On Fri, 7 Sep 2012, Ian Lance Taylor wrote:
On Fri, Sep 7, 2012 at 5:05 AM, Henrik Mannerström
<henrik.mannerstrom@xxxxxxxxx> wrote:
If I understand the Intel reference correctly, the CVTDQ2PD should allow
me to convert two 64 bit integers into two 64 bit doubles in one blow.
How should I write this in gcc C/C++?
Program 1 uses casting to illustrate the point, it outputs 0 and 1.
Program 2 was my naive attempt to use vectorization, it outputs 0 and
4.94066e-324, which is _not_ what I intended.
a.vd = __v2df(a.vi);
This is just a type cast of the vector as a whole. It doesn't convert
the individual vector elements.
I always found it strange that vectors act like values everywhere, except
for casts where they act like pointers. I understand this is convenient to
allow calling intrinsics with vector types that don't exactly match, but
it steals a good syntax that gcc's vector extensions can't use for true
conversions.
--
Marc Glisse
