[clang] [llvm] [InstCombine] Canonicalize `(sitofp x)` -> `(uitofp x)` if `x >= 0` (PR #82404)

[Artem Belevich via cfe-commits]

Artem-B wrote:

We happen have a back-end where we do not have conversion instructions between unsigned int and FP, so this patch complicates things. Would it make sense to enable this canonicalization only if the target wants it?


https://github.com/llvm/llvm-project/pull/82404