Re: move increase_alignment from simple to regular ipa pass

[Richard Biener <rguenther at suse dot de>]

On Fri, 10 Jun 2016, Prathamesh Kulkarni wrote:

> On 10 June 2016 at 01:53, Jan Hubicka <hubicka@ucw.cz> wrote:
> >> On 8 June 2016 at 20:38, Jan Hubicka <hubicka@ucw.cz> wrote:
> >> >> I think it would be nice to work towards transitioning
> >> >> flag_section_anchors to a flag on varpool nodes, thereby removing
> >> >> the Optimization flag from common.opt:fsection-anchors
> >> >>
> >> >> That would simplify the walk over varpool candidates.
> >> >
> >> > Makes sense to me, too. There are more candidates for sutff that should be
> >> > variable specific in common.opt (such as variable alignment, -fdata-sctions,
> >> > -fmerge-constants) and targets.  We may try to do it in an easy to extend way
> >> > so incrementally we can get rid of those global flags, too.
> >> In this version I removed Optimization from fsection-anchors entry in
> >> common.opt,
> >> and gated the increase_alignment pass on flag_section_anchors != 0.
> >> Cross tested on arm*-*-*, aarch64*-*-*.
> >> Does it look OK ?
> >
> > If you go this way you will need to do something sane for LTO.  Here one can compile
> > some object files with -fsection-anchors and other without and link with random setting
> > (because in traditional compilation linktime flags does not matter).
> >
> > For global flags we have magic in merge_and_complain that determines flags to pass
> > to the LTO compiler.
> > It is not very robust though.
> >> >
> >> > One thing that needs to be done for LTO is sane merging, I guess in this case
> >> > it is clear that the variable should be anchored when its previaling definition
> >> > is.
> >> Um could we determine during WPA if symbol is a section anchor for merging ?
> >> Seems to me SYMBOL_REF_ANCHOR_P is defined only on DECL_RTL and not at
> >> tree level.
> >> Do we have DECL_RTL info available during WPA ?
> >
> > We don't have anchros computed, but we can decide whether we want to potentially
> > anchor the variable if we can.
> >
> > I would say all you need is to have section_anchor flag in varpool node itself
> > which controls RTL production. At varpool_finalize_decl you will set it
> > according to flag_varpool and stream it to LTO objects. At WPA when doing
> > linking, the section_anchor flag of the previaling decl wins..
> Thanks for the suggestions.
> IIUC, we want to add new section_anchor flag to varpool_node class
> and set it in varpool_node::finalize_decl and stream it to LTO byte-code,
> and then during WPA set section_anchor_flag during symbol merging if it is set
> for prevailing decl.

Yes.

> In the increase_alignment_pass if a vnode has section_anchor flag set,
> we will walk all functions that reference it to check if they have
> -ftree-loop-vectorize set.
> Is that correct ?

Yes.

> Could you please elaborate a bit more on "at varpool_finalize_decl you will
> set section_anchor flag according to flag_varpool" ?
> flag_varpool doesn't appear to be defined.

flag_section_anchors.

Richard.

> Thanks,
> Prathamesh
> >
> > Honza
> >>
> >> Thanks,
> >> Prathamesh
> >> >
> >> > Honza
> >> >>
> >> >> Richard.
> >> >>
> >> >> > Thanks,
> >> >> > Prathamesh
> >> >> > >
> >> >> > > Honza
> >> >> > >>
> >> >> > >> Richard.
> >> >> >
> >> >> >
> >> >>
> >> >> --
> >> >> Richard Biener <rguenther@suse.de>
> >> >> SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)
> >
> >> diff --git a/gcc/common.opt b/gcc/common.opt
> >> index f0d7196..f93f26c 100644
> >> --- a/gcc/common.opt
> >> +++ b/gcc/common.opt
> >> @@ -2133,7 +2133,7 @@ Common Report Var(flag_sched_dep_count_heuristic) Init(1) Optimization
> >>  Enable the dependent count heuristic in the scheduler.
> >>
> >>  fsection-anchors
> >> -Common Report Var(flag_section_anchors) Optimization
> >> +Common Report Var(flag_section_anchors)
> >>  Access data in the same section from shared anchor points.
> >>
> >>  fsee
> >> diff --git a/gcc/passes.def b/gcc/passes.def
> >> index 3647e90..3a8063c 100644
> >> --- a/gcc/passes.def
> >> +++ b/gcc/passes.def
> >> @@ -138,12 +138,12 @@ along with GCC; see the file COPYING3.  If not see
> >>    PUSH_INSERT_PASSES_WITHIN (pass_ipa_tree_profile)
> >>        NEXT_PASS (pass_feedback_split_functions);
> >>    POP_INSERT_PASSES ()
> >> -  NEXT_PASS (pass_ipa_increase_alignment);
> >>    NEXT_PASS (pass_ipa_tm);
> >>    NEXT_PASS (pass_ipa_lower_emutls);
> >>    TERMINATE_PASS_LIST (all_small_ipa_passes)
> >>
> >>    INSERT_PASSES_AFTER (all_regular_ipa_passes)
> >> +  NEXT_PASS (pass_ipa_increase_alignment);
> >>    NEXT_PASS (pass_ipa_whole_program_visibility);
> >>    NEXT_PASS (pass_ipa_profile);
> >>    NEXT_PASS (pass_ipa_icf);
> >> diff --git a/gcc/testsuite/gcc.dg/vect/aligned-section-anchors-vect-73.c b/gcc/testsuite/gcc.dg/vect/aligned-section-anchors-vect-73.c
> >> new file mode 100644
> >> index 0000000..74eaed8
> >> --- /dev/null
> >> +++ b/gcc/testsuite/gcc.dg/vect/aligned-section-anchors-vect-73.c
> >> @@ -0,0 +1,25 @@
> >> +/* { dg-do compile } */
> >> +/* { dg-require-effective-target section_anchors } */
> >> +/* { dg-require-effective-target vect_int } */
> >> +
> >> +#define N 32
> >> +
> >> +/* Clone of section-anchors-vect-70.c with foo() having -fno-tree-loop-vectorize.  */
> >> +
> >> +static struct A {
> >> +  int p1, p2;
> >> +  int e[N];
> >> +} a, b, c;
> >> +
> >> +__attribute__((optimize("-fno-tree-loop-vectorize")))
> >> +int foo(void)
> >> +{
> >> +  for (int i = 0; i < N; i++)
> >> +    a.e[i] = b.e[i] + c.e[i];
> >> +
> >> +   return a.e[0];
> >> +}
> >> +
> >> +/* { dg-final { scan-ipa-dump-times "Increasing alignment of decl" 0 "increase_alignment" { target aarch64*-*-* } } } */
> >> +/* { dg-final { scan-ipa-dump-times "Increasing alignment of decl" 0 "increase_alignment" { target powerpc64*-*-* } } } */
> >> +/* { dg-final { scan-ipa-dump-times "Increasing alignment of decl" 0 "increase_alignment" { target arm*-*-* } } } */
> >> diff --git a/gcc/tree-pass.h b/gcc/tree-pass.h
> >> index 36299a6..d36aa1d 100644
> >> --- a/gcc/tree-pass.h
> >> +++ b/gcc/tree-pass.h
> >> @@ -483,7 +483,7 @@ extern simple_ipa_opt_pass *make_pass_local_optimization_passes (gcc::context *c
> >>
> >>  extern ipa_opt_pass_d *make_pass_ipa_whole_program_visibility (gcc::context
> >>                                                              *ctxt);
> >> -extern simple_ipa_opt_pass *make_pass_ipa_increase_alignment (gcc::context
> >> +extern ipa_opt_pass_d *make_pass_ipa_increase_alignment (gcc::context
> >>                                                             *ctxt);
> >>  extern ipa_opt_pass_d *make_pass_ipa_inline (gcc::context *ctxt);
> >>  extern simple_ipa_opt_pass *make_pass_ipa_free_lang_data (gcc::context *ctxt);
> >> diff --git a/gcc/tree-vectorizer.c b/gcc/tree-vectorizer.c
> >> index 2669813..d34e560 100644
> >> --- a/gcc/tree-vectorizer.c
> >> +++ b/gcc/tree-vectorizer.c
> >> @@ -899,6 +899,34 @@ get_vec_alignment_for_type (tree type)
> >>    return (alignment > TYPE_ALIGN (type)) ? alignment : 0;
> >>  }
> >>
> >> +/* Return true if alignment should be increased for this vnode.
> >> +   This is done if every function that references/referring to vnode
> >> +   has flag_tree_loop_vectorize and flag_section_anchors set.  */
> >> +
> >> +static bool
> >> +increase_alignment_p (varpool_node *vnode)
> >> +{
> >> +  ipa_ref *ref;
> >> +
> >> +  for (int i = 0; vnode->iterate_reference (i, ref); i++)
> >> +    if (cgraph_node *cnode = dyn_cast<cgraph_node *> (ref->referred))
> >> +      {
> >> +     struct cl_optimization *opts = opts_for_fn (cnode->decl);
> >> +     if (!opts->x_flag_tree_loop_vectorize)
> >> +       return false;
> >> +      }
> >> +
> >> +  for (int i = 0; vnode->iterate_referring (i, ref); i++)
> >> +    if (cgraph_node *cnode = dyn_cast<cgraph_node *> (ref->referring))
> >> +      {
> >> +     struct cl_optimization *opts = opts_for_fn (cnode->decl);
> >> +     if (!opts->x_flag_tree_loop_vectorize)
> >> +       return false;
> >> +      }
> >> +
> >> +  return true;
> >> +}
> >> +
> >>  /* Entry point to increase_alignment pass.  */
> >>  static unsigned int
> >>  increase_alignment (void)
> >> @@ -916,7 +944,8 @@ increase_alignment (void)
> >>
> >>        if ((decl_in_symtab_p (decl)
> >>         && !symtab_node::get (decl)->can_increase_alignment_p ())
> >> -       || DECL_USER_ALIGN (decl) || DECL_ARTIFICIAL (decl))
> >> +       || DECL_USER_ALIGN (decl) || DECL_ARTIFICIAL (decl)
> >> +       || !increase_alignment_p (vnode))
> >>       continue;
> >>
> >>        alignment = get_vec_alignment_for_type (TREE_TYPE (decl));
> >> @@ -938,7 +967,7 @@ namespace {
> >>
> >>  const pass_data pass_data_ipa_increase_alignment =
> >>  {
> >> -  SIMPLE_IPA_PASS, /* type */
> >> +  IPA_PASS, /* type */
> >>    "increase_alignment", /* name */
> >>    OPTGROUP_LOOP | OPTGROUP_VEC, /* optinfo_flags */
> >>    TV_IPA_OPT, /* tv_id */
> >> @@ -949,17 +978,26 @@ const pass_data pass_data_ipa_increase_alignment =
> >>    0, /* todo_flags_finish */
> >>  };
> >>
> >> -class pass_ipa_increase_alignment : public simple_ipa_opt_pass
> >> +class pass_ipa_increase_alignment : public ipa_opt_pass_d
> >>  {
> >>  public:
> >>    pass_ipa_increase_alignment (gcc::context *ctxt)
> >> -    : simple_ipa_opt_pass (pass_data_ipa_increase_alignment, ctxt)
> >> +    : ipa_opt_pass_d (pass_data_ipa_increase_alignment, ctxt,
> >> +                        NULL, /* generate_summary  */
> >> +                        NULL, /* write summary  */
> >> +                        NULL, /* read summary  */
> >> +                        NULL, /* write optimization summary  */
> >> +                        NULL, /* read optimization summary  */
> >> +                        NULL, /* stmt fixup  */
> >> +                        0, /* function_transform_todo_flags_start  */
> >> +                        NULL, /* transform function  */
> >> +                        NULL )/* variable transform  */
> >>    {}
> >>
> >>    /* opt_pass methods: */
> >>    virtual bool gate (function *)
> >>      {
> >> -      return flag_section_anchors && flag_tree_loop_vectorize;
> >> +      return flag_section_anchors != 0;
> >>      }
> >>
> >>    virtual unsigned int execute (function *) { return increase_alignment (); }
> >> @@ -968,7 +1006,7 @@ public:
> >>
> >>  } // anon namespace
> >>
> >> -simple_ipa_opt_pass *
> >> +ipa_opt_pass_d *
> >>  make_pass_ipa_increase_alignment (gcc::context *ctxt)
> >>  {
> >>    return new pass_ipa_increase_alignment (ctxt);
> >
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)