Teach LiveInterval::isZeroLength about null SlotIndexes.

When instructions are deleted, they leave tombstone SlotIndex entries.
The isZeroLength method should ignore these null indexes.

This causes RABasic to sometimes spill a callee-saved register in the
abi-isel.ll test, so don't run that test with -regalloc=basic.  Prioritizing
register allocation according to spill weight can cause more registers to be
used.

llvm-svn: 131436

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/CalcSpillWeights.cpp b/llvm/lib/CodeGen/CalcSpillWeights.cpp
index e5894b8cca9..5d722ee34f7 100644
--- a/llvm/lib/CodeGen/CalcSpillWeights.cpp
+++ b/llvm/lib/CodeGen/CalcSpillWeights.cpp
@@ -165,7 +165,7 @@ void VirtRegAuxInfo::CalculateWeightAndHint(LiveInterval &li) {
     return;
 
   // Mark li as unspillable if all live ranges are tiny.
-  if (li.isZeroLength()) {
+  if (li.isZeroLength(LIS.getSlotIndexes())) {
     li.markNotSpillable();
     return;
   }