3 files changed, 49 insertions, 5 deletions

diff --git a/lib/CodeGen/RegAllocGreedy.cpp b/lib/CodeGen/RegAllocGreedy.cpp
index 42758510d8..474594e796 100644
--- a/lib/CodeGen/RegAllocGreedy.cpp
+++ b/lib/CodeGen/RegAllocGreedy.cpp
@@ -53,6 +53,15 @@ STATISTIC(NumEvicted,      "Number of interferences evicted");
 
 static cl::opt<bool> CompactRegions("compact-regions", cl::init(true));
 
+static cl::opt<SplitEditor::ComplementSpillMode>
+SplitSpillMode("split-spill-mode", cl::Hidden,
+  cl::desc("Spill mode for splitting live ranges"),
+  cl::values(clEnumValN(SplitEditor::SM_Partition, "default", "Default"),
+             clEnumValN(SplitEditor::SM_Size,  "size",  "Optimize for size"),
+             clEnumValN(SplitEditor::SM_Speed, "speed", "Optimize for speed"),
+             clEnumValEnd),
+  cl::init(SplitEditor::SM_Partition));
+
 static RegisterRegAlloc greedyRegAlloc("greedy", "greedy register allocator",
                                        createGreedyRegisterAllocator);
 
@@ -1166,7 +1175,7 @@ unsigned RAGreedy::tryRegionSplit(LiveInterval &VirtReg, AllocationOrder &Order,
 
   // Prepare split editor.
   LiveRangeEdit LREdit(VirtReg, NewVRegs, this);
-  SE->reset(LREdit);
+  SE->reset(LREdit, SplitSpillMode);
 
   // Assign all edge bundles to the preferred candidate, or NoCand.
   BundleCand.assign(Bundles->getNumBundles(), NoCand);
@@ -1214,7 +1223,7 @@ unsigned RAGreedy::tryBlockSplit(LiveInterval &VirtReg, AllocationOrder &Order,
   unsigned Reg = VirtReg.reg;
   bool SingleInstrs = RegClassInfo.isProperSubClass(MRI->getRegClass(Reg));
   LiveRangeEdit LREdit(VirtReg, NewVRegs, this);
-  SE->reset(LREdit);
+  SE->reset(LREdit, SplitSpillMode);
   ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks();
   for (unsigned i = 0; i != UseBlocks.size(); ++i) {
     const SplitAnalysis::BlockInfo &BI = UseBlocks[i];
diff --git a/lib/CodeGen/SplitKit.cpp b/lib/CodeGen/SplitKit.cpp
index fe17e93c50..67a722e143 100644
--- a/lib/CodeGen/SplitKit.cpp
+++ b/lib/CodeGen/SplitKit.cpp
@@ -309,11 +309,13 @@ SplitEditor::SplitEditor(SplitAnalysis &sa,
     TRI(*vrm.getMachineFunction().getTarget().getRegisterInfo()),
     Edit(0),
     OpenIdx(0),
+    SpillMode(SM_Partition),
     RegAssign(Allocator)
 {}
 
-void SplitEditor::reset(LiveRangeEdit &lre) {
-  Edit = &lre;
+void SplitEditor::reset(LiveRangeEdit &LRE, ComplementSpillMode SM) {
+  Edit = &LRE;
+  SpillMode = SM;
   OpenIdx = 0;
   RegAssign.clear();
   Values.clear();
diff --git a/lib/CodeGen/SplitKit.h b/lib/CodeGen/SplitKit.h
index becd22ca53..7f74d3acf6 100644
--- a/lib/CodeGen/SplitKit.h
+++ b/lib/CodeGen/SplitKit.h
@@ -217,6 +217,36 @@ class SplitEditor {
   const TargetInstrInfo &TII;
   const TargetRegisterInfo &TRI;
 
+public:
+
+  /// ComplementSpillMode - Select how the complement live range should be
+  /// created.  SplitEditor automatically creates interval 0 to contain
+  /// anything that isn't added to another interval.  This complement interval
+  /// can get quite complicated, and it can sometimes be an advantage to allow
+  /// it to overlap the other intervals.  If it is going to spill anyway, no
+  /// registers are wasted by keeping a value in two places at the same time.
+  enum ComplementSpillMode {
+    /// SM_Partition(Default) - Try to create the complement interval so it
+    /// doesn't overlap any other intervals, and the original interval is
+    /// partitioned.  This may require a large number of back copies and extra
+    /// PHI-defs.  Only segments marked with overlapIntv will be overlapping.
+    SM_Partition,
+
+    /// SM_Size - Overlap intervals to minimize the number of inserted COPY
+    /// instructions.  Copies to the complement interval are hoisted to their
+    /// common dominator, so only one COPY is required per value in the
+    /// complement interval.  This also means that no extra PHI-defs need to be
+    /// inserted in the complement interval.
+    SM_Size,
+
+    /// SM_Speed - Overlap intervals to minimize the expected execution
+    /// frequency of the inserted copies.  This is very similar to SM_Size, but
+    /// the complement interval may get some extra PHI-defs.
+    SM_Speed
+  };
+
+private:
+
   /// Edit - The current parent register and new intervals created.
   LiveRangeEdit *Edit;
 
@@ -225,6 +255,9 @@ class SplitEditor {
   /// openIntv will be 1.
   unsigned OpenIdx;
 
+  /// The current spill mode, selected by reset().
+  ComplementSpillMode SpillMode;
+
   typedef IntervalMap<SlotIndex, unsigned> RegAssignMap;
 
   /// Allocator for the interval map. This will eventually be shared with
@@ -354,7 +387,7 @@ public:
               MachineDominatorTree&);
 
   /// reset - Prepare for a new split.
-  void reset(LiveRangeEdit&);
+  void reset(LiveRangeEdit&, ComplementSpillMode = SM_Partition);
 
   /// Create a new virtual register and live interval.
   /// Return the interval index, starting from 1. Interval index 0 is the