SSE (SIMD extensions) support in gcc
- by goldenmean
Hi,
I see a code as below:
include "stdio.h"
#define VECTOR_SIZE 4
typedef float v4sf __attribute__ ((vector_size(sizeof(float)*VECTOR_SIZE)));
// vector of four single floats
typedef union f4vector
{
v4sf v;
float f[VECTOR_SIZE];
} f4vector;
void print_vector (f4vector *v)
{
printf("%f,%f,%f,%f\n", v->f[0], v->f[1], v->f[2], v->f[3]);
}
int main()
{
union f4vector a, b, c;
a.v = (v4sf){1.2, 2.3, 3.4, 4.5};
b.v = (v4sf){5., 6., 7., 8.};
c.v = a.v + b.v;
print_vector(&a);
print_vector(&b);
print_vector(&c);
}
This code builds fine and works expectedly using gcc (it's inbuild SSE / MMX extensions and vector data types. this code is doing a SIMD vector addition using 4 single floats.
I want to understand in detail what does each keyword/function call on this typedef line means and does:
typedef float v4sf __attribute__ ((vector_size(sizeof(float)*VECTOR_SIZE)));
What is the vector_size() function return;
What is the __attribute__ keyword for
Here is the float data type being type defined to vfsf type?
I understand the rest part.
thanks,
-AD
