[Mesa-dev] Mesa (master): r600g: Use default mul/mad function for tgsi-to-llvm

[Alex Deucher]

On Sat, Dec 8, 2012 at 8:55 AM, Henri Verbeet <hverbeet at gmail.com> wrote:
> On 6 December 2012 21:34, Tom Stellard <tom at stellard.net> wrote:
>> I asked idr about this on IRC and he said that IEEE rules are required for
>> GLSL >= 1.30 and they are compliant, but not required for GLSL < 1.30.
>> stringfellow added that the d3d9 spec required 0*anything = 0, which is
>> probably why the hardware has those instructions.
>>
> That also means that this will break a couple of d3d9 applications in
> Wine. That's fine, if perhaps a bit unfortunate, since technically
> it's not something Wine can depend on anyway, and d3d10 is going to
> require IEEE conventions. At some point there was talk about a
> EXT_zero_mul_conventions extension to select one or the other
> behaviour at the context level. (The main consideration for doing it
> at the context level instead of e.g. per-shader was that apparently
> NVIDIA hardware doesn't have separate instructions for this, and
> instead only has a global switch.) I don't think that extension went
> anywhere, although I'm not all that clear on the reasons.

What about a mesa specific extension?  Most people will be using wine
on Linux anyway.

Alex