Question

Which header files provide the intrinsics for the different x86 SIMD instruction set extensions (MMX, SSE, AVX, …)? It seems impossible to find such a list online. Correct me if I’m wrong.

Answer 1

These days you should normally just include <immintrin.h>. It includes everything.

GCC and clang will stop you from using intrinsics for instructions you haven’t enabled at compile time (e.g. with -march=native or -mavx2 -mbmi2 -mpopcnt -mfma -mcx16 -mtune=znver1 or whatever.)

MSVC and ICC will let you use intrinsics without enabling anything at compile time, but you still should enable AVX before using AVX intrinsics.

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Historically (before immintrin.h pulled in everything) you had to manually include a header for the highest level of intrinsics you wanted.

This may still be useful with MSVC and ICC to stop yourself from using instruction-sets you don’t want to require.

<mmintrin.h>  MMX
<xmmintrin.h> SSE
<emmintrin.h> SSE2
<pmmintrin.h> SSE3
<tmmintrin.h> SSSE3
<smmintrin.h> SSE4.1
<nmmintrin.h> SSE4.2
<ammintrin.h> SSE4A
<wmmintrin.h> AES
<immintrin.h> AVX, AVX2, FMA

Including one of these pulls in all previous ones (except AMD-only SSE4A: immintrin.h doesn’t pull that in)

Some compilers also have <zmmintrin.h> for AVX512.