Re: Pointer arithmetic

[Hendrik Greving <hendrik.greving.intel@gmail.com>]

Yes I guess otherwise you could never produce a complex address like
that. Actually I think I remember that day that I found that C
explicitly leaves it undefined and to the machine.
Thanks
Hendrik

On Wed, Aug 7, 2013 at 1:40 PM, Oleg Endo <oleg.endo@t-online.de> wrote:
> On Tue, 2013-07-09 at 09:37 -0700, Hendrik Greving wrote:
>> On a machine with ABI ILP32LL64:
>>
>> (insn 123 122 124 (nil) (set (reg:SI 392)
>>         (mem:SI (plus:SI (reg/v:SI 386)
>>                 (reg/v:SI 349)) [0 sec 0 space 0, cmsmode 0 S4 A32])) -1 (nil)
>>     (nil))
>>
>> If we support legitimate memory addresses like [r1+r2] (e.g. indexed
>> addresses), can the above RTL match such a load?
>
> On 32 bit address machines it should match.
>
>> I am asking because
>> of overflows, I am not sure how that part is defined, and where the
>> Spec is. What do I need to check in the backend for such a definition?
>> Is this POINTER_SIZE? E.g. what if the machine supports > 32 bits, who
>> is responsible to make sure that there is no overflow > 32 bits in
>> this case? Compiler? Assembler? Or even the user?
>
> AFAIK overflow is undefined and thus anything can happen.  Induction
> variable and loop optimizations may produce interesting things if
> addresses overflow.  For example, see
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55190
>
> Cheers,
> Oleg
>