This is an attempt to solve https://github.com/llvm/llvm-project/issues/56679 by rejecting musttail in CoroSplitPass on ppc conditionally based on CallInst and target configuration.
TailCallOptimization is conditionally eligible on PPC as details explained in PPCTargetLowering::IsEligibleForTailCallOptimization_64SVR4(). The check happens during instruction selection.
Coroutines need to know the eligibility during transformation. From the CallInst provided, ppc can decide if indirect call can be turned into tail call.