[llvm] [AMDGPU] Refactor hazard recognizer for VALU-pipeline hazards. NFCI. (PR #168801)

[Jay Foad via llvm-commits]

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@@ -94,6 +98,9 @@ class GCNHazardRecognizer final : public ScheduleHazardRecognizer {
   int checkReadM0Hazards(MachineInstr *SMovRel);
   int checkNSAtoVMEMHazard(MachineInstr *MI);
   int checkFPAtomicToDenormModeHazard(MachineInstr *MI);
+  // emit V_NOP instructions. \p WaitStatesNeeded is the number of V_NOPs we
+  // need to insert, negative means not needed.
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jayfoad wrote:

Seems silly to use `int` here. Zero already means "not needed" so you don't need negative values.

https://github.com/llvm/llvm-project/pull/168801