[Mlir-commits] [mlir] [mlir][tensor] fix out-of-bound index in tensor.dim (PR #85901)

[Jianbang Yang]

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@@ -738,11 +741,11 @@ OpFoldResult DimOp::fold(FoldAdaptor adaptor) {
   if (!tensorType)
     return {};
 
-  // Out of bound indices produce undefined behavior but are still valid IR.
-  // Don't choke on them.
+  // Fold dim to posion if the index is out of bound. Poison represents
+  // undefined behavior.
   int64_t indexVal = index.getInt();
   if (indexVal < 0 || indexVal >= tensorType.getRank())
-    return {};
+    return ub::PoisonAttr::get(getContext());
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dynamicheart wrote:

Another question: is `ub.poison` is designed to be a valid IR and able to be compiled to a binary?

https://github.com/llvm/llvm-project/pull/85901