On 10/21/2014 11:53 PM, Jeff Law wrote:
So, in the end I'm torn. I don't like adding new hooks when they're not
needed, but I have some reservations about relying on the order of stuff
in CALL_INSN_FUNCTION_USAGE and I worry a bit that you might end up with
stuff other than arguments on that list -- the PA port could filter on
the hard registers used for passing arguments, so other stuff appearing
isn't a big deal.
This is another worry. Also, at the moment we don't actually add the
pseudos to CALL_INSN_FUNCTION_USAGE (that's patch 6/11), we use the regs
saved by the call_args hook to make proper USEs in a PARALLEL. I'm not
convinced the rest of the compiler would be too happy to see pseudos there.
So, in all I'd say it's probably possible to do it that way, but it
feels a lot iffier than I'd be happy with. I for one didn't know about
the PA requirement, so I could easily have broken it unknowingly if I'd
made some random change modifying call expansion.