[clang] [flang] [llvm] [mlir] Add FramePointerKind::NonLeafNoReserve (PR #163775)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

If unreserving a register causes a performance regression, that's a register allocation problem, which is not really related to this patch.  Please file a bug.

If this was causing widespread regressions, I'd consider implementing some kind of workaround, but not for 1% on one specific loop.

https://github.com/llvm/llvm-project/pull/163775