Re: the failure in store motion

[Jan Hubicka <jh at suse dot cz>]

> Hmmm.
> Let me give this a try.
> As I said, it only fails miserably on x86, so it's likely something
> very specific to that platform (like this type of thing).
> Nope, doesn't help.
> Even this, more conservative version doesn't work:
> 
> static int
> store_killed_in_insn (x, insn)
>      rtx x, insn;
> {
>   rtx set;
>   if (!INSN_P (insn))
>     return 0;
>  
>   if (GET_CODE (insn) == CALL_INSN)
>     {
>         return 1;
>     }
>   if (volatile_insn_p (PATTERN (insn)))
>      return 1;
>   if (multiple_sets (insn))
>      return 1;
>   set = single_set (insn);
>   if (set)
>     {
>       /* Check for memory stores to aliased objects.  */
>       if (GET_CODE (SET_DEST (set)) == MEM && !expr_equiv_p (SET_DEST (set), x))
>         {
>         if (find_loads (SET_DEST (set), x))
>           return 1;
>         }
>       return find_loads (SET_SRC (set), x);
>     }
>   else
>     return find_loads (PATTERN (insn), x);
> }
> 
> (I also changed find_loads to look at set dests the same way
> store_killed_in_insn does, so that it can handle parallels).
> 
> Even if you just tell it to remove available stores, we add testsuite
> failures.
> 
> I wonder if it has to do with trapping or something? (We kill trapping
> stores on abnormal edges before performing the reverse LCM, but we
> don't kill them before we remove available loads)
I duno, but as store motion is exciting thing, can you please send me the
patch you use and tell me what exactly fail so I can try to investigate it?

I would love to see that beast working, so we will be able to kill
mem hoisting in loop optimizer for instance.  It is the important
amount of loop.c code and I would love to see the code motion in loop.c
dead, as it de-facto isn't doing anything more than gcse/pre/load/store motion
should.
> So store_killed_in_insn isn't quite right, even in the above version.
I will try to take a look if I can come with something more specific.

Honza
> 
> --Dan
> 
> -- 
> "When I was a baby, I kept a diary.  Recently, I was rereading
> it.  It said, "Day 1 -- Still tired from the move.  Day 2 --
> Everybody talks to me like I'm an idiot."
> "-Steven Wright