diff options
Diffstat (limited to 'runtime/base/bit_utils.h')
| -rw-r--r-- | runtime/base/bit_utils.h | 23 |
1 files changed, 15 insertions, 8 deletions
diff --git a/runtime/base/bit_utils.h b/runtime/base/bit_utils.h index 1da6750b45..1b0d774419 100644 --- a/runtime/base/bit_utils.h +++ b/runtime/base/bit_utils.h @@ -29,21 +29,28 @@ namespace art { template<typename T> static constexpr int CLZ(T x) { static_assert(std::is_integral<T>::value, "T must be integral"); - // TODO: assert unsigned. There is currently many uses with signed values. + static_assert(std::is_unsigned<T>::value, "T must be unsigned"); static_assert(sizeof(T) <= sizeof(long long), // NOLINT [runtime/int] [4] "T too large, must be smaller than long long"); - return (sizeof(T) == sizeof(uint32_t)) - ? __builtin_clz(x) // TODO: __builtin_clz[ll] has undefined behavior for x=0 - : __builtin_clzll(x); + return + DCHECK_CONSTEXPR(x != 0, "x must not be zero", T(0)) + (sizeof(T) == sizeof(uint32_t)) + ? __builtin_clz(x) + : __builtin_clzll(x); } template<typename T> static constexpr int CTZ(T x) { static_assert(std::is_integral<T>::value, "T must be integral"); - // TODO: assert unsigned. There is currently many uses with signed values. - return (sizeof(T) == sizeof(uint32_t)) - ? __builtin_ctz(x) - : __builtin_ctzll(x); + // It is not unreasonable to ask for trailing zeros in a negative number. As such, do not check + // that T is an unsigned type. + static_assert(sizeof(T) <= sizeof(long long), // NOLINT [runtime/int] [4] + "T too large, must be smaller than long long"); + return + DCHECK_CONSTEXPR(x != 0, "x must not be zero", T(0)) + (sizeof(T) == sizeof(uint32_t)) + ? __builtin_ctz(x) + : __builtin_ctzll(x); } template<typename T> |