[llvm] [SandboxVectorizer][NFCI] Fix use of possibly-uninitialized scalar. (PR #122201)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-vectorizers

Author: Tyler Lanphear (tylanphear)

<details>
<summary>Changes</summary>

The `EraseCallbackID` field is not always initialized in the ctor for SeedCollector; if not, it will be used uninitialized by its dtor. This could potentially lead to the erasure of a random callback, leading to a bug.

Fixed by initializing to a purposefully invalid ID (`std::numeric_limits<ContextID>::max()`)

---
Full diff: https://github.com/llvm/llvm-project/pull/122201.diff


1 Files Affected:

- (modified) llvm/include/llvm/Transforms/Vectorize/SandboxVectorizer/SeedCollector.h (+3-1) 


``````````diff
diff --git a/llvm/include/llvm/Transforms/Vectorize/SandboxVectorizer/SeedCollector.h b/llvm/include/llvm/Transforms/Vectorize/SandboxVectorizer/SeedCollector.h
index 6e16a84d832e5e..cc4ebb5c508414 100644
--- a/llvm/include/llvm/Transforms/Vectorize/SandboxVectorizer/SeedCollector.h
+++ b/llvm/include/llvm/Transforms/Vectorize/SandboxVectorizer/SeedCollector.h
@@ -292,7 +292,9 @@ class SeedCollector {
   SeedContainer StoreSeeds;
   SeedContainer LoadSeeds;
   Context &Ctx;
-  Context::CallbackID EraseCallbackID;
+  Context::CallbackID EraseCallbackID =
+      std::numeric_limits<Context::CallbackID>::max();
+
   /// \Returns the number of SeedBundle groups for all seed types.
   /// This is to be used for limiting compilation time.
   unsigned totalNumSeedGroups() const {

``````````

</details>


https://github.com/llvm/llvm-project/pull/122201