Question about filling multi delay slots

Question about filling multi delay slots

[Amker.Cheng]

Hi All :
   It's possible to define multi delay slots for branch insns by using
define_delay,
and different slot should satisfy its own attribute test "delay-n".

   Here comes question, in function "fill_simple_delay_slots", seems
it only uses
slots_filled to record how many slots needs to fill, and puts slot
insns already found
in delay_list. I can't find any codes keeping the information about
which insn in
delay_list belongs to which slot(defined in "define_delay"). So, how does gcc
make sure that insns in delay_list go into right delay slot?

Thanks in advance.
-- 
Best Regards.

Re: Question about filling multi delay slots

[Jeff Law]

On 11/25/09 07:34, Amker.Cheng wrote:
> Hi All :
>     It's possible to define multi delay slots for branch insns by using
> define_delay,
> and different slot should satisfy its own attribute test "delay-n".
>
>     Here comes question, in function "fill_simple_delay_slots", seems
> it only uses
> slots_filled to record how many slots needs to fill, and puts slot
> insns already found
> in delay_list. I can't find any codes keeping the information about
> which insn in
> delay_list belongs to which slot(defined in "define_delay"). So, how does gcc
> make sure that insns in delay_list go into right delay slot?
>    
First, it's worth noting very few targets support multiple delay slots 
and as a result that code isn't tested nearly as well as handling of 
single delay slots.

I'm pretty sure we assume that the first insn we add to the delay list 
always goes in the first slot, 2nd insn in the 2nd slot and so-on.

Jeff

Re: Question about filling multi delay slots

[Amker.Cheng]

On Tue, Dec 1, 2009 at 5:31 AM, Jeff Law <law@redhat.com> wrote:
> On 11/25/09 07:34, Amker.Cheng wrote:

>
> First, it's worth noting very few targets support multiple delay slots and
> as a result that code isn't tested nearly as well as handling of single
> delay slots.
>
> I'm pretty sure we assume that the first insn we add to the delay list
> always goes in the first slot, 2nd insn in the 2nd slot and so-on.
>
> Jeff
>
>
>
Thanks for explanation, I will take closer look into at these codes.


-- 
Best Regards.