Intrinsic functions and data types, or intrinsics, provide similar functionality to inline assembly, and provide additional features like type checking and automatic register allocation. An intrinsic function appears as a function call in C or C++, but is replaced during compilation by a sequence of low-level instructions. This means you can express low-level architectural behavior in a high-level language.

In addition to giving the programmer direct access to instructions that do not normally map well onto high-level language statements, using intrinsics means the compiler can optimize the operation to improve performance. Using intrinsics means the developer does not have to consider register allocation and interlock issues, because the compiler handles these.

GCC and RVCT support the same NEON intrinsic syntax, making C or C++ code portable between the toolchains. To add support for NEON intrinsics, include the header file arm_neon.h. Example 1.3 implements the same functionality as the assembler examples, using intrinsics in C code instead of assembler instructions.

#include <arm_neon.h>

uint32x4_t double_elements(uint32x4_t input)
{
    return(vaddq_u32(input, input));
}