Re: [PATCH] libgccjit: Add new gcc_jit_context_new_blob entry point

[Andrea Corallo <andrea.corallo@arm.com>]

Andrea Corallo <andrea.corallo@arm.com> writes:

>> It occurred to me that the entrypoint is combining two things:
>> - creating a global char[]
>> - creating an initializer for that global
>>
>> which got me wondering if we should instead have a way to add
>> initializers for globals.
>>
>> My first thought was something like:
>>
>> gcc_jit_context_new_global_with_initializer
>>
>> which would be like gcc_jit_context_new_global but would have an
>> additional gcc_jit_rvalue *init_value param?
>> The global would have to be of kind GCC_JIT_GLOBAL_EXPORTED or
>> GCC_JIT_GLOBAL_INTERNAL, not GCC_JIT_GLOBAL_IMPORTED.
>>
>> Alternatively, maybe it would be better to have
>>
>> gcc_jit_global_set_initializer (gcc_jit_lvalue *global,
>> 				gcc_jit_rvalue *init_val);
>>
>> to make the API more flexible.
>>
>> But even if we had this, we'd still need some way to create the rvalue
>> for that initial value.  Also, maybe there ought to be a distinction
>> between rvalues that can vary at runtime vs those that can be computed
>> at compile-time (and are thus suitable for use in static
>> initialization).
>>
>> I suspect you may have gone through the same thought process and come
>> up with a simpler approach.   (I'm mostly just "thinking out loud"
>> here, sorry if it isn't very coherent).
>
> Yes I had kind of similar thoughs.
>
> Ideally would be good to have a generic solution, the complication is
> that as you mentioned not every rvalue is suitable for initializing
> every global, but rather the opposite.  My fear was that the space to be
> covered would be non trivial for a robust solution in this case.
>
> Also I believe we currently have no way to express in libgccjit rvalues
> an array with some content, so how to use this as initializer?  Perhaps
> also we should have a new type gcc_jit_initializer?
>
> On the other hand I thought that for simple things like integers the
> problem is tipically already solved with an assignment in some init code
> (infact I think so far nobody complained) while the real standing
> limitation is for blobs (perhaps I'm wrong).  And in the end if you can
> stuff some data in, you can use it later for any scope.
>
> Another "hybrid" solution would be to have specific entry point for each
> type of the subset we want to allow for static initialization.  This way
> we still control the creation of the initializer internally so it's
> safe.  In this view this blob entry point would be just one of these
> (probably with a different name like
> 'gcc_jit_context_new_glob_init_char_array').
>

Hi Dave,

wanted to ask if you formed an opinion about the patch and/or more in
general the problem of static initialize data.

Thanks

  Andrea