[llvm] [AMDGPU][InsertWaitCnts] Refactor some helper functions, NFC (PR #161160)

[Jay Foad via llvm-commits]

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@@ -748,6 +754,18 @@ class SIInstrInfo final : public AMDGPUGenInstrInfo {
     return isLDSDMA(MI) && MI.getOpcode() != AMDGPU::BUFFER_STORE_LDS_DWORD;
   }
 
+  static bool asynchronouslyWritesSCC(unsigned Opcode) {
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jayfoad wrote:

I think `isGFX12CacheInvOrWBInst` could do with some work too. I don't understand how and why it is supposed to be GFX12-specific. And if it's going to live in SIInstrInfo, it should probably _not_ be GFX12-specific.

https://github.com/llvm/llvm-project/pull/161160