[RFC] propagate malloc attribute in ipa-pure-const pass
Prathamesh Kulkarni
prathamesh.kulkarni@linaro.org
Mon Oct 23 09:37:00 GMT 2017
On 14 October 2017 at 03:20, Prathamesh Kulkarni
<prathamesh.kulkarni@linaro.org> wrote:
> On 7 October 2017 at 12:35, Prathamesh Kulkarni
> <prathamesh.kulkarni@linaro.org> wrote:
>> On 7 October 2017 at 11:23, Jan Hubicka <hubicka@ucw.cz> wrote:
>>>> 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 ?
>>>
>>> Don't you need to know that the returned pointer is new and does not alias
>>> with something else?
>> Yes, malloc_candidate_p enforces that locally by checking the returned
>> pointer is return value of callee and optionally has immediate uses
>> only within comparisons against 0. But whether the returned pointer is
>> new depends on whether callee itself can be annotated with malloc,
>> which is done in propagate_malloc.
>> IIUC pointer returned by a malloc annotated function, does not alias
>> anything else ?
>>
>> Thanks,
>> Prathamesh
>>>
>>> Honza
>>>>
>>>> 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.
> Hi Honza,
> I have done the suggested changes in this version.
> LTO Bootstrapped+tested on x86_64-unknown-linux-gnu, ppc64le-linux-gnu.
> Cross-tested on arm*-*-*, aarch64*-*-*
> Verified no functional regressions with SPEC2006.
> Would it be OK to commit this version of the patch ?
ping https://gcc.gnu.org/ml/gcc-patches/2017-10/msg00924.html
Thanks,
Prathamesh
>
> Thanks,
> Prathamesh
>>>> >
>>>> > OK with these changes. Thanks!
>>>> >
>>>> > Honza
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