[TTI] NFC: Change getCFInstrCost to return InstructionCost

This patch migrates the TTI cost interfaces to return an InstructionCost.

See this patch for the introduction of the type: https://reviews.llvm.org/D91174
See this thread for context: http://lists.llvm.org/pipermail/llvm-dev/2020-November/146408.html

Reviewed By: samparker

Differential Revision: https://reviews.llvm.org/D100313
diff --git a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
index c8eeb24..f8e7f5a 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
@@ -655,9 +655,9 @@
                                  CostKind);
 }
 
-unsigned AArch64TTIImpl::getCFInstrCost(unsigned Opcode,
-                                        TTI::TargetCostKind CostKind,
-                                        const Instruction *I) {
+InstructionCost AArch64TTIImpl::getCFInstrCost(unsigned Opcode,
+                                               TTI::TargetCostKind CostKind,
+                                               const Instruction *I) {
   if (CostKind != TTI::TCK_RecipThroughput)
     return Opcode == Instruction::PHI ? 0 : 1;
   assert(CostKind == TTI::TCK_RecipThroughput && "unexpected CostKind");