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Bug ID: 6523674 Allow different styles of java object fields allocation
6523674 : Allow different styles of java object fields allocation

Details
Type:
Enhancement
Submit Date:
2007-02-09
Status:
Resolved
Updated Date:
2010-05-22
Project Name:
JDK
Resolved Date:
2007-04-24
Component:
hotspot
OS:
solaris_9
Sub-Component:
compiler
CPU:
sparc
Priority:
P4
Resolution:
Fixed
Affected Versions:
7
Fixed Versions:
hs10

Related Reports
Backport:
JDK-2147849 - Allow different styles of java object fields allocation
Backport:
JDK-2176892 - Allow different styles of java object fields allocation
Relates:
JDK-7007564 - Align non-static fields size on byte instead of wordSize

Sub Tasks

Description
Currently HotSpot VM allocate java object fileds according to thir type
in the next order:

oops        (32-bits for LP32, 64-bits for LP64)
long/double (64-bits fileds)
int/float   (32-bits fileds)
short/char  (16-bits fileds)
byte        ( 8-bits fileds)  

The other stype could be source based.

Also we could compact fields by placeing them into gaps between fields in super class.

Comments
SUGGESTED FIX

Webrev:                 http://prt-web.sfbay.sun.com/net/prt-archiver.sfbay/data/archived_workspaces/main/c2_baseline/2007/20070323140227.kvn.6523674/workspace/webrevs/webrev-2007.03.23/index.html

Solution:
These changes implement straightforward approach by allocating oops fields 
last instead of first. Added the fields compacting by allocating fields in
available gap before a double/long field.
Added missed hard-coded offset checks in JavaClasses::check_offsets().
Changed generation of several prefetch instructions. Do it only for arrays 
and do it on sparc also.
2007-03-24 
EVALUATION

Different styles of java object nonstatic fields allocation provide
performance improvement.
2007-02-27


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