[Mesa-dev] [PATCH] Add an accelerated version of F_TO_I for x86_64

[Kenneth Graunke]

On Monday, July 28, 2014 05:34:59 PM Roland Scheidegger wrote:
> Looking all good, though it got me thinking about these numerous
> float-to-int rounding functions in mesa in various places a bit more.
> There is, for instance, a _mesa_round_to_even() function, which claims
> that the c99 lrintf() and friends functions can't be used because the
> environment might use a different rounding mode. This is of course true
> though I wonder why it would matter there and not here for instance,
> since of course cvtss2si is affected by that as well.

_mesa_round_to_even() is currently only used by the GLSL compiler.

The GLSL compiler implements round() as round-to-even on the GPU, so we want to make sure that CPU-side constant expression evaluation rounds the same way.

I don't think other code needs to be as paranoid.

--Ken
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