Teach the SLP Vectorizer that keeping some values live over a callsite can have a cost.

Some types, such as 128-bit vector types on AArch64, don't have any callee-saved registers. So if a value needs to stay live over a callsite, it must be spilled and refilled. This cost is now taken into account.

llvm-svn: 214859

1 files changed, 15 insertions, 0 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
index b1c931e96e8..2058dd06b21 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
@@ -124,6 +124,9 @@ public:
 
   unsigned getMemoryOpCost(unsigned Opcode, Type *Src, unsigned Alignment,
                            unsigned AddressSpace) const override;
+
+  unsigned getCostOfKeepingLiveOverCall(ArrayRef<Type*> Tys) const override;
+
   /// @}
 };
 
@@ -498,3 +501,15 @@ unsigned AArch64TTI::getMemoryOpCost(unsigned Opcode, Type *Src,
 
   return LT.first;
 }
+
+unsigned AArch64TTI::getCostOfKeepingLiveOverCall(ArrayRef<Type*> Tys) const {
+  unsigned Cost = 0;
+  for (auto *I : Tys) {
+    if (!I->isVectorTy())
+      continue;
+    if (I->getScalarSizeInBits() * I->getVectorNumElements() == 128)
+      Cost += getMemoryOpCost(Instruction::Store, I, 128, 0) +
+        getMemoryOpCost(Instruction::Load, I, 128, 0);
+  }
+  return Cost;
+}