2 files changed, 14 insertions, 1 deletions
diff --git a/llvm/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp b/llvm/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp
index 3290b5931ad..51aab0b635a 100644
--- a/llvm/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp
+++ b/llvm/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp
@@ -44,6 +44,14 @@ HexagonTTIImpl::getPopcntSupport(unsigned IntTyWidthInBit) const {
 void HexagonTTIImpl::getUnrollingPreferences(Loop *L, ScalarEvolution &SE,
                                              TTI::UnrollingPreferences &UP) {
   UP.Runtime = UP.Partial = true;
+  // Only try to peel innermost loops with small runtime trip counts.
+  if (L && L->empty() &&
+      SE.getSmallConstantTripCount(L) == 0 &&
+      SE.getSmallConstantMaxTripCount(L) > 0 &&
+      SE.getSmallConstantMaxTripCount(L) <= 5) {
+    UP.PeelCount = 2;
+    UP.AllowPeeling = true;
+  }
 }
 
 bool HexagonTTIImpl::shouldFavorPostInc() const {
diff --git a/llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp b/llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp
index 5f465f328b0..cfbecd59af3 100644
--- a/llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp
@@ -221,6 +221,9 @@ void llvm::computePeelCount(Loop *L, unsigned LoopSize,
                             TargetTransformInfo::UnrollingPreferences &UP,
                             unsigned &TripCount, ScalarEvolution &SE) {
   assert(LoopSize > 0 && "Zero loop size is not allowed!");
+  // Save the UP.PeelCount value set by the target in
+  // TTI.getUnrollingPreferences or by the flag -unroll-peel-count.
+  unsigned TargetPeelCount = UP.PeelCount;
   UP.PeelCount = 0;
   if (!canPeel(L))
     return;
@@ -240,7 +243,9 @@ void llvm::computePeelCount(Loop *L, unsigned LoopSize,
     SmallDenseMap<PHINode *, unsigned> IterationsToInvariance;
     // Now go through all Phis to calculate their the number of iterations they
     // need to become invariants.
-    unsigned DesiredPeelCount = 0;
+    // Start the max computation with the UP.PeelCount value set by the target
+    // in TTI.getUnrollingPreferences or by the flag -unroll-peel-count.
+    unsigned DesiredPeelCount = TargetPeelCount;
     BasicBlock *BackEdge = L->getLoopLatch();
     assert(BackEdge && "Loop is not in simplified form?");
     for (auto BI = L->getHeader()->begin(); isa<PHINode>(&*BI); ++BI) {