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If the live interval legnth is essentially zero, i.e. in every live range

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the use follows def immediately, it doesn't make sense to spill it and
hope it will be easier to allocate for this LI.

llvm-svn: 28217
This commit is contained in:
Evan Cheng 2006-05-10 22:30:41 +00:00
parent 12417fb32c
commit 03fa9eb65e
1 changed files with 15 additions and 1 deletions
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16
lib/CodeGen/RegAllocLinearScan.cpp
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@ -406,6 +406,14 @@ static void RevertVectorIteratorsTo(RA::IntervalPtrs &V, unsigned Point) {
}
}
static bool isZeroLengthInterval(LiveInterval *li) {
for (LiveInterval::Ranges::const_iterator
i = li->ranges.begin(), e = li->ranges.end(); i != e; ++i)
if (i->end - i->start > LiveIntervals::InstrSlots::NUM)
return false;
return true;
}
/// assignRegOrStackSlotAtInterval - assign a register if one is available, or
/// spill.
@ -557,10 +565,16 @@ void RA::assignRegOrStackSlotAtInterval(LiveInterval* cur)
DEBUG(std::cerr << "\t\tregister with min weight: "
<< mri_->getName(minReg) << " (" << minWeight << ")\n");
// If the live interval legnth is essentially zero, i.e. in every live range
// the use follows def immediately, it doesn't make sense to spill it and
// hope it will be easier to allocate for this li.
if (isZeroLengthInterval(cur))
DEBUG(std::cerr << "\t\tavoid spilling zero length live interval: "
<< *cur << '\n';);
// if the current has the minimum weight, we need to spill it and
// add any added intervals back to unhandled, and restart
// linearscan.
if (cur->weight <= minWeight) {
else if (cur->weight <= minWeight) {
DEBUG(std::cerr << "\t\t\tspilling(c): " << *cur << '\n';);
int slot = vrm_->assignVirt2StackSlot(cur->reg);
std::vector<LiveInterval*> added =