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[util] Make bitset more constexpr-friendly

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In order to more easily express constants as bitsets, add more constexpr
to util::bitset. This allows expressing uint64_t constants as bitsets in
the code instead, without changing the generated assembly, to make code
more readable.
This commit is contained in:
Justin C. Miller
2022-09-11 14:07:21 -07:00
parent e2f4dad288
commit 1d4c66a9a0
1 changed files with 30 additions and 12 deletions
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42
src/libraries/util/util/bitset.h
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@@ -10,7 +10,6 @@
#include <stdint.h> #include <stdint.h>
namespace util { namespace util {
/// A statically-sized templated bitset /// A statically-sized templated bitset
@@ -62,25 +61,36 @@ private:
uint64_t m_bits[num_elems] = {0}; uint64_t m_bits[num_elems] = {0};
}; };
namespace {
}
/// A statically-sized templated bitset /// A statically-sized templated bitset
template <> template <>
class bitset<64> class bitset<64>
{ {
static constexpr unsigned num_elems = 1; static constexpr unsigned num_elems = 1;
template <typename T>
static constexpr uint64_t bit_or(T b) { return 1ull << uint64_t(b); }
template <typename T, typename ...Args>
static constexpr uint64_t bit_or(T b, Args... bs) { return (1ull << uint64_t(b)) | bit_or(bs...); }
public: public:
bitset(uint64_t v = 0) : m_bits {v} {} bitset(uint64_t v = 0) : m_bits {v} {}
bitset(const bitset<64> &o) : m_bits {o.m_bits} {} bitset(const bitset<64> &o) : m_bits {o.m_bits} {}
template <typename ...Args>
constexpr explicit bitset(Args... args) : m_bits(bit_or(args...)) {}
template <typename T> template <typename T>
inline bitset & operator=(T v) { m_bits = static_cast<uint64_t>(v); return *this; } inline bitset & operator=(T v) { m_bits = static_cast<uint64_t>(v); return *this; }
inline operator uint64_t () const { return m_bits; } inline constexpr operator const uint64_t () const { return m_bits; }
template <typename T> template <typename T>
inline bool get(T i) const { inline constexpr bool get(T i) const {
assert(static_cast<unsigned>(i) < 64);
return m_bits & bit(i); return m_bits & bit(i);
} }
@@ -99,15 +109,15 @@ public:
} }
template <typename T> template <typename T>
inline bool operator[](T i) const { return get(i); } inline constexpr bool operator[](T i) const { return get(i); }
inline bool empty() const { return m_bits == 0; } inline constexpr bool empty() const { return m_bits == 0; }
inline uint64_t value() const { return m_bits; } inline constexpr uint64_t value() const { return m_bits; }
private: private:
template <typename T> template <typename T>
inline uint64_t bit(T i) const { return (1ull << static_cast<uint64_t>(i)); } inline constexpr uint64_t bit(T i) const { return (1ull << static_cast<uint64_t>(i)); }
uint64_t m_bits; uint64_t m_bits;
}; };
@@ -118,19 +128,27 @@ class bitset<32>
{ {
static constexpr unsigned num_elems = 1; static constexpr unsigned num_elems = 1;
template <typename T>
static constexpr uint32_t bit_or(T b) { return 1u << uint32_t(b); }
template <typename T, typename ...Args>
static constexpr uint32_t bit_or(T b, Args... bs) { return (1u << uint32_t(b)) | bit_or(bs...); }
public: public:
bitset(uint32_t v = 0) : m_bits {v} {} bitset(uint32_t v = 0) : m_bits {v} {}
bitset(const bitset<32> &o) : m_bits {o.m_bits} {} bitset(const bitset<32> &o) : m_bits {o.m_bits} {}
template <typename ...Args>
constexpr bitset(Args... args) : m_bits(bit_or(args...)) {}
template <typename T> template <typename T>
inline bitset & operator=(T v) { m_bits = static_cast<uint32_t>(v); return *this; } inline bitset & operator=(T v) { m_bits = static_cast<uint32_t>(v); return *this; }
inline operator uint32_t () const { return m_bits; } inline constexpr operator uint32_t () const { return m_bits; }
template <typename T> template <typename T>
inline bool get(T i) const { inline constexpr bool get(T i) const {
assert(static_cast<unsigned>(i) < 32);
return m_bits & bit(i); return m_bits & bit(i);
} }
@@ -153,7 +171,7 @@ public:
inline bool empty() const { return m_bits == 0; } inline bool empty() const { return m_bits == 0; }
inline uint32_t value() const { return m_bits; } inline constexpr uint32_t value() const { return m_bits; }
private: private:
template <typename T> template <typename T>