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Remove bsr2log10

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This commit is contained in:
Victor Zverovich 2021-06-04 21:33:05 -07:00
parent 7c3d3dfa29
commit 4678192c88
1 changed files with 7 additions and 12 deletions
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19
include/fmt/format.h
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@ -926,17 +926,6 @@ extern template struct basic_data<void>;
// This is a struct rather than an alias to avoid shadowing warnings in gcc.
struct data : basic_data<> {};
// Maps bsr(n) to ceil(log10(pow(2, bsr(n) + 1) - 1)).
// This is a function instead of an array to workaround a bug in GCC10 (#1810).
FMT_INLINE auto bsr2log10(int bsr) -> uint16_t {
static constexpr uint16_t data[] = {
1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5,
6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 9, 9, 9, 10, 10, 10,
10, 11, 11, 11, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 15, 15,
15, 16, 16, 16, 16, 17, 17, 17, 18, 18, 18, 19, 19, 19, 19, 20};
return data[bsr];
}
template <typename T> FMT_CONSTEXPR auto count_digits_fallback(T n) -> int {
int count = 1;
for (;;) {
@ -965,7 +954,13 @@ FMT_CONSTEXPR20 inline auto count_digits(uint64_t n) -> int {
}
#ifdef FMT_BUILTIN_CLZLL
// https://github.com/fmtlib/format-benchmark/blob/master/digits10
auto t = bsr2log10(FMT_BUILTIN_CLZLL(n | 1) ^ 63);
// Maps bsr(n) to ceil(log10(pow(2, bsr(n) + 1) - 1)).
FMT_STATIC_CONSTEXPR uint16_t bsr2log10[] = {
1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5,
6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 9, 9, 9, 10, 10, 10,
10, 11, 11, 11, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 15, 15,
15, 16, 16, 16, 16, 17, 17, 17, 18, 18, 18, 19, 19, 19, 19, 20};
auto t = bsr2log10[FMT_BUILTIN_CLZLL(n | 1) ^ 63];
constexpr const uint64_t zero_or_powers_of_10[] = {
0, 0, FMT_POWERS_OF_10(1U), FMT_POWERS_OF_10(1000000000ULL),
10000000000000000000ULL};