Re: gcc-specific array operator in C

[Daniel Berlin <dberlin at dberlin dot org>]

On Wednesday, October 2, 2002, at 08:30  AM, Nicolas Boulay wrote:

> Hello,
>
> I'm working in the f-cpu team. This project is to design a "free" cpu.
> It will be mainly SIMD (like SSE, MMX, altivec,...) for performance and
> hardware simplicity raison.
>
> As you know compiler aren't really nice with such feature. Vector
> compiler aren't common at all.
>
> I have seen that GCC introduice new data format and MACRO to access 
> such
> feature. That's nice for avoiding using ASM code but that's not 
> portable
> at all.
Actually, macros aren't necessary at all to use SIMD in gcc.
And binary operators on vector data types already works.
So you can portably do vector programming, like so:

int main(void)
{
float a __attribute__ ((mode (V4SF))) = { 1.0, 2.0, 3.0, 4.0};
float b __attribute__ ((mode (V4SF))) = { 1.0, 2.0, 3.0, 4.0};
a = a * b;
}

(V4SF = Vector of 4 Single Floats)
This will compile and work on all platforms (IE with or without vector 
hardware).
On those with vector hardware, it'll use the vector operations 
(assuming GCC has been informed they exist).
Otherwise, it'll synthesize the necessary operations.

You'll need GCC CVS to use this code, I don't think the code to allow 
binary and unary ops on vector datatypes was added until  after 3.2.

--Dan