3 ms·

What are you talking about? Intrinsics are perfectly valid C99 code. __int64i is a union with 8 different arrays in it, and intrinsics are library functions.

the_why_of_y 10y ago
The words "SIMD", "intrinsic", "__m64", "__m128" do not occur in the C11 draft text; the word "vector" occurs once in example code for an array-with-length struct. http://www.iso-9899.info/n1570.html http://www.iso-9899.info/n1570.html Intrinsics are not library functions - they would hardly provide the desired performance benefit if they were. Intrinsics are "magic" functions that the compiler has built-in support for, and thus I would call them language extensions. For example from GCC header avxintrin.h: extern __inline __m256d __attribute__((__gnu_inline__, __always_inline__, __artificial__)) _mm256_permute2f128_pd (__m256d __X, __m256d __Y, const int __C) { return (__m256d) __builtin_ia32_vperm2f128_pd256 ((__v4df)__X, (__v4df)__Y, __C); } Over here the word "__builtin_ia32_vperm2f128_pd256" occurs in the "cc1" and "cc1plus" binaries and "avxintrin.h", but nowhere else. Notably there is no externally visible definition.
- Const-me 10y ago
  I don’t know why authors of GCC invented that non-standard extended C dialect, you better ask them. In Visual C++, the prototype of that intrinsic is valid C99 code: extern __m256d __cdecl _mm256_permute2f128_pd(__m256d, __m256d, int);
  - the_why_of_y 10y ago
    Which library contains the definition of "_mm256_permute2f128_pd"? The likely answer is "none", as these are built-in to Visual C++ in a similar way to GCC, with only superficial differences such as an apparent lack of indirection to some __builtin_foo. https://msdn.microsoft.com/en-us/library/26td21ds(v=vs.100).aspx https://msdn.microsoft.com/en-us/library/26td21ds(v=vs.100).... "An intrinsic is a function known by the compiler that directly maps to a sequence of one or more assembly language instructions. Intrinsic functions are inherently more efficient than called functions because no calling linkage is required." https://msdn.microsoft.com/en-us/library/y0dh78ez(v=vs.100).aspx https://msdn.microsoft.com/en-us/library/y0dh78ez(v=vs.100).... "The use of intrinsics affects the portability of code, because intrinsics that are available in Visual C++ might not be available if the code is compiled with other compilers and some intrinsics that might be available for some target architectures are not available for all architectures."
    - Const-me 10y ago
      I know how intrinsic work, thanks. Use them a lot in C++. C99 language spec says nothing about the things you’re talking about. It only specifies the language, not how C compilers implement various features. From the programmer’s point of view (except when the programmer works on the compiler itself), intrinsics are just C library functions, only inline, and very performant if done right. Fully compliant with C99 and C++ language specs.

the_why_of_y 10y ago

The words "SIMD", "intrinsic", "__m64", "__m128" do not occur in the C11 draft text; the word "vector" occurs once in example code for an array-with-length struct. http://www.iso-9899.info/n1570.html http://www.iso-9899.info/n1570.html Intrinsics are not library functions - they would hardly provide the desired performance benefit if they were. Intrinsics are "magic" functions that the compiler has built-in support for, and thus I would call them language extensions. For example from GCC header avxintrin.h: extern __inline __m256d __attribute__((__gnu_inline__, __always_inline__, __artificial__)) _mm256_permute2f128_pd (__m256d __X, __m256d __Y, const int __C) { return (__m256d) __builtin_ia32_vperm2f128_pd256 ((__v4df)__X, (__v4df)__Y, __C); } Over here the word "__builtin_ia32_vperm2f128_pd256" occurs in the "cc1" and "cc1plus" binaries and "avxintrin.h", but nowhere else. Notably there is no externally visible definition.

Const-me 10y ago
I don’t know why authors of GCC invented that non-standard extended C dialect, you better ask them. In Visual C++, the prototype of that intrinsic is valid C99 code: extern __m256d __cdecl _mm256_permute2f128_pd(__m256d, __m256d, int);
- the_why_of_y 10y ago
  Which library contains the definition of "_mm256_permute2f128_pd"? The likely answer is "none", as these are built-in to Visual C++ in a similar way to GCC, with only superficial differences such as an apparent lack of indirection to some __builtin_foo. https://msdn.microsoft.com/en-us/library/26td21ds(v=vs.100).aspx https://msdn.microsoft.com/en-us/library/26td21ds(v=vs.100).... "An intrinsic is a function known by the compiler that directly maps to a sequence of one or more assembly language instructions. Intrinsic functions are inherently more efficient than called functions because no calling linkage is required." https://msdn.microsoft.com/en-us/library/y0dh78ez(v=vs.100).aspx https://msdn.microsoft.com/en-us/library/y0dh78ez(v=vs.100).... "The use of intrinsics affects the portability of code, because intrinsics that are available in Visual C++ might not be available if the code is compiled with other compilers and some intrinsics that might be available for some target architectures are not available for all architectures."
  - Const-me 10y ago
    I know how intrinsic work, thanks. Use them a lot in C++. C99 language spec says nothing about the things you’re talking about. It only specifies the language, not how C compilers implement various features. From the programmer’s point of view (except when the programmer works on the compiler itself), intrinsics are just C library functions, only inline, and very performant if done right. Fully compliant with C99 and C++ language specs.