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Re: No integral promotions when calling library function?
On Fri, Feb 19, 2010 at 12:03 AM, Dave Korn
<dave.korn.cygwin@googlemail.com> wrote:
> On 18/02/2010 07:17, Jie Zhang wrote:
>> We are trying to add a 16bit integer division library function for
>> bfin port. I just found GCC didn't do integral promotions when calling
>> library function.
>
>> Is this expected?
>
> ?I wasn't aware of this myself, but it kind-of makes sense given the way that
> macros such as FUNCTION_ARG and INIT_CUMULATIVE_ARGS don't get passed any type
> info in the case of libcalls; I'm guessing here, but that would imply to me
> that all libcalls are effectively using unnamed stdargs-style arg passing.
> Not sure how to check this theory without extensively reading the source
> though. ?I imagine it's done for efficiency, and there should always be
> libcall functions existing for the precise types you're passing?
>
I'm trying to use an existing division function as a library function.
This existing function does unsigned 16bit integral division and
expects both arguments have been zero extended to 32bit. It's a little
surprise for me that GCC does not do the promotion when calling
library function even TARGET_PROMOTE_PROTOTYPES is defined. I can
adjust the division function accordingly. But before I do that, I'd
like to know if library functions should follow the same convention as
the normal ones or not.
Jie