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Rework the global split cost calculation.

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The global cost is the sum of block frequencies for spill code that must be
inserted because preferences weren't met.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127062 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2011-03-05 03:28:51 +00:00
parent 89be0acecf
commit 874be74179
1 changed files with 30 additions and 21 deletions
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51
lib/CodeGen/RegAllocGreedy.cpp
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@ -558,24 +558,24 @@ float RAGreedy::calcSplitConstraints(const SmallVectorImpl<IndexPair> &Intf) {
///
float RAGreedy::calcGlobalSplitCost(const BitVector &LiveBundles) {
float GlobalCost = 0;
for (unsigned i = 0, e = SplitConstraints.size(); i != e; ++i) {
for (unsigned i = 0, e = SA->LiveBlocks.size(); i != e; ++i) {
SplitAnalysis::BlockInfo &BI = SA->LiveBlocks[i];
SpillPlacement::BlockConstraint &BC = SplitConstraints[i];
unsigned Inserts = 0;
// Broken entry preference?
Inserts += LiveBundles[Bundles->getBundle(BC.Number, 0)] !=
(BC.Entry == SpillPlacement::PrefReg);
// Broken exit preference?
Inserts += LiveBundles[Bundles->getBundle(BC.Number, 1)] !=
(BC.Exit == SpillPlacement::PrefReg);
if (Inserts)
GlobalCost += Inserts * SpillPlacer->getBlockFrequency(BC.Number);
bool RegIn = LiveBundles[Bundles->getBundle(BC.Number, 0)];
bool RegOut = LiveBundles[Bundles->getBundle(BC.Number, 1)];
unsigned Ins = 0;
if (!BI.Uses)
Ins += RegIn != RegOut;
else {
if (BI.LiveIn)
Ins += RegIn != (BC.Entry == SpillPlacement::PrefReg);
if (BI.LiveOut)
Ins += RegOut != (BC.Exit == SpillPlacement::PrefReg);
}
if (Ins)
GlobalCost += Ins * SpillPlacer->getBlockFrequency(BC.Number);
}
DEBUG({
dbgs() << "Global cost = " << GlobalCost << " with bundles";
for (int i = LiveBundles.find_first(); i>=0; i = LiveBundles.find_next(i))
dbgs() << " EB#" << i;
dbgs() << ".\n";
});
return GlobalCost;
}
@ -843,20 +843,29 @@ unsigned RAGreedy::tryRegionSplit(LiveInterval &VirtReg, AllocationOrder &Order,
mapGlobalInterference(PhysReg, GlobalCand[Cand].Interference);
float Cost = calcSplitConstraints(GlobalCand[Cand].Interference);
DEBUG(dbgs() << PrintReg(PhysReg, TRI) << " static split cost = " << Cost
<< '\n');
if (BestReg && Cost >= BestCost)
DEBUG(dbgs() << PrintReg(PhysReg, TRI) << "\tstatic = " << Cost);
if (BestReg && Cost >= BestCost) {
DEBUG(dbgs() << " higher.\n");
continue;
}
SpillPlacer->placeSpills(SplitConstraints, LiveBundles);
// No live bundles, defer to splitSingleBlocks().
if (!LiveBundles.any())
if (!LiveBundles.any()) {
DEBUG(dbgs() << " no bundles.\n");
continue;
}
Cost += calcGlobalSplitCost(LiveBundles);
DEBUG({
dbgs() << ", total = " << Cost << " with bundles";
for (int i = LiveBundles.find_first(); i>=0; i = LiveBundles.find_next(i))
dbgs() << " EB#" << i;
dbgs() << ".\n";
});
if (!BestReg || Cost < BestCost) {
BestReg = PhysReg;
BestCost = Cost;
BestCost = 0.98f * Cost; // Prevent rounding effects.
BestBundles.swap(LiveBundles);
}
}