[llvm-branch-commits] [llvm] [SelectionDAG] Track demanded concat elements in noundef checks (PR #200932)

[Simon Pilgrim via llvm-branch-commits]

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@@ -5665,6 +5665,32 @@ bool SelectionDAG::isGuaranteedNotToBeUndefOrPoison(SDValue Op,
     }
     return true;
 
+  case ISD::CONCAT_VECTORS: {
+    if (!DemandedElts)
+      return true;
+
+    EVT VT = Op.getValueType();
+    if (!VT.isFixedLengthVector())
+      return all_of(Op->ops(), [&](SDValue V) {
+        return isGuaranteedNotToBeUndefOrPoison(V, Kind, Depth + 1);
+      });
+
+    assert(DemandedElts.getBitWidth() == VT.getVectorNumElements() &&
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RKSimon wrote:

this should be done generically at the top of the function like SelectionDAG::computeKnownBits

https://github.com/llvm/llvm-project/pull/200932