> On September 26, 2020 12:04:24 AM GMT+02:00, Jan Hubicka <hubi...@ucw.cz>
> wrote:
> >Hi,
> >while adding check for gimple_clobber I reversed the return value
> >so instead of ignoring the statement ipa-modref gives up. Fixed thus.
> >This explains the drop between originally reported disambinguations
> >stats and ones I got later.
>
> I don't think you can ignore clobbers. They are barriers for code motion.
Hi,
this is fix I have installed after lto-bootstrapping/regtesting.
The statistics for cc1plus are almost unchanged that is sort of expected
given that I only measure late optimization by getting dump from LTO.
Thank for pointing this out, it may have triggered a nasty wrong code
bug :)
Honza
Alias oracle query stats:
refs_may_alias_p: 63013346 disambiguations, 73204989 queries
ref_maybe_used_by_call_p: 141350 disambiguations, 63909728 queries
call_may_clobber_ref_p: 23597 disambiguations, 29430 queries
nonoverlapping_component_refs_p: 0 disambiguations, 37763 queries
nonoverlapping_refs_since_match_p: 19444 disambiguations, 55671 must
overlaps, 75884 queries
aliasing_component_refs_p: 54749 disambiguations, 753947 queries
TBAA oracle: 24159888 disambiguations 56277876 queries
16064485 are in alias set 0
10340953 queries asked about the same object
125 queries asked about the same alias set
0 access volatile
3920604 are dependent in the DAG
1791821 are aritificially in conflict with void *
Modref stats:
modref use: 10444 disambiguations, 46994 queries
modref clobber: 1421468 disambiguations, 1954304 queries
4907798 tbaa queries (2.511277 per modref query)
396785 base compares (0.203031 per modref query)
PTA query stats:
pt_solution_includes: 976073 disambiguations, 13607833 queries
pt_solutions_intersect: 1026016 disambiguations, 13185678 queries
* ipa-modref.c (analyze_stmt): Do not skip clobbers in early pass.
* ipa-pure-const.c (analyze_stmt): Update comment.
diff --git a/gcc/ipa-modref.c b/gcc/ipa-modref.c
index 73a7900883a..728c6c1523d 100644
--- a/gcc/ipa-modref.c
+++ b/gcc/ipa-modref.c
@@ -676,13 +676,16 @@ static bool
analyze_stmt (modref_summary *summary, gimple *stmt, bool ipa,
vec <gimple *> *recursive_calls)
{
- /* There is no need to record clobbers. */
- if (gimple_clobber_p (stmt))
+ /* In general we can not ignore clobbers because they are barries for code
+ motion, however after inlining it is safe to do becuase local optimization
+ passes do not consider clobbers from other functions.
+ Similar logic is in ipa-pure-consts. */
+ if ((ipa || cfun->after_inlining) && gimple_clobber_p (stmt))
return true;
+
/* Analyze all loads and stores in STMT. */
walk_stmt_load_store_ops (stmt, summary,
analyze_load, analyze_store);
- /* or call analyze_load_ipa, analyze_store_ipa */
switch (gimple_code (stmt))
{
@@ -705,7 +708,7 @@ analyze_stmt (modref_summary *summary, gimple *stmt, bool
ipa,
}
}
-/* Analyze function F. IPA indicates whether we're running in tree mode
(false)
+/* Analyze function F. IPA indicates whether we're running in local mode
(false)
or the IPA mode (true). */
static void
diff --git a/gcc/ipa-pure-const.c b/gcc/ipa-pure-const.c
index bdbccd010dc..1af3206056e 100644
--- a/gcc/ipa-pure-const.c
+++ b/gcc/ipa-pure-const.c
@@ -742,6 +742,8 @@ check_stmt (gimple_stmt_iterator *gsip, funct_state local,
bool ipa)
/* Do consider clobber as side effects before IPA, so we rather inline
C++ destructors and keep clobber semantics than eliminate them.
+ Similar logic is in ipa-modref.
+
TODO: We may get smarter during early optimizations on these and let
functions containing only clobbers to be optimized more. This is a common
case of C++ destructors. */
