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Re: Reserving a number of consecutive registers


Yes, I have done that and now am looking to limit those numbers. For
example, I don't copy back the ones that are not live-out registers.
It works well but I am have an issue when recompiling the whole
compiler.

I've simplified this to this, if in my reorg function, I do only this  :

    FOR_EACH_BB (bb)
    {
        bitmap regs_forw = BITMAP_ALLOC (&reg_obstack);
        bitmap_copy (regs_forw, df_get_live_in (bb));
        BITMAP_FREE (regs_forw);
    }

It fails here:
/home/beyler/cyclops64/src/cyclops64-gcc-4.3.2/libgcc/../gcc/libgcc2.c:
In function '__divdi3':
/home/beyler/cyclops64/src/cyclops64-gcc-4.3.2/libgcc/../gcc/libgcc2.c:1102:
internal compiler error: Segmentation fault

I'm looking into that now, am I allowed to be doing this in the reorg ?
#0  df_get_live_in (bb=0xb7a9c8ac) at
/home/beyler/cyclops64/src/cyclops64-gcc-4.3.2/gcc/df-problems.c:93
93          return DF_LR_IN (bb);

Or is there a way to know if I'm allowed to do that copy?
Thanks again,
Jc

On Thu, Apr 30, 2009 at 3:16 PM, Eric Botcazou <ebotcazou@adacore.com> wrote:
>> Let's say I want to rename register r6 to r15. I can safely do that in
>> the block if I know that r15 is not used in that basic block and that
>> r6 is not a live-out of the basic block.
>>
>> However, how to handle the case where r6 is a live-out ? Then, I would
>> have to make sure that r15 is not defined in another basic block, thus
>> destroying my new live-out value?
>>
>> It seems to be a cat-mouse game:
>>
>> - I could copy back r15 to r6 in that case though I would like to try
>> to not have to do that because that requires an extra copy at the end
>> of the block
>
> Yes, you need to make a copy in this case but its cost could be offsetted by
> the gain from the load_multiple. ?Or it could be eliminated by running a new
> instance of cprop_hardreg. ?You need to experiment and tune the pass.
>
> --
> Eric Botcazou
>


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