> 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 = .....
}
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
>
