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

[Matt Arsenault via llvm-commits]

================
@@ -7798,6 +7801,10 @@ SDValue DAGTypeLegalizer::GenWidenVectorLoads(SmallVectorImpl<SDValue> &LdChain,
   // Load information
   SDValue Chain = LD->getChain();
   SDValue BasePtr = LD->getBasePtr();
+  // Lower to undef if BasePtr is Poison
+  if (BasePtr.getNode()->isPoison())
+    BasePtr = DAG.getUNDEF(BasePtr.getValueType());
----------------
arsenm wrote:

LGTM except for this part 

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