[llvm] [RISCV] AddEdge between first mask producer and user of V0 (PR #146855)

[Craig Topper via llvm-commits]

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@@ -68,11 +72,24 @@ class RISCVVectorMaskDAGMutation : public ScheduleDAGMutation {
 
   void apply(ScheduleDAGInstrs *DAG) override {
     SUnit *NearestUseV0SU = nullptr;
+    SmallVector<SUnit *, 2> DefMask;
     for (SUnit &SU : DAG->SUnits) {
       const MachineInstr *MI = SU.getInstr();
-      if (MI->findRegisterUseOperand(RISCV::V0, TRI))
+      if (isSoleUseCopyToV0(SU))
+        DefMask.push_back(&SU);
+
+      if (MI->findRegisterUseOperand(RISCV::V0, TRI)) {
         NearestUseV0SU = &SU;
 
+        // Copy may not be a real use, so skip it here.
+        if (DefMask.size() > 1 && !MI->isCopy())
+          for (SUnit *Def : DefMask)
+            DAG->addEdge(Def, SDep(&SU, SDep::Artificial));
+
+        if (DefMask.size() > 0)
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topperc wrote:

!DefMask.empty()

https://github.com/llvm/llvm-project/pull/146855