Re: GCC Vector Extensions

[Andrew Haley <aph at gcc dot gnu dot org>]

Christian Schoenebeck writes:
 > Es geschah am Wednesday, 19. April 2006 10:30 als Andrew Haley schrieb:
 > >  > Unfortunately we found a case [1] which did not work at all: a type cast
 > >  > from float vector to integer vector, like:
 > >  >
 > >  >     typedef float   v4sf  __attribute__ ((vector_size(16),aligned(16)));
 > >  >     typedef int     v4i   __attribute__ ((vector_size(sizeof(int)*4)));
 > >  >
 > >  >     int main() {
 > >  >         const v4sf v = { 1.2f ,2.2f ,3.3f, 4.4f };
 > >  >         const v4i vRes = (v4i) v;
 > >  >     }
 > >  >
 > >  > The resulting integer vector vRes would simply contain crap.
 > >  > Is this a bug, not implemented yet or even intentional?
 > >
 > > I don't know, because there's not enough information here.  Can you
 > > produce a runnable test case?
 > 
 > Ok, attached you find one with output. When you run it, it should actually 
 > show this:
 > 
 > 	v4sf v = { 1.200000, 2.200000, 3.300000, 4.400000 }
 > 	v4i vRes = { 1, 2, 3, 4 }
 > 
 > but instead I get this:
 > 
 > 	v4sf v = { 1.200000, 2.200000, 3.300000, 4.400000 }
 > 	v4i vRes = { 1067030938, 1074580685, 1079194419, 1082969293 }
 > 
 > I can hardly believe this is intentional, is it?

I've started a conversation on the gcc discuss list, and we think it's
probably a bug.  There's a thread at
http://gcc.gnu.org/ml/gcc/2006-04/msg00349.html.

Andrew.