[LoopPeel][NFC] Exit early if there is no room for peeling

Differential Revision: https://reviews.llvm.org/D123864

llvm/lib/Transforms/Utils/LoopPeel.cpp

@@ -386,6 +386,10 @@ void llvm::computePeelCount(Loop *L, unsigned LoopSize,
   if (!PP.AllowPeeling)
     return;
 
+  // Check that we can peel at least one iteration.
+  if (2 * LoopSize > Threshold)
+    return;
+
   unsigned AlreadyPeeled = 0;
   if (auto Peeled = getOptionalIntLoopAttribute(L, PeeledCountMetaData))
     AlreadyPeeled = *Peeled;
@@ -398,8 +402,7 @@ void llvm::computePeelCount(Loop *L, unsigned LoopSize,
   // which every Phi is guaranteed to become an invariant, and try to peel the
   // maximum number of iterations among these values, thus turning all those
   // Phis into invariants.
-  // First, check that we can peel at least one iteration.
-  if (2 * LoopSize <= Threshold && UnrollPeelMaxCount > 0) {
+
   // Store the pre-calculated values here.
   SmallDenseMap<PHINode *, Optional<unsigned>> IterationsToInvariance;
   // Now go through all Phis to calculate their the number of iterations they
@@ -411,8 +414,8 @@ void llvm::computePeelCount(Loop *L, unsigned LoopSize,
   assert(BackEdge && "Loop is not in simplified form?");
   for (auto BI = L->getHeader()->begin(); isa<PHINode>(&*BI); ++BI) {
     PHINode *Phi = cast<PHINode>(&*BI);
-      auto ToInvariance = calculateIterationsToInvariance(
-          Phi, L, BackEdge, IterationsToInvariance);
+    auto ToInvariance = calculateIterationsToInvariance(Phi, L, BackEdge,
+                                                        IterationsToInvariance);
     if (ToInvariance)
       DesiredPeelCount = std::max(DesiredPeelCount, *ToInvariance);
   }
@@ -440,7 +443,6 @@ void llvm::computePeelCount(Loop *L, unsigned LoopSize,
       return;
     }
   }
-  }
 
   // Bail if we know the statically calculated trip count.
   // In this case we rather prefer partial unrolling.