[英]Global bitwise shift of 128, 256, 512 bit registry using intrinsics?
您可能想看看std::bitset
,它是編譯時已知的許多位的容器。 如果我對您的問題理解正確,那就是您要嘗試使用數組模擬的內容。 bitset類包含重載的>>
和<<
運算符以執行移位,並且可以在您的編譯器/標准庫組合中優化這些實現。
以下是一些x86左移函數,這些函數通過內部函數使用xmm和ymm寄存器。 進行相應的右移功能應該不難。 它們取自軟件lfsr基准測試 :
//----------------------------------------------------------------------------
// bit shift left a 128-bit value using xmm registers
// __m128i *data - data to shift
// int count - number of bits to shift
// return: __m128i - carry out bit(s)
static __m128i bitShiftLeft128xmm (__m128i *data, int count)
{
__m128i innerCarry, carryOut;
innerCarry = _mm_srli_epi64 (*data, 64 - count); // carry outs in bit 0 of each qword
carryOut = _mm_shuffle_epi32 (innerCarry, 0xFE); // upper carry in xmm bit 0, others zero
innerCarry = _mm_shuffle_epi32 (innerCarry, 0xCF); // lower carry in xmm bit 64, others zero
*data = _mm_slli_epi64 (*data, count); // shift all qwords left
*data = _mm_or_si128 (*data, innerCarry); // propagate carry out from low qword
return carryOut;
}
//----------------------------------------------------------------------------
// bit shift left a 256-bit value using xmm registers
// __m128i *data - data to shift, ls part stored first
// int count - number of bits to shift
// return: __m128i - carry out bit(s)
static __m128i bitShiftLeft256xmm (__m128i *data, int count)
{
__m128i carryOut0, carryOut1;
carryOut0 = bitShiftLeft128xmm (&data [0], count);
carryOut1 = bitShiftLeft128xmm (&data [1], count);
data [1] = _mm_or_si128 (data [1], carryOut0);
return carryOut1;
}
//----------------------------------------------------------------------------
// bit shift left a 512-bit value using xmm registers
// __m128i *data - data to shift, ls part stored first
// int count - number of bits to shift
// return: __m128i - carry out bit(s)
static __m128i bitShiftLeft512xmm (__m128i *data, int count)
{
__m128i carryOut0, carryOut1;
carryOut0 = bitShiftLeft256xmm (&data [0], count);
carryOut1 = bitShiftLeft256xmm (&data [2], count);
data [2] = _mm_or_si128 (data [2], carryOut0);
return carryOut1;
}
//----------------------------------------------------------------------------
// bit shift left a 256-bit value using ymm registers
// __m256i *data - data to shift
// int count - number of bits to shift
// return: __m256i - carry out bit(s)
static __m256i bitShiftLeft256ymm (__m256i *data, int count)
{
__m256i innerCarry, carryOut, rotate;
innerCarry = _mm256_srli_epi64 (*data, 64 - count); // carry outs in bit 0 of each qword
rotate = _mm256_permute4x64_epi64 (innerCarry, 0x93); // rotate ymm left 64 bits
innerCarry = _mm256_blend_epi32 (_mm256_setzero_si256 (), rotate, 0xFC); // clear lower qword
*data = _mm256_slli_epi64 (*data, count); // shift all qwords left
*data = _mm256_or_si256 (*data, innerCarry); // propagate carrys from low qwords
carryOut = _mm256_xor_si256 (innerCarry, rotate); // clear all except lower qword
return carryOut;
}
//----------------------------------------------------------------------------
// bit shift left a 512-bit value using ymm registers
// __m256i *data - data to shift, ls part stored first
// int count - number of bits to shift
// return: __m256i - carry out bit(s)
static __m256i bitShiftLeft512ymm (__m256i *data, int count)
{
__m256i carryOut0, carryOut1;
carryOut0 = bitShiftLeft256ymm (&data [0], count);
carryOut1 = bitShiftLeft256ymm (&data [1], count);
data [1] = _mm256_or_si256 (data [1], carryOut0);
return carryOut1;
}
//----------------------------------------------------------------------------
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