* Copyright 2014, Paweł Dziepak, pdziepak@quarnos.org.
* Distributed under the terms of the MIT License.
*/
#include <array>
#include <cstddef>
#include <cstdint>
#include <emmintrin.h>
static inline void
memset_repstos(uint8_t* destination, uint8_t value, size_t length)
{
__asm__ __volatile__("rep stosb"
: "+D" (destination), "+c" (length)
: "a" (value)
: "memory");
}
static inline void
memset_sse(uint8_t* destination, uint8_t value, size_t length)
{
__m128i packed = _mm_set1_epi8(value);
auto end = reinterpret_cast<__m128i*>(destination + length - 16);
auto diff = reinterpret_cast<uintptr_t>(destination) % 16;
if (diff) {
diff = 16 - diff;
length -= diff;
_mm_storeu_si128(reinterpret_cast<__m128i*>(destination), packed);
}
auto ptr = reinterpret_cast<__m128i*>(destination + diff);
while (length >= 64) {
_mm_store_si128(ptr++, packed);
_mm_store_si128(ptr++, packed);
_mm_store_si128(ptr++, packed);
_mm_store_si128(ptr++, packed);
length -= 64;
}
while (length >= 16) {
_mm_store_si128(ptr++, packed);
length -= 16;
}
_mm_storeu_si128(end, packed);
}
static inline void
memset_small(uint8_t* destination, uint8_t value, size_t length)
{
if (length >= 8) {
auto packed = value * 0x101010101010101ul;
auto ptr = reinterpret_cast<uint64_t*>(destination);
auto end = reinterpret_cast<uint64_t*>(destination + length - 8);
while (length >= 8) {
*ptr++ = packed;
length -= 8;
}
*end = packed;
} else {
while (length--) {
*destination++ = value;
}
}
}
extern "C" void*
memset(void* ptr, int chr, size_t length)
{
auto value = static_cast<unsigned char>(chr);
auto destination = static_cast<uint8_t*>(ptr);
if (length < 32) {
memset_small(destination, value, length);
return ptr;
}
if (length < 2048) {
memset_sse(destination, value, length);
return ptr;
}
memset_repstos(destination, value, length);
return ptr;
}
