diff options
| -rw-r--r-- | lib/stdlib/src/gen_statem.erl | 59 |
1 files changed, 7 insertions, 52 deletions
diff --git a/lib/stdlib/src/gen_statem.erl b/lib/stdlib/src/gen_statem.erl index 2c03b4fff6..513118a874 100644 --- a/lib/stdlib/src/gen_statem.erl +++ b/lib/stdlib/src/gen_statem.erl @@ -1948,24 +1948,6 @@ loop_timeouts( Timers_1, Seen#{TimeoutType => true}, TimeoutEvents) end end. -%% -%% Helper function for the ugly mis-optimization workaround -%% loop_timeouts_cancel below -%% -%% Do not inline! -%% -loop_timeouts( - P, Debug, S, - Events, NextState_NewData, - NextEventsR, Hibernate, TimeoutsR, Postponed, - Timers, Seen, TimeoutEvents, - TimeoutType) -> - %% - loop_timeouts( - P, Debug, S, - Events, NextState_NewData, - NextEventsR, Hibernate, TimeoutsR, Postponed, - Timers, Seen#{TimeoutType => true}, TimeoutEvents). %% Loop helper to cancel a timeout %% @@ -1975,8 +1957,6 @@ loop_timeouts_cancel( NextEventsR, Hibernate, TimeoutsR, Postponed, {TimerRefs,TimeoutTypes} = Timers, Seen, TimeoutEvents, TimeoutType) -> - %% Ugly mis-optimization workaround - %% %% This function body should have been: %% Timers_1 = cancel_timer_by_type(TimeoutType, Timers), %% loop_timeouts( @@ -1985,36 +1965,12 @@ loop_timeouts_cancel( %% NextEventsR, Hibernate, TimeoutsR, Postponed, %% Timers_1, Seen#{TimeoutType => true}, TimeoutEvents). %% - %% Since cancel_timer_by_type is inlined there is a code path - %% that checks if TimeoutType is a key in the map TimeoutTypes - %% and if not simply makes Timers_1 = Timers and then does - %% the map update of Seen and loops back to loop_timeouts/12. - %% This code path does not contain any external call and the - %% map update is an instruction, so that should be a simple - %% and fast path. - %% - %% The other code path when TimeoutType is a key in the map - %% TimeoutTypes calls erlang:cancel_timer/1 which forces - %% all live registers (about 13 of them) out on the stack - %% and back again afterwards. - %% - %% Unfortunately the optimization of common subexpressions - %% sees that both these function exits are identical and - %% joins them. Then during register allocation the common - %% function exit is adapted for the code path that spills - %% all live registers to the stack. So also the simple - %% and fast path spills all live registers around its - %% map update... Bummer! - %% - %% So this workaround duplicates cancel_timer_by_type/2 here, - %% and makes the function exits differ - the slow case - %% calls a helper function above to update Seen, and - %% the fast case updates Seen in this function. This tricks - %% the common subexpression optimizer into not joining - %% these two code paths. - %% - %% So the helper function above must not be inlined, please! - %% + %% Explicitly separate cases to get separate code paths for when + %% the map key exists vs. not, since otherwise the external call + %% to erlang:cancel_timer/1 and to map:remove/2 within + %% cancel_timer_by_type/2 would cause all live registers + %% to be saved to and restored from the stack also for + %% the case when the map key TimeoutType does not exist case TimeoutTypes of #{TimeoutType := TimerRef} -> Timers_1 = @@ -2024,8 +1980,7 @@ loop_timeouts_cancel( P, Debug, S, Events, NextState_NewData, NextEventsR, Hibernate, TimeoutsR, Postponed, - Timers_1, Seen, TimeoutEvents, - TimeoutType); + Timers_1, Seen#{TimeoutType => true}, TimeoutEvents); #{} -> loop_timeouts( P, Debug, S, |