[llvm-branch-commits] [llvm] AMDGPU: Handle gfx950 valu write vdst + permlane read hazard (PR #117287)

[Matt Arsenault via llvm-branch-commits]

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@@ -2551,8 +2551,34 @@ int GCNHazardRecognizer::checkPermlaneHazards(MachineInstr *MI) {
     return isVCmpXWritesExec(*TII, *TRI, MI);
   };
 
-  const int NumWaitStates = 4;
-  return NumWaitStates - getWaitStatesSince(IsVCmpXWritesExecFn, NumWaitStates);
+  auto IsVALUFn = [](const MachineInstr &MI) {
+    return SIInstrInfo::isVALU(MI);
+  };
+
+  const int VCmpXWritesExecWaitStates = 4;
+  const int VALUWritesVDstWaitStates = 2;
+  int WaitStatesNeeded = 0;
+
+  for (const MachineOperand &Op : MI->explicit_uses()) {
+    if (!Op.isReg() || !TRI->isVGPR(MF.getRegInfo(), Op.getReg()))
+      continue;
+    Register Reg = Op.getReg();
+
+    int WaitStatesSinceDef =
+        VALUWritesVDstWaitStates -
+        getWaitStatesSinceDef(Reg, IsVALUFn,
+                              /*MaxWaitStates=*/VALUWritesVDstWaitStates);
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arsenm wrote:

The usage doesn't exactly map to the definition name though 

https://github.com/llvm/llvm-project/pull/117287