================
@@ -3713,7 +3713,10 @@ bool
SimplifyCFGOpt::foldCondBranchOnValueKnownInPredecessor(CondBrInst *BI) {
// Note: If BB is a loop header then there is a risk that threading
introduces
// a non-canonical loop by moving a back edge. So we avoid this optimization
// for loop headers if NeedCanonicalLoop is set.
- if (Options.NeedCanonicalLoop && is_contained(LoopHeaders, BI->getParent()))
+ // Also avoid threading loop headers in convergent functions, since changing
+ // the branch structure can change the dynamic instances of convergent ops.
+ if ((Options.NeedCanonicalLoop || BI->getFunction()->isConvergent()) &&
+ is_contained(LoopHeaders, BI->getParent()))
----------------
XChy wrote:
AFAIK, JumpThreading performs similar transformations and uses `LoopHeaders`
too. But it is just for heuristics.
https://github.com/llvm/llvm-project/pull/204958
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