Bug 68127

Summary:

DFG JIT should not speculate integer if the value is always going to be used as a double anyway

Product:

WebKit

Reporter:

Filip Pizlo <fpizlo>

Component:

JavaScriptCore

Assignee:

Nobody <webkit-unassigned>

Status:

RESOLVED FIXED

Severity:

Normal

Priority:

Version:

528+ (Nightly build)

Hardware:

All

OS:

All

Attachments:

Description	Flags
the patch	oliver: review+

Description Filip Pizlo 2011-09-14 15:30:42 PDT

The DFG JIT will speculate that a value is an integer if the prediction logic tells us so.  But this is dangerously unnecessary if the value will always be used as a double.  For example, if o.f is predicted integer but is always used as o.f * 1.5, then there is no point to speculating that o.f is an integer because even if we do, we still have to convert it to a double.

Comment 1 Filip Pizlo 2011-09-14 15:34:30 PDT

Created attachment 107408 [details]
the patch

Comment 2 Filip Pizlo 2011-09-14 16:06:35 PDT

Landed in r95136.