Bug 153897 - REGRESSION(192409): Cannot rely on add32() to zero-extend
Summary: REGRESSION(192409): Cannot rely on add32() to zero-extend
Status: RESOLVED FIXED
Alias: None
Product: WebKit
Classification: Unclassified
Component: JavaScriptCore (show other bugs)
Version: WebKit Nightly Build
Hardware: All All
: P2 Normal
Assignee: Nobody
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2016-02-04 15:05 PST by Filip Pizlo
Modified: 2016-02-04 15:23 PST (History)
0 users

See Also:

Attachments
Add an attachment (proposed patch, testcase, etc.)

Note You need to log in before you can comment on or make changes to this bug.
Description Filip Pizlo 2016-02-04 15:05:07 PST 
Callers of add32() and other 32-bit arithmetic ops rely on the fact that the destination register is zero-extended.  The optimizations in r192409 broke this feature, and this causes crashes on some obscure code.
Comment 1 Filip Pizlo 2016-02-04 15:16:34 PST 
rdar://problem/24289839
Comment 2 Filip Pizlo 2016-02-04 15:20:26 PST 
I tried writing a test, but actually hitting this issue is sooooper hard.
Comment 3 Filip Pizlo 2016-02-04 15:23:58 PST 
Landed in http://trac.webkit.org/changeset/196152