[Beignet] [PATCH] GBE: disable spill register under simd16 mode.

[Zhigang Gong]

On Wed, Nov 26, 2014 at 7:55 AM, Matt Turner <mattst88 at gmail.com> wrote:
> On Thu, Nov 20, 2014 at 8:09 PM, Zhigang Gong <zhigang.gong at intel.com> wrote:
>> Register spilling awlays cost much more than fallback to simd8
>> which could avoid register spilling or at least reduce the spilled
>> registers.
>
> For what it's worth, we made the same decision in the i965 Mesa driver.
>
> There has been some conjecture that a spilling SIMD16 program *could*
> potentially be faster than a non-spilling SIMD8 program, but I don't
> know of any hard evidence.

Thanks for the comment. I thought if a kernel is totally computational
intensity and most
of the computation occurs in a loop and we just spill a few registers
out of any loops.
Then it may be faster than a non-spilling simd8 kernel. But all the
real case we have could
only prove that spilling simd16 is much slower than non-spilling simd8.

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