On Fri, Mar 1, 2013 at 3:43 PM, Ian Lance Taylor <i...@google.com> wrote:
> On Fri, Mar 1, 2013 at 4:57 AM, Uros Bizjak <ubiz...@gmail.com> wrote:
>>
>> Due to the fact that libFFI does not handle C99 _Complex arguments
>> correctly [1], libgo passes Complex64 and Complex128 arguments via a
>> temporary structure. However, passing parts of complex number in a
>> structure is not the same as passing true C99 _Complex value, so this
>> workaround introduces ABI mismatch between caller and callee. This
>> mismatch results in wrong passed values of complex types.
>>
>> Fortunately all x86 ABIs tolerate this mismatch, but other targets
>> (i.e. alpha) don't have this privilege.
>
> Is there a PR open against libffi?
>
> Do we have any idea which targets pass complex in a manner different
> than a struct of two float/doubles? Your patch assumes that only x86
> targets work, but I would expect that many targets work that way.
$ grep -R "define TARGET_SPLIT_COMPLEX_ARG" config
config/rs6000/rs6000.c:#define TARGET_SPLIT_COMPLEX_ARG
hook_bool_const_tree_true
config/xtensa/xtensa.c:#define TARGET_SPLIT_COMPLEX_ARG
hook_bool_const_tree_true
config/alpha/alpha.c:#define TARGET_SPLIT_COMPLEX_ARG alpha_split_complex_arg
We can probably define Complex64 type as "struct { float re, im; }"
and Complex128 as "struct { double re, im; }" for these targets. What
do you think about this approach?
Uros.
