Hi Iain, Thanks for the reply, this is my first time contributing and I am looking forward to your input.
One other related thing I would like to investigate is reducing the number of compiler generated variables in the frame, particularly _Coro_destroy_fn and _Coro_self_handle. As I understand it, _Coro_destroy_fn just sets a flag in _Coro_resume_index and calls _Coro_resume_fn; it should be possible to move this logic to __builtin_coro_destroy, so that only _Coro_resume_fn is stored in the frame; this would however change the coroutine ABI - I don't know if that's a problem. The _Coro_self_handle should be constructible on-demand from the frame address. Do you have any advice / opinions on this before I try to implement it? Michal On Jul 12 2022, at 4:08 pm, Iain Sandoe <i...@sandoe.co.uk> wrote: > Hi Michal, > >> On 12 Jul 2022, at 14:35, Michal Jankovič via Gcc-patches >> <gcc-patches@gcc.gnu.org> wrote: >> >> Currently, coroutine frames store all variables of a coroutine separately, >> even if their lifetime does not overlap (they are in distinct >> scopes). This >> patch implements overlapping distinct variable scopes in the >> coroutine frame, >> by storing the frame fields in nested unions of structs. This lowers >> the size >> of the frame for larger coroutines significantly, and makes them more usable >> on systems with limited memory. > > not a review (I will try to take a look at the weekend). > > but … this is one of the two main optimisations on my TODO - so cool > for doing it. > > (the other related optimisation is to eliminate frame entries for > scopes without any suspend > points - which has the potential to save even more space for code with > sparse use of co_xxxx) > > Iain > >> Bootstrapped and regression tested on x86_64-pc-linux-gnu; new test fails >> before the patch and succeeds after with no regressions. >> >> PR c++/105989 >> >> gcc/cp/ChangeLog: >> >> * coroutines.cc (struct local_var_info): Add field_access_path. >> (build_local_var_frame_access_expr): New. >> (transform_local_var_uses): Use build_local_var_frame_access_expr. >> (coro_make_frame_entry_id): New. >> (coro_make_frame_entry): Delegate to coro_make_frame_entry_id. >> (struct local_vars_frame_data): Add orig, field_access_path. >> (register_local_var_uses): Generate new frame layout. Create access >> paths to vars. >> (morph_fn_to_coro): Set new fields in local_vars_frame_data. >> >> gcc/testsuite/ChangeLog: >> >> * g++.dg/coroutines/pr105989.C: New test. >> >> <pr105989.patch> > >
