diff options
Diffstat (limited to 'src/liblzma/check/crc64_x86.S')
| -rw-r--r-- | src/liblzma/check/crc64_x86.S | 203 |
1 files changed, 203 insertions, 0 deletions
diff --git a/src/liblzma/check/crc64_x86.S b/src/liblzma/check/crc64_x86.S new file mode 100644 index 00000000..7ad3d889 --- /dev/null +++ b/src/liblzma/check/crc64_x86.S @@ -0,0 +1,203 @@ +/* + * Speed-optimized CRC64 using slicing-by-four algorithm + * Instruction set: i386 + * Optimized for: i686 + * + * This code has been put into the public domain by its authors: + * Igor Pavlov <http://7-zip.org/> + * Lasse Collin <lasse.collin@tukaani.org> + * + * This code needs lzma_crc64_table, which can be created using the + * following C code: + +uint64_t lzma_crc64_table[4][256]; + +void +init_table(void) +{ + static const uint64_t poly64 = UINT64_C(0xC96C5795D7870F42); + + for (size_t s = 0; s < 4; ++s) { + for (size_t b = 0; b < 256; ++b) { + uint64_t r = s == 0 ? b : lzma_crc64_table[s - 1][b]; + + for (size_t i = 0; i < 8; ++i) { + if (r & 1) + r = (r >> 1) ^ poly64; + else + r >>= 1; + } + + lzma_crc64_table[s][b] = r; + } + } +} + + * The prototype of the CRC64 function: + * extern uint64_t lzma_crc64(const uint8_t *buf, size_t size, uint64_t crc); + */ + + .text + .globl lzma_crc64 + .type lzma_crc64, @function + + .align 16 +lzma_crc64: + /* + * Register usage: + * %eax crc LSB + * %edx crc MSB + * %esi buf + * %edi size or buf + size + * %ebx lzma_crc64_table + * %ebp Table index + * %ecx Temporary + */ + pushl %ebx + pushl %esi + pushl %edi + pushl %ebp + movl 0x14(%esp), %esi /* buf */ + movl 0x18(%esp), %edi /* size */ + movl 0x1C(%esp), %eax /* crc LSB */ + movl 0x20(%esp), %edx /* crc MSB */ + + /* + * Store the address of lzma_crc64_table to %ebx. This is needed to + * get position-independent code (PIC). + */ + call .L_PIC +.L_PIC: + popl %ebx + addl $_GLOBAL_OFFSET_TABLE_+[.-.L_PIC], %ebx + movl lzma_crc64_table@GOT(%ebx), %ebx + + /* Complement the initial value. */ + notl %eax + notl %edx + +.L_align: + /* + * Check if there is enough input to use slicing-by-four. + * We need eight bytes, because the loop pre-reads four bytes. + */ + cmpl $8, %edi + jl .L_rest + + /* Check if we have reached alignment of four bytes. */ + testl $3, %esi + jz .L_slice + + /* Calculate CRC of the next input byte. */ + movzbl (%esi), %ebp + incl %esi + movzbl %al, %ecx + xorl %ecx, %ebp + shrdl $8, %edx, %eax + xorl (%ebx, %ebp, 8), %eax + shrl $8, %edx + xorl 4(%ebx, %ebp, 8), %edx + decl %edi + jmp .L_align + +.L_slice: + /* + * If we get here, there's at least eight bytes of aligned input + * available. Make %edi multiple of four bytes. Store the possible + * remainder over the "size" variable in the argument stack. + */ + movl %edi, 0x18(%esp) + andl $-4, %edi + subl %edi, 0x18(%esp) + + /* + * Let %edi be buf + size - 4 while running the main loop. This way + * we can compare for equality to determine when exit the loop. + */ + addl %esi, %edi + subl $4, %edi + + /* Read in the first four aligned bytes. */ + movl (%esi), %ecx + +.L_loop: + xorl %eax, %ecx + movzbl %cl, %ebp + movl 0x1800(%ebx, %ebp, 8), %eax + xorl %edx, %eax + movl 0x1804(%ebx, %ebp, 8), %edx + movzbl %ch, %ebp + xorl 0x1000(%ebx, %ebp, 8), %eax + xorl 0x1004(%ebx, %ebp, 8), %edx + shrl $16, %ecx + movzbl %cl, %ebp + xorl 0x0800(%ebx, %ebp, 8), %eax + xorl 0x0804(%ebx, %ebp, 8), %edx + movzbl %ch, %ebp + addl $4, %esi + xorl (%ebx, %ebp, 8), %eax + xorl 4(%ebx, %ebp, 8), %edx + + /* Check for end of aligned input. */ + cmpl %edi, %esi + + /* + * Copy the next input byte to %ecx. It is slightly faster to + * read it here than at the top of the loop. + */ + movl (%esi), %ecx + jl .L_loop + + /* + * Process the remaining four bytes, which we have already + * copied to %ecx. + */ + xorl %eax, %ecx + movzbl %cl, %ebp + movl 0x1800(%ebx, %ebp, 8), %eax + xorl %edx, %eax + movl 0x1804(%ebx, %ebp, 8), %edx + movzbl %ch, %ebp + xorl 0x1000(%ebx, %ebp, 8), %eax + xorl 0x1004(%ebx, %ebp, 8), %edx + shrl $16, %ecx + movzbl %cl, %ebp + xorl 0x0800(%ebx, %ebp, 8), %eax + xorl 0x0804(%ebx, %ebp, 8), %edx + movzbl %ch, %ebp + addl $4, %esi + xorl (%ebx, %ebp, 8), %eax + xorl 4(%ebx, %ebp, 8), %edx + + /* Copy the number of remaining bytes to %edi. */ + movl 0x18(%esp), %edi + +.L_rest: + /* Check for end of input. */ + testl %edi, %edi + jz .L_return + + /* Calculate CRC of the next input byte. */ + movzbl (%esi), %ebp + incl %esi + movzbl %al, %ecx + xorl %ecx, %ebp + shrdl $8, %edx, %eax + xorl (%ebx, %ebp, 8), %eax + shrl $8, %edx + xorl 4(%ebx, %ebp, 8), %edx + decl %edi + jmp .L_rest + +.L_return: + /* Complement the final value. */ + notl %eax + notl %edx + + popl %ebp + popl %edi + popl %esi + popl %ebx + ret + + .size lzma_crc64, .-lzma_crc64 |