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 > Best regards > David
