calling c-function with a vector

Hi all,

I have the following problem: I want to call a function from llvm
(tryf in the following) which takes a vector as an argument. The
function tryf is a c-function and should output the whole vector. But
I only get 0.0. Looks like a problem with how the arguments are
passed. I havn't found anything in the docs about how vectors are
passed. Any help would be appreciated.

The llvm-code looks like this:
declare void @tryf(<4 x float>)
define i32 @main() {
entry:
call void @tryf(<4 x float> <float 0x3FFB0A3D40000000, float
6.250000e+00, float 0x3F847AE160000000, float 1.600000e+01>)
ret i32 3
}

The C-function is defined like this:
#include <stdio.h>
void tryf(float *a1)
{
    fprintf(stderr, "%f ",*a1);
    a1++;
    fprintf(stderr, "%f ",*a1);
    a1++;
    fprintf(stderr, "%f ",*a1);
    a1++;
    fprintf(stderr, "%f\n",*a1);
}

Thanks & Regards,

Jörg

Jörg Werner wrote:

Hi all,

I have the following problem: I want to call a function from llvm
(tryf in the following) which takes a vector as an argument. The
function tryf is a c-function and should output the whole vector. But
I only get 0.0. Looks like a problem with how the arguments are
passed. I havn't found anything in the docs about how vectors are
passed. Any help would be appreciated.

The llvm-code looks like this:
declare void @tryf(<4 x float>)
define i32 @main() {
entry:
   call void @tryf(<4 x float> <float 0x3FFB0A3D40000000, float
6.250000e+00, float 0x3F847AE160000000, float 1.600000e+01>)
   ret i32 3
}

The C-function is defined like this:
#include<stdio.h>
void tryf(float *a1)

That's not a vector. That's a pointer to a float. Assuming you're using clang, try this:

   #include <stdio.h>
   typedef float float4 __attribute__((ext_vector_type(4)));

   void tryf(float4 a1) {
     fprintf(stderr, "%f %f %f %f\n", a1.x, a1.y, a1.z, a1.w);
   }

There's also a syntax for this with gcc using 'vector_size' instead of 'ext_vector_type' but I don't know it offhand.

Nick