kou commented on code in PR #13376:
URL: https://github.com/apache/arrow/pull/13376#discussion_r896152027
##########
cpp/src/arrow/util/bit_util.h:
##########
@@ -67,7 +67,14 @@ static constexpr uint8_t kBytePopcount[] = {
5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 3, 4, 4, 5,
4, 5, 5, 6,
4, 5, 5, 6, 5, 6, 6, 7, 4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8};
-static inline uint64_t PopCount(uint64_t bitmap) { return
ARROW_POPCOUNT64(bitmap); }
+static inline uint64_t PopCount(uint64_t bitmap) {
+#if defined(_MSC_VER) && !defined(_M_AMD64) && !defined(_M_X64)
+ const uint32_t* p = reinterpret_cast<const uint32_t*>((void*)(&bitmap));
+ return ARROW_POPCOUNT32(*p) + ARROW_POPCOUNT32(*(p + 1));
Review Comment:
I'm not sure which is better for performance but it seems that we can use
bit operations to split `uint64_t` value to `uint32_t` values:
```c++
return ARROW_POPCOUNT32((bitmap >> 32) & UINT32_MAX) +
ARROW_POPCOUNT32(bitmap & UINT32_MAX);
```
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