On Wed, 8 Jun 2016, James Greenhalgh wrote:
> My question is whether you consider the different behaviour between scalar
> float16_t and vector-of-float16_t types to be a bug? I can think of some
No, because it matches how things work for vectors of integer types.
E.g.:
typedef unsigned char vuc __attribute__((vector_size(8)));
vuc a = { 128, 128, 128, 128, 128, 128, 128, 128 }, b;
int
main (void)
{
b = a / (a + a);
return 0;
}
(Does a divide-by-zero, because (a + a) is evaluated without promotion to
vector of int.)
It's a general rule for vector operations that there are no promotions
that change the bit-size of the vectors, so arithmetic is done directly on
unsigned char in this case, even though it normally would not be.
Conversions when the types match apart from signedness are, as the comment
in c_common_type notes, not fully defined.
/* If one type is a vector type, return that type. (How the usual
arithmetic conversions apply to the vector types extension is not
precisely specified.) */
--
Joseph S. Myers
jos...@codesourcery.com
