Re: [PATCH 7/7] Plug ipa-prop escape analysis into gimple_call_arg_flags

[Richard Biener <richard dot guenther at gmail dot com>]

On Wed, May 21, 2014 at 3:16 PM, Martin Jambor <mjambor@suse.cz> wrote:
> Hi,
>
> this demonstrates how results of ipa-prop escape analysis from
> previous patches can be used at a later stage of compilation by
> directly returning them from gimple_call_arg_flags which currently
> relies on fnspec annotations.
>
> Bootstrapped and tested on x86_64-linux and also passes LTO bootstrap.
> I have only had a brief look at behavior of this in SPEC 2006 and for
> example in astar 1.19% of invocations of gimple_call_arg_flags return
> noescape where we previously never did and in calculix this increases
> from 15.62% (from annotations) to 18.14%.  Noclobber flag is reported
> far less often still but for example in gamess that number raises from
> 5.21% to 7.66%.
>
> Thanks,
>
> Martin
>
>
> 2014-04-30  Martin Jambor  <mjambor@suse.cz>
>
>         * gimple.c: Include cgraph.h.
>         (gimple_call_arg_flags): Also query bitmaps in cgraph_node.
>
> Index: src/gcc/gimple.c
> ===================================================================
> --- src.orig/gcc/gimple.c
> +++ src/gcc/gimple.c
> @@ -47,7 +47,7 @@ along with GCC; see the file COPYING3.
>  #include "demangle.h"
>  #include "langhooks.h"
>  #include "bitmap.h"
> -
> +#include "cgraph.h"
>
>  /* All the tuples have their operand vector (if present) at the very bottom
>     of the structure.  Therefore, the offset required to find the
> @@ -1349,32 +1349,50 @@ int
>  gimple_call_arg_flags (const_gimple stmt, unsigned arg)
>  {
>    tree attr = gimple_call_fnspec (stmt);
> +  int ret;
>
> -  if (!attr || 1 + arg >= (unsigned) TREE_STRING_LENGTH (attr))
> -    return 0;
> -
> -  switch (TREE_STRING_POINTER (attr)[1 + arg])
> +  if (attr && 1 + arg < (unsigned) TREE_STRING_LENGTH (attr))
>      {
> -    case 'x':
> -    case 'X':
> -      return EAF_UNUSED;
> -
> -    case 'R':
> -      return EAF_DIRECT | EAF_NOCLOBBER | EAF_NOESCAPE;
> -
> -    case 'r':
> -      return EAF_NOCLOBBER | EAF_NOESCAPE;
> -
> -    case 'W':
> -      return EAF_DIRECT | EAF_NOESCAPE;
> -
> -    case 'w':
> -      return EAF_NOESCAPE;
> +      switch (TREE_STRING_POINTER (attr)[1 + arg])
> +       {
> +       case 'x':
> +       case 'X':
> +         ret = EAF_UNUSED;
> +         break;
> +       case 'R':
> +         ret = EAF_DIRECT | EAF_NOCLOBBER | EAF_NOESCAPE;
> +         break;
> +       case 'r':
> +         ret = EAF_NOCLOBBER | EAF_NOESCAPE;
> +         break;
> +       case 'W':
> +         ret = EAF_DIRECT | EAF_NOESCAPE;
> +         break;
> +       case 'w':
> +         ret = EAF_NOESCAPE;
> +         break;
> +       case '.':
> +       default:
> +         ret = 0;
> +       }
> +    }
> +  else
> +    ret = 0;
>
> -    case '.':
> -    default:
> -      return 0;
> +  tree callee_decl = gimple_call_fndecl (stmt);
> +  if (callee_decl)
> +    {
> +      cgraph_node *callee_node = cgraph_get_node (callee_decl);
> +      if (callee_node)
> +       {
> +         if (cgraph_param_noescape_p (callee_node, arg))
> +           ret |= EAF_NOESCAPE;
> +         if (cgraph_param_noclobber_p (callee_node, arg))
> +           ret |= EAF_NOCLOBBER;

That's quite expensive.  I guess we need a better way to store
those?

> +       }
>      }
> +
> +  return ret;
>  }
>
>  /* Detects return flags for the call STMT.  */
>