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refactor: remove builtin and asm popcount implementation (#7443)

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Yat Ho 2025-03-04 22:16:39 +08:00 • committed by GitHub
parent 05797a9e93
commit 48ba0fd2d8
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1 changed files with 0 additions and 69 deletions
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69
libtransmission/tr-popcount.h
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@ -19,19 +19,6 @@
#define TR_HAVE_STD_POPCOUNT #define TR_HAVE_STD_POPCOUNT
#endif #endif
#if (defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 2))) || \
(defined(__clang__) && (__clang_major__ > 3 || (__clang_major__ == 3 && __clang_minor__ >= 0)))
#ifdef __has_builtin
#if __has_builtin(__builtin_popcount)
#define TR_HAVE_BUILTIN_POPCOUNT
#endif
#endif
#if (defined(__x86_64__) || defined(__i386__)) && defined(__POPCNT__)
#define TR_HAVE_ASM_POPCNT
#endif
#endif
#if defined(TR_HAVE_STD_POPCOUNT) #if defined(TR_HAVE_STD_POPCOUNT)
#include <bit> #include <bit>
#endif #endif
@ -58,62 +45,6 @@ struct tr_popcnt
unsigned_T unsigned_v = static_cast<unsigned_T>(v); unsigned_T unsigned_v = static_cast<unsigned_T>(v);
return static_cast<unsigned>(std::popcount(unsigned_v)); return static_cast<unsigned>(std::popcount(unsigned_v));
} }
#elif defined(TR_HAVE_BUILTIN_POPCOUNT)
/* Use __builtin as opposed to straight assembly to avoid any
strain the latter puts on the optimized. */
static unsigned count(T v)
{
/* Make sure we know how to find that right __builtin_popcount. */
static_assert(
sizeof(T) == sizeof(long long) || sizeof(T) == sizeof(long) || sizeof(T) <= sizeof(int),
"Unknown type size!");
if constexpr (sizeof(T) == sizeof(long long))
{
return __builtin_popcountll(v);
}
else if constexpr (sizeof(T) == sizeof(long))
{
return __builtin_popcountl(v);
}
else if constexpr (sizeof(T) == sizeof(int))
{
return __builtin_popcount(v);
}
else
{
static_assert(sizeof(T) < sizeof(int));
/* Need to avoid sign extension. */
unsigned_T unsigned_v = static_cast<unsigned_T>(v);
return __builtin_popcount(unsigned_v);
}
}
#elif defined(TR_HAVE_ASM_POPCNT)
/* raw assembly. This prohibits constexpr so may be worth dropping if there
* is need for count() to be constexpr. */
static inline unsigned count(T v)
{
unsigned_T unsigned_v = static_cast<unsigned_T>(v);
if constexpr (sizeof(T) >= sizeof(uint32_t))
{
/* Make sure dst == src to avoid false dependency on many x86
* implementations. */
__asm__ __volatile__("popcnt %1, %0" : "=r"(unsigned_v) : "0"(unsigned_v) : "cc");
return unsigned_v;
}
else
{
/* No popcnt instruct for register size < 32. */
uint32_t unsigned_v32 = static_cast<uint32_t>(unsigned_v);
/* Make sure dst == src to avoid false dependency on many x86
* implementations. */
__asm__ __volatile__("popcnt %1, %0" : "=r"(unsigned_v32) : "0"(unsigned_v32) : "cc");
return unsigned_v32;
}
}
#else #else
/* Generic implementation. */ /* Generic implementation. */
static inline unsigned count(T v) static inline unsigned count(T v)