[TableGen] Add a backend to generate MacroFusion predicators (#72222)

`FusionPredicate` is used to predicate if target instruction matches
 the requirement. The targets can be firstMI, secondMI or both.

The `Fusion` contains a list of `FusionPredicate`. The generated code
will be like:
```
bool isNAME(const TargetInstrInfo &TII,
            const TargetSubtargetInfo &STI,
            const MachineInstr *FirstMI,
            const MachineInstr &SecondMI) {
  auto &MRI = SecondMI.getMF()->getRegInfo();
  /* Predicates */
  return true;
}
```

A boilerplate class called `SimpleFusion` is added. `SimpleFusion` has
a predefined structure of predicates and accepts predicate for
`firstMI`, predicate for `secondMI` and epilog/prolog as arguments.
The generated code for `SimpleFusion` will be like:
```
bool isNAME(const TargetInstrInfo &TII,
            const TargetSubtargetInfo &STI,
            const MachineInstr *FirstMI,
            const MachineInstr &SecondMI) {
  auto &MRI = SecondMI.getMF()->getRegInfo();
  /* Prolog */
  /* Predicate for `SecondMI` */
  /* Wildcard */
  /* Predicate for `FirstMI` */
  /* Check One Use */
  /* Tie registers */
  /* Epilog */
  return true;
}
```

0 files changed, 0 insertions, 0 deletions