hw-prim-bits-0.1.0.2: cbits/bits.c

#include "bits.h"

uint32_t fast_pdep32(
    uint32_t src,
    uint32_t mask) {
  uint32_t result;

  __asm__ __volatile__("pdepl  %%ecx,%%ebx,%%eax"
                       :"=a"(result)
                       :"a"(result), "b"(src), "c"(mask)
                       );

  return result;
}

uint32_t slow_pdep32(
    uint32_t src,
    uint32_t mask) {
  uint32_t result = 0;

  while (1) {
    const uint32_t lowest = (-mask & mask);

    if (lowest == 0) {
      break;
    }

    const uint32_t lsb = (uint32_t)((int32_t)(src << 63) >> 63);

    result |= lsb & lowest;
    mask &= ~lowest;
    src >>= 1;
  }

  return result;
}

uint64_t fast_pdep64(
    uint64_t src,
    uint64_t mask) {
  uint64_t result;

  __asm__ __volatile__("pdepq  %%rcx,%%rbx,%%rax"
                       :"=a"(result)
                       :"a"(result), "b"(src), "c"(mask)
                       );

  return result;
}

uint64_t slow_pdep64(
    uint64_t src,
    uint64_t mask) {
  uint64_t result = 0;

  while (1) {
    const uint64_t lowest = (-mask & mask);

    if (lowest == 0) {
      break;
    }

    const uint64_t lsb = (uint64_t)((int64_t)(src << 63) >> 63);

    result |= lsb & lowest;
    mask &= ~lowest;
    src >>= 1;
  }

  return result;
}