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7039652: Performance regression after 7004547 changes

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Use unrolled_count() to limit unrolling and use the stride check only for initial stride value.

Reviewed-by: never
This commit is contained in:
Vladimir Kozlov 2011-04-28 16:40:23 -07:00
parent eb8db40092
commit 2683d5390b
1 changed files with 6 additions and 3 deletions
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9
hotspot/src/share/vm/opto/loopTransform.cpp
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@ -632,6 +632,8 @@ bool IdealLoopTree::policy_maximally_unroll( PhaseIdealLoop *phase ) const {
}
#define MAX_UNROLL 16 // maximum number of unrolls for main loop
//------------------------------policy_unroll----------------------------------
// Return TRUE or FALSE if the loop should be unrolled or not. Unroll if
// the loop is a CountedLoop and the body is small enough.
@ -646,10 +648,11 @@ bool IdealLoopTree::policy_unroll( PhaseIdealLoop *phase ) const {
// protect against over-unrolling
if (cl->trip_count() <= 1) return false;
// Check for stride being a small enough constant
if (abs(cl->stride_con()) > (1<<3)) return false;
int future_unroll_ct = cl->unrolled_count() * 2;
if (future_unroll_ct > MAX_UNROLL) return false;
// Check for initial stride being a small enough constant
if (abs(cl->stride_con()) > (1<<2)*future_unroll_ct) return false;
// Don't unroll if the next round of unrolling would push us
// over the expected trip count of the loop. One is subtracted