Re: RFC: Automatically test IFUNC implementations

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Sun, Sep 23, 2012 at 6:02 PM, Andreas Jaeger <aj@suse.com> wrote:
> On 09/23/2012 06:05 PM, H.J. Lu wrote:
>>
>> Hi,
>>
>> http://sourceware.org/bugzilla/show_bug.cgi?id=14602
>>
>> shows that we need to test all IFUNC implementations as much as we can.
>> I created hjl/ifunc/test branch to automatically test IFUNC
>> implementations.  Its goals are
>>
>> 1. Provide an infrastructure to tests all implementations supported
>> on build machine automatically.
>
>
> Yes, this is something we really need.
>
>
>> 2. No changes to IFUNC selectors.
>> 3. Test the new IFUNC implementation by adding it to the list of
>> IFUNC functions.
>>
>> Change IFUNC selector is not the goal of this branch.  Any comments?
>
>
> I haven't looked at the branch in detail - and don't understand what you
> mean with 3.
>

Takes x86-64 memcpy as example,  libc-func.c has

extern __typeof (memcpy) __memcpy_sse2;
extern __typeof (memcpy) __memcpy_ssse3;
extern __typeof (memcpy) __memcpy_ssse3_back;

static const struct libc_func_test memcpy_list[] =
{
  LIBC_FUNC_INIT (__memcpy_ssse3_back),
  LIBC_FUNC_INIT (__memcpy_ssse3),
  LIBC_FUNC_INIT (__memcpy_sse2),
  { NULL, NULL },
};

static const struct libc_func_test *
find_memcpy (void)
{
  return memcpy_list + (HAS_SSSE3 ? 0 : 2);
}

const struct libc_func_test *
__libc_func (const char *name)
{
 ...
  if (strcmp (name, "memcpy") == 0)
    return find_memcpy ();

__libc_func ("memcpy") returns a list of memcpy functions
supported in build machine.  When we add an AVX optimized
memcpy,  all what we have to do is

extern __typeof (memcpy) __memcpy_sse2;
extern __typeof (memcpy) __memcpy_ssse3;
extern __typeof (memcpy) __memcpy_ssse3_back;
extern __typeof (memcpy) __memcpy_avx;

static const struct libc_func_test memcpy_list[] =
{
  LIBC_FUNC_INIT (__memcpy_avx),
  LIBC_FUNC_INIT (__memcpy_ssse3_back),
  LIBC_FUNC_INIT (__memcpy_ssse3),
  LIBC_FUNC_INIT (__memcpy_sse2),
  { NULL, NULL },
};

static const struct libc_func_test *
find_memcpy (void)
{
  return memcpy_list + (HAS_AVX ? 0 : (HAS_SSSE3 ? 1: 3));
}

Now AVX memcpy will be tested automatically on AVX
build machine.  This commit:

http://sourceware.org/git/?p=glibc.git;a=patch;h=9728fd2ccffac52c3ab3212158646b2e170c76a1

is an example to test new IFUNC implementations.

Thanks.

-- 
H.J.