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Keep track of the number of positively biased nodes when adding constraints.

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If there are no positive nodes, the algorithm can be aborted early.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129021 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2011-04-06 19:14:00 +00:00
parent 9efa2a263e
commit 70d4370b47
3 changed files with 16 additions and 3 deletions
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1
lib/CodeGen/RegAllocGreedy.cpp
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@ -772,6 +772,7 @@ unsigned RAGreedy::tryRegionSplit(LiveInterval &VirtReg, AllocationOrder &Order,
SpillPlacer->prepare(LiveBundles);
SpillPlacer->addConstraints(SplitConstraints);
DEBUG(dbgs() << ", " << SpillPlacer->getPositiveNodes() << " biased nodes");
SpillPlacer->finish();
// No live bundles, defer to splitSingleBlocks().

11
lib/CodeGen/SpillPlacement.cpp
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@ -134,10 +134,14 @@ struct SpillPlacement::Node {
}
/// addBias - Bias this node from an ingoing[0] or outgoing[1] link.
void addBias(float w, bool out) {
/// Return the change to the total number of positive biases.
int addBias(float w, bool out) {
// Normalize w relative to all connected blocks from that direction.
w /= Frequency[out];
int Before = Bias > 0;
Bias += w;
int After = Bias > 0;
return After - Before;
}
/// update - Recompute Value from Bias and Links. Return true when node
@ -237,14 +241,14 @@ void SpillPlacement::addConstraints(ArrayRef<BlockConstraint> LiveBlocks) {
if (I->Entry != DontCare) {
unsigned ib = bundles->getBundle(I->Number, 0);
activate(ib);
nodes[ib].addBias(Freq * Bias[I->Entry], 1);
PositiveNodes += nodes[ib].addBias(Freq * Bias[I->Entry], 1);
}
// Live-out from block?
if (I->Exit != DontCare) {
unsigned ob = bundles->getBundle(I->Number, 1);
activate(ob);
nodes[ob].addBias(Freq * Bias[I->Exit], 0);
PositiveNodes += nodes[ob].addBias(Freq * Bias[I->Exit], 0);
}
}
}
@ -292,6 +296,7 @@ void SpillPlacement::prepare(BitVector &RegBundles) {
ActiveNodes = &RegBundles;
ActiveNodes->clear();
ActiveNodes->resize(bundles->getNumBundles());
PositiveNodes = 0;
}
bool

7
lib/CodeGen/SpillPlacement.h
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@ -49,6 +49,9 @@ class SpillPlacement : public MachineFunctionPass {
// caller.
BitVector *ActiveNodes;
// The number of active nodes with a positive bias.
unsigned PositiveNodes;
// Block frequencies are computed once. Indexed by block number.
SmallVector<float, 4> BlockFrequency;
@ -91,6 +94,10 @@ public:
/// out, but not live in.
void addConstraints(ArrayRef<BlockConstraint> LiveBlocks);
/// getPositiveNodes - Return the total number of graph nodes with a positive
/// bias after adding constraints.
unsigned getPositiveNodes() const { return PositiveNodes; }
/// finish - Compute the optimal spill code placement given the
/// constraints. No MustSpill constraints will be violated, and the smallest
/// possible number of PrefX constraints will be violated, weighted by