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Fix MSVC implementation of CountBits() function #72

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Merged
sipa merged 2 commits into from
Oct 18, 2022
Merged

Fix MSVC implementation of CountBits() function #72

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1c77291
Fix MSVC implementation of `CountBits()` function
hebasto Oct 18, 2022
0078bed
Ignore `HAVE_CLZ` macro when building with MSVC
hebasto Oct 18, 2022
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24 changes: 12 additions & 12 deletions src/int_utils.h
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Original file line number Diff line number Diff line change
Expand Up @@ -129,17 +129,7 @@ constexpr inline I Mask() { return ((I((I(-1)) << (std::numeric_limits<I>::digit
/** Compute the smallest power of two that is larger than val. */
template<typename I>
static inline int CountBits(I val, int max) {
#ifdef HAVE_CLZ
(void)max;
if (val == 0) return 0;
if (std::numeric_limits<unsigned>::digits >= std::numeric_limits<I>::digits) {
return std::numeric_limits<unsigned>::digits - __builtin_clz(val);
} else if (std::numeric_limits<unsigned long>::digits >= std::numeric_limits<I>::digits) {
return std::numeric_limits<unsigned long>::digits - __builtin_clzl(val);
} else {
return std::numeric_limits<unsigned long long>::digits - __builtin_clzll(val);
}
#elif _MSC_VER
#ifdef _MSC_VER
(void)max;
unsigned long index;
unsigned char ret;
Expand All @@ -149,7 +139,17 @@ static inline int CountBits(I val, int max) {
ret = _BitScanReverse64(&index, val);
}
if (!ret) return 0;
return index;
return index + 1;
#elif HAVE_CLZ
(void)max;
if (val == 0) return 0;
if (std::numeric_limits<unsigned>::digits >= std::numeric_limits<I>::digits) {
return std::numeric_limits<unsigned>::digits - __builtin_clz(val);
} else if (std::numeric_limits<unsigned long>::digits >= std::numeric_limits<I>::digits) {
return std::numeric_limits<unsigned long>::digits - __builtin_clzl(val);
} else {
return std::numeric_limits<unsigned long long>::digits - __builtin_clzll(val);
}
#else
while (max && (val >> (max - 1) == 0)) --max;
return max;
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