c++ data types __m128i

__m128i

The __m128i data type, for use with the Streaming SIMD Extensions 2 (SSE2) instructions intrinsics, is defined in <emmintrin.h>.

eg: /usr/local/gcc-9.3.0/lib/gcc/x86_64-pc-linux-gnu/9.3.0/include/emmintrin.h

// data_types__m128i.cpp
#include <emmintrin.h>
int main() {
   __m128i x;
}

Remarks

Using variables of type __m128i will cause the compiler to generate the SSE2 movdqa instruction. This instruction does not cause a fault on Pentium III processors but will result in silent failure, with possible side effects caused by whatever instructions movdqa translates into on Pentium III processors.

You should not access the __m128i fields directly. You can, however, see these types in the debugger.
A variable of type __m128i maps to the XMM[0-7] registers.
Variables of type __m128i are automatically aligned on 16-byte boundaries.
The __m128i data type is not supported on ARM processors.