[llvm] [LV] Add assertion for loop predecessor (and terminator of) existing when checking out of loop inst for poison (PR #154603)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-vectorizers

Author: None (calebwat)

<details>
<summary>Changes</summary>

In LoopVectorizationLegality, TheLoop->getLoopPredecessor() and [...]Predecessor()->getTerminator() are used without a null check. This patch adds an assert that they are non-null, since they are expected to be defined.

---
Full diff: https://github.com/llvm/llvm-project/pull/154603.diff


1 Files Affected:

- (modified) llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp (+5) 


``````````diff
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
index 789047a2a28e7..5882b2b5466d9 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
@@ -1527,6 +1527,11 @@ bool LoopVectorizationLegality::canVectorizeWithIfConvert() {
           if (!CurrI || !TheLoop->contains(CurrI)) {
             // If operands from outside the loop may be poison then Ptr may also
             // be poison.
+            assert((TheLoop->getLoopPredecessor() &&
+                    TheLoop->getLoopPredecessor()->getTerminator()) &&
+                   "No loop predecessor/pred terminator found while checking "
+                   "out of loop instruction for poison");
+
             if (!isGuaranteedNotToBePoison(CurrV, AC,
                                            TheLoop->getLoopPredecessor()
                                                ->getTerminator()

``````````

</details>


https://github.com/llvm/llvm-project/pull/154603