On Thu, 19 Feb 2009 23:05:34 +0300, Andrei Alexandrescu
<[email protected]> wrote:
Denis Koroskin wrote:
On Thu, 19 Feb 2009 22:25:04 +0300, Mattias Holm
<[email protected]> wrote:
Since (SIMD) vectors are so common and every reasonabe system support
them in one way or the other (and scalar emulation of this is rather
simple), why not have support for this in D directly?
Yes, the array operations are nice (and one of the main reasons for
why I like D :) ), but have the problem that an array of floats must
be aligned on float boundaries and not vector boundaries. In my mind
vectors are a primitive data type that should be exposed by the
programming language.
Something OpenCL-like:
float4 vec;
vec.xyzw = {1.0,1.0, 1.0, 1.0}; // assignment
vec.xyzw = vec.wyxz; // permutation
vec[i] = 1.0; // indexing
And then we can easily immagine some extra nice features to have with
respect to operators:
vec ^ vec2; // 3d cross product for float vectors, for int vectors
xor
Has this been discussed before?
/ Mattias
I don't see any reason why float4 can't be made a library type.
Yah, I was thinking the same:
struct float4
{
__align(16) float[4] data; // right syntax and value?
alias data this;
}
This looks like something that should go into std.matrix pronto. It even
has value semantics even though fixed arrays don't :o/.
Andrei
That would be great. If float4 gets its way into D, I'll share our blazing fast
math code with community (most common operations on vectors, matrices,
quaternions etc). It is written entirely in SSE (intrinsics, not asm; there is
a problem with inlining asm in D, IIRC. Can anyone elaborate on this?) and
*very* fast. According to our benchmarks, that's the best we get squeeze out of
hardware.
I know LLVM have support for *very* wide range of intrinsics:
http://www.cs.ucla.edu/classes/spring08/cs259/llvm-2.2/include/llvm/Intrinsics.gen
Hopefully they will get into LDC (and DMD *hint* Walter *hint*) very soon.
