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The use of compiler intrinsics offers a number of performance benefits:
The low-level instructions substituted for an intrinsic might be more efficient than
corresponding implementations in C or C++, resulting in both reduced instruction and
cycle counts. To implement the intrinsic, the compiler automatically generates the best
sequence of instructions for the specified target architecture. For example, the
L_add intrinsic maps directly to the ARM v5TE assembly language
QADD r0, r0, r1 /* Assuming r0 = a, r1 = b on entry */
More information is given to the compiler than the underlying C and C++ language is able to convey. This enables the compiler to perform optimizations and to generate instruction sequences that it could not otherwise have performed.
These performance benefits can be significant for real-time processing applications. However, care is required because the use of intrinsics can decrease code portability.