[Mesa-dev] [PATCH] i965/blorp: retype destination register for texture SEND instruction to UW.

[Eric Anholt]

Paul Berry <stereotype441 at gmail.com> writes:

> From the bspec documentation of the SEND instruction:
>
>     "destination region cannot cross the 256-bit register boundary."
>
> To avoid violating this restriction when executing SIMD16 texturing
> operations (such as those used by blorp), we need to ensure that the
> destination of the SEND instruction doesn't exceed 256 bits in size.
> An easy way to do this is to set the type of the destination register
> to UW (unsigned word), since 16 unsigned words can fit inside a
> 256-bit register.  Fortunately, this has no effect on the sampling
> operation, since the sampler always infers the destination data type
> from the sampler message rather than from the type of the instruction
> operand.
>
> Previously, we did this for texturing operations issued by the vec4
> and fs back-ends, but not for blorp.  This patch makes blorp use the
> same trick.
>
> I haven't observed any behavioural difference on actual hardware due
> to this patch, but it avoids a warning from the simulator so it seems
> like the right thing to do.

Reviewed-by: Eric Anholt <eric at anholt.net>
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