GCC implements extensions for C and C++ as described in the Arm C Language Extensions (ACLE) specification, which can be found at https://arm-software.github.io/acle/main/.
As a part of ACLE, GCC implements extensions for Arm Vector extensions as described in the Arm C Language Extensions Specification. The complete list of Arm Vector extension intrinsics is available at https://arm-software.github.io/acle/main/. The built-in intrinsics for the Arm vector extensions are available when the respective extensions are enabled.
Not all aspects of ACLE are supported. Support for each feature of the ACLE
is determined with the __ARM_FEATURE_X macros.
See ARM Options and AArch64 Options for more information on the availability of extensions.