[LoopPeel] Pass TripCount to computePeelCount by value instead of by reference. NFC

The TripCount is not modified by the function so it doesn't need
to be passed by reference. Verified by passing it as const reference
before changing to value.

Reviewed By: reames

Differential Revision: https://reviews.llvm.org/D117735

llvm/include/llvm/Transforms/Utils/LoopPeel.h

@@ -32,7 +32,7 @@ gatherPeelingPreferences(Loop *L, ScalarEvolution &SE,
 
 void computePeelCount(Loop *L, unsigned LoopSize,
                       TargetTransformInfo::PeelingPreferences &PP,
-                      unsigned &TripCount, DominatorTree &DT,
+                      unsigned TripCount, DominatorTree &DT,
                       ScalarEvolution &SE, unsigned Threshold = UINT_MAX);
 
 } // end namespace llvm

llvm/lib/Transforms/Utils/LoopPeel.cpp

@@ -359,7 +359,7 @@ static bool violatesLegacyMultiExitLoopCheck(Loop *L) {
 // Return the number of iterations we want to peel off.
 void llvm::computePeelCount(Loop *L, unsigned LoopSize,
                             TargetTransformInfo::PeelingPreferences &PP,
-                            unsigned &TripCount, DominatorTree &DT,
+                            unsigned TripCount, DominatorTree &DT,
                             ScalarEvolution &SE, unsigned Threshold) {
   assert(LoopSize > 0 && "Zero loop size is not allowed!");
   // Save the PP.PeelCount value set by the target in