Re: [RFC] propagate malloc attribute in ipa-pure-const pass

[Prathamesh Kulkarni <prathamesh.kulkarni@linaro.org>]

On 6 October 2017 at 06:04, Jan Hubicka <hubicka@ucw.cz> wrote:
>> Hi Honza,
>> Thanks for the detailed suggestions, I have updated the patch accordingly.
>> I have following questions on call_summary:
>> 1] I added field bool is_return_callee in ipa_call_summary to track
>> whether the caller possibly returns value returned by callee, which
>> gets rid of return_callees_map. I assume ipa_call_summary_t::remove()
>> and ipa_call_summary_t::duplicate() will already take care of handling
>> late insertion/removal of cgraph nodes ? I just initialized
>> is_return_callee to false in ipa_call_summary::reset and that seems to
>> work. I am not sure though if I have handled it correctly. Could you
>> please check that ?
>
> I was actually thinking to introduce separate summary for ipa-pure-const pass,
> but this seems fine to me too (for one bit definitly more effecient)
> ipa_call_summary_t::duplicate copies all the fields, so indeed you should be
> safe here.
>
> Also it is possible for functions to be inserted late.  Updating of call summaries
> is currently handled by ipa_fn_summary_t::insert
>>
>> 2] ipa_inline() called ipa_free_fn_summary, which made
>> ipa_call_summaries unavailable during ipa-pure-const pass. I removed
>> call to ipa_free_fn_summary from ipa_inline, and moved it to
>> ipa_pure_const::execute(). Is that OK ?
>
> Seems OK to me.
>>
>> Patch passes bootstrap+test and lto bootstrap+test on x86_64-unknown-linux-gnu.
>> Verfiied SPEC2k6 compiles and runs without miscompares with LTO
>> enabled on aarch64-linux-gnu.
>> Cross-tested on arm*-*-* and aarch64*-*-*. I will additionally test
>> the patch by building chromium or firefox.
>> Would it be OK to commit if it passes above validations ?
>>
>> Thanks,
>> Prathamesh
>> >
>> > Thanks,
>> > Honza
>
>> 2017-10-05  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>
>>
>>       * cgraph.h (set_malloc_flag): Declare.
>>       * cgraph.c (set_malloc_flag_1): New function.
>>       (set_malloc_flag): Likewise.
>>       * ipa-fnsummary.h (ipa_call_summary): Add new field is_return_callee.
>>       * ipa-fnsummary.c (ipa_call_summary::reset): Set is_return_callee to
>>       false.
>>       (read_ipa_call_summary): Add support for reading is_return_callee.
>>       (write_ipa_call_summary): Stream is_return_callee.
>>       * ipa-inline.c (ipa_inline): Remove call to ipa_free_fn_summary.
>>       * ipa-pure-const.c: Add headers ssa.h, alloc-pool.h, symbol-summary.h,
>>       ipa-prop.h, ipa-fnsummary.h.
>>       (malloc_state_e): Define.
>>       (malloc_state_names): Define.
>>       (funct_state_d): Add field malloc_state.
>>       (varying_state): Set malloc_state to STATE_MALLOC_BOTTOM.
>>       (check_retval_uses): New function.
>>       (malloc_candidate_p): Likewise.
>>       (analyze_function): Add support for malloc attribute.
>>       (pure_const_write_summary): Stream malloc_state.
>>       (pure_const_read_summary): Add support for reading malloc_state.
>>       (dump_malloc_lattice): New function.
>>       (propagate_malloc): New function.
>>       (ipa_pure_const::execute): Call propagate_malloc and
>>       ipa_free_fn_summary.
>>       (pass_local_pure_const::execute): Add support for malloc attribute.
>>       * ssa-iterators.h (RETURN_FROM_IMM_USE_STMT): New macro.
>>
>> testsuite/
>>       * gcc.dg/ipa/propmalloc-1.c: New test-case.
>>       * gcc.dg/ipa/propmalloc-2.c: Likewise.
>>       * gcc.dg/ipa/propmalloc-3.c: Likewise.
>>
>> diff --git a/gcc/cgraph.c b/gcc/cgraph.c
>> index 3d0cefbd46b..0aad90d59ea 100644
>> --- a/gcc/cgraph.c
>> +++ b/gcc/cgraph.c
>> @@ -2530,6 +2530,53 @@ cgraph_node::set_nothrow_flag (bool nothrow)
>>    return changed;
>>  }
>>
>> +/* Worker to set malloc flag.  */
> New line here I guess (it is below)
>> +static void
>> +set_malloc_flag_1 (cgraph_node *node, bool malloc_p, bool *changed)
>> +{
>> +  if (malloc_p && !DECL_IS_MALLOC (node->decl))
>> +    {
>> +      DECL_IS_MALLOC (node->decl) = true;
>> +      *changed = true;
>> +    }
>> +
>> +  ipa_ref *ref;
>> +  FOR_EACH_ALIAS (node, ref)
>> +    {
>> +      cgraph_node *alias = dyn_cast<cgraph_node *> (ref->referring);
>> +      if (!malloc_p || alias->get_availability () > AVAIL_INTERPOSABLE)
>> +     set_malloc_flag_1 (alias, malloc_p, changed);
>> +    }
>> +
>> +  for (cgraph_edge *e = node->callers; e; e = e->next_caller)
>> +    if (e->caller->thunk.thunk_p
>> +     && (!malloc_p || e->caller->get_availability () > AVAIL_INTERPOSABLE))
>> +      set_malloc_flag_1 (e->caller, malloc_p, changed);
>> +}
>> +
>> +/* Set DECL_IS_MALLOC on NODE's decl and on NODE's aliases if any.  */
>> +
>> +bool
>> +cgraph_node::set_malloc_flag (bool malloc_p)
>> +{
>> +  bool changed = false;
>> +
>> +  if (!malloc_p || get_availability () > AVAIL_INTERPOSABLE)
>> +    set_malloc_flag_1 (this, malloc_p, &changed);
>> +  else
>> +    {
>> +      ipa_ref *ref;
>> +
>> +      FOR_EACH_ALIAS (this, ref)
>> +     {
>> +       cgraph_node *alias = dyn_cast<cgraph_node *> (ref->referring);
>> +       if (!malloc_p || alias->get_availability () > AVAIL_INTERPOSABLE)
>> +         set_malloc_flag_1 (alias, malloc_p, &changed);
>> +     }
>> +    }
>> +  return changed;
>> +}
>> +
>> diff --git a/gcc/ipa-fnsummary.h b/gcc/ipa-fnsummary.h
>> index f50d6806e61..613a2b6f625 100644
>> --- a/gcc/ipa-fnsummary.h
>> +++ b/gcc/ipa-fnsummary.h
>> @@ -197,7 +197,9 @@ struct ipa_call_summary
>>    int call_stmt_time;
>>    /* Depth of loop nest, 0 means no nesting.  */
>>    unsigned int loop_depth;
>> -
>> +  /* Indicates whether the caller returns the value of it's callee.  */
> Perhaps add a comment when it is initialized.
> Don't you also check that the calle is not captured? In that case I would
> is_return_callee_uncaptured or so, so someone does not try to use it with
> different meaning.
Sorry, I didn't understand "Don't you also check that callee is not captured ?"
What does capturing mean in this context ?

Thanks,
Prathamesh
>
>> @@ -69,6 +74,15 @@ enum pure_const_state_e
>>
>>  const char *pure_const_names[3] = {"const", "pure", "neither"};
>>
>> +enum malloc_state_e
>> +{
>> +  STATE_MALLOC_TOP,
>> +  STATE_MALLOC,
>> +  STATE_MALLOC_BOTTOM
>> +};
>> +
>> +const char *malloc_state_names[] = {"malloc_top", "malloc", "malloc_bottom"};
>
> Seems static is missing in all those declarations, please fix it.
>
> OK with these changes. Thanks!
>
> Honza