Vc issue

[Matthias Kretz]

Hi,

I just found a workaround in ICC's zmmintrin.h. If I #define 
__INTEL_COMPILER_USE_INTRINSIC_PROTOTYPES the old (and documented) interface 
is restored. See:
https://github.com/VcDevel/Vc/commit/f86080d0e0195257d3b2142ab7f13023d10cbc63

Maybe this helps to track down the issue in ICC.

Cheers,
  Matthias

On Thursday 10 September 2015 17:16:41 Matthias Kretz wrote:
> On Thursday 10 September 2015 14:15:02 Duhem, Laurent wrote:
> > I had a look at your ./mic/intrinsics.h file.
> > 
> > Machine instruction for those kind of intrinsic have a field of 3 bits in
> > the mnemonic to specify the conversion argument (so called MVEX.SSS field)
> > – same for the memory hint: the hint is represented by one bit ( MVEX.EH).
> > 
> > Hence the compiler can’t generate the final machine instruction unless the
> > conversion and hit are a fixed compile time constant.
> 
> I know. And that's the case here. The argument used for conv is a constant
> expression. And that's not the issue for the compilation error. ICC doesn't
> complain about the argument not being an immediate value - it doesn't even
> get so far as to check it. ICC fails earlier.
> 
> This testcase should hopefully make it clear:
> #include <immintrin.h>
> struct A
> {
>     constexpr operator _MM_DOWNCONV_EPI32_ENUM() const { return
> _MM_DOWNCONV_EPI32_NONE; }
>     constexpr operator _MM_UPCONV_EPI32_ENUM() const { return
> _MM_UPCONV_EPI32_NONE; }
> };
> 
> int f(_MM_DOWNCONV_EPI32_ENUM) { return 0; }
> 
> int main()
> {
>     f(A());
>     _mm512_i32extscatter_epi32(nullptr, __m512i(), __m512i(), A(), 1, 0);
>     return 0;
> }
> 
> The expression f(A()) is not ambiguous, while
> _mm512_i32extscatter_epi32(..., A(), ...) is. This would be impossible if
> the fourth parameter of
> _mm512_i32extscatter_epi32 were of type _MM_DOWNCONV_EPI32_ENUM. The
> compiler error says the parameter is of type unsigned int: 'error: more
> than one conversion function from "A" to "unsigned int" applies'.
> 
> My complaint is about the type of the conv argument of
> _mm512_i32extscatter_epi32. It's unsigned int. It was
> _MM_DOWNCONV_EPI32_ENUM in previous ICC versions and it still is documented
> as _MM_DOWNCONV_EPI32_ENUM in the ICC 16 documentation.
> 
> _______________________________________________
> Vc mailing list
>[please enable javascript to see the address]
> https://compeng.uni-frankfurt.de/mailman/listinfo/vc