This section describes the C++ language-level features supporting the Intel® Streaming SIMD Extensions 2 (Intel® SSE2) in the Intel® C++ Compiler Classic. The features are divided into two categories:
Floating-Point Intrinsics -- describes the arithmetic, logical, compare, conversion, memory, and initialization intrinsics for the double-precision floating-point data type (__m128d).
Integer Intrinsics -- describes the arithmetic, logical, compare, conversion, memory, and initialization intrinsics for the extended-precision integer data type (__m128i).
The prototypes for Intel® SSE2 intrinsics are in the emmintrin.h header file.
To use these intrinsics, include the immintrin.h file as follows:
#include <immintrin.h>
There are no intrinsics for floating-point move operations. To move data from one register to another, a simple assignment, A = B, suffices, where A and B are the source and target registers for the move operation.
Some intrinsics are "composites" - they require more than one instruction to implement them. Intrinsics that require one instruction to implement them are referred to as "simple".
You should be familiar with the hardware features provided by Intel® SSE2 when writing programs with the intrinsics. The following are three important issues to keep in mind:
Certain intrinsics, such as _mm_loadr_pd and _mm_cmpgt_sd, are not directly supported by the instruction set. While these intrinsics are convenient programming aids, be mindful of their implementation cost.
Data loaded or stored as __m128d objects must be generally 16-byte-aligned.
Some intrinsics require that their argument be immediates, that is, constant integers (literals), due to the nature of the instruction.