[FFmpeg-devel] [WIP][PATCH] Opus Piramid Vector Quantization Search in x86 SIMD asm
james.darnley at gmail.com
Mon Jun 12 02:31:51 EEST 2017
On 2017-06-11 11:34, Ivan Kalvachev wrote:
> On 6/10/17, James Darnley <james.darnley at gmail.com> wrote:
>> On 2017-06-09 13:41, Ivan Kalvachev wrote:
>>> const_*_edge is used on only one place is the code.
>>> Would you check if this patch fixes the issue.
>>> I expected that the addresses would be pre-calculated
>>> by n/yasm as one value and indexed
>>> relative to the section start.
>>> Instead it seems that each entry is represented with
>>> its own address and offset from it.
>>> Since the offset is negative it uses all 64 bits and
>>> it makes difference if it is truncated to 32 bits.
>>> Same issue could happen with clang tools.
>> The problem is with the relative addressing. You need to load the real
>> address first before you can offset with another register at runtime. So
>> something like:
>>> mov reg1, [read_only_const]
> lea ?
Yes, sorry about that.
> --- a/libavcodec/x86/opus_pvq_search.asm
> +++ b/libavcodec/x86/opus_pvq_search.asm
> @@ -406,7 +406,7 @@ align 16
> ; uint32 N - Number of vector elements. Must be 0 < N < 8192
> %macro PVQ_FAST_SEARCH 0
> -cglobal pvq_search,4,5,8, mmsize, inX, outY, K, N
> +cglobal pvq_search,4,6,8, mmsize, inX, outY, K, N
> %define tmpX rsp
> ; movsxdifnidn Nq, Nd
> @@ -419,7 +419,12 @@ cglobal pvq_search,4,5,8, mmsize, inX, outY, K, N
> add Nq, r4q ; Nq = align(Nq, mmsize)
> sub rsp, Nq ; allocate tmpX[Nq]
> +%ifdef PIC
> + lea r5q, [const_align_abs_edge] ; rip+const
> + movups m3, [r5q+r4q-mmsize] ; this is the bit mask for the padded read at the end of the input
> movups m3, [const_align_abs_edge-mmsize+r4q] ; this is the bit mask for the padded read at the end of the input
> lea r4q, [Nq-mmsize] ; Nq is rounded up (aligned up) to mmsize, so r4q can't become negative here, unless N=0.
> movups m2, [inXq + r4q]
FYI that diff works just fine, when I correct the line wrapping. I can
compile and run on Win64. This is not a comment about the original patch.
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