SSE

i have a problem regarding SSE asm. code snippet is like this:

//det contains 4 single-pres floating-point no.
//andmask is 7fffffff 7fffffff 7fffffff 7fffffff
  .
  .
  movaps  xmm1,det;
  andps   xmm1,andmask;
  .
  .

basically i want to turn all the SP FP in xmm1 into positive by zero-ing the sign bit.but the code didn't give me what i want.
am i missing something here?

barrelroll xmm1,det;

What does it give you?

Maybe your andmask is in the wrong byte order? I remember reading that SSE had some rather strange ideas about how those packed floating-point bits are stored in memory.

That's why I really dislike x86, actually -- something halfway decent like SSE was developed for the Katmai P3s, and therefore was designed with the Katmai core's particular unorthogonalities in mind. Guess what though, Intel got son-of-Katmai out a year later, when some of the things could've been done better, but noooooooo... we're still stuck in 8 SSE regs and "aligned vs. non-aligned load and store" land.

It's no fucking wonder Altivec owns so much. Now if there was a good mainstream processor that implemented it... I mean, the G4 macs do get a kick out of those optimizations, but who the fuck has a G4 anyway? (besides little ol' powerpc fetishist me.)

On a more serious note, isn't it a better idea to do SSE routines using the intrinsics? Just xmmintrin.h and you're good to go. Might want to get emmintrin.h and possibly pmmintrin.h too. No more byte order snags, and you get loop unrolling and register allocation courtesy of the compiler too.

Also, GCC 4.1 does _some_ (not much) vector optimization if you know how to tickle it.

>>5
worked thanks

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