Bug 68677 - The DFG should not attempt to guess types in the absence of value profiles
Summary: The DFG should not attempt to guess types in the absence of value profiles
Status: RESOLVED FIXED
Alias: None
Product: WebKit
Classification: Unclassified
Component: JavaScriptCore (show other bugs)
Version: 528+ (Nightly build)
Hardware: All All
: P2 Normal
Assignee: Nobody
URL:
Keywords:
Depends on: 68676 68723 68763
Blocks: 68593
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Reported: 2011-09-22 20:30 PDT by Filip Pizlo
Modified: 2011-09-24 15:38 PDT (History)
2 users (show)

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Attachments
the patch (17.38 KB, patch)
2011-09-24 15:30 PDT, Filip Pizlo 		oliver: review+
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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.