[llvm] [AMDGPU] Refine GCNHazardRecognizer hasHazard() (PR #138841)

[Jay Foad via llvm-commits]

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@@ -441,42 +441,106 @@ using IsExpiredFn = function_ref<bool(const MachineInstr &, int WaitStates)>;
 using GetNumWaitStatesFn = function_ref<unsigned int(const MachineInstr &)>;
 
 // Search for a hazard in a block and its predecessors.
-template <typename StateT>
+template <typename StateT, typename StateTraitsT>
 static bool
-hasHazard(StateT State,
+hasHazard(StateT InitialState,
           function_ref<HazardFnResult(StateT &, const MachineInstr &)> IsHazard,
           function_ref<void(StateT &, const MachineInstr &)> UpdateState,
-          const MachineBasicBlock *MBB,
-          MachineBasicBlock::const_reverse_instr_iterator I,
-          DenseSet<const MachineBasicBlock *> &Visited) {
-  for (auto E = MBB->instr_rend(); I != E; ++I) {
-    // No need to look at parent BUNDLE instructions.
-    if (I->isBundle())
-      continue;
-
-    switch (IsHazard(State, *I)) {
-    case HazardFound:
-      return true;
-    case HazardExpired:
-      return false;
-    default:
-      // Continue search
-      break;
+          const MachineBasicBlock *InitialMBB,
+          MachineBasicBlock::const_reverse_instr_iterator InitialI) {
+  struct StateMapKey {
+    SmallVectorImpl<StateT> *States;
+    unsigned Idx;
+    static bool isEqual(const StateMapKey &LHS, const StateMapKey &RHS) {
+      return LHS.States == RHS.States && LHS.Idx == RHS.Idx;
+    }
+  };
+  struct StateMapKeyTraits : DenseMapInfo<StateMapKey> {
----------------
jayfoad wrote:

I think you would normally do this by specializing `DenseMapInfo`:
```suggestion
  template <> struct DenseMapInfo<StateMapKey> {
```
Then there's no need to name it, or to mention it when you declare the StateMap below.

https://github.com/llvm/llvm-project/pull/138841