[flac-dev] [PATCH] MSVC2015U2 workaround, version 2

lvqcl lvqcl.mail at gmail.com
Mon May 2 19:11:18 UTC 2016

Here's a new version of a patch that fixes a problem with MSVC2105 update2,
but it doesn't disable any optimization, so the resulting encoding
performance should be almost unaffected by this workaround.

MSVC compiles

     abs_residual_partition_sums[partition] = (FLAC__uint32)_mm_cvtsi128_si32(mm_sum);

into this:

     movq    QWORD PTR [rsi], xmm2

while it should be

     movd    eax, xmm2
     mov     QWORD PTR [rsi], rax

With this patch, MSVC emits

     movq    QWORD PTR [rsi], xmm2
     mov     DWORD PTR [rsi+4], r9d

so the price of this workaround is 1 extra write instruction per partition.
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