[llvm] [SelectionDAG][RISCV] Avoid store merging across function calls (PR #130430)

[Philip Reames via llvm-commits]

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@@ -21152,6 +21158,48 @@ bool DAGCombiner::checkMergeStoreCandidatesForDependencies(
   return true;
 }
 
+bool DAGCombiner::hasCallInLdStChain(SmallVectorImpl<MemOpLink> &StoreNodes,
+                                     SmallVectorImpl<MemOpLink> &LoadNodes,
+                                     unsigned NumStores) {
+  for (unsigned i = 0; i < NumStores; ++i) {
+    StoreSDNode *St = cast<StoreSDNode>(StoreNodes[i].MemNode);
+    LoadSDNode *Ld = cast<LoadSDNode>(LoadNodes[i].MemNode);
+    assert(Ld == cast<LoadSDNode>(peekThroughBitcasts(St->getValue())) &&
+           "Load and store mismatch");
+
+    SmallPtrSet<const SDNode *, 32> Visited;
+    SmallVector<std::pair<const SDNode *, bool>, 8> Worklist;
+    Worklist.emplace_back(St->getChain().getNode(), false);
+
+    while (!Worklist.empty()) {
+      auto [Node, FoundCall] = Worklist.pop_back_val();
+      if (!Visited.insert(Node).second || Node->getNumOperands() == 0)
+        continue;
+
+      switch (Node->getOpcode()) {
+      case ISD::CALLSEQ_END:
+        Worklist.emplace_back(Node->getOperand(0).getNode(), true);
+        break;
+      case ISD::TokenFactor:
+        for (SDValue Op : Node->ops())
+          Worklist.emplace_back(Op.getNode(), FoundCall);
+        break;
+      case ISD::LOAD:
+        if (Node == Ld)
+          return FoundCall;
+        [[fallthrough]];
+      default:
+        assert(Node->getOperand(0).getValueType() == MVT::Other &&
+               "Invalid chain type");
+        Worklist.emplace_back(Node->getOperand(0).getNode(), FoundCall);
+        break;
+      }
+    }
+    return false;
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preames wrote:

See ca0fe95a5, doesn't look like we do any of the aliasing/reordering games.  

https://github.com/llvm/llvm-project/pull/130430