Re: move increase_alignment from simple to regular ipa pass

[Jan Hubicka <hubicka at ucw dot cz>]

> 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..

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);