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bgsegm: Enable __popcnt intrinsic for MSVC on ARM to fix LSBP test failure #3953

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bgsegm: Enable __popcnt intrinsic for MSVC on ARM to fix LSBP test failure #3953

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354660a
Remove ARM exclusion for __popcnt on MSVC
pratham-mcw Jun 12, 2025
1cb9449
fix popcnt for msvc on arm64 compilation
pratham-mcw Jun 24, 2025
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2 changes: 1 addition & 1 deletion modules/bgsegm/src/bgfg_gsoc.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -70,7 +70,7 @@ const float LSBPtau = 0.05f;
inline int LSBPDist32(unsigned n) {
#if defined(__GNUC__) || defined(__clang__)
return __builtin_popcount(n);
#elif defined(_MSC_VER)
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Why "less" in _MSC_VER < 1941? Most probably it's a mistake.

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Why "less" in _MSC_VER < 1941? Most probably it's a mistake.

The condition _MSC_VER < 1941 was added to exclude _M_ARM64 only on older MSVC versions where __popcnt isn’t supported. The logic ensures that __popcnt is used only when compiling with MSVC 1941 or newer on ARM64.

#elif defined(_MSC_VER) && !(defined(_M_ARM) || (defined(_M_ARM64) && _MSC_VER < 1941))
return __popcnt(n);
#else
// Taken from http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
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