Bug 37862

Summary: Use BLX and BX to keep happy the return stack predictor above ARMv4
Product: WebKit Reporter: Gabor Loki <loki>
Component: JavaScriptCoreAssignee: Nobody <webkit-unassigned>
Status: RESOLVED FIXED    
Severity: Enhancement CC: barraclough, commit-queue
Priority: P2    
Version: 528+ (Nightly build)   
Hardware: Other   
OS: Other   
Attachments:
Description Flags
Use BLX and BX to keep happy the return stack predictor above ARMv4
none
The results on ARMv7 none

Gabor Loki
Reported 2010-04-20 08:31:25 PDT
The following kind of instruction sequences break the return stack predictor: MOV LR, PC MOV PC, Rx We should avoid it above v4. The BLX instruction should be used for predicted calls on ARMv5 and above. The patch gives 2% performance progression.
Attachments
Use BLX and BX to keep happy the return stack predictor above ARMv4 (10.44 KB, patch)
2010-04-20 08:32 PDT, Gabor Loki 		no flags
DetailsFormatted DiffDiff
The results on ARMv7 (6.44 KB, text/plain)
2010-04-20 08:35 PDT, Gabor Loki 		no flags
Details
View All Add attachment proposed patch, testcase, etc.
Gabor Loki
Comment 1 2010-04-20 08:32:44 PDT
Created attachment 53824 [details] Use BLX and BX to keep happy the return stack predictor above ARMv4
Gabor Loki
Comment 2 2010-04-20 08:35:07 PDT
Created attachment 53826 [details] The results on ARMv7
WebKit Commit Bot
Comment 3 2010-04-22 06:25:05 PDT
Comment on attachment 53824 [details] Use BLX and BX to keep happy the return stack predictor above ARMv4 Clearing flags on attachment: 53824 Committed r58091: <http://trac.webkit.org/changeset/58091>
WebKit Commit Bot
Comment 4 2010-04-22 06:25:09 PDT
All reviewed patches have been landed. Closing bug.
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