JDK-6667595 : Set probability FAIR for pre-, post- loops and ALWAYS for main loop
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: hs12
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • OS: solaris_10
  • CPU: sparc
  • Submitted: 2008-02-26
  • Updated: 2010-04-03
  • Resolved: 2008-11-04
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JDK 6 JDK 7 Other
6u14Fixed 7Fixed hs14Fixed
Related Reports
Relates :  
C2 clone original loop's probability when it constructs pre-, main, post- loops.
Then C2 adds zero-trip guard for main loop with probability FAIR.
As result a main loop's probability could be half of a pre-loop's probability
and RA may generates stack spills in the main loop and not in the pre-loop.

SUGGESTED FIX - Fix loop's probability. - Prevent some ideal optimizations for loop's trip counter to avoid having two live values which could cause spilling. - Add several ideal optimizations to improve code from a loop cloning. - Improve a spill copy removal in post allocation.

EVALUATION http://hg.openjdk.java.net/jdk7/hotspot-comp/hotspot/rev/cc80376deb0c