[llvm] Handle #dbg_values in SROA. (PR #94070)

[Stephen Tozer via llvm-commits]

SLTozer wrote:

> This change causes a 4% compile-time regression on tramp3d-v4 with full LTO:

The most likely guess it that this is due to the new processing of all dbg_values for fragments processed by SROA; if there aren't any shortcuts to reduce the amount of processing time, an intermediate step may be to make the `for_each(findDVRValues(...), ...)` calls conditional on the language being swift (not sure how best this could be done, but the easiest would be a `cl::opt<boolOrDefault>` with a default value set by the swift frontend).

This change may be preserving extra debug info for C/C++ as well that we'd be losing (slight file-size increase on the compile time tracker build suggests this), but it's a small gain for the performance cost atm.

https://github.com/llvm/llvm-project/pull/94070