Georg-Johann Lay <a...@gjlay.de> writes: > The trouble is this: If a callee gets some arguments passed on the > stack or in call-saved regs, the callee is not ok for a sibling > call. That's because sibcall_epilogue executes before sibcall insns.
I'm having trouble with your terminology "call-saved regs". Do that mean "caller-saved regs" or "callee-saved regs"? I gather that in the case where f wants to make a sibling call to g, the problem is that this fails if g accepts arguments anywhere other than in registers which are neither caller-saved nor callee-saved. I would expect that that would be fairly easy to determine from the call expression. You can be conservative when doing something odd like passing a struct: the only effect would be that in an extremely small number of cases gcc would make a regular call when it could make a sibling call. > Introduce a new backend hook > bool targetm.function_ok_for_sibcall_with_cum (tree, tree, > CUMULATIVE_ARGS*); > and call it with &args_so_far from calls.c:expand_call It would be OK to change the existing hook to add a CUMULATIVE_ARGS* parameter, but unfortunately you don't have the CUMULATIVE_ARGS at the point where it is called. Adding another one does seem pretty ugly. Ian
