[llvm] [AMDGPU] Correctly insert s_nops for implicit read of SDWA (PR #100276)

[Stanislav Mekhanoshin via llvm-commits]

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@@ -875,13 +875,47 @@ GCNHazardRecognizer::checkVALUHazardsHelper(const MachineOperand &Def,
     return DataIdx >= 0 &&
            TRI->regsOverlap(MI.getOperand(DataIdx).getReg(), Reg);
   };
+
   int WaitStatesNeededForDef =
     VALUWaitStates - getWaitStatesSince(IsHazardFn, VALUWaitStates);
   WaitStatesNeeded = std::max(WaitStatesNeeded, WaitStatesNeededForDef);
 
   return WaitStatesNeeded;
 }
 
+static const MachineOperand *
+getDstSelForwardingOperand(const MachineInstr &MI, const GCNSubtarget &ST) {
+  const SIInstrInfo *TII = ST.getInstrInfo();
+  if (SIInstrInfo::isVALU(MI) && SIInstrInfo::isSDWA(MI)) {
+    if (auto *DstSel = TII->getNamedOperand(MI, AMDGPU::OpName::dst_sel))
+      if (DstSel->getImm() == AMDGPU::SDWA::DWORD)
+        return nullptr;
+  } else if (SIInstrInfo::isVALU(MI)) {
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rampitec wrote:

Just do the inlineasm stuff at the top, then check `!isVALU(MI)` at the top and bail. It will be less branching and isVALU checks.

https://github.com/llvm/llvm-project/pull/100276