On 16/01/12 17:51, Martin Nowak wrote:
On Mon, 16 Jan 2012 17:17:44 +0100, Andrei Alexandrescu
<seewebsiteforem...@erdani.org> wrote:
On 1/15/12 12:56 AM, Walter Bright wrote:
I get a 2 to 2.5 speedup with the vector instructions on 64 bit Linux.
Anyhow, it's good enough now to play around with. Consider it alpha
quality. Expect bugs - but make bug reports, as there's a serious lack
of source code to test it with.
-----------------------
import core.simd;
void test1a(float[4] a) { }
void test1()
{
float[4] a = 1.2;
a[] = a[] * 3 + 7;
test1a(a);
}
void test2a(float4 a) { }
void test2()
{
float4 a = 1.2;
a = a * 3 + 7;
test2a(a);
}
These two functions should have the same speed. The function that
ought to be slower is:
void test1()
{
float[5] a = 1.2;
float[] b = a[1 .. $];
b[] = b[] * 3 + 7;
test1a(a);
}
Andrei
Unfortunately druntime's array ops are a mess and fail
to speed up anything below 16 floats.
Additionally there is overhead for a function call and
they have to check alignment at runtime.
martin
Yes. The structural problem in the compiler is that array ops get turned
into function calls far too early. It happens in the semantic pass, but
it shouldn't happen in the front-end at all -- it should be done in the
glue layer, at the beginning of code generation.
Incidentally, this is the reason that CTFE doesn't work with array ops.
