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arcfour-amd64.S
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/*
** RC4 implementation optimized for AMD64.
**
** Author: Marc Bevand <bevand_m (at) epita.fr>
** Licence: I hereby disclaim the copyright on this code and place it
** in the public domain.
**
** The throughput achieved by this code is about 320 MBytes/sec, on
** a 1.8 GHz AMD Opteron (rev C0) processor.
**
** 2013/12/20 <jussi.kivilinna@iki.fi>:
** - Integrated to libgcrypt
** - 4.18 cycles/byte on Intel i5-4570
*/
#ifdef __x86_64__
#include <config.h>
#if defined(USE_ARCFOUR) && (defined(HAVE_COMPATIBLE_GCC_AMD64_PLATFORM_AS) || \
defined(HAVE_COMPATIBLE_GCC_WIN64_PLATFORM_AS))
#include "asm-common-amd64.h"
.text
.align 16
.globl _gcry_arcfour_amd64
ELF(.type _gcry_arcfour_amd64,@function)
_gcry_arcfour_amd64:
CFI_STARTPROC()
ENTER_SYSV_FUNC_PARAMS_0_4
push %rbp
CFI_PUSH(%rbp)
push %rbx
CFI_PUSH(%rbx)
mov %rdi, %rbp # key = ARG(key)
mov %rsi, %rbx # rbx = ARG(len)
mov %rdx, %rsi # in = ARG(in)
mov %rcx, %rdi # out = ARG(out)
mov (4*256)(%rbp), %ecx # x = key->x
mov (4*256+4)(%rbp),%edx # y = key->y
inc %rcx # x++
and $255, %rcx # x &= 0xff
lea -8(%rbx,%rsi), %rbx # rbx = in+len-8
mov %rbx, %r9 # tmp = in+len-8
mov (%rbp,%rcx,4), %eax # tx = d[x]
cmp %rsi, %rbx # cmp in with in+len-8
jl .Lend # jump if (in+len-8 < in)
.Lstart:
add $8, %rsi # increment in
add $8, %rdi # increment out
# generate the next 8 bytes of the rc4 stream into %r8
mov $8, %r11 # byte counter
1: add %al, %dl # y += tx
mov (%rbp,%rdx,4), %ebx # ty = d[y]
mov %ebx, (%rbp,%rcx,4) # d[x] = ty
add %al, %bl # val = ty + tx
mov %eax, (%rbp,%rdx,4) # d[y] = tx
inc %cl # x++ (NEXT ROUND)
mov (%rbp,%rcx,4), %eax # tx = d[x] (NEXT ROUND)
shl $8, %r8
movb (%rbp,%rbx,4), %r8b # val = d[val]
dec %r11b
jnz 1b
# xor 8 bytes
bswap %r8
xor -8(%rsi), %r8
cmp %r9, %rsi # cmp in+len-8 with in
mov %r8, -8(%rdi)
jle .Lstart # jump if (in <= in+len-8)
.Lend:
add $8, %r9 # tmp = in+len
# handle the last bytes, one by one
1: cmp %rsi, %r9 # cmp in with in+len
jle .Lfinished # jump if (in+len <= in)
add %al, %dl # y += tx
mov (%rbp,%rdx,4), %ebx # ty = d[y]
mov %ebx, (%rbp,%rcx,4) # d[x] = ty
add %al, %bl # val = ty + tx
mov %eax, (%rbp,%rdx,4) # d[y] = tx
inc %cl # x++ (NEXT ROUND)
mov (%rbp,%rcx,4), %eax # tx = d[x] (NEXT ROUND)
movb (%rbp,%rbx,4), %r8b # val = d[val]
xor (%rsi), %r8b # xor 1 byte
movb %r8b, (%rdi)
inc %rsi # in++
inc %rdi # out++
jmp 1b
.Lfinished:
dec %rcx # x--
movb %cl, (4*256)(%rbp) # key->y = y
movb %dl, (4*256+4)(%rbp) # key->x = x
pop %rbx
CFI_POP(%rbx)
pop %rbp
CFI_POP(%rbp)
EXIT_SYSV_FUNC
ret
CFI_ENDPROC()
.L__gcry_arcfour_amd64_end:
ELF(.size _gcry_arcfour_amd64,.L__gcry_arcfour_amd64_end-_gcry_arcfour_amd64)
#endif
#endif

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