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MathExtras: Parametrize count(Trailing|Leading)Zeros on the type size.

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Otherwise we will always select the generic version for e.g. unsigned
long if uint64_t is typedef'd to 'unsigned long long'. Also remove
enable_if hacks in favor of static_assert.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228921 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer 2015-02-12 13:47:29 +00:00
parent b0d513e1eb
commit 9df4111876
1 changed files with 112 additions and 124 deletions
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236
include/llvm/Support/MathExtras.h
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@ -35,6 +35,65 @@ enum ZeroBehavior {
ZB_Width
};
namespace detail {
template <typename T, std::size_t SizeOfT> struct TrailingZerosCounter {
static std::size_t count(T Val, ZeroBehavior) {
if (!Val)
return std::numeric_limits<T>::digits;
if (Val & 0x1)
return 0;
// Bisection method.
std::size_t ZeroBits = 0;
T Shift = std::numeric_limits<T>::digits >> 1;
T Mask = std::numeric_limits<T>::max() >> Shift;
while (Shift) {
if ((Val & Mask) == 0) {
Val >>= Shift;
ZeroBits |= Shift;
}
Shift >>= 1;
Mask >>= Shift;
}
return ZeroBits;
}
};
#if __GNUC__ >= 4 || _MSC_VER
template <typename T> struct TrailingZerosCounter<T, 4> {
static std::size_t count(T Val, ZeroBehavior ZB) {
if (ZB != ZB_Undefined && Val == 0)
return 32;
#if __has_builtin(__builtin_ctz) || LLVM_GNUC_PREREQ(4, 0, 0)
return __builtin_ctz(Val);
#elif _MSC_VER
unsigned long Index;
_BitScanForward(&Index, Val);
return Index;
#endif
}
};
#if !defined(_MSC_VER) || defined(_M_X64)
template <typename T> struct TrailingZerosCounter<T, 8> {
static std::size_t count(T Val, ZeroBehavior ZB) {
if (ZB != ZB_Undefined && Val == 0)
return 64;
#if __has_builtin(__builtin_ctzll) || LLVM_GNUC_PREREQ(4, 0, 0)
return __builtin_ctzll(Val);
#elif _MSC_VER
unsigned long Index;
_BitScanForward64(&Index, Val);
return Index;
#endif
}
};
#endif
#endif
} // namespace detail
/// \brief Count number of 0's from the least significant bit to the most
/// stopping at the first 1.
///
@ -43,68 +102,66 @@ enum ZeroBehavior {
/// \param ZB the behavior on an input of 0. Only ZB_Width and ZB_Undefined are
/// valid arguments.
template <typename T>
typename std::enable_if<std::numeric_limits<T>::is_integer &&
!std::numeric_limits<T>::is_signed, std::size_t>::type
countTrailingZeros(T Val, ZeroBehavior ZB = ZB_Width) {
(void)ZB;
if (!Val)
return std::numeric_limits<T>::digits;
if (Val & 0x1)
return 0;
// Bisection method.
std::size_t ZeroBits = 0;
T Shift = std::numeric_limits<T>::digits >> 1;
T Mask = std::numeric_limits<T>::max() >> Shift;
while (Shift) {
if ((Val & Mask) == 0) {
Val >>= Shift;
ZeroBits |= Shift;
}
Shift >>= 1;
Mask >>= Shift;
}
return ZeroBits;
std::size_t countTrailingZeros(T Val, ZeroBehavior ZB = ZB_Width) {
static_assert(std::numeric_limits<T>::is_integer &&
!std::numeric_limits<T>::is_signed,
"Only unsigned integral types are allowed.");
return detail::TrailingZerosCounter<T, sizeof(T)>::count(Val, ZB);
}
// Disable signed.
template <typename T>
typename std::enable_if<std::numeric_limits<T>::is_integer &&
std::numeric_limits<T>::is_signed, std::size_t>::type
countTrailingZeros(T, ZeroBehavior = ZB_Width) LLVM_DELETED_FUNCTION;
namespace detail {
template <typename T, std::size_t SizeOfT> struct LeadingZerosCounter {
static std::size_t count(T Val, ZeroBehavior) {
if (!Val)
return std::numeric_limits<T>::digits;
// Bisection method.
std::size_t ZeroBits = 0;
for (T Shift = std::numeric_limits<T>::digits >> 1; Shift; Shift >>= 1) {
T Tmp = Val >> Shift;
if (Tmp)
Val = Tmp;
else
ZeroBits |= Shift;
}
return ZeroBits;
}
};
#if __GNUC__ >= 4 || _MSC_VER
template <>
inline std::size_t countTrailingZeros<uint32_t>(uint32_t Val, ZeroBehavior ZB) {
if (ZB != ZB_Undefined && Val == 0)
return 32;
template <typename T> struct LeadingZerosCounter<T, 4> {
static std::size_t count(T Val, ZeroBehavior ZB) {
if (ZB != ZB_Undefined && Val == 0)
return 32;
#if __has_builtin(__builtin_ctz) || LLVM_GNUC_PREREQ(4, 0, 0)
return __builtin_ctz(Val);
#if __has_builtin(__builtin_clz) || LLVM_GNUC_PREREQ(4, 0, 0)
return __builtin_clz(Val);
#elif _MSC_VER
unsigned long Index;
_BitScanForward(&Index, Val);
return Index;
unsigned long Index;
_BitScanReverse(&Index, Val);
return Index ^ 31;
#endif
}
}
};
#if !defined(_MSC_VER) || defined(_M_X64)
template <>
inline std::size_t countTrailingZeros<uint64_t>(uint64_t Val, ZeroBehavior ZB) {
if (ZB != ZB_Undefined && Val == 0)
return 64;
template <typename T> struct LeadingZerosCounter<T, 8> {
static std::size_t count(T Val, ZeroBehavior ZB) {
if (ZB != ZB_Undefined && Val == 0)
return 64;
#if __has_builtin(__builtin_ctzll) || LLVM_GNUC_PREREQ(4, 0, 0)
return __builtin_ctzll(Val);
#if __has_builtin(__builtin_clzll) || LLVM_GNUC_PREREQ(4, 0, 0)
return __builtin_clzll(Val);
#elif _MSC_VER
unsigned long Index;
_BitScanForward64(&Index, Val);
return Index;
unsigned long Index;
_BitScanReverse64(&Index, Val);
return Index ^ 63;
#endif
}
}
};
#endif
#endif
} // namespace detail
/// \brief Count number of 0's from the most significant bit to the least
/// stopping at the first 1.
@ -114,64 +171,13 @@ inline std::size_t countTrailingZeros<uint64_t>(uint64_t Val, ZeroBehavior ZB) {
/// \param ZB the behavior on an input of 0. Only ZB_Width and ZB_Undefined are
/// valid arguments.
template <typename T>
typename std::enable_if<std::numeric_limits<T>::is_integer &&
!std::numeric_limits<T>::is_signed, std::size_t>::type
countLeadingZeros(T Val, ZeroBehavior ZB = ZB_Width) {
(void)ZB;
if (!Val)
return std::numeric_limits<T>::digits;
// Bisection method.
std::size_t ZeroBits = 0;
for (T Shift = std::numeric_limits<T>::digits >> 1; Shift; Shift >>= 1) {
T Tmp = Val >> Shift;
if (Tmp)
Val = Tmp;
else
ZeroBits |= Shift;
}
return ZeroBits;
std::size_t countLeadingZeros(T Val, ZeroBehavior ZB = ZB_Width) {
static_assert(std::numeric_limits<T>::is_integer &&
!std::numeric_limits<T>::is_signed,
"Only unsigned integral types are allowed.");
return detail::LeadingZerosCounter<T, sizeof(T)>::count(Val, ZB);
}
// Disable signed.
template <typename T>
typename std::enable_if<std::numeric_limits<T>::is_integer &&
std::numeric_limits<T>::is_signed, std::size_t>::type
countLeadingZeros(T, ZeroBehavior = ZB_Width) LLVM_DELETED_FUNCTION;
#if __GNUC__ >= 4 || _MSC_VER
template <>
inline std::size_t countLeadingZeros<uint32_t>(uint32_t Val, ZeroBehavior ZB) {
if (ZB != ZB_Undefined && Val == 0)
return 32;
#if __has_builtin(__builtin_clz) || LLVM_GNUC_PREREQ(4, 0, 0)
return __builtin_clz(Val);
#elif _MSC_VER
unsigned long Index;
_BitScanReverse(&Index, Val);
return Index ^ 31;
#endif
}
#if !defined(_MSC_VER) || defined(_M_X64)
template <>
inline std::size_t countLeadingZeros<uint64_t>(uint64_t Val, ZeroBehavior ZB) {
if (ZB != ZB_Undefined && Val == 0)
return 64;
#if __has_builtin(__builtin_clzll) || LLVM_GNUC_PREREQ(4, 0, 0)
return __builtin_clzll(Val);
#elif _MSC_VER
unsigned long Index;
_BitScanReverse64(&Index, Val);
return Index ^ 63;
#endif
}
#endif
#endif
/// \brief Get the index of the first set bit starting from the least
/// significant bit.
///
@ -179,22 +185,13 @@ inline std::size_t countLeadingZeros<uint64_t>(uint64_t Val, ZeroBehavior ZB) {
///
/// \param ZB the behavior on an input of 0. Only ZB_Max and ZB_Undefined are
/// valid arguments.
template <typename T>
typename std::enable_if<std::numeric_limits<T>::is_integer &&
!std::numeric_limits<T>::is_signed, T>::type
findFirstSet(T Val, ZeroBehavior ZB = ZB_Max) {
template <typename T> T findFirstSet(T Val, ZeroBehavior ZB = ZB_Max) {
if (ZB == ZB_Max && Val == 0)
return std::numeric_limits<T>::max();
return countTrailingZeros(Val, ZB_Undefined);
}
// Disable signed.
template <typename T>
typename std::enable_if<std::numeric_limits<T>::is_integer &&
std::numeric_limits<T>::is_signed, T>::type
findFirstSet(T, ZeroBehavior = ZB_Max) LLVM_DELETED_FUNCTION;
/// \brief Get the index of the last set bit starting from the least
/// significant bit.
///
@ -202,10 +199,7 @@ findFirstSet(T, ZeroBehavior = ZB_Max) LLVM_DELETED_FUNCTION;
///
/// \param ZB the behavior on an input of 0. Only ZB_Max and ZB_Undefined are
/// valid arguments.
template <typename T>
typename std::enable_if<std::numeric_limits<T>::is_integer &&
!std::numeric_limits<T>::is_signed, T>::type
findLastSet(T Val, ZeroBehavior ZB = ZB_Max) {
template <typename T> T findLastSet(T Val, ZeroBehavior ZB = ZB_Max) {
if (ZB == ZB_Max && Val == 0)
return std::numeric_limits<T>::max();
@ -215,12 +209,6 @@ findLastSet(T Val, ZeroBehavior ZB = ZB_Max) {
(std::numeric_limits<T>::digits - 1);
}
// Disable signed.
template <typename T>
typename std::enable_if<std::numeric_limits<T>::is_integer &&
std::numeric_limits<T>::is_signed, T>::type
findLastSet(T, ZeroBehavior = ZB_Max) LLVM_DELETED_FUNCTION;
/// \brief Macro compressed bit reversal table for 256 bits.
///
/// http://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable