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| author | Xionghu Luo <luoxhu@linux.ibm.com> | 2021-12-20 21:10:09 -0600 |
|---|---|---|
| committer | Xionghu Luo <luoxhu@linux.ibm.com> | 2021-12-20 21:10:46 -0600 |
| commit | 46bfe1b0e11c4797c5926e0754fae2848026376c (patch) | |
| tree | 5beec987ad5bc59b1bf4b2ef7f84aec397aaef6a | |
| parent | 460d53f816fe30093653cb22ef0feeb4bddc0895 (diff) | |
| download | gcc-46bfe1b0e11c4797c5926e0754fae2848026376c.zip gcc-46bfe1b0e11c4797c5926e0754fae2848026376c.tar.gz gcc-46bfe1b0e11c4797c5926e0754fae2848026376c.tar.bz2 | |
Fix incorrect loop exit edge probability [PR103270]
r12-4526 cancelled jump thread path rotates loop. It exposes a issue in
profile-estimate when predict_extra_loop_exits, outer loop's exit edge
is marked as inner loop's extra loop exit and set with incorrect
prediction, then a hot inner loop will become cold loop finally through
optimizations, this patch add loop check when searching extra exit edges
to avoid unexpected predict_edge from predict_paths_for_bb.
Regression tested on P8LE.
gcc/ChangeLog:
2021-12-21 Xionghu Luo <luoxhu@linux.ibm.com>
PR middle-end/103270
* predict.c (predict_extra_loop_exits): Add loop parameter.
(predict_loops): Call with loop argument.
gcc/testsuite/ChangeLog:
2021-12-21 Xionghu Luo <luoxhu@linux.ibm.com>
PR middle-end/103270
* gcc.dg/pr103270.c: New test.
| -rw-r--r-- | gcc/predict.c | 10 | ||||
| -rw-r--r-- | gcc/testsuite/gcc.dg/pr103270.c | 19 |
2 files changed, 25 insertions, 4 deletions
diff --git a/gcc/predict.c b/gcc/predict.c index 1a1da7e..1316ca8 100644 --- a/gcc/predict.c +++ b/gcc/predict.c @@ -1859,7 +1859,7 @@ predict_iv_comparison (class loop *loop, basic_block bb, exits to predict them using PRED_LOOP_EXTRA_EXIT. */ static void -predict_extra_loop_exits (edge exit_edge) +predict_extra_loop_exits (class loop *loop, edge exit_edge) { unsigned i; bool check_value_one; @@ -1912,12 +1912,14 @@ predict_extra_loop_exits (edge exit_edge) continue; if (EDGE_COUNT (e->src->succs) != 1) { - predict_paths_leading_to_edge (e, PRED_LOOP_EXTRA_EXIT, NOT_TAKEN); + predict_paths_leading_to_edge (e, PRED_LOOP_EXTRA_EXIT, NOT_TAKEN, + loop); continue; } FOR_EACH_EDGE (e1, ei, e->src->preds) - predict_paths_leading_to_edge (e1, PRED_LOOP_EXTRA_EXIT, NOT_TAKEN); + predict_paths_leading_to_edge (e1, PRED_LOOP_EXTRA_EXIT, NOT_TAKEN, + loop); } } @@ -2008,7 +2010,7 @@ predict_loops (void) ex->src->index, ex->dest->index); continue; } - predict_extra_loop_exits (ex); + predict_extra_loop_exits (loop, ex); if (number_of_iterations_exit (loop, ex, &niter_desc, false, false)) niter = niter_desc.niter; diff --git a/gcc/testsuite/gcc.dg/pr103270.c b/gcc/testsuite/gcc.dg/pr103270.c new file mode 100644 index 0000000..819310e --- /dev/null +++ b/gcc/testsuite/gcc.dg/pr103270.c @@ -0,0 +1,19 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -fdump-tree-profile_estimate" } */ + +void test(int a, int* i) +{ + for (; a < 5; ++a) + { + int b = 0; + int c = 0; + for (; b != -11; b--) + for (int d = 0; d ==0; d++) + { + *i += c & a; + c = b; + } + } +} + +/* { dg-final { scan-tree-dump-not "extra loop exit heuristics of edge\[^:\]*:" "profile_estimate"} } */ |