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

Henri Verbeet hverbeet at gmail.com
Sat Dec 8 05:55:32 PST 2012

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.

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