[llvm] Guard against self-assignment in the DominatorTreeBase move assignment operator. (PR #116464)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-support

Author: Tom Honermann (tahonermann)

<details>
<summary>Changes</summary>

The `DominatorTreeBase` move assignment operator was not self-assignment safe because the last thing it does before returning is to release all resources held by the source object. This issue was reported by a static analysis tool; no self-assignment is known to occur in practice.

---
Full diff: https://github.com/llvm/llvm-project/pull/116464.diff


1 Files Affected:

- (modified) llvm/include/llvm/Support/GenericDomTree.h (+2) 


``````````diff
diff --git a/llvm/include/llvm/Support/GenericDomTree.h b/llvm/include/llvm/Support/GenericDomTree.h
index 45ef38b965b752..d0eec2070b4d7e 100644
--- a/llvm/include/llvm/Support/GenericDomTree.h
+++ b/llvm/include/llvm/Support/GenericDomTree.h
@@ -287,6 +287,8 @@ class DominatorTreeBase {
   }
 
   DominatorTreeBase &operator=(DominatorTreeBase &&RHS) {
+    if (this == &RHS)
+      return *this;
     Roots = std::move(RHS.Roots);
     DomTreeNodes = std::move(RHS.DomTreeNodes);
     NodeNumberMap = std::move(RHS.NodeNumberMap);

``````````

</details>


https://github.com/llvm/llvm-project/pull/116464