1 files changed, 33 insertions, 0 deletions
diff --git a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
index eb60b966c8e0..0ee813688411 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
@@ -61,6 +61,11 @@ static cl::opt<bool> EnableOrLikeSelectOpt("enable-aarch64-or-like-select",
 static cl::opt<bool> EnableLSRCostOpt("enable-aarch64-lsr-cost-opt",
                                       cl::init(true), cl::Hidden);
 
+// A complete guess as to a reasonable cost.
+static cl::opt<unsigned>
+    BaseHistCntCost("aarch64-base-histcnt-cost", cl::init(8), cl::Hidden,
+                    cl::desc("The cost of a histcnt instruction"));
+
 namespace {
 class TailFoldingOption {
   // These bitfields will only ever be set to something non-zero in operator=,
@@ -508,11 +513,39 @@ static bool isUnpackedVectorVT(EVT VecVT) {
          VecVT.getSizeInBits().getKnownMinValue() < AArch64::SVEBitsPerBlock;
 }
 
+static InstructionCost getHistogramCost(const IntrinsicCostAttributes &ICA) {
+  Type *BucketPtrsTy = ICA.getArgTypes()[0]; // Type of vector of pointers
+  Type *EltTy = ICA.getArgTypes()[1];        // Type of bucket elements
+
+  // Only allow (32b and 64b) integers or pointers for now...
+  if ((!EltTy->isIntegerTy() && !EltTy->isPointerTy()) ||
+      (EltTy->getScalarSizeInBits() != 32 &&
+       EltTy->getScalarSizeInBits() != 64))
+    return InstructionCost::getInvalid();
+
+  // FIXME: Hacky check for legal vector types. We can promote smaller types
+  //        but we cannot legalize vectors via splitting for histcnt.
+  // FIXME: We should be able to generate histcnt for fixed-length vectors
+  //        using ptrue with a specific VL.
+  if (VectorType *VTy = dyn_cast<VectorType>(BucketPtrsTy))
+    if ((VTy->getElementCount().getKnownMinValue() != 2 &&
+         VTy->getElementCount().getKnownMinValue() != 4) ||
+        VTy->getPrimitiveSizeInBits().getKnownMinValue() > 128 ||
+        !VTy->isScalableTy())
+      return InstructionCost::getInvalid();
+
+  return InstructionCost(BaseHistCntCost);
+}
+
 InstructionCost
 AArch64TTIImpl::getIntrinsicInstrCost(const IntrinsicCostAttributes &ICA,
                                       TTI::TargetCostKind CostKind) {
   auto *RetTy = ICA.getReturnType();
   switch (ICA.getID()) {
+  case Intrinsic::experimental_vector_histogram_add:
+    if (!ST->hasSVE2())
+      return InstructionCost::getInvalid();
+    return getHistogramCost(ICA);
   case Intrinsic::umin:
   case Intrinsic::umax:
   case Intrinsic::smin: