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comparison src/share/vm/opto/chaitin.cpp @ 1008:e90521d61f9a

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6875959: CTW fails hotspot/src/share/vm/opto/reg_split.cpp:1087 Summary: To break spill ties choose bound live range over unbound to free register or one with smaller cost to spill. Reviewed-by: never, jrose
author kvn
date Wed, 07 Oct 2009 12:43:50 -0700
parents 04fa5affa478
children 5f29a958a545
comparison
equal deleted inserted replaced
1007:1ce3281a8e93 1008:e90521d61f9a
983 983
984 // Time to pick a potential spill guy 984 // Time to pick a potential spill guy
985 uint lo_score = _hi_degree; 985 uint lo_score = _hi_degree;
986 double score = lrgs(lo_score).score(); 986 double score = lrgs(lo_score).score();
987 double area = lrgs(lo_score)._area; 987 double area = lrgs(lo_score)._area;
988 double cost = lrgs(lo_score)._cost;
989 bool bound = lrgs(lo_score)._is_bound;
988 990
989 // Find cheapest guy 991 // Find cheapest guy
990 debug_only( int lo_no_simplify=0; ); 992 debug_only( int lo_no_simplify=0; );
991 for( uint i = _hi_degree; i; i = lrgs(i)._next ) { 993 for( uint i = lrgs(lo_score)._next; i; i = lrgs(i)._next ) {
992 assert( !(*_ifg->_yanked)[i], "" ); 994 assert( !(*_ifg->_yanked)[i], "" );
993 // It's just vaguely possible to move hi-degree to lo-degree without 995 // It's just vaguely possible to move hi-degree to lo-degree without
994 // going through a just-lo-degree stage: If you remove a double from 996 // going through a just-lo-degree stage: If you remove a double from
995 // a float live range it's degree will drop by 2 and you can skip the 997 // a float live range it's degree will drop by 2 and you can skip the
996 // just-lo-degree stage. It's very rare (shows up after 5000+ methods 998 // just-lo-degree stage. It's very rare (shows up after 5000+ methods
1000 break; 1002 break;
1001 } 1003 }
1002 debug_only( if( lrgs(i)._was_lo ) lo_no_simplify=i; ); 1004 debug_only( if( lrgs(i)._was_lo ) lo_no_simplify=i; );
1003 double iscore = lrgs(i).score(); 1005 double iscore = lrgs(i).score();
1004 double iarea = lrgs(i)._area; 1006 double iarea = lrgs(i)._area;
1007 double icost = lrgs(i)._cost;
1008 bool ibound = lrgs(i)._is_bound;
1005 1009
1006 // Compare cost/area of i vs cost/area of lo_score. Smaller cost/area 1010 // Compare cost/area of i vs cost/area of lo_score. Smaller cost/area
1007 // wins. Ties happen because all live ranges in question have spilled 1011 // wins. Ties happen because all live ranges in question have spilled
1008 // a few times before and the spill-score adds a huge number which 1012 // a few times before and the spill-score adds a huge number which
1009 // washes out the low order bits. We are choosing the lesser of 2 1013 // washes out the low order bits. We are choosing the lesser of 2
1010 // evils; in this case pick largest area to spill. 1014 // evils; in this case pick largest area to spill.
1015 // Ties also happen when live ranges are defined and used only inside
1016 // one block. In which case their area is 0 and score set to max.
1017 // In such case choose bound live range over unbound to free registers
1018 // or with smaller cost to spill.
1011 if( iscore < score || 1019 if( iscore < score ||
1012 (iscore == score && iarea > area && lrgs(lo_score)._was_spilled2) ) { 1020 (iscore == score && iarea > area && lrgs(lo_score)._was_spilled2) ||
1021 (iscore == score && iarea == area &&
1022 ( (ibound && !bound) || ibound == bound && (icost < cost) )) ) {
1013 lo_score = i; 1023 lo_score = i;
1014 score = iscore; 1024 score = iscore;
1015 area = iarea; 1025 area = iarea;
1026 cost = icost;
1027 bound = ibound;
1016 } 1028 }
1017 } 1029 }
1018 LRG *lo_lrg = &lrgs(lo_score); 1030 LRG *lo_lrg = &lrgs(lo_score);
1019 // The live range we choose for spilling is either hi-degree, or very 1031 // The live range we choose for spilling is either hi-degree, or very
1020 // rarely it can be low-degree. If we choose a hi-degree live range 1032 // rarely it can be low-degree. If we choose a hi-degree live range