Adding a target-specific TargetTransformInfo implementation

If you remember what you read in Chapter 4, you will know that the TargetTransformInfo class, from the Analysis library, is used to get some information about the cost of lowering LLVM IR constructs.

In this section, you will learn how to create your own TargetTransformInfo implementation to match what your target supports.

Establishing a connection to your target-specific information

The targeting of TargetTransformInfo goes through a helper class, BasicTTIImplBase, from the CodeGen library, which uses the curiously recurring template pattern (CRTP).

Concretely, you must retarget this helper class and then register it with TargetTransformInfo through your TargetMachine.

Let’s start with the retargeting of BasicTTIImplBase.

The following snippet does exactly this:

class H2BLBTTIImpl : public BasicTTIImplBase<H2BLBTTIImpl> {
  using BaseT = BasicTTIImplBase<H2BLBTTIImpl>;
  using...