Add CLI option to set the min count

Author: wangpc-pp

llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp

@@ -37,6 +37,12 @@ static cl::opt<unsigned> SLPMaxVF(
         "exclusively by SLP vectorizer."),
     cl::Hidden);
 
+static cl::opt<unsigned>
+    RVVMinTripCount("riscv-min-trip-count",
+                    cl::desc("Set the lower bound of a trip count to decide on "
+                             "vectorization while tail-folding."),
+                    cl::init(5), cl::Hidden);
+
 InstructionCost
 RISCVTTIImpl::getRISCVInstructionCost(ArrayRef<unsigned> OpCodes, MVT VT,
                                       TTI::TargetCostKind CostKind) {
@@ -2598,6 +2604,10 @@ unsigned RISCVTTIImpl::getMaximumVF(unsigned ElemWidth, unsigned Opcode) const {
   return std::max<unsigned>(1U, RegWidth.getFixedValue() / ElemWidth);
 }
 
+unsigned RISCVTTIImpl::getMinTripCountTailFoldingThreshold() const {
+  return RVVMinTripCount;
+}
+
 TTI::AddressingModeKind
 RISCVTTIImpl::getPreferredAddressingMode(const Loop *L,
                                          ScalarEvolution *SE) const {

llvm/lib/Target/RISCV/RISCVTargetTransformInfo.h

@@ -388,9 +388,7 @@ class RISCVTTIImpl : public BasicTTIImplBase<RISCVTTIImpl> {
 
   bool enableInterleavedAccessVectorization() { return true; }
 
-  unsigned getMinTripCountTailFoldingThreshold() const {
-    return ST->hasVInstructions() ? 5 : 0;
-  }
+  unsigned getMinTripCountTailFoldingThreshold() const;
 
   enum RISCVRegisterClass { GPRRC, FPRRC, VRRC };
   unsigned getNumberOfRegisters(unsigned ClassID) const {