Question

Can anyone explain what they are and why I would need them? What kind of applications am I building if I need to use intrinsics?

Answer 1

Normally, “intrinsics” refers to functions that are built-in — i.e. most standard library functions that the compiler can/will generate inline instead of calling an actual function in the library. For example, a call like: memset(array1, 10, 0) could be compiled for an x86 as something like:

 mov ecx, 10
 xor eax, eax
 mov edi, offset FLAT:array1
 rep stosb

Intrinsics like this are purely an optimization. “Needing” intrinsics would most likely be a situation where the compiler supports intrinsics that let you generate code that the compiler can’t (or usually won’t) generate directly. For an obvious example, quite a few compilers for x86 have “MMX Intrinsics” that let you use “functions” that are really just direct representations of MMX instructions.