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| author | Cyril SIX <cyril.six@kalray.eu> | 2020-12-04 12:00:26 +0100 |
|---|---|---|
| committer | Cyril SIX <cyril.six@kalray.eu> | 2020-12-04 12:00:26 +0100 |
| commit | 718a7da96aa18c278cde43fbc77a50135cd71e94 (patch) | |
| tree | a74c97be2d6a65f185b4042576e7379fb1da2a63 /backend/Duplicateaux.ml | |
| parent | 2bbb2af733b98913a66a196cd985fef61b4eb594 (diff) | |
| download | compcert-kvx-718a7da96aa18c278cde43fbc77a50135cd71e94.tar.gz compcert-kvx-718a7da96aa18c278cde43fbc77a50135cd71e94.zip | |
Less aggressive tail duplication
In some cases of two imbricated loops, we would tail-duplicate too much,
because of the input trace traversing both loop headers.
Diffstat (limited to 'backend/Duplicateaux.ml')
| -rw-r--r-- | backend/Duplicateaux.ml | 17 |
1 files changed, 11 insertions, 6 deletions
diff --git a/backend/Duplicateaux.ml b/backend/Duplicateaux.ml index 3121f0fa..196d15f2 100644 --- a/backend/Duplicateaux.ml +++ b/backend/Duplicateaux.ml @@ -547,7 +547,7 @@ let is_a_nop code n = * preds: mapping node -> predecessors * ptree: the revmap * trace: the trace to follow tail duplication on *) -let tail_duplicate code preds ptree trace = +let tail_duplicate code preds is_loop_header ptree trace = debug "Tail_duplicate on that trace: %a\n" print_trace trace; (* next_int: unused integer that can be used for the next duplication *) let next_int = ref (next_free_pc code) @@ -563,8 +563,12 @@ let tail_duplicate code preds ptree trace = if is_first then (code, ptree) (* first node is never duplicated regardless of its inputs *) else let node_preds = ptree_get_some n preds - in let node_preds_nolast = List.filter (fun e -> e <> get_some !last_node) node_preds - in let node_preds_nolast = List.filter (fun e -> not @@ List.mem e t) node_preds_nolast + in let node_preds_nolast = + (* We traverse loop headers without initiating tail duplication + * (see case of two imbricated loops) *) + if (get_some @@ PTree.get n is_loop_header) then [] + else List.filter (fun e -> e <> get_some !last_node) node_preds + (* in let node_preds_nolast = List.filter (fun e -> not @@ List.mem e t) node_preds_nolast *) in let final_node_preds = match !last_duplicate with | None -> node_preds_nolast | Some n' -> n' :: node_preds_nolast @@ -585,12 +589,12 @@ let tail_duplicate code preds ptree trace = in let new_code, new_ptree = f code ptree true trace in (new_code, new_ptree, !nb_duplicated) -let superblockify_traces code preds traces ptree = +let superblockify_traces code preds is_loop_header traces ptree = let max_nb_duplicated = !Clflags.option_ftailduplicate (* FIXME - should be architecture dependent *) in let rec f code ptree = function | [] -> (code, ptree, 0) | trace :: traces -> - let new_code, new_ptree, nb_duplicated = tail_duplicate code preds ptree trace + let new_code, new_ptree, nb_duplicated = tail_duplicate code preds is_loop_header ptree trace in if (nb_duplicated < max_nb_duplicated) then (debug "End duplication\n"; f new_code new_ptree traces) else (debug "Too many duplicated nodes, aborting tail duplication\n"; (code, ptree, 0)) @@ -1019,6 +1023,7 @@ let tail_duplicate f = if !Clflags.option_ftailduplicate > 0 then let traces = select_traces code entrypoint in let preds = get_predecessors_rtl code in - superblockify_traces code preds traces revmap + let is_loop_header = get_loop_headers code entrypoint in + superblockify_traces code preds is_loop_header traces revmap else (code, revmap) in ((code, entrypoint), revmap) |