[FFmpeg-devel] libavcodec/exr : add x86 SIMD for predictor

Henrik Gramner henrik at gramner.com
Sun Oct 1 17:35:33 EEST 2017

On Sun, Oct 1, 2017 at 4:14 PM, James Almer <jamrial at gmail.com> wrote:
> We normally use int for counters, and don't mix declaration and statements.
> And in any case ptrdiff_t would be "more correct" for this.

Ah right. C90, ugh. Too used to C99.

Yeah, feel free to use whatever datatype that's most appropriate for
the FFmpeg standard, wouldn't size_t make more sense than ptrdiff_t
for a size though?

> We have both of those in constants.c, so use instead
> cextern pb_15
> cextern pb_80

Good point. Any idea why the heck is it called pb_80 btw? Seems like a
very inconsistent mix of decimal and hex.

> Does that apply to Haswell and newer? Was wondering why so many of the
> AVX functions that only used the three operand instructions were
> reported to be as fast or even slower than <= SSE4 versions for me.

Since Ivy Bridge on Intel IIRC. No idea about AMD. Eliminating reg-reg
moves with AVX also saves a little bit of code size (and thus cache)
as well, which might add up over hundreds of functions.

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