[llvm] Introducing a new ISD::POISON SDNode to represent the poison value in the IR. (PR #125883)

[Craig Topper via llvm-commits]

================
@@ -9244,6 +9248,11 @@ SDValue SelectionDAG::getLoad(ISD::MemIndexedMode AM, ISD::LoadExtType ExtType,
 
   SDVTList VTs = Indexed ?
     getVTList(VT, Ptr.getValueType(), MVT::Other) : getVTList(VT, MVT::Other);
+
+  // Lower poison to undef.
+  if (Ptr.getNode()->isPoison())
----------------
topperc wrote:

`Ptr->isPoison()`. We have `SDValue::operator->` to avoid explicit calls to getNode()

https://github.com/llvm/llvm-project/pull/125883