Add getScaledIntervalSize, which gives a measure of the size of an interval that...

the function due to empty index slots.  This is suitable for use in backend heuristics that need to reason about the density
of an interval.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52652 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/CodeGen/LiveIntervalAnalysis.h b/include/llvm/CodeGen/LiveIntervalAnalysis.h
index 473cc8e099694acd35a1143580b46a2be7b7dd34..92c3b844c9cf53b3e67447da8dd2dd845a106151 100644 (file)
--- a/include/llvm/CodeGen/LiveIntervalAnalysis.h
+++ b/include/llvm/CodeGen/LiveIntervalAnalysis.h
@@ -169,6 +169,15 @@ namespace llvm {
       return MBB2IdxMap[MBBNo].second;
     }
 
+    /// getIntervalSize - get the size of an interval in "units,"
+    /// where every function is composed of one thousand units.  This
+    /// measure scales properly with empty index slots in the function.
+    unsigned getScaledIntervalSize(LiveInterval& I) {
+      // Factor of 250 comes from 1000 units per function divided
+      // by four slots per instruction.
+      return (250 * I.getSize()) / i2miMap_.size();
+    }
+
     /// getMBBFromIndex - given an index in any instruction of an
     /// MBB return a pointer the MBB
     MachineBasicBlock* getMBBFromIndex(unsigned index) const {