[LoopUnroll] Don't modify TripCount/TripMultiple in computeUnrollCount() (NFCI)

As these are no longer passed to UnrollLoop(), there is no need to
modify them in computeUnrollCount(). Make them non-reference parameters.

Differential Revision: https://reviews.llvm.org/D104590

Author: nikic

llvm/include/llvm/Transforms/Utils/UnrollLoop.h

@@ -101,9 +101,9 @@ bool isSafeToUnrollAndJam(Loop *L, ScalarEvolution &SE, DominatorTree &DT,
 bool computeUnrollCount(Loop *L, const TargetTransformInfo &TTI,
                         DominatorTree &DT, LoopInfo *LI, ScalarEvolution &SE,
                         const SmallPtrSetImpl<const Value *> &EphValues,
-                        OptimizationRemarkEmitter *ORE, unsigned &TripCount,
+                        OptimizationRemarkEmitter *ORE, unsigned TripCount,
                         unsigned MaxTripCount, bool MaxOrZero,
-                        unsigned &TripMultiple, unsigned LoopSize,
+                        unsigned TripMultiple, unsigned LoopSize,
                         TargetTransformInfo::UnrollingPreferences &UP,
                         TargetTransformInfo::PeelingPreferences &PP,
                         bool &UseUpperBound);

llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp

@@ -764,8 +764,8 @@ class UnrollCostEstimator {
 bool llvm::computeUnrollCount(
     Loop *L, const TargetTransformInfo &TTI, DominatorTree &DT, LoopInfo *LI,
     ScalarEvolution &SE, const SmallPtrSetImpl<const Value *> &EphValues,
-    OptimizationRemarkEmitter *ORE, unsigned &TripCount, unsigned MaxTripCount,
-    bool MaxOrZero, unsigned &TripMultiple, unsigned LoopSize,
+    OptimizationRemarkEmitter *ORE, unsigned TripCount, unsigned MaxTripCount,
+    bool MaxOrZero, unsigned TripMultiple, unsigned LoopSize,
     TargetTransformInfo::UnrollingPreferences &UP,
     TargetTransformInfo::PeelingPreferences &PP, bool &UseUpperBound) {
 
@@ -829,8 +829,6 @@ bool llvm::computeUnrollCount(
   // Full unroll makes sense only when TripCount or its upper bound could be
   // statically calculated.
   // Also we need to check if we exceed FullUnrollMaxCount.
-  // If using the upper bound to unroll, TripMultiple should be set to 1 because
-  // we do not know when loop may exit.
 
   // We can unroll by the upper bound amount if it's generally allowed or if
   // we know that the loop is executed either the upper bound or zero times.
@@ -859,8 +857,6 @@ bool llvm::computeUnrollCount(
     // like the rest of the loop body.
     if (UCE.getUnrolledLoopSize(UP) < UP.Threshold) {
       UseUpperBound = (FullUnrollMaxTripCount == FullUnrollTripCount);
-      TripCount = FullUnrollTripCount;
-      TripMultiple = UP.UpperBound ? 1 : TripMultiple;
       return ExplicitUnroll;
     } else {
       // The loop isn't that small, but we still can fully unroll it if that
@@ -874,8 +870,6 @@ bool llvm::computeUnrollCount(
             getFullUnrollBoostingFactor(*Cost, UP.MaxPercentThresholdBoost);
         if (Cost->UnrolledCost < UP.Threshold * Boost / 100) {
           UseUpperBound = (FullUnrollMaxTripCount == FullUnrollTripCount);
-          TripCount = FullUnrollTripCount;
-          TripMultiple = UP.UpperBound ? 1 : TripMultiple;
           return ExplicitUnroll;
         }
       }
@@ -1177,9 +1171,6 @@ static LoopUnrollResult tryToUnrollLoop(
       TripMultiple, LoopSize, UP, PP, UseUpperBound);
   if (!UP.Count)
     return LoopUnrollResult::Unmodified;
-  // Unroll factor (Count) must be less or equal to TripCount.
-  if (TripCount && UP.Count > TripCount)
-    UP.Count = TripCount;
 
   if (PP.PeelCount) {
     assert(UP.Count == 1 && "Cannot perform peel and unroll in the same step");