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When joining intervals, join intervals in deeply nested loops first. This

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is a simple change, but seems to improve code a little.  For example, on
256.bzip2, we went from 75.0s -> 73.33s (2% speedup).

llvm-svn: 15004
This commit is contained in:
Chris Lattner 2004-07-19 14:40:29 +00:00
parent 997f36e53f
commit bc53c119ac
1 changed files with 34 additions and 4 deletions
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36
lib/CodeGen/LiveIntervals.cpp
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@ -109,7 +109,6 @@ bool LiveIntervals::runOnMachineFunction(MachineFunction &fn) {
// join intervals if requested
if (EnableJoining) joinIntervals();
//DEBUG(mf_->viewCFG());
numIntervalsAfter += intervals_.size();
@ -581,13 +580,44 @@ void LiveIntervals::joinIntervalsInMachineBB(MachineBasicBlock *MBB) {
}
}
void LiveIntervals::joinIntervals()
{
namespace {
// DepthMBBCompare - Comparison predicate that sort first based on the loop
// depth of the basic block (the unsigned), and then on the MBB number.
struct DepthMBBCompare {
typedef std::pair<unsigned, MachineBasicBlock*> DepthMBBPair;
bool operator()(const DepthMBBPair &LHS, const DepthMBBPair &RHS) const {
if (LHS.first > RHS.first) return true; // Deeper loops first
return LHS.first == RHS.first &&
LHS.second->getNumber() < RHS.second->getNumber();
}
};
}
void LiveIntervals::joinIntervals() {
DEBUG(std::cerr << "********** JOINING INTERVALS ***********\n");
const LoopInfo &LI = getAnalysis<LoopInfo>();
if (LI.begin() == LI.end()) {
// If there are no loops in the function, join intervals in function order.
for (MachineFunction::iterator I = mf_->begin(), E = mf_->end();
I != E; ++I)
joinIntervalsInMachineBB(I);
} else {
// Otherwise, join intervals in inner loops before other intervals.
// Unfortunately we can't just iterate over loop hierarchy here because
// there may be more MBB's than BB's. Collect MBB's for sorting.
std::vector<std::pair<unsigned, MachineBasicBlock*> > MBBs;
for (MachineFunction::iterator I = mf_->begin(), E = mf_->end();
I != E; ++I)
MBBs.push_back(std::make_pair(LI.getLoopDepth(I->getBasicBlock()), I));
// Sort by loop depth.
std::sort(MBBs.begin(), MBBs.end(), DepthMBBCompare());
// Finally, join intervals in loop nest order.
for (unsigned i = 0, e = MBBs.size(); i != e; ++i)
joinIntervalsInMachineBB(MBBs[i].second);
}
}
bool LiveIntervals::overlapsAliases(const LiveInterval& lhs,