Bug 210694 - VM should have a bottomCellForSetLocal that is understood to be a true bottom value by the DFG
Summary: VM should have a bottomCellForSetLocal that is understood to be a true bottom...
Status: NEW
Alias: None
Product: WebKit
Classification: Unclassified
Component: JavaScriptCore (show other bugs)
Version: WebKit Nightly Build
Hardware: Unspecified Unspecified
: P2 Normal
Assignee: Nobody
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2020-04-18 12:26 PDT by Keith Miller
Modified: 2020-04-18 12:26 PDT (History)
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Description Keith Miller 2020-04-18 12:26:46 PDT
Right now we handle bottom values semantically needed for a SetLocal by vending a JSValue that roughly matches the predicted value for the non-bottom path. This comes up for op_iterator_open/next. Unfortunately, this still causes AI to be unhappy. If we had a constant cell that was understood by the DFG to be a bottom value (and presumably crashes whenever accessed), the DFG would generate better code for op_iterator_open/next.