Bug 196116

Summary:

Remove an invalid assertion in DFG::SpeculativeJIT::nonSpeculativeNonPeepholeCompareNullOrUndefined().

Product:

WebKit

Reporter:

Mark Lam <mark.lam>

Component:

JavaScriptCore

Assignee:

Mark Lam <mark.lam>

Status:

RESOLVED FIXED

Severity:

Normal

CC:

fpizlo, keith_miller, msaboff, rmorisset, saam, tzagallo, webkit-bug-importer, ysuzuki

Priority:

Keywords:

InRadar

Version:

WebKit Nightly Build

Hardware:

Unspecified

OS:

Unspecified

Attachments:

Description	Flags
proposed patch.	fpizlo: review+

Description Mark Lam 2019-03-21 16:17:38 PDT

The DFG backend should not make assumptions about what optimizations the front end will or will not do.  The assertion asserts that the operand cannot be known to be a cell.  However, it is not guaranteed that the front end will fold away this case.  Also, the DFG backend is perfectly capable of generating code to handle the case where the operand is a cell.

<rdar://problem/48976951>

Comment 1 Mark Lam 2019-03-21 16:24:59 PDT

Created attachment 365639 [details]
proposed patch.

Comment 2 Filip Pizlo 2019-03-21 16:26:52 PDT

Comment on attachment 365639 [details]
proposed patch.

View in context: https://bugs.webkit.org/attachment.cgi?id=365639&action=review

> Source/JavaScriptCore/ChangeLog:10
> +        The DFG backend should not make assumptions about what optimizations the front end
> +        will or will not do.  The assertion asserts that the operand cannot be known to be

You're right - the DFG is making a back assumption here because optimizations should be optional.

Comment 3 Filip Pizlo 2019-03-21 16:27:06 PDT

(In reply to Filip Pizlo from comment #2)
> Comment on attachment 365639 [details]
> proposed patch.
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=365639&action=review
> 
> > Source/JavaScriptCore/ChangeLog:10
> > +        The DFG backend should not make assumptions about what optimizations the front end
> > +        will or will not do.  The assertion asserts that the operand cannot be known to be
> 
> You're right - the DFG is making a back assumption here because
> optimizations should be optional.

*bad assumption

Comment 4 Mark Lam 2019-03-21 16:35:33 PDT

Thanks for the review.  Landed in r243344: <http://trac.webkit.org/r243344>.

Comment 5 Saam Barati 2019-03-21 19:22:01 PDT

Comment on attachment 365639 [details]
proposed patch.

LGTM too.