AuroraSupport/AuROXTL
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[+] AuBitScanForwardItr

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[+] AuBitScanReverseItr
[*] u64 on 32bit CPU fixes mostly under reverse bit itrs
This commit is contained in:
Reece Wilson 2024-09-22 21:06:05 +01:00
parent a563ba611f
commit 4d7f4fab7d
1 changed files with 51 additions and 7 deletions
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58
Include/auROXTL/auBitsUtils.hpp
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@ -106,6 +106,9 @@ static auline void AuBitClear(T &value, AuUInt8 idx)
value &= ~(T(1) << T(idx));
}
/// Bit scan forward from LSB to MSB, returning LSB-indexed offset in index and true if found.
/// xref MSDN for "_BitScanForward" intrin
/// (+ u64 variants work on 32bit targets)
template <class T>
static auline bool AuBitScanForward(AuUInt8 &index, T value)
{
@ -144,7 +147,7 @@ static auline bool AuBitScanForward(AuUInt8 &index, T value)
if constexpr (sizeof(T) == sizeof(AuUInt64))
{
#if defined(AURORA_IS_32BIT)
auto lower = static_cast<AuUInt32>(value & 0xffffffff));
auto lower = static_cast<AuUInt32>(value & 0xffffffff);
if (lower == 0)
{
ret = __builtin_ctzl(static_cast<AuUInt32>((value >> 32) & 0xffffffff));
@ -173,6 +176,9 @@ static auline bool AuBitScanForward(AuUInt8 &index, T value)
return success;
}
/// Bit scan reverse from MSB to LSB, returning LSB-indexed offset in index and true if found.
/// xref MSDN for "_BitScanReverse" intrin
/// (+ u64 variants work on 32bit targets)
template <class T>
static auline bool AuBitScanReverse(AuUInt8 &index, T value)
{
@ -192,6 +198,9 @@ static auline bool AuBitScanReverse(AuUInt8 &index, T value)
{
return false;
}
}
else
{
ret += 32;
}
#else
@ -211,16 +220,16 @@ static auline bool AuBitScanReverse(AuUInt8 &index, T value)
if constexpr (sizeof(T) == sizeof(AuUInt64))
{
#if defined(AURORA_IS_32BIT)
auto lower = static_cast<AuUInt32>((value >> 32) & 0xffffffff);
if (lower == 0)
auto higher = static_cast<AuUInt32>((value >> 32) & 0xffffffff);
if (higher == 0)
{
ret = __builtin_clzl(static_cast<AuUInt32>(value & 0xffffffff)));
ret = 63 - ret;
ret = __builtin_clzl(static_cast<AuUInt32>(value & 0xffffffff));
ret = 31 - ret;
}
else
{
ret = __builtin_clzl(static_cast<AuUInt32>(lower));
ret = 31 - ret;
ret = __builtin_clzl(static_cast<AuUInt32>(higher));
ret = 63 - ret;
}
#else
ret = __builtin_clzll(static_cast<AuUInt64>(value));
@ -258,6 +267,41 @@ static auline bool AuBitScanReverse(AuUInt8 &index, T value)
return success;
}
/// AuBitScanForward utility - offsets value by uOffset of last uIndex
template <class T>
static auline bool AuBitScanForwardItr(AuUInt8 &uIndex, T value, AuUInt8 uOffset = 0)
{
if (AuBitScanForward<T>(uIndex, value >> uOffset))
{
uIndex += uOffset;
return true;
}
else
{
return false;
}
}
/// AuBitScanReverse utility - offsets value by uOffset of last uIndex, starting at end bit offset, to break/false on 0.
template <class T>
static auline bool AuBitScanReverseItr(AuUInt8 &uIndex, T value, AuUInt8 uOffset = sizeof(T) * 8)
{
if (uOffset == 0)
{
return false;
}
AuUInt32 uBitOffset2 = AuUInt32(8 * sizeof(T)) - uOffset;
if (AuBitScanReverse<T>(uIndex, (T(value) << uBitOffset2)))
{
uIndex -= uBitOffset2;
return true;
}
else
{
return false;
}
}
template <class T>
struct AuHalfWord
{