diff options
Diffstat (limited to 'lib/CodeGen')
| -rw-r--r-- | lib/CodeGen/RegAllocLinearScan.cpp | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/lib/CodeGen/RegAllocLinearScan.cpp b/lib/CodeGen/RegAllocLinearScan.cpp index 59467c1e0f..fd7d5a6d76 100644 --- a/lib/CodeGen/RegAllocLinearScan.cpp +++ b/lib/CodeGen/RegAllocLinearScan.cpp @@ -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 = |