Implement RAGreedy::splitAroundRegion and remove loop splitting.

Region splitting includes loop splitting as a subset, and it is more generic.
The splitting heuristics for variables that are live in more than one block are
now:

1. Try to create a region that covers multiple basic blocks.
2. Try to create a new live range for each block with multiple uses.
3. Spill.

Steps 2 and 3 are similar to what the standard spiller is doing.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123853 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/SplitKit.cpp

@@ -867,9 +867,7 @@ void SplitEditor::leaveIntvAtTop(MachineBasicBlock &MBB) {
 /// LiveInterval, and ranges can be trimmed.
 void SplitEditor::closeIntv() {
   assert(openli_.getLI() && "openIntv not called before closeIntv");
-
-  DEBUG(dbgs() << "    closeIntv cleaning up\n");
-  DEBUG(dbgs() << "    open " << *openli_.getLI() << '\n');
+  DEBUG(dbgs() << "    closeIntv " << *openli_.getLI() << '\n');
   openli_.reset(0);
 }
 
@@ -966,6 +964,8 @@ void SplitEditor::computeRemainder() {
   // FIXME: If a single value is redefined, just move the def and truncate.
   LiveInterval &parent = edit_.getParent();
 
+  DEBUG(dbgs() << "computeRemainder from " << parent << '\n');
+
   // Values that are fully contained in the split intervals.
   SmallPtrSet<const VNInfo*, 8> deadValues;
   // Map all curli values that should have live defs in dupli.