On Thu, Oct 05, 2023 at 01:52:30PM +0200, Jan Hubicka wrote:
> > From: Sergei Trofimovich <siarh...@google.com>
> >
> > r14-3459-g0c78240fd7d519 "Check that passes do not forget to define profile"
> > exposed check failures in cases when gcc produces uninitialized profile
> > probabilities. In case of PR/111559 uninitialized profile is generated
> > by edges executed 0 times reported by IPA profile:
> >
> > $ gcc -O2 -fprofile-generate pr111559.c -o b -fopt-info
> > $ ./b
> > $ gcc -O2 -fprofile-use -fprofile-correction pr111559.c -o b -fopt-info
> >
> > pr111559.c: In function 'rule1':
> > pr111559.c:6:13: error: probability of edge 3->4 not initialized
> > 6 | static void rule1(void) { if (p) edge(); }
> > | ^~~~~
> > during GIMPLE pass: fixup_cfg
> > pr111559.c:6:13: internal compiler error: verify_flow_info failed
> >
> > The change conservatively ignores updates with uninitialized values and
> > uses initially assigned probabilities (`always` probability in case of
> > the example).
> >
> > PR ipa/111283
> > PR gcov-profile/111559
> >
> > gcc/
> > * ipa-utils.cc (ipa_merge_profiles): Avoid producing
> > uninitialized probabilities when merging counters with zero
> > denominators.
> >
> > gcc/testsuite/
> > * gcc.dg/tree-prof/pr111559.c: New test.
> > ---
> > gcc/ipa-utils.cc | 6 +++++-
> > gcc/testsuite/gcc.dg/tree-prof/pr111559.c | 16 ++++++++++++++++
> > 2 files changed, 21 insertions(+), 1 deletion(-)
> > create mode 100644 gcc/testsuite/gcc.dg/tree-prof/pr111559.c
> >
> > diff --git a/gcc/ipa-utils.cc b/gcc/ipa-utils.cc
> > index 956c6294fd7..7c53ae9dd45 100644
> > --- a/gcc/ipa-utils.cc
> > +++ b/gcc/ipa-utils.cc
> > @@ -651,13 +651,17 @@ ipa_merge_profiles (struct cgraph_node *dst,
> > {
> > edge srce = EDGE_SUCC (srcbb, i);
> > edge dste = EDGE_SUCC (dstbb, i);
> > - dste->probability =
> > + profile_probability merged =
> > dste->probability * dstbb->count.ipa ().probability_in
> > (dstbb->count.ipa ()
> > + srccount.ipa ())
> > + srce->probability * srcbb->count.ipa ().probability_in
> > (dstbb->count.ipa ()
> > + srccount.ipa ());
> > + /* We produce uninitialized probabilities when
> > + denominator is zero: https://gcc.gnu.org/PR111559. */
> > + if (merged.initialized_p ())
> > + dste->probability = merged;
>
> Thanks for the patch.
> We usually avoid the uninitialized value here by simply checking that
> parameter of probability_in satifies nonzero_p. So I think it would be
> more consistent doing it here to:
>
> profile_probability sum = dstbb->count.ipa () + srccount.ipa ()
> if (sum.nonzero_p ())
> {
> dste->probability = .....
> }
Aha, sounds good! I had to do `s/profile_probability/profile_count` as
it's a denominator value for probability.
Attached v3 just in case.
> OK with this change.
> Honza
> > }
> > dstbb->count = dstbb->count.ipa () + srccount.ipa ();
> > }
> > diff --git a/gcc/testsuite/gcc.dg/tree-prof/pr111559.c
> > b/gcc/testsuite/gcc.dg/tree-prof/pr111559.c
> > new file mode 100644
> > index 00000000000..43202c6c888
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/tree-prof/pr111559.c
> > @@ -0,0 +1,16 @@
> > +/* { dg-options "-O2" } */
> > +
> > +__attribute__((noipa)) static void edge(void) {}
> > +
> > +int p = 0;
> > +
> > +__attribute__((noinline))
> > +static void rule1(void) { if (p) edge(); }
> > +
> > +__attribute__((noinline))
> > +static void rule1_same(void) { if (p) edge(); }
> > +
> > +__attribute__((noipa)) int main(void) {
> > + rule1();
> > + rule1_same();
> > +}
> > --
> > 2.42.0
> >
--
Sergei
>From 97122ebae5a7ed43b6c31574c761a54bee3a96ec Mon Sep 17 00:00:00 2001
From: Sergei Trofimovich <siarh...@google.com>
Date: Wed, 27 Sep 2023 14:29:12 +0100
Subject: [PATCH v3] ipa-utils: avoid uninitialized probabilities on ICF
[PR111559]
r14-3459-g0c78240fd7d519 "Check that passes do not forget to define profile"
exposed check failures in cases when gcc produces uninitialized profile
probabilities. In case of PR/111559 uninitialized profile is generated
by edges executed 0 times reported by IPA profile:
$ gcc -O2 -fprofile-generate pr111559.c -o b -fopt-info
$ ./b
$ gcc -O2 -fprofile-use -fprofile-correction pr111559.c -o b -fopt-info
pr111559.c: In function 'rule1':
pr111559.c:6:13: error: probability of edge 3->4 not initialized
6 | static void rule1(void) { if (p) edge(); }
| ^~~~~
during GIMPLE pass: fixup_cfg
pr111559.c:6:13: internal compiler error: verify_flow_info failed
The change conservatively ignores updates with zero execution counts and
uses initially assigned probabilities (`always` probability in case of
the example).
PR ipa/111283
PR gcov-profile/111559
gcc/
* ipa-utils.cc (ipa_merge_profiles): Avoid producing
uninitialized probabilities when merging counters with zero
denominators.
gcc/testsuite/
* gcc.dg/tree-prof/pr111559.c: New test.
---
gcc/ipa-utils.cc | 17 ++++++++++-------
gcc/testsuite/gcc.dg/tree-prof/pr111559.c | 16 ++++++++++++++++
2 files changed, 26 insertions(+), 7 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/tree-prof/pr111559.c
diff --git a/gcc/ipa-utils.cc b/gcc/ipa-utils.cc
index 956c6294fd7..1355ccac6f0 100644
--- a/gcc/ipa-utils.cc
+++ b/gcc/ipa-utils.cc
@@ -651,13 +651,16 @@ ipa_merge_profiles (struct cgraph_node *dst,
{
edge srce = EDGE_SUCC (srcbb, i);
edge dste = EDGE_SUCC (dstbb, i);
- dste->probability =
- dste->probability * dstbb->count.ipa ().probability_in
- (dstbb->count.ipa ()
- + srccount.ipa ())
- + srce->probability * srcbb->count.ipa ().probability_in
- (dstbb->count.ipa ()
- + srccount.ipa ());
+ profile_count sum =
+ dstbb->count.ipa () + srccount.ipa ();
+ if (sum.nonzero_p ())
+ dste->probability =
+ dste->probability * dstbb->count.ipa ().probability_in
+ (dstbb->count.ipa ()
+ + srccount.ipa ())
+ + srce->probability * srcbb->count.ipa ().probability_in
+ (dstbb->count.ipa ()
+ + srccount.ipa ());
}
dstbb->count = dstbb->count.ipa () + srccount.ipa ();
}
diff --git a/gcc/testsuite/gcc.dg/tree-prof/pr111559.c
b/gcc/testsuite/gcc.dg/tree-prof/pr111559.c
new file mode 100644
index 00000000000..43202c6c888
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-prof/pr111559.c
@@ -0,0 +1,16 @@
+/* { dg-options "-O2" } */
+
+__attribute__((noipa)) static void edge(void) {}
+
+int p = 0;
+
+__attribute__((noinline))
+static void rule1(void) { if (p) edge(); }
+
+__attribute__((noinline))
+static void rule1_same(void) { if (p) edge(); }
+
+__attribute__((noipa)) int main(void) {
+ rule1();
+ rule1_same();
+}
--
2.42.0
