Data types for x86-64 processors

Question

What are these data types for? __m64, __m128, __m256 ?

Answer 1

A quick google-search gives me:

• The __m64 data type is for use with the MMX and 3DNow! intrinsics
• The __m128 data type, for use with the Streaming SIMD Extensions and Streaming SIMD Extensions 2 instructions intrinsics

Unfortunately I can't readily find what __m256 is but I suspect it is along the same lines.

Basically, data structures for MMX and similar technologies.

Answer 2

MMX Technology Packed Arithmetic Intrinsics (C++).

Answer 3

they are SSE instructions, including new AVX extension. http://www.serc.iisc.ernet.in/ComputingFacilities/systems/Dell_Doc/Intel_C++_Compiler/en_US/compiler_c/main_cls/intref_cls/common/intref_avx_details.htm and here

they store vectors - multiple values at the same time. you can do calculations on all values in a vector simultaneously with special instructions. Chech links