[llvm] [DebugInfo][InstCombine] When replacing bswap idiom, add DebugLoc to new insts (PR #114231)

[Stephen Tozer via llvm-commits]

SLTozer wrote:

That's how I'm thinking about it, I just think the term "replace" is a bit tricky since by most appearances, the intermediate instructions are being replaced by the folded instruction. Also, the existing policy explicitly states that mul+add=>fma should use a merged location, so changing that at least is a change in policy.

https://github.com/llvm/llvm-project/pull/114231