ARM cost model: Penalize insertelement into D subregisters

Swift has a renaming dependency if we load into D subregisters. We don't have a
way of distinguishing between insertelement operations of values from loads and
other values. Therefore, we are pessimistic for now (The performance problem
showed up in example 14 of gcc-loops).

radar://13096933

llvm-svn: 174300

1 files changed, 13 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp b/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
index 61cb1f6b9a3..2ded63f8f71 100644
--- a/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
+++ b/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
@@ -117,6 +117,7 @@ public:
   unsigned getCastInstrCost(unsigned Opcode, Type *Dst,
                                       Type *Src) const;
 
+  unsigned getVectorInstrCost(unsigned Opcode, Type *Val, unsigned Index) const;
   /// @}
 };
 
@@ -197,3 +198,15 @@ unsigned ARMTTI::getCastInstrCost(unsigned Opcode, Type *Dst,
 
   return TargetTransformInfo::getCastInstrCost(Opcode, Dst, Src);
 }
+
+unsigned ARMTTI::getVectorInstrCost(unsigned Opcode, Type *ValTy,
+                                    unsigned Index) const {
+  // Penalize inserting into an D-subregister.
+  if (ST->isSwift() &&
+      Opcode == Instruction::InsertElement &&
+      ValTy->isVectorTy() &&
+      ValTy->getScalarSizeInBits() <= 32)
+    return 2;
+
+  return TargetTransformInfo::getVectorInstrCost(Opcode, ValTy, Index);
+}