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Use __builtin_clz whenever it is available

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This commit is contained in:
Victor Zverovich
2015-02-21 06:21:29 -08:00
parent e87a24633b
commit cbc46d9e78
1 changed files with 8 additions and 7 deletions
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15
format.h
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@ -581,13 +581,6 @@ inline unsigned count_digits(uint64_t n) {
unsigned t = (64 - FMT_BUILTIN_CLZLL(n | 1)) * 1233 >> 12; unsigned t = (64 - FMT_BUILTIN_CLZLL(n | 1)) * 1233 >> 12;
return t - (n < Data::POWERS_OF_10_64[t]) + 1; return t - (n < Data::POWERS_OF_10_64[t]) + 1;
} }
# ifdef FMT_BUILTIN_CLZ
// Optional version of count_digits for better performance on 32-bit platforms.
inline unsigned count_digits(uint32_t n) {
uint32_t t = (32 - FMT_BUILTIN_CLZ(n | 1)) * 1233 >> 12;
return t - (n < Data::POWERS_OF_10_32[t]) + 1;
}
# endif
#else #else
// Fallback version of count_digits used when __builtin_clz is not available. // Fallback version of count_digits used when __builtin_clz is not available.
inline unsigned count_digits(uint64_t n) { inline unsigned count_digits(uint64_t n) {
@ -606,6 +599,14 @@ inline unsigned count_digits(uint64_t n) {
} }
#endif #endif
#ifdef FMT_BUILTIN_CLZ
// Optional version of count_digits for better performance on 32-bit platforms.
inline unsigned count_digits(uint32_t n) {
uint32_t t = (32 - FMT_BUILTIN_CLZ(n | 1)) * 1233 >> 12;
return t - (n < Data::POWERS_OF_10_32[t]) + 1;
}
#endif
// Formats a decimal unsigned integer value writing into buffer. // Formats a decimal unsigned integer value writing into buffer.
template <typename UInt, typename Char> template <typename UInt, typename Char>
inline void format_decimal(Char *buffer, UInt value, unsigned num_digits) { inline void format_decimal(Char *buffer, UInt value, unsigned num_digits) {