Your First Intrinsic

Intel intrinsics are C functions that map directly to SIMD assembly instructions. They give you the power of assembly with the convenience of C.

The Intrinsic Naming Convention#

Most AVX2 intrinsics follow this pattern:

_mm256_<operation>_<type>

• _mm256 -- 256-bit operation (use _mm for 128-bit)
• <operation> -- what it does: add, sub, mul, load, store, etc.
• <type> -- element type: epi32 (32-bit int), ps (float), pd (double)

Load, Add, Store#

The most basic SIMD pattern:

#include <immintrin.h>

void add_arrays(int* a, int* b, int* result, int n) {
    for (int i = 0; i < n; i += 8) {
        // Load 8 ints from each array
        __m256i va = _mm256_loadu_si256((__m256i*)(a + i));
        __m256i vb = _mm256_loadu_si256((__m256i*)(b + i));

        // Add them (8 additions in one instruction)
        __m256i vr = _mm256_add_epi32(va, vb);

        // Store the result
        _mm256_storeu_si256((__m256i*)(result + i), vr);
    }
}

Key Intrinsics Used#

Try It#

Head to the Problems page and try the introductory challenges to practice this pattern!