On Thu, Apr 11, 2013 at 1:05 PM, Sriraman Tallam <tmsri...@google.com> wrote:
> On Thu, Apr 11, 2013 at 12:43 PM, Xinliang David Li <davi...@google.com>
> wrote:
>> What is the compile time impact for turning it on? Code not including
>> the intrinsic headers should not be affected too much. If the impact
>> is small, why not turning on this option by default -- which seems to
>> be the behavior of ICC.
>
> I will get back with data on this.
>
>>
>> With this option, all functions without the appropriate target options
>> will be allowed to reference not supported builtins, without warnings
>> or errors. Is it possible to delay the check till the builtin
>> expansion time?
>
> Right now, an error is generated if a function accesses an unsupported
> builtin. Since the intrinsic functions are marked inline and call some
> target builtin, this will always be caught.
To be clear, same example without the target attribute and with
-mgenerate-builtins results in an error:
#include <smmintrin.h>
__m128i foo(__m128i *V)
{
return _mm_stream_load_si128(V);
}
$ g++ test.cc -mgenerate-builtins
smmintrin.h:582:59: error: ‘__builtin_ia32_movntdqa’ needs isa option
-m32 -msse4.1
return (__m128i) __builtin_ia32_movntdqa ((__v2di *) __X);
>
> Sri
>
>>
>> thanks,
>>
>> David
>>
>> On Thu, Apr 11, 2013 at 12:05 PM, Sriraman Tallam <tmsri...@google.com>
>> wrote:
>>> Hi,
>>>
>>> *mmintrin headers does not work with function specific opts.
>>>
>>> Example 1:
>>>
>>>
>>> #include <smmintrin.h>
>>>
>>> __attribute__((target("sse4.1")))
>>> __m128i foo(__m128i *V)
>>> {
>>> return _mm_stream_load_si128(V);
>>> }
>>>
>>>
>>> $ g++ test.cc
>>> smmintrin.h:31:3: error: #error "SSE4.1 instruction set not enabled"
>>> # error "SSE4.1 instruction set not enabled"
>>>
>>> This error happens even though foo is marked "sse4.1"
>>>
>>> There are multiple issues at play here. One, the headers are guarded
>>> by macros that are switched on only when the target specific options,
>>> like -msse4.1 in this case, are present in the command line. Also, the
>>> target specific builtins, like __builtin_ia32_movntdqa called by
>>> _mm_stream_load_si128, are exposed only in the presence of the
>>> appropriate target ISA option.
>>>
>>>
>>> I have attached a patch that fixes this. I have added an option
>>> "-mgenerate-builtins" that will do two things. It will define a macro
>>> "__ALL_ISA__" which will expose the *intrin.h functions. It will also
>>> expose all the target specific builtins. -mgenerate-builtins will not
>>> affect code generation.
>>>
>>> This feature will greatly benefit the function multiversioning usability
>>> too.
>>>
>>> Comments?
>>>
>>> Thanks
>>> Sri
