OpenJDK's (HotSpot) stack maps do support callee-saved registers -- and they are used in some special cases, like safepoint stubs (that spill all registers at a

OpenJDK's (HotSpot) stack maps do support callee-saved registers -- and they are used in some special cases, like safepoint stubs (that spill all registers at a poll-point if a safepoint is triggered) -- but you're correct that they've been removed from ordinary Java calls altogether on all platforms, now.