Why does inferattrs run before and after lowering?

[VictorYing]

The -inferattrs pass is run both before and after lowering:

Tapir-LLVM/lib/Transforms/IPO/PassManagerBuilder.cpp

Line 741 in 89bb9a7

MPM.add(createInferFunctionAttrsLegacyPass());

I am wondering why this is. Note that this is distinct from the -functionattrs pass that can deduce attributes based on the contents of functions. The -inferattrs pass only infers attributes of library API declarations based on the name and signature, using the big list here:

Tapir-LLVM/lib/Transforms/Utils/BuildLibCalls.cpp

Line 108 in 6d439c5

bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {

I don't see anything CilkABI-related in the list, so I'm wondering: how does -inferattrs help lowering? Is that pass actually unneeded and can it be removed?

[wsmoses]

At one point this was necessary to ensure certain properties about the reference pipeline being true, though I don't believe that's presently the case so it probably can be removed.