[llvm] [RISCV] Use TableGen-based macro fusion (PR #72224)

[Wang Pengcheng via llvm-commits]

================
@@ -1,210 +0,0 @@
-//===- RISCVMacroFusion.cpp - RISC-V Macro Fusion -------------------------===//
----------------
wangpc-pp wrote:

No, you don't need to.
You can keep this file and override `getMacroFusions()` in `RISCVSubtarget`:
```cpp
  std::vector<MacroFusionPredTy> getMacroFusions() const override {
    std::vector<MacroFusionPredTy> Fusions =
        RISCVGenSubtargetInfo::getMacroFusions();
    Fusions.push_back(shouldScheduleAdjacent);
    return Fusions;
  }
```
`shouldScheduleAdjacent` is the predicator for your downstream macrofusions.

https://github.com/llvm/llvm-project/pull/72224