[Bug target/48510] Does not vectorize loops involving casts from floating point to unsigned integer types

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48510

--- Comment #4 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-07-19 
10:57:07 UTC ---
We can now vectorize the conversion to unsigned int, it is not possible to
directly convert from double to unsigned long as far as I can see - only
cvttpd2dq exists which is a signed conversion.  Biasing the input value
from [0, ULONG_MAX] to [-LONG_MIN, LONG_MAX] is not possible because of
the different truncation behavior for signed/unsigned values.

As a side-note, C specifies that float -> unsigned integer truncation
only has defined behavior for inputs in the range (-1, Utype_MAX+1).

ICC seems to use some clever range-dependent operations, finally mixing
three cases together with bitwise operations.