[VPlan][Coverity] Fix coverity CID1579964.

[offsake]

Fix for the Coverity hit with CID1579964 in VPlan.cpp.

Coverity message with some context follows.

[Cov] var_compare_op: Comparing TermBr to null implies that TermBr might be null.
434 } else if (TermBr && !TermBr->isConditional()) {
435 TermBr->setSuccessor(0, NewBB);
436 } else {
437 // Set each forward successor here when it is created, excluding
438 // backedges. A backward successor is set when the branch is created.
439 unsigned idx = PredVPSuccessors.front() == this ? 0 : 1;

[Cov] CID 1579964: (#1 of 1): Dereference after null check (FORWARD_NULL)
[Cov] var_deref_model: Passing null pointer TermBr to getSuccessor, which dereferences it.

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[llvmbot]

@llvm/pr-subscribers-vectorizers

@llvm/pr-subscribers-llvm-transforms

Author: None (offsake)

Changes

Fix for the Coverity hit with CID1579964 in VPlan.cpp.

---

Full diff: https://github.com/llvm/llvm-project/pull/121805.diff

1 Files Affected:

• (modified) llvm/lib/Transforms/Vectorize/VPlan.cpp (+4-4)

diff --git a/llvm/lib/Transforms/Vectorize/VPlan.cpp b/llvm/lib/Transforms/Vectorize/VPlan.cpp
index e804f81c36dba0..aa41c41e90c4c4 100644
--- a/llvm/lib/Transforms/Vectorize/VPlan.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlan.cpp
@@ -438,10 +438,10 @@ void VPBasicBlock::connectToPredecessors(VPTransformState::CFGState &CFG) {
       // Set each forward successor here when it is created, excluding
       // backedges. A backward successor is set when the branch is created.
       unsigned idx = PredVPSuccessors.front() == this ? 0 : 1;
-      assert(
-          (!TermBr->getSuccessor(idx) ||
-           (isa<VPIRBasicBlock>(this) && TermBr->getSuccessor(idx) == NewBB)) &&
-          "Trying to reset an existing successor block.");
+      assert((TermBr && (!TermBr->getSuccessor(idx) ||
+                         (isa<VPIRBasicBlock>(this) &&
+                          TermBr->getSuccessor(idx) == NewBB))) &&
+             "Trying to reset an existing successor block.");
       TermBr->setSuccessor(idx, NewBB);
     }
     CFG.DTU.applyUpdates({{DominatorTree::Insert, PredBB, NewBB}});

[offsake]

Hi @fhahn,

could you please review as I expect the relevant code was introduced with:

commit 416a508
Author: Florian Hahn [email protected]
Date: Sat Jun 4 21:22:32 2022 +0100

[VPlan] Update vector latch terminator edge to exit block after execution.

Coverity hit link for reference:
https://scan6.scan.coverity.com/#/project-view/60645/10600?selectedIssue=1579964

Also, could you please merge the patch if it looks good to you since I don't have writ permission to the repo?

Thanks!

[fhahn]

Thanks for the patch! Could you update the description to say what the issue was with the original code and how this patch fixes it?

I cannot view the covertity link; it asks for a password.

[offsake]

Thanks for the patch! Could you update the description to say what the issue was with the original code and how this patch fixes it?

I cannot view the covertity link; it asks for a password.

Just did.
Thanks!

[fhahn]

LGTM, thanks

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