Re: Where the fact that -msse2 has to be used with -O documented?

[Marc Glisse <marc dot glisse at inria dot fr>]

On Mon, 21 Jan 2013, Peng Yu wrote:

> The following commands showed that -msse2 has to be used with -O (or
> its variants -O1, -O2, etc.) But I don't find this documented in the
> gcc manual. Does anybody know where this is documented? Thanks!

It is just luck that makes it sometimes work.

> #include <xmmintrin.h>
> #include <stdio.h>
>
> int main() {
>  float p[4]={1,2,3,4};
>  __m128 a = _mm_load_ps(p);

_mm_load_ps requires a 16-byte alignment.

>  float p1[4];
>  _mm_store_ps(p1, a);
>  for(int i=0; i < 4; i++) {
>    printf("%g\n", p1[i]);
>  }
> }

--
Marc Glisse