>Can I infer from this that XR/XGR, all else being equal, >is to be preferred (slightly) over LHI/LGHI?
I thought an ordered list would pretty much answer that question and not require an inference. XR is certainly preferred. The main reason is the shorter instruction, thus possibly reducing the I-cache footprint. Apparently that is a slightly bigger factor than setting the CC (perhaps related to the fact that no one would intentionally write code that checked the CC after an XR for which both operands are the same reg). I suppose the other reason is "because the people who know best so" (that's not me, that's the people from whom I got the info). Peter Relson z/OS Core Technology Design
