Hi,
On Mon, 6 Jan 2020, ian wrote:
Did I miss something ?
It seemed to me that it was dealing with application side of things.
Sure, Rasmus asked to have this extension in TCC to be able to use it for
writing libraries or apps; i.e. he asked if TCC could be extended to
compile code like this:
---------------------
typedef int v4si __attribute__ ((vector_size (16)));
void foo (void) {
v4si a = {1,2,3,4}, b = {5,6,7,8}, c;
c = a + b;
bar(c[0], c[1], c[2], c[3]);
}
---------------------
For that TCC would need to be extended somewhat, and I was alluding to the
fact that this extension isn't totally trivial if it shouldn't generate
very low quality code. If it's okay to generate low quality code and
not adhere to the psABI for parameter passing of these types then it's not
too much work.
If you were asking if such extension is really a must have in a
compiler: no, otherwise it wouldn't be an extension. It's a nice to have,
and I can see why Rasmus wants it, but it comes at a non-trivial cost to
support it in a small compiler.
Ciao,
Michael.
Like, say, libraries. For the least, as long as compilers does not care
about maths or physics....
If I'm wrong, please, explain to me where...
ian
Le 06/01/2020 à 21:46, Michael Matz a écrit :
Hi,
On Mon, 6 Jan 2020, ian wrote:
Is the support for data structures and calculations
a real "need to" for a compiler ????
Um, I don't know how to answer this. As it seems the
alternative to calculations is guessing, yes, I do think
calculations and data structures are indeed necessary for a
compiler, or any program whatsoever.
Ciao,
Michael.
regards,
ian
Le 06/01/2020 à 20:36, Michael Matz a écrit :
Hello,
On Mon, 6 Jan 2020, Rasmus Riiner via
Tinycc-devel wrote:
See here:
https://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html
This is one of those things that doesn't
come up in
a lot of types of programming, but is
indispensable
in some, namely anything to do with 2D
or 3D math.
The ability to just write `position +=
velocity *
dt;` style statements might be one of
the most
important reasons most game developers
choose C++
over C. It's certainly the only thing
keeping me
from using TCC in the development of my
own project.
Actually emitting SSE instructions might
be beyond
the scope of tcc (Tiny after all),
supporting the
expressions though would be a huge help.
Without proper support in the backends for
vector instructions
the generated code for this extension from TCC
would be of
abysmal quality. Technically it wouldn't be
too much work to
semantically support that, but the values
would need to be
committed to memory (instead of vector
registers) and regarded
as constant sized arrays (at which point the
function call ABI
would be different from the respective native
ABI, which, again,
would be hard to fix without proper support
for vector insns in
the backends).
That extension really doesn't feel very well
suited for a simple
compiler like TCC ;-) But perhaps it can be
done
non-intrusively enough.
I sat down yesterday in an attempt to do
this
myself, but it turns out I'm not good
enough for the
job. I couldn't make heads or tails of
it. However,
this might be a breeze for someone that
knows TCC
like the back of their hand.
So, any takers?
Ciao,
Michael.
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