LLVM is currently not suitable for SPARC at all; it's existing SPARC backend was, to put it kindly, not written by someone intimately familiar with the architecture. There are problems on other architectures as well. ARM and x86 are really the best maintained (unsurprising).
Regardless, one of LLVM's biggest problems internally is the number of unaligned accesses, which hurts its performance on many architectures (except x86 of course, where the penalty is very minor). That's not specific to SPARC, but it does hurt performance there quite a bit as well as cause other problems.
Regardless, one of LLVM's biggest problems internally is the number of unaligned accesses, which hurts its performance on many architectures (except x86 of course, where the penalty is very minor). That's not specific to SPARC, but it does hurt performance there quite a bit as well as cause other problems.