move increase_alignment from simple to regular ipa pass

[Jan Hubicka]

> diff --git a/gcc/cgraph.h b/gcc/cgraph.h
> index ecafe63..41ac408 100644
> --- a/gcc/cgraph.h
> +++ b/gcc/cgraph.h
> @@ -1874,6 +1874,9 @@ public:
>       if we did not do any inter-procedural code movement.  */
>    unsigned used_by_single_function : 1;
>  
> +  /* Set if -fsection-anchors is set.  */
> +  unsigned section_anchor : 1;
> +
>  private:
>    /* Assemble thunks and aliases associated to varpool node.  */
>    void assemble_aliases (void);
> diff --git a/gcc/cgraphunit.c b/gcc/cgraphunit.c
> index 4bfcad7..e75d5c0 100644
> --- a/gcc/cgraphunit.c
> +++ b/gcc/cgraphunit.c
> @@ -800,6 +800,9 @@ varpool_node::finalize_decl (tree decl)
>       it is available to notice_global_symbol.  */
>    node->definition = true;
>    notice_global_symbol (decl);
> +
> +  node->section_anchor = flag_section_anchors;
> +
>    if (TREE_THIS_VOLATILE (decl) || DECL_PRESERVE_P (decl)
>        /* Traditionally we do not eliminate static variables when not
>  	 optimizing and when not doing toplevel reoder.  */
> diff --git a/gcc/common.opt b/gcc/common.opt
> index f0d7196..e497795 100644
> --- a/gcc/common.opt
> +++ b/gcc/common.opt
> @@ -1590,6 +1590,10 @@ fira-algorithm=
>  Common Joined RejectNegative Enum(ira_algorithm) Var(flag_ira_algorithm) Init(IRA_ALGORITHM_CB) Optimization
>  -fira-algorithm=[CB|priority] Set the used IRA algorithm.
>  
> +fipa-increase_alignment
> +Common Report Var(flag_ipa_increase_alignment) Init(0) Optimization
> +Option to gate increase_alignment ipa pass.
> +
>  Enum
>  Name(ira_algorithm) Type(enum ira_algorithm) UnknownError(unknown IRA algorithm %qs)
>  
> @@ -2133,7 +2137,7 @@ 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/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
> index a0db3a4..1482566 100644
> --- a/gcc/config/aarch64/aarch64.c
> +++ b/gcc/config/aarch64/aarch64.c
> @@ -8252,6 +8252,8 @@ aarch64_override_options (void)
>  
>    aarch64_register_fma_steering ();
>  
> +  /* Enable increase_alignment pass.  */
> +  flag_ipa_increase_alignment = 1;

I would rather enable it always on targets that do support anchors.
> diff --git a/gcc/lto/lto-symtab.c b/gcc/lto/lto-symtab.c
> index ce9e146..7f09f3a 100644
> --- a/gcc/lto/lto-symtab.c
> +++ b/gcc/lto/lto-symtab.c
> @@ -342,6 +342,13 @@ lto_symtab_merge (symtab_node *prevailing, symtab_node *entry)
>       The type compatibility checks or the completing of types has properly
>       dealt with most issues.  */
>  
> +  /* ??? is this assert necessary ?  */
> +  varpool_node *v_prevailing = dyn_cast<varpool_node *> (prevailing);
> +  varpool_node *v_entry = dyn_cast<varpool_node *> (entry);
> +  gcc_assert (v_prevailing && v_entry);
> +  /* section_anchor of prevailing_decl wins.  */
> +  v_entry->section_anchor = v_prevailing->section_anchor;
> +
Other flags are merged in lto_varpool_replace_node so please move this there.
> +/* 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 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;
> +      }

If you take address of function that has vectorizer enabled probably doesn't
imply need to increase alignment of that var. So please drop the loop.

You only want function that read/writes or takes address of the symbol. But
onthe other hand, you need to walk all aliases of the symbol by
call_for_symbol_and_aliases
> +
> +  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)
> @@ -914,9 +942,12 @@ increase_alignment (void)
>        tree decl = vnode->decl;
>        unsigned int alignment;
>  
> -      if ((decl_in_symtab_p (decl)
> -	  && !symtab_node::get (decl)->can_increase_alignment_p ())
> -	  || DECL_USER_ALIGN (decl) || DECL_ARTIFICIAL (decl))
> +      if (!vnode->section_anchor
> +	  || (decl_in_symtab_p (decl)
> +	      && !symtab_node::get (decl)->can_increase_alignment_p ())
> +	  || DECL_USER_ALIGN (decl)
> +	  || DECL_ARTIFICIAL (decl)
> +	  || !increase_alignment_p (vnode))

Incrementally we probably should do more testing whether the variable looks like
someting that can be vectorized, i.e. it contains array, has address taken or the
accesses are array accesses within loop.
This can be done by the analysis phase of the IPA pass inspecting the function
bodies.

I think it is important waste to bump up everything including error messages etc.
At least on i386 the effect on firefox datasegment of various alignment setting is
very visible.

Looks OK to me otherwise. please send updated patch.

Honza