[llvm] [MachinePipeliner] Add an abstract layer to manipulate Data Dependenc… (PR #109918)

[via llvm-commits]

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@@ -1953,26 +1924,33 @@ void SwingSchedulerDAG::computeNodeFunctions(NodeSetType &NodeSets) {
 /// as the predecessors of the elements of NodeOrder that are not also in
 /// NodeOrder.
 static bool pred_L(SetVector<SUnit *> &NodeOrder,
-                   SmallSetVector<SUnit *, 8> &Preds,
+                   SmallSetVector<SUnit *, 8> &Preds, SwingSchedulerDDG *DDG,
                    const NodeSet *S = nullptr) {
   Preds.clear();
-  for (const SUnit *SU : NodeOrder) {
-    for (const SDep &Pred : SU->Preds) {
-      if (S && S->count(Pred.getSUnit()) == 0)
+
+  for (SUnit *SU : NodeOrder) {
+    for (const auto &IE : DDG->getInEdges(SU)) {
+      SUnit *PredSU = IE.getSrc();
+      if (S && S->count(PredSU) == 0)
         continue;
-      if (ignoreDependence(Pred, true))
+      if (IE.ignoreDependence(true))
         continue;
-      if (NodeOrder.count(Pred.getSUnit()) == 0)
-        Preds.insert(Pred.getSUnit());
+      if (NodeOrder.count(PredSU) == 0)
+        Preds.insert(PredSU);
     }
-    // Back-edges are predecessors with an anti-dependence.
-    for (const SDep &Succ : SU->Succs) {
-      if (Succ.getKind() != SDep::Anti)
+
+    // FIXME: The following loop-carried dependencies may also need to be
+    // considered.
+    //   - Physical register dependnecies (true-dependnece and WAW).
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aankit-ca wrote:

*dependnecies -> dependencies
*true-dependnece -> true-dependence

https://github.com/llvm/llvm-project/pull/109918