without knowing any information about how the code will run.  This is unnecessary now that we have continuous optimization.  The DFG should never attempt to speculate statically; instead points in the code where no sensible speculation can be made should turn into immediate OSR points into the old JIT.
Comment 1 Filip Pizlo 2011-09-22 20:31:37 PDT
This blocks https://bugs.webkit.org/show_bug.cgi?id=68593 because live range splitting should be done after parsing, but static predictions are made during parsing.  So, implementing 68593 while having to still deal with static predictions will result in a lot more cruft than we should have to put up with.
Comment 2 Filip Pizlo 2011-09-24 15:30:31 PDT
Created attachment 108592 [details]
the patch
Comment 3 Filip Pizlo 2011-09-24 15:38:53 PDT
Landed in r95916.