[PATCH] Improve RTL ifcvt for empty else_bb (PR rtl-optimization/80491)

[Jeff Law]

On 04/26/2017 05:25 AM, Jakub Jelinek wrote:
> On Tue, Apr 25, 2017 at 09:31:00PM +0200, Jakub Jelinek wrote:
>> This patch let us search for x's setter earlier in the bb.
>> During testing I found that modified_in_p/modified_in_between_p don't
>> actually take into account calls that could change MEMs, so the patch
>> handles that too.
> 
> Or shall we just:
> --- gcc/alias.c	2017-04-25 15:51:31.072923325 +0200
> +++ gcc/alias.c	2017-04-26 13:23:55.595048464 +0200
> @@ -3221,6 +3221,8 @@ memory_modified_in_insn_p (const_rtx mem
>   {
>     if (!INSN_P (insn))
>       return false;
> +  if (CALL_P (insn))
> +    return true;
>     memory_modified = false;
>     note_stores (PATTERN (insn), memory_modified_1, CONST_CAST_RTX(mem));
>     return memory_modified;
> 
> instead of the call_crossed hacks?  Then modified_between_p and
> modified_in_p would return true for !MEM_READONLY_P MEMs crossing a call.
This seems like a good idea as well.  I'm a bit surprised we're not 
handling it this way already.  If you want to go w ith this and simplify 
the patch for 80491, that's fine too.

jeff