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Go back to comparing spill weights when deciding if interference can be evicted.

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It gives better results. Sometimes, a live range can be large and still have
high spill weight. Such a range should not be spilled.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127036 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2011-03-04 21:32:50 +00:00
parent 38b5e86b9c
commit d17924b1bd
1 changed files with 5 additions and 9 deletions
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14
lib/CodeGen/RegAllocGreedy.cpp
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@ -154,7 +154,7 @@ private:
SlotIndex getPrevMappedIndex(const MachineInstr*);
void calcPrevSlots();
unsigned nextSplitPoint(unsigned);
bool canEvictInterference(LiveInterval&, unsigned, unsigned, float&);
bool canEvictInterference(LiveInterval&, unsigned, float&);
unsigned tryReassign(LiveInterval&, AllocationOrder&,
SmallVectorImpl<LiveInterval*>&);
@ -357,7 +357,7 @@ unsigned RAGreedy::tryReassign(LiveInterval &VirtReg, AllocationOrder &Order,
/// canEvict - Return true if all interferences between VirtReg and PhysReg can
/// be evicted. Set maxWeight to the maximal spill weight of an interference.
bool RAGreedy::canEvictInterference(LiveInterval &VirtReg, unsigned PhysReg,
unsigned Size, float &MaxWeight) {
float &MaxWeight) {
float Weight = 0;
for (const unsigned *AliasI = TRI->getOverlaps(PhysReg); *AliasI; ++AliasI) {
LiveIntervalUnion::Query &Q = query(VirtReg, *AliasI);
@ -365,12 +365,12 @@ bool RAGreedy::canEvictInterference(LiveInterval &VirtReg, unsigned PhysReg,
if (Q.collectInterferingVRegs(10) >= 10)
return false;
// CHeck if any interfering live range is shorter than VirtReg.
// Check if any interfering live range is heavier than VirtReg.
for (unsigned i = 0, e = Q.interferingVRegs().size(); i != e; ++i) {
LiveInterval *Intf = Q.interferingVRegs()[i];
if (TargetRegisterInfo::isPhysicalRegister(Intf->reg))
return false;
if (Intf->getSize() <= Size)
if (Intf->weight >= VirtReg.weight)
return false;
Weight = std::max(Weight, Intf->weight);
}
@ -388,10 +388,6 @@ unsigned RAGreedy::tryEvict(LiveInterval &VirtReg,
SmallVectorImpl<LiveInterval*> &NewVRegs){
NamedRegionTimer T("Evict", TimerGroupName, TimePassesIsEnabled);
// We can only evict interference if all interfering registers are virtual and
// longer than VirtReg.
const unsigned Size = VirtReg.getSize();
// Keep track of the lightest single interference seen so far.
float BestWeight = 0;
unsigned BestPhys = 0;
@ -399,7 +395,7 @@ unsigned RAGreedy::tryEvict(LiveInterval &VirtReg,
Order.rewind();
while (unsigned PhysReg = Order.next()) {
float Weight = 0;
if (!canEvictInterference(VirtReg, PhysReg, Size, Weight))
if (!canEvictInterference(VirtReg, PhysReg, Weight))
continue;
// This is an eviction candidate.