[llvm] [X86] Resolve FIXME: Create cld only when needed (PR #82415)

[Craig Topper via llvm-commits]

topperc wrote:

> @AtariDreams I don't know if I'm missing something, but shouldn't we emit cld for any string instruction, not just rep?

I don't think the X86 backend ever emits a string instruction without REP.

https://github.com/llvm/llvm-project/pull/82415