On 7 June 2017 08:44:13 CEST, Jan Hubicka <hubi...@ucw.cz> wrote:
>Hi
>the following patch makes cfgbuild to preserve profile when loops are
>introduced at RTL level (not very well, but at least do not throw it
>all
>away) and also avoids re-computing probabilities when there are no
>changes to CFG.
>
>Bootstrapped/regtested x86_64-linux. Comitted.
>
>Honza
>
>Index: cfgbuild.c
>===================================================================
>--- cfgbuild.c (revision 248915)
>+++ cfgbuild.c (working copy)
>@@ -475,6 +475,10 @@ find_bb_boundaries (basic_block bb)
>
> bb = fallthru->dest;
> remove_edge (fallthru);
>+ /* BB is unreachable at this point - we need to determine its
>profile
>+ once edges are built. */
>+ bb->frequency = 0;
>+ bb->count = profile_count::uninitialized ();
> flow_transfer_insn = NULL;
> if (code == CODE_LABEL && LABEL_ALT_ENTRY_P (insn))
> make_edge (ENTRY_BLOCK_PTR_FOR_FN (cfun), bb, 0);
>@@ -577,7 +581,7 @@ compute_outgoing_frequencies (basic_bloc
> guess_outgoing_edge_probabilities (b);
> }
>
>- if (b->count > profile_count::zero ())
>+ if (b->count.initialized_p ())
> FOR_EACH_EDGE (e, ei, b->succs)
> e->count = b->count.apply_probability (e->probability);
> }
>@@ -590,6 +594,9 @@ void
> find_many_sub_basic_blocks (sbitmap blocks)
> {
> basic_block bb, min, max;
>+ bool found = false;
>+ auto_vec<unsigned int> n_succs;
>+ n_succs.safe_grow_cleared (last_basic_block_for_fn (cfun));
>
> FOR_EACH_BB_FN (bb, cfun)
> SET_STATE (bb,
>@@ -597,11 +604,24 @@ find_many_sub_basic_blocks (sbitmap bloc
>
> FOR_EACH_BB_FN (bb, cfun)
> if (STATE (bb) == BLOCK_TO_SPLIT)
>- find_bb_boundaries (bb);
>+ {
>+ int n = last_basic_block_for_fn (cfun);
>+ unsigned int ns = EDGE_COUNT (bb->succs);
>+
>+ find_bb_boundaries (bb);
>+ if (n == last_basic_block_for_fn (cfun) && ns == EDGE_COUNT
>(bb->succs))
>+ n_succs[bb->index] = EDGE_COUNT (bb->succs);
>+ }
>
> FOR_EACH_BB_FN (bb, cfun)
> if (STATE (bb) != BLOCK_ORIGINAL)
>- break;
>+ {
>+ found = true;
>+ break;
>+ }
>+
>+ if (!found)
>+ return;
>
> min = max = bb;
> for (; bb != EXIT_BLOCK_PTR_FOR_FN (cfun); bb = bb->next_bb)
>@@ -624,14 +644,37 @@ find_many_sub_basic_blocks (sbitmap bloc
> continue;
> if (STATE (bb) == BLOCK_NEW)
> {
>+ bool initialized_src = false, uninitialized_src = false;
> bb->count = profile_count::zero ();
> bb->frequency = 0;
> FOR_EACH_EDGE (e, ei, bb->preds)
> {
>- bb->count += e->count;
>+ if (e->count.initialized_p ())
>+ {
>+ bb->count += e->count;
>+ initialized_src = true;
>+ }
>+ else
>+ uninitialized_src = false;
false?
Please explain false respectively the initializer (false too) in the light of
the condition in the hunk below?
thanks,
> bb->frequency += EDGE_FREQUENCY (e);
> }
>+ /* When some edges are missing with read profile, this is
>+ most likely because RTL expansion introduced loop.
>+ When profile is guessed we may have BB that is reachable
>+ from unlikely path as well as from normal path.
>+
>+ TODO: We should handle loops created during BB expansion
>+ correctly here. For now we assume all those loop to cycle
>+ precisely once. */
>+ if (!initialized_src
>+ || (uninitialized_src
>+ && profile_status_for_fn (cfun) != PROFILE_READ))
>+ bb->count = profile_count::uninitialized ();
> }
>+ else
>+ /* If nothing changed, there is no need to create new BBs. */
>+ if (EDGE_COUNT (bb->succs) == n_succs[bb->index])
>+ continue;
>
> compute_outgoing_frequencies (bb);
> }
