+unsigned BasicTTI::getAltShuffleOverhead(Type *Ty) const {
+ assert(Ty->isVectorTy() && "Can only shuffle vectors");
+ unsigned Cost = 0;
+ // Shuffle cost is equal to the cost of extracting element from its argument
+ // plus the cost of inserting them onto the result vector.
+
+ // e.g. <4 x float> has a mask of <0,5,2,7> i.e we need to extract from index
+ // 0 of first vector, index 1 of second vector,index 2 of first vector and
+ // finally index 3 of second vector and insert them at index <0,1,2,3> of
+ // result vector.
+ for (int i = 0, e = Ty->getVectorNumElements(); i < e; ++i) {
+ Cost += TopTTI->getVectorInstrCost(Instruction::InsertElement, Ty, i);
+ Cost += TopTTI->getVectorInstrCost(Instruction::ExtractElement, Ty, i);
+ }
+ return Cost;
+}
+