[llvm] [NFC][Coroutines] Remove integer indexing in several CoroSplit loops (PR #115954)

[Yuxuan Chen via llvm-commits]

yuxuanchen1997 wrote:

> > For `llvm::enumerate` I think you can also have structured binding instead of `CS.value()` or `CS.index()` calls.
> > ```
> > for (const auto &[Index, Value] : llvm::enumerate(Vec)) { ... }
> > ```
> 
> Thanks! I will try this again and post another PR. I briefly tried it in one place, but it caused some build errors:
> 
> **> for (auto [Arg, Index] : llvm::enumerate(Args))** llvm-project/llvm/lib/Transforms/Coroutines/CoroSplit.cpp:633:42: error: cannot initialize a parameter of type 'llvm::Value *' with an lvalue of type 'std::tuple_element<0, std::tuple<unsigned long, llvm::Value *&>>::type' (aka 'unsigned long') Agg = Builder.CreateInsertValue(Agg, Arg, Index); ^~~ /home/tyler/llvm-project/llvm/include/llvm/IR/IRBuilder.h:2549:47: note: passing argument to parameter 'Val' here Value *CreateInsertValue(Value *Agg, Value *Val, ArrayRef Idxs,
> 
> **> for (auto &[Arg, Index] : llvm::enumerate(Args))** /home/tyler/llvm-project/llvm/lib/Transforms/Coroutines/CoroSplit.cpp:632:14: error: non-const lvalue reference to type 'enumerator_result<...>' cannot bind to a temporary of type 'enumerator_result<...>' for (auto &[Arg, Index] : llvm::enumerate(Args)) ^ ~ /home/tyler/llvm-project/llvm/include/llvm/ADT/STLExtras.h:827:12: note: selected 'begin' function with iterator type 'llvm::detail::zippy<llvm::detail::zip_enumerator, llvm::detail::index_stream, llvm::SmallVector<llvm::Value *, 8> &>::iterator' (aka 'zip_enumerator<llvm::detail::index_iterator, llvm::Value **>') iterator begin() { return begin_impl(IndexSequence{}); }

This just means that you have `Arg` and `Index` in incorrect order, right?

https://github.com/llvm/llvm-project/pull/115954