[ARM] MVE sext costs

This adds some sext costs for MVE, taken from the length of assembly sequences
that we currently generate.

Differential Revision: https://reviews.llvm.org/D66010

llvm-svn: 369244

1 files changed, 25 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp b/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
index e94b9bd9b9e..6a128e85301 100644
--- a/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
+++ b/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
@@ -349,6 +349,31 @@ int ARMTTIImpl::getCastInstrCost(unsigned Opcode, Type *Dst, Type *Src,
       return Entry->Cost;
   }
 
+  // MVE extend costs, taken from codegen tests. i8->i16 or i16->i32 is one
+  // instruction, i8->i32 is two. i64 zexts are an VAND with a constant, sext
+  // are linearised so take more.
+  static const TypeConversionCostTblEntry MVEVectorConversionTbl[] = {
+    { ISD::SIGN_EXTEND, MVT::v8i16, MVT::v8i8, 1 },
+    { ISD::ZERO_EXTEND, MVT::v8i16, MVT::v8i8, 1 },
+    { ISD::SIGN_EXTEND, MVT::v4i32, MVT::v4i8, 2 },
+    { ISD::ZERO_EXTEND, MVT::v4i32, MVT::v4i8, 2 },
+    { ISD::SIGN_EXTEND, MVT::v2i64, MVT::v2i8, 10 },
+    { ISD::ZERO_EXTEND, MVT::v2i64, MVT::v2i8, 2 },
+    { ISD::SIGN_EXTEND, MVT::v4i32, MVT::v4i16, 1 },
+    { ISD::ZERO_EXTEND, MVT::v4i32, MVT::v4i16, 1 },
+    { ISD::SIGN_EXTEND, MVT::v2i64, MVT::v2i16, 10 },
+    { ISD::ZERO_EXTEND, MVT::v2i64, MVT::v2i16, 2 },
+    { ISD::SIGN_EXTEND, MVT::v2i64, MVT::v2i32, 8 },
+    { ISD::ZERO_EXTEND, MVT::v2i64, MVT::v2i32, 2 },
+  };
+
+  if (SrcTy.isVector() && ST->hasMVEIntegerOps()) {
+    if (const auto *Entry = ConvertCostTableLookup(MVEVectorConversionTbl,
+                                                   ISD, DstTy.getSimpleVT(),
+                                                   SrcTy.getSimpleVT()))
+      return Entry->Cost * ST->getMVEVectorCostFactor();
+  }
+
   // Scalar integer conversion costs.
   static const TypeConversionCostTblEntry ARMIntegerConversionTbl[] = {
     // i16 -> i64 requires two dependent operations.