Bug 148649

Summary:

DFG AI assertions about not having to do type checks at the point of a Known use kind are unsound

Product:

WebKit

Reporter:

Filip Pizlo <fpizlo>

Component:

JavaScriptCore

Assignee:

Filip Pizlo <fpizlo>

Status:

RESOLVED FIXED

Severity:

Normal

Priority:

Version:

Other

Hardware:

All

OS:

All

Bug Depends on:

Bug Blocks:

148610

Attachments:

Description	Flags
the patch	saam: review+

Description Filip Pizlo 2015-08-31 15:10:33 PDT

We often generate IR like:

Check(Int32:@x)
...
Foo(KnownInt32:@x)

It would be valid for any optimization that somehow proves the type of @x to remove the Check node entirely.  But then, AI might fail on an assertion at Foo() because of the KnownInt32 use kind, if AI isn't smart enough to construct the same proof that the former optimization used for removing the Check.

The correct solution is probably to remove the compile-time assertions about Known use kinds having already been checked.  It's OK for those to be debug-only JIT assertions.

Comment 1 Filip Pizlo 2015-08-31 15:11:41 PDT

I might end up fixing this before I do property type inference. It looks like that code might reveal this bug.

Comment 2 Filip Pizlo 2015-09-01 10:42:52 PDT

Created attachment 260369 [details]
the patch

Comment 3 Saam Barati 2015-09-01 10:44:19 PDT

Comment on attachment 260369 [details]
the patch

r=me

Comment 4 Filip Pizlo 2015-09-01 11:27:51 PDT

Landed in http://trac.webkit.org/changeset/189219