1 files changed, 12 insertions, 2 deletions

diff --git a/include/llvm/CodeGen/LiveIntervalAnalysis.h b/include/llvm/CodeGen/LiveIntervalAnalysis.h
index d7ff8da02a51a..e8856ac10377d 100644
--- a/include/llvm/CodeGen/LiveIntervalAnalysis.h
+++ b/include/llvm/CodeGen/LiveIntervalAnalysis.h
@@ -70,8 +70,15 @@ namespace llvm {
     static char ID; // Pass identification, replacement for typeid
     LiveIntervals() : MachineFunctionPass(&ID) {}
 
-    static float getSpillWeight(bool isDef, bool isUse, unsigned loopDepth) {
-      return (isDef + isUse) * powf(10.0F, (float)loopDepth);
+    // Calculate the spill weight to assign to a single instruction.
+    static float getSpillWeight(bool isDef, bool isUse, unsigned loopDepth);
+
+    // After summing the spill weights of all defs and uses, the final weight
+    // should be normalized, dividing the weight of the interval by its size.
+    // This encourages spilling of intervals that are large and have few uses,
+    // and discourages spilling of small intervals with many uses.
+    void normalizeSpillWeight(LiveInterval &li) {
+      li.weight /= getApproximateInstructionCount(li) + 25;
     }
 
     typedef Reg2IntervalMap::iterator iterator;
@@ -409,6 +416,9 @@ namespace llvm {
         DenseMap<unsigned,unsigned> &MBBVRegsMap,
         std::vector<LiveInterval*> &NewLIs);
 
+    // Normalize the spill weight of all the intervals in NewLIs.
+    void normalizeSpillWeights(std::vector<LiveInterval*> &NewLIs);
+
     static LiveInterval* createInterval(unsigned Reg);
 
     void printInstrs(raw_ostream &O) const;