*/
/*
- * Copyright (C) 2012, 2013 Eric Biggers
+ * Copyright (C) 2012, 2013, 2014 Eric Biggers
*
* This file is part of wimlib, a library for working with WIM files.
*
#include <string.h>
+#ifdef __SSE2__
+# include <emmintrin.h>
+#endif
+
/* Huffman decoding tables and maps from symbols to code lengths. */
struct lzx_tables {
}
static void
-undo_call_insn_translation(u32 *call_insn_target, s32 input_pos,
- s32 file_size)
+undo_call_insn_translation(u32 *call_insn_target, s32 input_pos)
{
s32 abs_offset;
s32 rel_offset;
abs_offset = le32_to_cpu(*call_insn_target);
- if (abs_offset >= -input_pos && abs_offset < file_size) {
+ if (abs_offset >= -input_pos && abs_offset < LZX_WIM_MAGIC_FILESIZE) {
if (abs_offset >= 0) {
/* "good translation" */
rel_offset = abs_offset - input_pos;
} else {
/* "compensating translation" */
- rel_offset = abs_offset + file_size;
+ rel_offset = abs_offset + LZX_WIM_MAGIC_FILESIZE;
}
*call_insn_target = cpu_to_le32(rel_offset);
}
* as it is used in calculating the translated jump targets. But in WIM files,
* this file size is always the same (LZX_WIM_MAGIC_FILESIZE == 12000000).*/
static void
-undo_call_insn_preprocessing(u8 *uncompressed_data, s32 uncompressed_size)
+undo_call_insn_preprocessing(u8 *uncompressed_data, size_t uncompressed_size)
{
- for (s32 i = 0; i < uncompressed_size - 10; i++) {
- if (uncompressed_data[i] == 0xe8) {
- undo_call_insn_translation((u32*)&uncompressed_data[i + 1],
- i,
- LZX_WIM_MAGIC_FILESIZE);
- i += 4;
- }
+#ifdef __SSE2__
+
+ /* SSE2 vectorized implementation for x86_64. This speeds up LZX
+ * decompression by about 5-8% overall. (Usually --- the performance
+ * actually regresses slightly in the degenerate case that the data
+ * consists entirely of 0xe8 bytes.) */
+ __m128i *p128 = (__m128i *)uncompressed_data;
+ u32 valid_mask = 0xFFFFFFFF;
+
+ if (uncompressed_size >= 32 &&
+ ((uintptr_t)uncompressed_data % 16 == 0))
+ {
+ __m128i * const end128 = p128 + uncompressed_size / 16 - 1;
+
+ /* Create a vector of all 0xe8 bytes */
+ const __m128i e8_bytes = _mm_set1_epi8(0xe8);
+
+ /* Iterate through the 16-byte vectors in the input. */
+ do {
+ /* Compare the current 16-byte vector with the vector of
+ * all 0xe8 bytes. This produces 0xff where the byte is
+ * 0xe8 and 0x00 where it is not. */
+ __m128i cmpresult = _mm_cmpeq_epi8(*p128, e8_bytes);
+
+ /* Map the comparison results into a single 16-bit
+ * number. It will contain a 1 bit when the
+ * corresponding byte in the current 16-byte vector is
+ * an e8 byte. Note: the low-order bit corresponds to
+ * the first (lowest address) byte. */
+ u32 e8_mask = _mm_movemask_epi8(cmpresult);
+
+ if (!e8_mask) {
+ /* If e8_mask is 0, then none of these 16 bytes
+ * have value 0xe8. No e8 translation is
+ * needed, and there is no restriction that
+ * carries over to the next 16 bytes. */
+ valid_mask = 0xFFFFFFFF;
+ } else {
+ /* At least one byte has value 0xe8.
+ *
+ * The AND with valid_mask accounts for the fact
+ * that we can't start an e8 translation that
+ * overlaps the previous one. */
+ while ((e8_mask &= valid_mask)) {
+
+ /* Count the number of trailing zeroes
+ * in e8_mask. This will produce the
+ * index of the byte, within the 16, at
+ * which the next e8 translation should
+ * be done. */
+ u32 bit = __builtin_ctz(e8_mask);
+
+ /* Do the e8 translation. */
+ u8 *p8 = (u8 *)p128 + bit;
+ undo_call_insn_translation((s32 *)(p8 + 1),
+ p8 - uncompressed_data);
+
+ /* Don't start an e8 translation in the
+ * next 4 bytes. */
+ valid_mask &= ~((u32)0x1F << bit);
+ }
+ /* Moving on to the next vector. Shift and set
+ * valid_mask accordingly. */
+ valid_mask >>= 16;
+ valid_mask |= 0xFFFF0000;
+ }
+ } while (++p128 < end128);
+ }
+
+ u8 *p8 = (u8 *)p128;
+ while (!(valid_mask & 1)) {
+ p8++;
+ valid_mask >>= 1;
+ }
+#else /* __SSE2__ */
+ u8 *p8 = uncompressed_data;
+#endif /* !__SSE2__ */
+
+ if (uncompressed_size > 10) {
+ /* Finish any bytes that weren't processed by the vectorized
+ * implementation. */
+ u8 *p8_end = uncompressed_data + uncompressed_size - 10;
+ do {
+ if (*p8 == 0xe8) {
+ undo_call_insn_translation((s32 *)(p8 + 1),
+ p8 - uncompressed_data);
+ p8 += 5;
+ } else {
+ p8++;
+ }
+ } while (p8 < p8_end);
}
}