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Add countl_zero function

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Signed-off-by: Vladislav Shchapov <vladislav@shchapov.ru>
This commit is contained in:
Vladislav Shchapov 2022-11-30 22:32:32 +05:00 committed by Victor Zverovich
parent 8d50d814db
commit d24be2e95c
2 changed files with 21 additions and 1 deletions
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12
include/fmt/format.h
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@ -472,6 +472,16 @@ inline auto bit_cast(const From& from) -> To {
return result;
}
FMT_CONSTEXPR20 inline auto countl_zero(uint32_t n) -> int {
#ifdef FMT_BUILTIN_CLZ
if (!is_constant_evaluated()) return FMT_BUILTIN_CLZ(n);
#endif
int lz = 0;
constexpr uint32_t msb_mask = 1u << (num_bits<uint32_t>() - 1);
for (; (n & msb_mask) == 0; n <<= 1) lz++;
return lz;
}
FMT_INLINE void assume(bool condition) {
(void)condition;
#if FMT_HAS_BUILTIN(__builtin_assume) && !FMT_ICC_VERSION
@ -3149,7 +3159,7 @@ FMT_CONSTEXPR20 void format_hexfloat(Float value, int precision,
const auto leading_mask = carrier_uint(0xF) << leading_shift;
const auto leading_xdigit =
static_cast<uint32_t>((f.f & leading_mask) >> leading_shift);
if (leading_xdigit > 1) f.e -= (32 - FMT_BUILTIN_CLZ(leading_xdigit) - 1);
if (leading_xdigit > 1) f.e -= (32 - countl_zero(leading_xdigit) - 1);
int print_xdigits = num_xdigits - 1;
if (precision >= 0 && print_xdigits > precision) {

10
test/format-impl-test.cc
View File

@ -353,6 +353,16 @@ TEST(format_impl_test, count_digits) {
test_count_digits<uint64_t>();
}
TEST(format_impl_test, countl_zero) {
constexpr auto num_bits = fmt::detail::num_bits<uint32_t>();
uint32_t n = 1u;
for (int i = 1; i < num_bits - 1; i++) {
n <<= 1;
EXPECT_EQ(fmt::detail::countl_zero(n - 1), num_bits - i);
EXPECT_EQ(fmt::detail::countl_zero(n), num_bits - i - 1);
}
}
#if FMT_USE_FLOAT128
TEST(format_impl_test, write_float128) {
auto s = std::string();