> On 15 Jan 2025, at 15:51, David Aldrich <david.aldrich.ntml@xxxxxxxxx> wrote: > > On Wed, Jan 15, 2025 at 1:54 PM Kyrylo Tkachov <ktkachov@xxxxxxxxxx> wrote: >> >> Hi David, >> >>> On 15 Jan 2025, at 13:33, David Aldrich via Gcc-help <gcc-help@xxxxxxxxxxx> wrote: >>> >>> Hi >>> >>> The gcc Arm compiler aarch64-linux-gnu (v14) provides the following >>> Arm intrinsics header file: >>> >>> \usr\lib\gcc\aarch64-linux-gnu\14\include\arm_sve.h >>> >>> However, this header file uses a pragma to generate the definitions: >>> >>> /* NOTE: This implementation of arm_sve.h is intentionally short. It does >>> not define the SVE types and intrinsic functions directly in C and C++ >>> code, but instead uses the following pragma to tell GCC to insert the >>> necessary type and function definitions itself. The net effect is the >>> same, and the file is a complete implementation of arm_sve.h. */ >>> #pragma GCC aarch64 "arm_sve.h" >>> >>> I don't understand how this works. >>> >> >> The idea is that rather than implementing every ACLE intrinsic as a wrapper around an builtin, annotated with attributes like always_inline etc the compiler injects >> the necessary intrinsic definitions directly into the language when it encounters this aarch64-specific pragma. >> This has a number of advantages, among others: >> * It avoids having to parse a large regular .h file during compilation >> * It allows the compiler to handle some of the more elaborate features of SVE intrinsics such as overloading and type deduction during name resolution. >> * It allows for more powerful custom validation of intrinsic arguments (like enforcing strict compile-time literal arguments for vector lanes) and more helpful error message >> >>> I would like to inspect the actual definitions of the intrinsics. Is >>> it possible to view the actual definitions? >>> >> >> The downside is there’s no single self-contained file that interested readers can look at. >> You can find the code that creates these definitions for SVE in the GCC source in the files named aarch64-sve-builtins-*.cc under the gcc/config/aarch64 subdirectory: >> https://gcc.gnu.org/git/?p=gcc.git;a=tree;f=gcc/config/aarch64;h=7f0aea8187549eefa9c3c6d046a3f56183dc2a69;hb=HEAD >> >> Thanks, >> Kyrill >> > > Hi Kyrill > > Thanks very much for your explanation. I looked at > aarch64-sve-builtins-*.cc but don't think it will help me. > > Unfortunately, another downside is that IDE assistance such as > Microsoft Visual Studio's Intellisense can't provide help with these > functions, unless the internal compiler understands how to generate > the definitions, which is unlikely. > I see. I guess it depends on what exactly you’re after. If you want a human-readable/searchable reference of the available SVE intrinsics then the intrinsics documentation is the better resource: https://developer.arm.com/architectures/instruction-sets/intrinsics/#f:@navigationhierarchiessimdisa=[sve] <https://developer.arm.com/architectures/instruction-sets/intrinsics/#f:@navigationhierarchiessimdisa=%5Bsve%5D> That page describes everything that the user should care about in the intrinsic: name, type signature, expected assembly, argument preparation etc. If you want something that a tool would parse then for the Neon/Advanced SIMD intrinsics there is a CSV-style list in the ACLE GitHub: https://github.com/ARM-software/acle/blob/main/neon_intrinsics/advsimd.md But I’m not sure if there’s such a resource for the SVE ones. The contents of the compiler-provided headers like arm_sve.h, arm_neon.h and others aren’t intended to be user-legible and are considered to be an implementation detail so I wouldn’t try relying on their exact contents unless it’s for your personal education. Thanks, Kyrill > Best regards > David
