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| author | Eugene Rozenfeld <erozen@microsoft.com> | 2021-12-02 18:37:09 -0800 |
|---|---|---|
| committer | Eugene Rozenfeld <erozen@microsoft.com> | 2021-12-06 16:59:31 -0800 |
| commit | 3d9e6767939e9658260e2506e81ec32b37cba041 (patch) | |
| tree | 5c370b6ac6c2e973dffae64ef2678868dee685e4 /gcc/auto-profile.c | |
| parent | 3a580f967e55733303d2aa29d1f9e75bed81af83 (diff) | |
| download | gcc-3d9e6767939e9658260e2506e81ec32b37cba041.zip gcc-3d9e6767939e9658260e2506e81ec32b37cba041.tar.gz gcc-3d9e6767939e9658260e2506e81ec32b37cba041.tar.bz2 | |
Improve AutoFDO count propagation algorithm
When a basic block A has been annotated with a count and it has only one
successor (or predecessor) B, we can propagate the A's count to B.
The algoritm without this change could leave B without an annotation if B had
other unannotated predecessors (or successors). For example, in the test case I added,
the loop header block was left unannotated, which prevented loop unrolling.
gcc/ChangeLog:
* auto-profile.c (afdo_propagate_edge): Improve count propagation algorithm.
gcc/testsuite/ChangeLog:
* gcc.dg/tree-prof/init-array.c: New test for unrolling inner loops.
Diffstat (limited to 'gcc/auto-profile.c')
| -rw-r--r-- | gcc/auto-profile.c | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/gcc/auto-profile.c b/gcc/auto-profile.c index 4c1fc6b..dfcd681 100644 --- a/gcc/auto-profile.c +++ b/gcc/auto-profile.c @@ -1192,7 +1192,8 @@ afdo_find_equiv_class (bb_set *annotated_bb) /* If a basic block's count is known, and only one of its in/out edges' count is unknown, its count can be calculated. Meanwhile, if all of the in/out edges' counts are known, then the basic block's unknown count can also be - calculated. + calculated. Also, if a block has a single predecessor or successor, the block's + count can be propagated to that predecessor or successor. IS_SUCC is true if out edges of a basic blocks are examined. Update ANNOTATED_BB accordingly. Return TRUE if any basic block/edge count is changed. */ @@ -1208,6 +1209,7 @@ afdo_propagate_edge (bool is_succ, bb_set *annotated_bb) edge e, unknown_edge = NULL; edge_iterator ei; int num_unknown_edge = 0; + int num_edge = 0; profile_count total_known_count = profile_count::zero ().afdo (); FOR_EACH_EDGE (e, ei, is_succ ? bb->succs : bb->preds) @@ -1217,6 +1219,7 @@ afdo_propagate_edge (bool is_succ, bb_set *annotated_bb) num_unknown_edge++, unknown_edge = e; else total_known_count += AFDO_EINFO (e)->get_count (); + num_edge++; } /* Be careful not to annotate block with no successor in special cases. */ @@ -1230,7 +1233,20 @@ afdo_propagate_edge (bool is_succ, bb_set *annotated_bb) else if (num_unknown_edge == 1 && is_bb_annotated (bb, *annotated_bb)) { if (bb->count > total_known_count) - AFDO_EINFO (unknown_edge)->set_count (bb->count - total_known_count); + { + profile_count new_count = bb->count - total_known_count; + AFDO_EINFO(unknown_edge)->set_count(new_count); + if (num_edge == 1) + { + basic_block succ_or_pred_bb = is_succ ? unknown_edge->dest : unknown_edge->src; + if (new_count > succ_or_pred_bb->count) + { + succ_or_pred_bb->count = new_count; + if (!is_bb_annotated (succ_or_pred_bb, *annotated_bb)) + set_bb_annotated (succ_or_pred_bb, annotated_bb); + } + } + } else AFDO_EINFO (unknown_edge)->set_count (profile_count::zero().afdo ()); AFDO_EINFO (unknown_edge)->set_annotated (); |