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Added 32- and 64-bit population count utilities. Only used in ARM7 core for now. Requires -msse4.2 or -mpopcnt to use CPU feature on x86, requires -mpopcntb to use CPU feature on POWER.

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This commit is contained in:
Vas Crabb 2017-10-24 17:41:38 +11:00
parent 9b7d323a47
commit 6ab19ed5bc
2 changed files with 64 additions and 9 deletions
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10
src/devices/cpu/arm7/arm7ops.cpp
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@ -263,15 +263,7 @@ int arm7_cpu_device::storeInc(uint32_t pat, uint32_t rbv, int mode)
int arm7_cpu_device::storeDec(uint32_t pat, uint32_t rbv, int mode)
{
// pre-count the # of registers being stored
// TODO[RH]: This is just a popcnt. Consider eminline intrinsic.
int result = 0;
for (int i = 15; i >= 0; i--)
{
if ((pat >> i) & 1)
{
result++;
}
}
int const result = population_count_32(pat & 0x0000ffff);
// adjust starting address
rbv -= (result << 2);

63
src/osd/eminline.h
View File

@ -295,6 +295,69 @@ inline uint8_t count_leading_ones(uint32_t val)
#endif
/*-------------------------------------------------
population_count_32 - return the number of
one bits in a 32-bit value
-------------------------------------------------*/
#ifndef population_count_32
inline unsigned population_count_32(uint32_t val)
{
#if defined(__GNUC__)
// uses CPU feature if available, otherwise falls back to implementation similar to what follows
static_assert(sizeof(val) == sizeof(unsigned));
return unsigned(__builtin_popcount(static_cast<unsigned>(val)));
#else
// optimal Hamming weight assuing fast 32*32->32
constexpr uint32_t m1(0x55555555);
constexpr uint32_t m2(0x33333333);
constexpr uint32_t m4(0x0f0f0f0f);
constexpr uint32_t h01(0x01010101);
val -= (val >> 1) & m1;
val = (val & m2) + ((val >> 2) & m2);
val = (val + (val >> 4)) & m4;
return unsigned((val * h01) >> 24);
#endif
}
#endif
/*-------------------------------------------------
population_count_64 - return the number of
one bits in a 64-bit value
-------------------------------------------------*/
#ifndef population_count_64
inline unsigned population_count_64(uint64_t val)
{
#if defined(__GNUC__)
// uses CPU feature if available, otherwise falls back to implementation similar to what follows
static_assert(sizeof(val) == sizeof(unsigned long long));
return unsigned(__builtin_popcountll(static_cast<unsigned long long>(val)));
#else
// guess that architectures with 64-bit pointers have 64-bit multiplier
if (sizeof(void *) >= sizeof(uint64_t))
{
// optimal Hamming weight assuming fast 64*64->64
constexpr uint64_t m1(0x5555555555555555);
constexpr uint64_t m2(0x3333333333333333);
constexpr uint64_t m4(0x0f0f0f0f0f0f0f0f);
constexpr uint64_t h01(0x0101010101010101);
val -= (val >> 1) & m1;
val = (val & m2) + ((val >> 2) & m2);
val = (val + (val >> 4)) & m4;
return unsigned((val * h01) >> 56);
}
else
{
// fall back to two 32-bit operations to avoid slow multiply
return population_count_32(uint32_t(val)) + population_count_32(uint32_t(val >> 32));
}
#endif
}
#endif
/***************************************************************************
INLINE TIMING FUNCTIONS
***************************************************************************/