Bug 68677

Summary:

The DFG should not attempt to guess types in the absence of value profiles

Product:

WebKit

Reporter:

Filip Pizlo <fpizlo>

Component:

JavaScriptCore

Assignee:

Nobody <webkit-unassigned>

Status:

RESOLVED FIXED

Severity:

Normal

CC:

fpizlo, oliver

Priority:

Version:

528+ (Nightly build)

Hardware:

All

OS:

All

Bug Depends on:

68676, 68723, 68763

Bug Blocks:

68593

Attachments:

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.