如何使用SSE指令？

Question

I have some problem with SSE on ubuntu linux system.

example source code on msdn(sse4) use sse4.1 operation on linux

gcc -o test test.c -msse4.1

then error message:

error: request for member 'm128i_u16' in something not a structure or union

How can I use this example code? Or any example code can use?

Answer 1

The title of the code sample is "Microsoft Specific". This means that those functions are specific to the microsoft implementation of c++, and aren't cross-platform. Here are some Intel-specific guides to SSE instructions. Here is gcc documentation concerning command-line flags for specific assembly optimizations, including SSE. Good luck, SSE can get a bit hairy.

Answer 2

This is not so much about Microsoft-specific intrinsic functions, it is about the datatype. The actual intrinsics are 100% identical in both compilers, and are de facto standard (stemming from Intel).

The problem you are facing is that the __m128i type is -- as a convenience feature -- a union under MSVC, which includes fields such as m128i_u16 . The code sample you link to assumes this.

Under gcc, __m128i is not a union and therefore, unsurprisingly, does not have these fields. This is not really a downside, because accessing fields in an union like this anihilates any gains you might have from using SSE in the first place, so other than in demo snippets like the above, you will (almost) never want to use such a thing.