[clang] [llvm] [LLVM][IR] Use splat syntax when printing Constant[Data]Vector. (PR #112548)

[Paul Walker via cfe-commits]

paulwalker-arm wrote:

The flags are only intended to control the C++ representation of constant splats and do not affect the parsing[1] or printing.

After this PR the expected behaviour is to unify the textual representation of constant splats.  I did not anticipate there being a need to control the behaviour.  The parsing code has accepted the newer syntax for a while now and there shouldn't be any change in C++ change caused by using the newer syntax unless the `--use-constant-###` flags in use. Are you seeing something different or is your IR going via a route that does not support the new syntax?

[1] Naturally the flags change the IR created but everything sits inside the common `ConstantVector::get()` interface.

https://github.com/llvm/llvm-project/pull/112548