在C中返回结构的函数中的编译错误

Question

I keep getting this compilation error:

error: expected ';', ',' or ')' before '&' token

on the marked line below:

//128 bit vector struct (4 integers)
typedef struct {
  int w, x, y, z;
} iVector4;

iVector4 SSEadd(iVector4 &v1, iVector4 &v2)  // <-- this line
{
  iVector4 vr;
  asm
  {
    MOV EAX v1
    MOV EBX v2
    //
    MOVUPS XMM0, [EAX]
    MOVUPS XMM1, [EBX]
    //
    PADDD XMM0 XMM1
    MOVUPS [rv]
  }
  return rv;
}

I really can't see what's wrong: What seems to be the problem?

EDIT:

Hi thanks for all the responses.

I'm using gcc as a compiler, and I realize that the assembly code that I had provided was also incorrect.I was wondering if its best to use the built_in functions from -msse/-msse2.

Also, what's the most efficient way to load and extract values from a vector such as v4si?

I'm finding that loading and extracting from the vector is a costly ooperation.

When you say sse intrinsics, what exactly did you mean?

Thanks for all the help.

Answer 1

C does not have references. You need to compile as C++ for those.

Answer 2

C doesn't have references. You should use a pointer instead, or use C++.

iVector4 SSEadd(iVector4 *v1, iVector4 *v2)

Now the next question - can you return objects in C? My C is rusty. If that's the not case, you'd need:

void  SSEadd(iVector4 *v1, iVector4 *v2, iVector4 *vOut)

EDIT: As Justin pointed out, it is possible, so you don't need to go that route. You still could though - depending on the circumstances, it could be more performant.

Answer 3

我认为您的函数定义实际上应该是：

iVector4 SSEadd(iVector4 *v1, iVector4 *v2);

Answer 4

您可能还想考虑使用SSE内在函数，而不是看起来像在做什么。