Hello.
During investigation of another issue, I accidentally came a profile
inconsistency
mentioned in the PR. Problem is that flag_ipa_bit_cp is enabled in use stage of
PGO
and not in instrumentation stage. That causes ccp1 to find nonzero bits and
that leads
to a CFG changes as a condition can be folded away.
Solution is to enable the same flag in generate phase. However I've got one
more question:
In -fprofile-generate we have 2 more functions available in symtab:
_GLOBAL__sub_I_00100_0_c ()
{
<bb 2> [0.00%]:
__gcov_init (&*.LPBX0);
return;
}
_GLOBAL__sub_D_00100_1_c ()
{
<bb 2> [0.00%]:
__gcov_exit ();
return;
}
I'm wondering whether it can potentially influence early inlining decision?
Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.
Ready to be installed?
Martin
>From 170193b48d41b90bc8b0f73a7dce2c1933430fc1 Mon Sep 17 00:00:00 2001
From: marxin <mli...@suse.cz>
Date: Mon, 30 Jan 2017 10:55:36 +0100
Subject: [PATCH] Fix profile corruption with -O1 (PR gcov-profile/79259)
gcc/ChangeLog:
2017-01-30 Martin Liska <mli...@suse.cz>
PR gcov-profile/79259
* opts.c (common_handle_option): Enable flag_ipa_bit_cp w/
-fprofile-generate.
gcc/testsuite/ChangeLog:
2017-01-30 Martin Liska <mli...@suse.cz>
PR gcov-profile/79259
* g++.dg/tree-prof/pr79259.C: New test.
---
gcc/opts.c | 2 ++
gcc/testsuite/g++.dg/tree-prof/pr79259.C | 20 ++++++++++++++++++++
2 files changed, 22 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/tree-prof/pr79259.C
diff --git a/gcc/opts.c b/gcc/opts.c
index 5f573a16ff1..b38e9b4f3a7 100644
--- a/gcc/opts.c
+++ b/gcc/opts.c
@@ -2150,6 +2150,8 @@ common_handle_option (struct gcc_options *opts,
opts->x_flag_profile_values = value;
if (!opts_set->x_flag_inline_functions)
opts->x_flag_inline_functions = value;
+ if (!opts_set->x_flag_ipa_bit_cp)
+ opts->x_flag_ipa_bit_cp = value;
/* FIXME: Instrumentation we insert makes ipa-reference bitmaps
quadratic. Disable the pass until better memory representation
is done. */
diff --git a/gcc/testsuite/g++.dg/tree-prof/pr79259.C b/gcc/testsuite/g++.dg/tree-prof/pr79259.C
new file mode 100644
index 00000000000..a55172b62d2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/tree-prof/pr79259.C
@@ -0,0 +1,20 @@
+/* { dg-options "-O1" } */
+
+inline bool
+a (int b)
+{
+ return (b & 5) != b;
+}
+int c;
+int
+fn2 ()
+{
+ if (a (c == 0))
+ return 0;
+}
+
+int main()
+{
+ fn2();
+}
+
--
2.11.0
