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6875959: CTW fails hotspot/src/share/vm/opto/reg_split.cpp:1087

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To break spill ties choose bound live range over unbound to free register or one with smaller cost to spill.

Reviewed-by: never, jrose
This commit is contained in:
Vladimir Kozlov 2009-10-07 12:43:50 -07:00
parent 930f3d4570
commit ba951dbf36
1 changed files with 14 additions and 2 deletions

16
hotspot/src/share/vm/opto/chaitin.cpp

@ -985,10 +985,12 @@ void PhaseChaitin::Simplify( ) {
uint lo_score = _hi_degree;
double score = lrgs(lo_score).score();
double area = lrgs(lo_score)._area;
double cost = lrgs(lo_score)._cost;
bool bound = lrgs(lo_score)._is_bound;
// Find cheapest guy
debug_only( int lo_no_simplify=0; );
for( uint i = _hi_degree; i; i = lrgs(i)._next ) {
for( uint i = lrgs(lo_score)._next; i; i = lrgs(i)._next ) {
assert( !(*_ifg->_yanked)[i], "" );
// It's just vaguely possible to move hi-degree to lo-degree without
// going through a just-lo-degree stage: If you remove a double from
@ -1002,17 +1004,27 @@ void PhaseChaitin::Simplify( ) {
debug_only( if( lrgs(i)._was_lo ) lo_no_simplify=i; );
double iscore = lrgs(i).score();
double iarea = lrgs(i)._area;
double icost = lrgs(i)._cost;
bool ibound = lrgs(i)._is_bound;
// Compare cost/area of i vs cost/area of lo_score. Smaller cost/area
// wins. Ties happen because all live ranges in question have spilled
// a few times before and the spill-score adds a huge number which
// washes out the low order bits. We are choosing the lesser of 2
// evils; in this case pick largest area to spill.
// Ties also happen when live ranges are defined and used only inside
// one block. In which case their area is 0 and score set to max.
// In such case choose bound live range over unbound to free registers
// or with smaller cost to spill.
if( iscore < score ||
(iscore == score && iarea > area && lrgs(lo_score)._was_spilled2) ) {
(iscore == score && iarea > area && lrgs(lo_score)._was_spilled2) ||
(iscore == score && iarea == area &&
( (ibound && !bound) || ibound == bound && (icost < cost) )) ) {
lo_score = i;
score = iscore;
area = iarea;
cost = icost;
bound = ibound;
}
}
LRG *lo_lrg = &lrgs(lo_score);