[llvm] [SimplifyCFG] Avoid introducing complex phi when removing empty blocks (PR #104887)

[via llvm-commits]

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@@ -1040,6 +1045,42 @@ CanRedirectPredsOfEmptyBBToSucc(BasicBlock *BB, BasicBlock *Succ,
   return true;
 }
 
+// Check whether removing BB will make the phis in its Succ will have too
+// many incoming entries. This function does not check whether BB is foldable
+// or not.
+static bool introduceTooComplexPhi(BasicBlock *BB) {
+  // Check BB only has phi and an unconditional branch
+  BranchInst *Branch = dyn_cast<BranchInst>(BB->getFirstNonPHIOrDbg(true));
+  assert(Branch && Branch->isUnconditional() && "BB is not an empty block");
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Chengjunp wrote:

I see. Thank you for pointing this out. I will update this.

https://github.com/llvm/llvm-project/pull/104887