[AVR] Removed regalloc hack from CalcSpillWeights

The hack was in place as a fix for issue #1 (documented in AVR-LLVM) and
corresponds to LLVM bug PR14879. The hack is being removed so that a
better fix can be created.

Author: Dylan McKay

lib/CodeGen/CalcSpillWeights.cpp

@@ -180,20 +180,7 @@ VirtRegAuxInfo::calculateSpillWeightAndHint(LiveInterval &li) {
 
   // Mark li as unspillable if all live ranges are tiny.
   if (li.isZeroLength(LIS.getSlotIndexes())) {
-     // HACK HACK: This is a workaround until PR14879 gets fixed!
-     // This code allows us to compile memory intensive functions when only the Z
-     // register is available, otherwise we get the "Ran out of registers ..."
-     // assertion inside the regalloc.
-     // Here we avoid marking as not spillable live intervals that use the
-     // PTRDISPREGS class and have a size greater than 8, smaller ones
-     // get filtered out, generating better code.
-     if (strcmp(MF.getSubtarget().getRegisterInfo()->getRegClassName(mri.getRegClass(li.reg)), "PTRDISPREGS") == 0 &&
-         li.getSize() > 8) {
-             totalWeight *= 10000.0F;
-             li.weight = normalizeSpillWeight(totalWeight, li.getSize(), numInstr);
-         } else {
-             li.markNotSpillable();
-     }
+    li.markNotSpillable();
     return;
   }