[mlir][Transforms] Dialect conversion: Fix bug in UnresolvedMaterializationRewrite rollback

When an unresolved materializations (`unrealized_conversion_cast` op) is rolled back, the mapping should be rolled back as well, regardless of whether it is a source, target or argument materialization. Otherwise, we accumulate pointers to erased IR in the `mapping`. This is harmless in most cases, but can cause issues when a new operation is allocated at the same memory location and the pointer is "reused".

It is not possible to write a test case for this because I cannot trigger the pointer reuse programmatically.

Author: matthias-springer

mlir/lib/Transforms/Utils/DialectConversion.cpp

@@ -1062,10 +1062,8 @@ void CreateOperationRewrite::rollback() {
 }
 
 void UnresolvedMaterializationRewrite::rollback() {
-  if (getMaterializationKind() == MaterializationKind::Target) {
-    for (Value input : op->getOperands())
-      rewriterImpl.mapping.erase(input);
-  }
+  for (Value input : op->getOperands())
+    rewriterImpl.mapping.erase(input);
   op->erase();
 }