JDK-8005522 : use fast-string instructions on x86 for zeroing
- Type: Enhancement
- Component: hotspot
- Sub-Component: compiler
- Priority: P4
- Status: Resolved
- Resolution: Fixed
- CPU: x86
- Submitted: 2012-12-26
- Updated: 2013-06-26
- Resolved: 2013-01-04
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| JDK 7 | JDK 8 | Other |
|---|---|---|
7u40Fixed  |
8Fixed |
hs24Fixed |
Related Reports
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Description
New x86 processors enhanced the operation of the REP MOVSB and REP STOSB instructions. A processors supports these enhancements if CPUID.(EAX=07H, ECX=0H):EBX[bit 9] is 1 (ERMS bit). VM uses stosq/stosd instructions to zero new java objects, replace them with fast-string stosb instructions when they are available. Note: we can't use REP MOVSB for arraycopy because it is not JMM compliant (not atomic and out of order).