diff options
| -rw-r--r-- | lib/hipe/flow/cfg.inc | 78 |
1 files changed, 53 insertions, 25 deletions
diff --git a/lib/hipe/flow/cfg.inc b/lib/hipe/flow/cfg.inc index 0bad2a8dd7..a18bfbc526 100644 --- a/lib/hipe/flow/cfg.inc +++ b/lib/hipe/flow/cfg.inc @@ -343,7 +343,7 @@ remove_pred(HT, FromL, PredL) -> case gb_trees:lookup(FromL, HT) of {value, {Block, Succ, Preds}} -> Code = hipe_bb:code(Block), - NewCode = remove_pred_from_phis(Code, PredL, []), + NewCode = remove_pred_from_phis(PredL, Code), NewBlock = hipe_bb:code_update(Block, NewCode), gb_trees:update(FromL, {NewBlock,Succ,lists:delete(PredL,Preds)}, HT); none -> @@ -374,20 +374,20 @@ add_pred(HT, ToL, PredL) -> -ifdef(CFG_CAN_HAVE_PHI_NODES). %% phi-instructions in a removed block's successors must be aware of %% the change. -remove_pred_from_phis(List = [I|Left], Label, Acc) -> +remove_pred_from_phis(Label, List = [I|Left]) -> case is_phi(I) of - true -> - NewAcc = [phi_remove_pred(I, Label)|Acc], - remove_pred_from_phis(Left, Label, NewAcc); + true -> + NewI = phi_remove_pred(I, Label), + [NewI | remove_pred_from_phis(Label, Left)]; false -> - lists:reverse(Acc) ++ List + List end; -remove_pred_from_phis([], _Label, Acc) -> - lists:reverse(Acc). +remove_pred_from_phis(_Label, []) -> + []. -else. %% this is used for code representations like those of back-ends which %% do not have phi-nodes. -remove_pred_from_phis(Code, _Label, _Acc) -> +remove_pred_from_phis(_Label, Code) -> Code. -endif. @@ -927,24 +927,52 @@ merge(BB, BB2, BB2_Label) -> remove_unreachable_code(CFG) -> Start = start_label(CFG), - Reachable = find_reachable([Start], CFG, gb_sets:from_list([Start])), - %% Reachable is an ordset: it comes from gb_sets:to_list/1. - %% So use ordset:subtract instead of '--' below. - Labels = ordsets:from_list(labels(CFG)), - case ordsets:subtract(Labels, Reachable) of - [] -> - CFG; + %% No unreachable block will make another block reachable, so no fixpoint + %% looping is required + Reachable = find_reachable([], [Start], CFG, #{Start=>[]}), + case [L || L <- labels(CFG), not maps:is_key(L, Reachable)] of + [] -> CFG; Remove -> - NewCFG = lists:foldl(fun(X, Acc) -> bb_remove(Acc, X) end, CFG, Remove), - remove_unreachable_code(NewCFG) + HT0 = CFG#cfg.table, + HT1 = lists:foldl(fun gb_trees:delete/2, HT0, Remove), + ReachableP = fun(Lbl) -> maps:is_key(Lbl, Reachable) end, + HT = gb_trees:map(fun(_,B)->prune_preds(B, ReachableP)end, HT1), + CFG#cfg{table=HT} end. -find_reachable([Label|Left], CFG, Acc) -> - NewAcc = gb_sets:add(Label, Acc), - Succ = succ(CFG, Label), - find_reachable([X || X <- Succ, not gb_sets:is_member(X, Acc)] ++ Left, - CFG, NewAcc); -find_reachable([], _CFG, Acc) -> - gb_sets:to_list(Acc). +find_reachable([], [], _CFG, Acc) -> Acc; +find_reachable([Succ|Succs], Left, CFG, Acc) -> + case Acc of + #{Succ := _} -> find_reachable(Succs, Left, CFG, Acc); + #{} -> find_reachable(Succs, [Succ|Left], CFG, Acc#{Succ => []}) + end; +find_reachable([], [Label|Left], CFG, Acc) -> + find_reachable(succ(CFG, Label), Left, CFG, Acc). + +%% Batch prune unreachable predecessors. Asymptotically faster than deleting +%% unreachable blocks one at a time with bb_remove, at least when +%% CFG_CAN_HAVE_PHI_NODES is undefined. Otherwise a phi_remove_preds might be +%% needed to achieve that. +prune_preds(B={Block, Succ, Preds}, ReachableP) -> + case lists:partition(ReachableP, Preds) of + {_, []} -> B; + {NewPreds, Unreach} -> + NewCode = remove_preds_from_phis(Unreach, hipe_bb:code(Block)), + {hipe_bb:code_update(Block, NewCode), Succ, NewPreds} + end. +-ifdef(CFG_CAN_HAVE_PHI_NODES). +remove_preds_from_phis(_, []) -> []; +remove_preds_from_phis(Preds, List=[I|Left]) -> + case is_phi(I) of + false -> List; + true -> + NewI = lists:foldl(fun(L,IA)->phi_remove_pred(IA,L)end, + I, Preds), + [NewI | remove_preds_from_phis(Preds, Left)] + end. +-else. +remove_preds_from_phis(_, Code) -> Code. -endif. + +-endif. %% -ifdef(REMOVE_UNREACHABLE_CODE) |