[Pixman] [PATCH 1/4] pixman-fast-path: Add over_n_8888 fast path (disabled)

Matt Turner mattst88 at gmail.com
Sat Aug 22 13:14:08 PDT 2015

On Thu, Aug 20, 2015 at 6:58 AM, Pekka Paalanen <ppaalanen at gmail.com> wrote:
> From: Ben Avison <bavison at riscosopen.org>
> This is a C fast path, useful for reference or for platforms that don't
> have their own fast path for this operation.
> This new fast path is initially disabled by putting the entries in the
> lookup table after the sentinel. The compiler cannot tell the new code
> is not used, so it cannot eliminate the code. Also the lookup table size
> will include the new fast path. When the follow-up patch then enables
> the new fast path, the binary layout (alignments, size, etc.) will stay
> the same compared to the disabled case.
> Keeping the binary layout identical is important for benchmarking on
> Raspberry Pi 1. The addresses at which functions are loaded will have a
> significant impact on benchmark results, causing unexpected performance
> changes. Keeping all function addresses the same across the patch
> enabling a new fast path improves the reliability of benchmarks.
> Benchmark results are included in the patch enabling this fast path.
> [Pekka: disabled the fast path, commit message]
> Signed-off-by: Pekka Paalanen <pekka.paalanen at collabora.co.uk>

I don't care strongly, but I might just squash 1+2, 3+4 together and
make a mention in the commit message of exactly what the benchmark
numbers are comparing.

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