This is the mail archive of the
gcc@gcc.gnu.org
mailing list for the GCC project.
Re: target specific builtin expansion (middle end and back end definition inconsistence problem?).
On Mon, Apr 23, 2012 at 8:03 PM, Ian Lance Taylor <iant@google.com> wrote:
> Feng LI <nemokingdom@gmail.com> writes:
>
>>>>>> Yes, you are right. But how could I reference to a backend defined builtin
>>>>>> function in the middle end (I need to generate the builtin function in the
>>>>>> middle end and expand it in x86 backend)?
>>>>>
>>>>> If the function doesn't have a machine-independent definition, then use
>>>>> a target hook.
>>>>
>>>> Then I remove the duplicate builtin definition in x86 backend.
>>>> I define the builtin function with built_in_class as BUILT_IN_MD in
>>>> builtins.def.
>>>
>>> Sorry, I meant use a target hook to actually generate the call
>>> expression. ?The target hook can refer to the target-specific builtin
>>> function.
>> Just for confirmation, do you mean by calling this hook:
>> targetm.builtin_decl (unsigned code, bool initialized_p)
>> in the middle end for getting the builtin definition in the backend?
>>
>> Probably I'm asking a silly question, when is the time of the initialization
>> of the backend builtin functions. I'm refering it in gcc middle end, near
>> OPENMP expansion (omp-low.c) pass.
>
> No, I mean adding a new target hook build_my_magic_call and calling
> that. ?That target hook would be build a call to the function.
>
> You haven't really described the background, so I suppose I don't know
> if this is appropriate. ?It's not the right approach if you want to
> contribute this back to GCC mainline, but then of course GCC mainline
> also doesn't want a target-specific function in builtins.def.
Just to add some 2 cents - target specific builtins are either covering
a generic concept (and thus can be created by the middle-end by
involving a target hook), or they can be completely target specific,
in which case they are _not_created by the middle-end at all.
Richard.
> Ian