From: Xionghu Luo <luoxhu@linux.ibm.com>
To: gcc-patches@gcc.gnu.org
Cc: segher@kernel.crashing.org, dje.gcc@gmail.com,
wschmidt@linux.ibm.com, guojiufu@linux.ibm.com,
linkw@gcc.gnu.org, hubicka@kam.mff.cuni.cz,
richard.guenther@gmail.com, Xionghu Luo <luoxhu@linux.ibm.com>
Subject: [PATCH 2/3] Fix incorrect loop exit edge probability [PR103270]
Date: Tue, 7 Dec 2021 23:54:15 -0600 [thread overview]
Message-ID: <20211208055416.1415283-3-luoxhu@linux.ibm.com> (raw)
In-Reply-To: <20211208055416.1415283-1-luoxhu@linux.ibm.com>
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, OK for master?
gcc/ChangeLog:
PR middle-end/103270
* predict.c (predict_extra_loop_exits): Add loop parameter.
(predict_loops): Call with loop argument.
gcc/testsuite/ChangeLog:
PR middle-end/103270
* gcc.dg/pr103270.c: New test.
---
gcc/predict.c | 10 ++++++----
gcc/testsuite/gcc.dg/pr103270.c | 19 +++++++++++++++++++
2 files changed, 25 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/pr103270.c
diff --git a/gcc/predict.c b/gcc/predict.c
index 3cb4e3c0eb5..5b6e0cf722b 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 00000000000..819310e360e
--- /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"} } */
--
2.25.1
next prev parent reply other threads:[~2021-12-08 5:54 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-08 5:54 [PATCH 0/3] Dependency patches for hoist LIM code to cold loop Xionghu Luo
2021-12-08 5:54 ` [PATCH 1/3] loop-invariant: Don't move cold bb instructions to preheader in RTL Xionghu Luo
2021-12-08 23:26 ` Jeff Law
2021-12-13 9:14 ` Jan Hubicka
2021-12-13 10:24 ` Jan Hubicka
2021-12-14 9:21 ` Xionghu Luo
2021-12-16 11:20 ` Jan Hubicka
2021-12-17 1:30 ` Xionghu Luo
2021-12-29 1:43 ` Xionghu Luo
2021-12-29 12:55 ` Jan Hubicka
2021-12-30 6:08 ` Xionghu Luo
2021-12-08 5:54 ` Xionghu Luo [this message]
2021-12-08 23:28 ` [PATCH 2/3] Fix incorrect loop exit edge probability [PR103270] Jeff Law
2021-12-13 9:25 ` Jan Hubicka
2021-12-14 9:27 ` Xionghu Luo
2021-12-15 6:40 ` Xionghu Luo
2021-12-16 11:18 ` Jan Hubicka
2021-12-21 3:56 ` Xionghu Luo
2021-12-08 5:54 ` [PATCH 3/3] Fix loop split incorrect count and probability Xionghu Luo
2021-12-08 23:47 ` Jeff Law
2021-12-13 8:57 ` Xionghu Luo
2021-12-21 3:57 ` Xionghu Luo
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