[Bug rtl-optimization/44194] struct returned by value generates useless stores

[rguenther at suse dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44194

--- Comment #14 from rguenther at suse dot de <rguenther at suse dot de> 2011-04-15 19:31:36 UTC ---
On Fri, 15 Apr 2011, eraman at google dot com wrote:

> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44194
> 
> Easwaran Raman <eraman at google dot com> changed:
> 
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>                  CC|                            |eraman at google dot com
> 
> --- Comment #13 from Easwaran Raman <eraman at google dot com> 2011-04-15 19:18:25 UTC ---
> Richard, did you mean to write
> 
> static bool
> can_escape (tree expr)
> {
>   tree base;
>   if (!expr)
>     return true;
>   base = get_base_address (expr);
>   if (DECL_P (base)
>       && (!may_be_aliased (base)
>           && !pt_solution_includes (&cfun->gimple_df->escaped, base)))
>     return false;
>   return true;
> }
> 
> Only case when we know it doesn't escape is if bas is a DECL_P and is not in
> cfun->gimple_df->escaped and not aliased, right? Actually, I'm wondering if it
> is sufficient to test just
> DECL_P (base) && !pt_solution_includes (&cfun->gimple_df->escaped, base).

No, because if the escaped solution for example includes ANYTHING then
the test will return true.  That !may-aliased variables are not
contained in ANYTHING isn't known w/o context.

Richard.