[PATCH v7] Missed function specialization + partial devirtualization

[David Malcolm]

On Mon, 2020-01-13 at 11:23 +0800, luoxhu wrote:
> On 2020/1/10 19:08, Jan Hubicka wrote:
> > OK. You will need to do the obvious updates for Martin's patch
> > which turned some member functions into static functions.
> > 
> > Honza
> 
> Thanks a lot!  Rebased & updated, will commit below patch shortly
> when git push is ready.
> 
> 
> v8:
>  1. Rebase to master with Martin's static function (r280043) comments
> merge.
>     Boostrap/testsuite/SPEC2017 tested pass on Power8-LE.
>  2. TODO:
>     2.1. C++ devirt for multiple speculative call targets.
>     2.2. ipa-icf ipa_merge_profiles refine with COMDAT inline
> testcase.

[...]

> diff --git a/gcc/ipa-profile.c b/gcc/ipa-profile.c

[...]

> +static ipa_profile_call_summaries *call_sums = NULL;

[...]
 
>  static void
>  ipa_profile_generate_summary (void)
> @@ -169,7 +261,10 @@ ipa_profile_generate_summary (void)
>    basic_block bb;
>  
>    hash_table<histogram_hash> hashtable (10);
> -  
> +
> +  gcc_checking_assert (!call_sums);
> +  call_sums = new ipa_profile_call_summaries (symtab);
> +

[...]

Unfortunately, this assertion is failing for most of the testcases in
jit.dg, reducing the number of PASS results in jit.sum from 10473 down
to 3254 in my builds.


Counter-intuitively, "jit" is not in --enable-languages=all (as it also
needs --enable-host-shared at configure time, which slows down the
built compiler code).


The jit code expects to be able to invoke the compiler code more than
once within the same process, purging all state.

It looks like this "call_sums" state needs deleting and resetting to
NULL after the compiler has run (or else we'll likely get an ICE due to
using old symtab/call summaries in subsequent in-process runs of the
compiler).

Is there a natural place to do that within the IPA hooks?  


Alternatively the following patch seems to fix things (not yet fully
tested though); hopefully it seems sane.

gcc/ChangeLog:
        * ipa-profile.c (ipa_profile_c_finalize): New function.
        * toplev.c (toplev::finalize): Call it.
        * toplev.h (ipa_profile_c_finalize): New decl.
---
 gcc/ipa-profile.c | 10 ++++++++++
 gcc/toplev.c      |  1 +
 gcc/toplev.h      |  2 ++
 3 files changed, 13 insertions(+)

diff --git a/gcc/ipa-profile.c b/gcc/ipa-profile.c
index fc231c916b7..699419ead19 100644
--- a/gcc/ipa-profile.c
+++ b/gcc/ipa-profile.c
@@ -1069,3 +1069,13 @@ make_pass_ipa_profile (gcc::context *ctxt)
 {
   return new pass_ipa_profile (ctxt);
 }
+
+/* Reset all state within ipa-profile.c so that we can rerun the compiler
+   within the same process.  For use by toplev::finalize.  */
+
+void
+ipa_profile_c_finalize ()
+{
+  delete call_sums;
+  call_sums = NULL;
+}
diff --git a/gcc/toplev.c b/gcc/toplev.c
index 4c8be502c71..ca0515583c7 100644
--- a/gcc/toplev.c
+++ b/gcc/toplev.c
@@ -2453,6 +2453,7 @@ toplev::finalize (void)
   this_target_rtl->target_specific_initialized = false;
 
   /* Needs to be called before cgraph_c_finalize since it uses symtab.  */
+  ipa_profile_c_finalize ();
   ipa_reference_c_finalize ();
   ipa_fnsummary_c_finalize ();
 
diff --git a/gcc/toplev.h b/gcc/toplev.h
index d6c316962b0..10611691608 100644
--- a/gcc/toplev.h
+++ b/gcc/toplev.h
@@ -103,4 +103,6 @@ extern void parse_alignment_opts (void);
 
 extern void initialize_rtl (void);
 
+extern void ipa_profile_c_finalize (void);
+
 #endif /* ! GCC_TOPLEV_H */
-- 
2.21.0