diff --git a/llvm/include/llvm/CodeGen/TargetInstrInfo.h b/llvm/include/llvm/CodeGen/TargetInstrInfo.h
--- a/llvm/include/llvm/CodeGen/TargetInstrInfo.h
+++ b/llvm/include/llvm/CodeGen/TargetInstrInfo.h
@@ -734,12 +734,16 @@
     virtual bool shouldIgnoreForPipelining(const MachineInstr *MI) const = 0;
 
     /// Create a condition to determine if the trip count of the loop is greater
-    /// than TC.
+    /// than TC, where TC is always one more than for the previous prologue or
+    /// 0 if this is being called for the outermost prologue.
     ///
     /// If the trip count is statically known to be greater than TC, return
     /// true. If the trip count is statically known to be not greater than TC,
     /// return false. Otherwise return nullopt and fill out Cond with the test
     /// condition.
+    ///
+    /// Note: This hook is guaranteed to be called from the innermost to the
+    /// outermost prologue of the loop being software pipelined.
     virtual Optional<bool>
     createTripCountGreaterCondition(int TC, MachineBasicBlock &MBB,
                                     SmallVectorImpl<MachineOperand> &Cond) = 0;