gcc 中的 SSE（SIMD 扩展）支持
我看到如下代码：
#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);
}
此代码使用 gcc 构建良好并按预期工作（它是内置 SSE / MMX 扩展和向量数据类型。此代码使用 4 个单浮点进行 SIMD 向量加法。
我想详细了解每个浮点数的作用此 typedef 行上的关键字/函数调用的含义和作用是：
typedef float v4sf __attribute__ ((vector_size(sizeof(float)*VECTOR_SIZE)));
Vector_size() 函数返回是什么；
__attribute__ 关键字是什么
Here is the float data type being type Defined to vfsf type 的
？休息部分，
谢谢，
-AD
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
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__attribute__是 GCC 从编译器公开 C 或 C++ 标准中不包含的功能的方式。__attribute__((vector_size(x)))指示 GCC 将类型视为大小为 x 的向量。对于 SSE，这是 16 个字节。但是，我建议使用各种
<*mmintrin.h>标头中找到的 __m128、__m128i 或 __m128d 类型。它们在编译器之间更具可移植性。__attribute__is GCCs way of exposing functionality from the compiler that isn't in the C or C++ standards.__attribute__((vector_size(x)))instructs GCC to treat the type as a vector of size x. For SSE this is 16 bytes.However, I would suggest using the __m128, __m128i or __m128d types found in the various
<*mmintrin.h>headers. They are more portable across compilers.