[llvm] [DAG] canCreateUndefOrPoison - explicitly state the AssertSext/Zext/Align/NoFPClass can create poison (PR #146493)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-selectiondag

Author: Simon Pilgrim (RKSimon)

<details>
<summary>Changes</summary>

This keeps getting forgotten (e.g. #<!-- -->66603) - so make a point of adding it here to make it more clear instead of relying on the implicit default of returning true.

---
Full diff: https://github.com/llvm/llvm-project/pull/146493.diff


1 Files Affected:

- (modified) llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp (+7) 


``````````diff
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index ad941a1964683..a1e4d706ef6b2 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -5522,6 +5522,13 @@ bool SelectionDAG::canCreateUndefOrPoison(SDValue Op, const APInt &DemandedElts,
 
   unsigned Opcode = Op.getOpcode();
   switch (Opcode) {
+  case ISD::AssertSext:
+  case ISD::AssertZext:
+  case ISD::AssertAlign:
+  case ISD::AssertNoFPClass:
+    // Assertion nodes can create poison if the assertion fails.
+    return true;
+
   case ISD::FREEZE:
   case ISD::CONCAT_VECTORS:
   case ISD::INSERT_SUBVECTOR:

``````````

</details>


https://github.com/llvm/llvm-project/pull/146493