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liblzma: Set LZMA_MEMCMPLEN_EXTRA depending on the compare method.

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This commit is contained in:
Lasse Collin 2015-01-26 21:24:39 +02:00
parent 3c500174ed
commit c45757135f
1 changed files with 10 additions and 5 deletions
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15
src/liblzma/common/memcmplen.h
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@ -19,11 +19,6 @@
# include <immintrin.h>
#endif
/// How many extra bytes lzma_memcmplen() may read. This depends on
/// the method but since it is just a few bytes the biggest possible
/// value is used here.
#define LZMA_MEMCMPLEN_EXTRA 16
/// Find out how many equal bytes the two buffers have.
///
@ -39,6 +34,11 @@
///
/// \return Number of equal bytes in the buffers is returned.
/// This is always at least len and at most limit.
///
/// \note LZMA_MEMCMPLEN_EXTRA defines how many extra bytes may be read.
/// It's rounded up to 2^n. This extra amount needs to be
/// allocated in the buffers being used. It needs to be
/// initialized too to keep Valgrind quiet.
static inline uint32_t lzma_attribute((__always_inline__))
lzma_memcmplen(const uint8_t *buf1, const uint8_t *buf2,
uint32_t len, uint32_t limit)
@ -59,6 +59,7 @@ lzma_memcmplen(const uint8_t *buf1, const uint8_t *buf2,
// to be a good method. This may be fine on other 64-bit CPUs too.
// On big endian one should use xor instead of subtraction and switch
// to __builtin_clzll().
#define LZMA_MEMCMPLEN_EXTRA 8
while (len < limit) {
const uint64_t x = *(const uint64_t *)(buf1 + len)
- *(const uint64_t *)(buf2 + len);
@ -91,6 +92,7 @@ lzma_memcmplen(const uint8_t *buf1, const uint8_t *buf2,
// version is sometimes significantly faster and sometimes
// slightly slower than this SSE2 version, so this SSE2
// version isn't used on x86-64.
# define LZMA_MEMCMPLEN_EXTRA 16
while (len < limit) {
const uint32_t x = 0xFFFF ^ _mm_movemask_epi8(_mm_cmpeq_epi8(
_mm_loadu_si128((const __m128i *)(buf1 + len)),
@ -116,6 +118,7 @@ lzma_memcmplen(const uint8_t *buf1, const uint8_t *buf2,
#elif defined(TUKLIB_FAST_UNALIGNED_ACCESS) && !defined(WORDS_BIGENDIAN)
// Generic 32-bit little endian method
# define LZMA_MEMCMPLEN_EXTRA 4
while (len < limit) {
uint32_t x = *(const uint32_t *)(buf1 + len)
- *(const uint32_t *)(buf2 + len);
@ -138,6 +141,7 @@ lzma_memcmplen(const uint8_t *buf1, const uint8_t *buf2,
#elif defined(TUKLIB_FAST_UNALIGNED_ACCESS) && defined(WORDS_BIGENDIAN)
// Generic 32-bit big endian method
# define LZMA_MEMCMPLEN_EXTRA 4
while (len < limit) {
uint32_t x = *(const uint32_t *)(buf1 + len)
^ *(const uint32_t *)(buf2 + len);
@ -160,6 +164,7 @@ lzma_memcmplen(const uint8_t *buf1, const uint8_t *buf2,
#else
// Simple portable version that doesn't use unaligned access.
# define LZMA_MEMCMPLEN_EXTRA 0
while (len < limit && buf1[len] == buf2[len])
++len;