Re: [LAD] is this a compiler issue??

#include <xmmintrin.h>

#define CPUID(f,ax,bx,cx,dx) __asm__ __volatile__ \
("cpuid": "=a" (ax), "=b" (bx), "=c" (cx), "=d" (dx) : "a" (f))

// denormal protection

static int set_DAZ_and_FTZ(int /*bool*/ on)
{
   int sse_level = 0;
   
   if(on)
   {
      unsigned long ax, bx, cx, dx;
      
      CPUID(0x00,ax,bx,cx,dx);
      CPUID(0x01,ax,bx,cx,dx);
            
      if (dx & 0x02000000)
      {
         sse_level = 1;
         // set FLUSH_TO_ZERO to ON and
         // set round towards zero (RZ)
         _mm_setcsr(_mm_getcsr() | 0x8000|0x6000);

         if (dx & 0x04000000)
         {
            sse_level = 2;
              
            if (cx & 0x00000001)
            {
               sse_level = 3;
               // set DENORMALS_ARE_ZERO to ON
               _mm_setcsr(_mm_getcsr() | 0x0040);
            }
            // we should have checked for AMD K8 without SSE3 here:
            // if(AMD_K8_NO_SSE3)
            // .. but I can't recall how to that :-/
         }
      }
   } else
      // clear underflow and precision flags
      // and set DAZ and FTZ to OFF
      // and restore round to nearest (RN)
      _mm_setcsr(_mm_getcsr() & ~(0x0030|0x8000|0x0040|0x6000));
   
   return sse_level;
}

On Wed, 2009-08-19 at 12:37 +0200, Tim Goetze wrote:
> [Conrad Berhörster]
> >But i try to understand, what happens here. Is the compiler overoptimizing
> >zeros.
>
> It'd be a lot more helpful to see the full source but from what you're
> writing I'd be willing to bet you're encountering denormals.
>
> Cheers, Tim

_______________________________________________
Linux-audio-dev mailing list
Linux-audio-dev@email-addr-hidden
http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev
Received on Wed Aug 19 16:15:02 2009