[ARM] MVE shuffle broadcast costs

A VDUP will perform a vector broadcast in a single instruction. Update the cost
model for MVE accordingly.

Code originally by David Sherwood.

Differential Revision: https://reviews.llvm.org/D63448

llvm-svn: 368589

1 files changed, 17 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp b/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
index 4e87f254893..f3da1b83765 100644
--- a/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
+++ b/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
@@ -514,6 +514,23 @@ int ARMTTIImpl::getShuffleCost(TTI::ShuffleKind Kind, Type *Tp, int Index,
         return LT.first * Entry->Cost;
     }
   }
+  if (ST->hasMVEIntegerOps()) {
+    if (Kind == TTI::SK_Broadcast) {
+      static const CostTblEntry MVEDupTbl[] = {
+          // VDUP handles these cases.
+          {ISD::VECTOR_SHUFFLE, MVT::v4i32, 1},
+          {ISD::VECTOR_SHUFFLE, MVT::v8i16, 1},
+          {ISD::VECTOR_SHUFFLE, MVT::v16i8, 1},
+          {ISD::VECTOR_SHUFFLE, MVT::v4f32, 1},
+          {ISD::VECTOR_SHUFFLE, MVT::v8f16, 1}};
+
+      std::pair<int, MVT> LT = TLI->getTypeLegalizationCost(DL, Tp);
+
+      if (const auto *Entry = CostTableLookup(MVEDupTbl, ISD::VECTOR_SHUFFLE,
+                                              LT.second))
+        return LT.first * Entry->Cost;
+    }
+  }
   return BaseT::getShuffleCost(Kind, Tp, Index, SubTp);
 }