[llvm] [AMDGPU] Use alias info to relax waitcounts for LDS DMA (PR #74537)

[Matt Arsenault via llvm-commits]

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@@ -704,7 +719,36 @@ void WaitcntBrackets::updateByEvent(const SIInstrInfo *TII,
       }
     }
     if (Inst.mayStore() && (TII->isDS(Inst) || mayWriteLDSThroughDMA(Inst))) {
-      setRegScore(SQ_MAX_PGM_VGPRS + EXTRA_VGPR_LDS, T, CurrScore);
+      unsigned Slot = 0;
+      for (const auto *MemOp : Inst.memoperands()) {
+        if (MemOp->isStore() &&
+            MemOp->getAddrSpace() == AMDGPUAS::LOCAL_ADDRESS) {
+          // Comparing just AA info does not guarantee memoperands are equal
+          // in general, but this is so for LDS DMA on practice.
+          auto AAI = MemOp->getAAInfo();
+          if (!AAI)
+            break;
+          auto I = llvm::find_if(LDSDMAStores, [&AAI](const MachineInstr *I) {
+            for (const auto *MemOp : I->memoperands()) {
+              if (MemOp->isStore())
+                return AAI == MemOp->getAAInfo();
+            }
+            return false;
+          });
+          if (I != LDSDMAStores.end()) {
+            Slot = I - LDSDMAStores.begin() + 1;
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arsenm wrote:

I don't understand this iterator logic

https://github.com/llvm/llvm-project/pull/74537