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AK+Everywhere: Replace __builtin bit functions

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In order to reduce our reliance on __builtin_{ffs, clz, ctz, popcount},
this commit removes all calls to these functions and replaces them with
the equivalent functions in AK/BuiltinWrappers.h.
This commit is contained in:
Nick Johnson 2021-12-19 15:46:55 -06:00 • committed by Andreas Kling
parent 26bb3e1acf
commit 08e4a1a4dc
20 changed files with 108 additions and 115 deletions
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23
AK/BuiltinWrappers.h
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@ -7,7 +7,6 @@
#pragma once
#include "Concepts.h"
#include "Platform.h"
template<Unsigned IntType>
inline constexpr int popcount(IntType value)
@ -108,3 +107,25 @@ inline constexpr int count_leading_zeroes_safe(IntType value)
return 8 * sizeof(IntType);
return count_leading_zeroes(value);
}
// The function will return the number of leading zeroes in the type. If
// the given number is zero, this function will return the number of bits
// in the IntType.
template<Integral IntType>
inline constexpr int bit_scan_forward(IntType value)
{
#if defined(__GNUC__) || defined(__clang__)
static_assert(sizeof(IntType) <= sizeof(unsigned long long));
if constexpr (sizeof(IntType) <= sizeof(unsigned int))
return __builtin_ffs(value);
if constexpr (sizeof(IntType) == sizeof(unsigned long))
return __builtin_ffsl(value);
if constexpr (sizeof(IntType) == sizeof(unsigned long long))
return __builtin_ffsll(value);
VERIFY_NOT_REACHED();
#else
if (value == 0)
return 0;
return 1 + count_trailing_zeroes(static_cast<MakeUnsigned<IntType>>(value));
#endif
}