user: 下面的汇编指令对应的C源代码是什么:

```asm
<salsa20_8>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  sub    $0x70,%rsp
  mov    %rdi,-0x68(%rbp)
  mov    %fs:0x28,%rax
  mov    %rax,-0x8(%rbp)
  xor    %eax,%eax
  mov    -0x68(%rbp),%rcx
  lea    -0x50(%rbp),%rax
  mov    $0x40,%edx
  mov    %rcx,%rsi
  mov    %rax,%rdi
  call   <blkcpy@plt>
  movq   $0x0,-0x58(%rbp)
  jmp    L0
L4:
  mov    -0x40(%rbp),%edx
  mov    -0x50(%rbp),%ecx
  mov    -0x20(%rbp),%eax
  add    %ecx,%eax
  shl    $0x7,%eax
  mov    %eax,%esi
  mov    -0x50(%rbp),%ecx
  mov    -0x20(%rbp),%eax
  add    %ecx,%eax
  sar    $0x19,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x40(%rbp)
  mov    -0x30(%rbp),%edx
  mov    -0x40(%rbp),%ecx
  mov    -0x50(%rbp),%eax
  add    %ecx,%eax
  shl    $0x9,%eax
  mov    %eax,%esi
  mov    -0x40(%rbp),%ecx
  mov    -0x50(%rbp),%eax
  add    %ecx,%eax
  sar    $0x17,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x30(%rbp)
  mov    -0x20(%rbp),%edx
  mov    -0x30(%rbp),%ecx
  mov    -0x40(%rbp),%eax
  add    %ecx,%eax
  shl    $0xd,%eax
  mov    %eax,%esi
  mov    -0x30(%rbp),%ecx
  mov    -0x40(%rbp),%eax
  add    %ecx,%eax
  sar    $0x13,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x20(%rbp)
  mov    -0x50(%rbp),%edx
  mov    -0x20(%rbp),%ecx
  mov    -0x30(%rbp),%eax
  add    %ecx,%eax
  shl    $0x12,%eax
  mov    %eax,%esi
  mov    -0x20(%rbp),%ecx
  mov    -0x30(%rbp),%eax
  add    %ecx,%eax
  sar    $0xe,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x50(%rbp)
  mov    -0x2c(%rbp),%edx
  mov    -0x3c(%rbp),%ecx
  mov    -0x4c(%rbp),%eax
  add    %ecx,%eax
  shl    $0x7,%eax
  mov    %eax,%esi
  mov    -0x3c(%rbp),%ecx
  mov    -0x4c(%rbp),%eax
  add    %ecx,%eax
  sar    $0x19,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x2c(%rbp)
  mov    -0x1c(%rbp),%edx
  mov    -0x2c(%rbp),%ecx
  mov    -0x3c(%rbp),%eax
  add    %ecx,%eax
  shl    $0x9,%eax
  mov    %eax,%esi
  mov    -0x2c(%rbp),%ecx
  mov    -0x3c(%rbp),%eax
  add    %ecx,%eax
  sar    $0x17,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x1c(%rbp)
  mov    -0x4c(%rbp),%edx
  mov    -0x1c(%rbp),%ecx
  mov    -0x2c(%rbp),%eax
  add    %ecx,%eax
  shl    $0xd,%eax
  mov    %eax,%esi
  mov    -0x1c(%rbp),%ecx
  mov    -0x2c(%rbp),%eax
  add    %ecx,%eax
  sar    $0x13,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x4c(%rbp)
  mov    -0x3c(%rbp),%edx
  mov    -0x4c(%rbp),%ecx
  mov    -0x1c(%rbp),%eax
  add    %ecx,%eax
  shl    $0x12,%eax
  mov    %eax,%esi
  mov    -0x4c(%rbp),%ecx
  mov    -0x1c(%rbp),%eax
  add    %ecx,%eax
  sar    $0xe,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x3c(%rbp)
  mov    -0x18(%rbp),%edx
  mov    -0x28(%rbp),%ecx
  mov    -0x38(%rbp),%eax
  add    %ecx,%eax
  shl    $0x7,%eax
  mov    %eax,%esi
  mov    -0x28(%rbp),%ecx
  mov    -0x38(%rbp),%eax
  add    %ecx,%eax
  sar    $0x19,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x18(%rbp)
  mov    -0x48(%rbp),%edx
  mov    -0x18(%rbp),%ecx
  mov    -0x28(%rbp),%eax
  add    %ecx,%eax
  shl    $0x9,%eax
  mov    %eax,%esi
  mov    -0x18(%rbp),%ecx
  mov    -0x28(%rbp),%eax
  add    %ecx,%eax
  sar    $0x17,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x48(%rbp)
  mov    -0x38(%rbp),%edx
  mov    -0x48(%rbp),%ecx
  mov    -0x18(%rbp),%eax
  add    %ecx,%eax
  shl    $0xd,%eax
  mov    %eax,%esi
  mov    -0x48(%rbp),%ecx
  mov    -0x18(%rbp),%eax
  add    %ecx,%eax
  sar    $0x13,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x38(%rbp)
  mov    -0x28(%rbp),%edx
  mov    -0x38(%rbp),%ecx
  mov    -0x48(%rbp),%eax
  add    %ecx,%eax
  shl    $0x12,%eax
  mov    %eax,%esi
  mov    -0x38(%rbp),%ecx
  mov    -0x48(%rbp),%eax
  add    %ecx,%eax
  sar    $0xe,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x28(%rbp)
  mov    -0x44(%rbp),%edx
  mov    -0x14(%rbp),%ecx
  mov    -0x24(%rbp),%eax
  add    %ecx,%eax
  shl    $0x7,%eax
  mov    %eax,%esi
  mov    -0x14(%rbp),%ecx
  mov    -0x24(%rbp),%eax
  add    %ecx,%eax
  sar    $0x19,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x44(%rbp)
  mov    -0x34(%rbp),%edx
  mov    -0x44(%rbp),%ecx
  mov    -0x14(%rbp),%eax
  add    %ecx,%eax
  shl    $0x9,%eax
  mov    %eax,%esi
  mov    -0x44(%rbp),%ecx
  mov    -0x14(%rbp),%eax
  add    %ecx,%eax
  sar    $0x17,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x34(%rbp)
  mov    -0x24(%rbp),%edx
  mov    -0x34(%rbp),%ecx
  mov    -0x44(%rbp),%eax
  add    %ecx,%eax
  shl    $0xd,%eax
  mov    %eax,%esi
  mov    -0x34(%rbp),%ecx
  mov    -0x44(%rbp),%eax
  add    %ecx,%eax
  sar    $0x13,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x24(%rbp)
  mov    -0x14(%rbp),%edx
  mov    -0x24(%rbp),%ecx
  mov    -0x34(%rbp),%eax
  add    %ecx,%eax
  shl    $0x12,%eax
  mov    %eax,%esi
  mov    -0x24(%rbp),%ecx
  mov    -0x34(%rbp),%eax
  add    %ecx,%eax
  sar    $0xe,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x14(%rbp)
  mov    -0x4c(%rbp),%edx
  mov    -0x50(%rbp),%ecx
  mov    -0x44(%rbp),%eax
  add    %ecx,%eax
  shl    $0x7,%eax
  mov    %eax,%esi
  mov    -0x50(%rbp),%ecx
  mov    -0x44(%rbp),%eax
  add    %ecx,%eax
  sar    $0x19,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x4c(%rbp)
  mov    -0x48(%rbp),%edx
  mov    -0x4c(%rbp),%ecx
  mov    -0x50(%rbp),%eax
  add    %ecx,%eax
  shl    $0x9,%eax
  mov    %eax,%esi
  mov    -0x4c(%rbp),%ecx
  mov    -0x50(%rbp),%eax
  add    %ecx,%eax
  sar    $0x17,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x48(%rbp)
  mov    -0x44(%rbp),%edx
  mov    -0x48(%rbp),%ecx
  mov    -0x4c(%rbp),%eax
  add    %ecx,%eax
  shl    $0xd,%eax
  mov    %eax,%esi
  mov    -0x48(%rbp),%ecx
  mov    -0x4c(%rbp),%eax
  add    %ecx,%eax
  sar    $0x13,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x44(%rbp)
  mov    -0x50(%rbp),%edx
  mov    -0x44(%rbp),%ecx
  mov    -0x48(%rbp),%eax
  add    %ecx,%eax
  shl    $0x12,%eax
  mov    %eax,%esi
  mov    -0x44(%rbp),%ecx
  mov    -0x48(%rbp),%eax
  add    %ecx,%eax
  sar    $0xe,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x50(%rbp)
  mov    -0x38(%rbp),%edx
  mov    -0x3c(%rbp),%ecx
  mov    -0x40(%rbp),%eax
  add    %ecx,%eax
  shl    $0x7,%eax
  mov    %eax,%esi
  mov    -0x3c(%rbp),%ecx
  mov    -0x40(%rbp),%eax
  add    %ecx,%eax
  sar    $0x19,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x38(%rbp)
  mov    -0x34(%rbp),%edx
  mov    -0x38(%rbp),%ecx
  mov    -0x3c(%rbp),%eax
  add    %ecx,%eax
  shl    $0x9,%eax
  mov    %eax,%esi
  mov    -0x38(%rbp),%ecx
  mov    -0x3c(%rbp),%eax
  add    %ecx,%eax
  sar    $0x17,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x34(%rbp)
  mov    -0x40(%rbp),%edx
  mov    -0x34(%rbp),%ecx
  mov    -0x38(%rbp),%eax
  add    %ecx,%eax
  shl    $0xd,%eax
  mov    %eax,%esi
  mov    -0x34(%rbp),%ecx
  mov    -0x38(%rbp),%eax
  add    %ecx,%eax
  sar    $0x13,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x40(%rbp)
  mov    -0x3c(%rbp),%edx
  mov    -0x40(%rbp),%ecx
  mov    -0x34(%rbp),%eax
  add    %ecx,%eax
  shl    $0x12,%eax
  mov    %eax,%esi
  mov    -0x40(%rbp),%ecx
  mov    -0x34(%rbp),%eax
  add    %ecx,%eax
  sar    $0xe,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x3c(%rbp)
  mov    -0x24(%rbp),%edx
  mov    -0x28(%rbp),%ecx
  mov    -0x2c(%rbp),%eax
  add    %ecx,%eax
  shl    $0x7,%eax
  mov    %eax,%esi
  mov    -0x28(%rbp),%ecx
  mov    -0x2c(%rbp),%eax
  add    %ecx,%eax
  sar    $0x19,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x24(%rbp)
  mov    -0x30(%rbp),%edx
  mov    -0x24(%rbp),%ecx
  mov    -0x28(%rbp),%eax
  add    %ecx,%eax
  shl    $0x9,%eax
  mov    %eax,%esi
  mov    -0x24(%rbp),%ecx
  mov    -0x28(%rbp),%eax
  add    %ecx,%eax
  sar    $0x17,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x30(%rbp)
  mov    -0x2c(%rbp),%edx
  mov    -0x30(%rbp),%ecx
  mov    -0x24(%rbp),%eax
  add    %ecx,%eax
  shl    $0xd,%eax
  mov    %eax,%esi
  mov    -0x30(%rbp),%ecx
  mov    -0x24(%rbp),%eax
  add    %ecx,%eax
  sar    $0x13,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x2c(%rbp)
  mov    -0x28(%rbp),%edx
  mov    -0x2c(%rbp),%ecx
  mov    -0x30(%rbp),%eax
  add    %ecx,%eax
  shl    $0x12,%eax
  mov    %eax,%esi
  mov    -0x2c(%rbp),%ecx
  mov    -0x30(%rbp),%eax
  add    %ecx,%eax
  sar    $0xe,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x28(%rbp)
  mov    -0x20(%rbp),%edx
  mov    -0x14(%rbp),%ecx
  mov    -0x18(%rbp),%eax
  add    %ecx,%eax
  shl    $0x7,%eax
  mov    %eax,%esi
  mov    -0x14(%rbp),%ecx
  mov    -0x18(%rbp),%eax
  add    %ecx,%eax
  sar    $0x19,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x20(%rbp)
  mov    -0x1c(%rbp),%edx
  mov    -0x20(%rbp),%ecx
  mov    -0x14(%rbp),%eax
  add    %ecx,%eax
  shl    $0x9,%eax
  mov    %eax,%esi
  mov    -0x20(%rbp),%ecx
  mov    -0x14(%rbp),%eax
  add    %ecx,%eax
  sar    $0x17,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x1c(%rbp)
  mov    -0x18(%rbp),%edx
  mov    -0x1c(%rbp),%ecx
  mov    -0x20(%rbp),%eax
  add    %ecx,%eax
  shl    $0xd,%eax
  mov    %eax,%esi
  mov    -0x1c(%rbp),%ecx
  mov    -0x20(%rbp),%eax
  add    %ecx,%eax
  sar    $0x13,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x18(%rbp)
  mov    -0x14(%rbp),%edx
  mov    -0x18(%rbp),%ecx
  mov    -0x1c(%rbp),%eax
  add    %ecx,%eax
  shl    $0x12,%eax
  mov    %eax,%esi
  mov    -0x18(%rbp),%ecx
  mov    -0x1c(%rbp),%eax
  add    %ecx,%eax
  sar    $0xe,%eax
  or     %esi,%eax
  xor    %edx,%eax
  mov    %eax,-0x14(%rbp)
  addq   $0x2,-0x58(%rbp)
L0:
  cmpq   $0x7,-0x58(%rbp)
  jbe    L4
  movq   $0x0,-0x58(%rbp)
  jmp    L9
L27:
  mov    -0x58(%rbp),%rax
  lea    0x0(,%rax,4),%rdx
  mov    -0x68(%rbp),%rax
  add    %rdx,%rax
  mov    (%rax),%ecx
  mov    -0x58(%rbp),%rax
  mov    -0x50(%rbp,%rax,4),%edx
  mov    -0x58(%rbp),%rax
  lea    0x0(,%rax,4),%rsi
  mov    -0x68(%rbp),%rax
  add    %rsi,%rax
  add    %ecx,%edx
  mov    %edx,(%rax)
  addq   $0x1,-0x58(%rbp)
L9:
  cmpq   $0xf,-0x58(%rbp)
  jbe    L27
  nop
  mov    -0x8(%rbp),%rax
  sub    %fs:0x28,%rax
  je     L28
  call   <__stack_chk_fail@plt>
L28:
  leave
  ret
```

assistant: ```c
void salsa20_8(uint32_t B[16]) {
  uint32_t x[16];
  size_t i;
  blkcpy(x, B, 64);
  for (i = 0; i < 8; i += 2) {
    x[4] ^= (((x[0] + x[12]) << (7)) | ((x[0] + x[12]) >> (32 - (7))));
    x[8] ^= (((x[4] + x[0]) << (9)) | ((x[4] + x[0]) >> (32 - (9))));
    x[12] ^= (((x[8] + x[4]) << (13)) | ((x[8] + x[4]) >> (32 - (13))));
    x[0] ^= (((x[12] + x[8]) << (18)) | ((x[12] + x[8]) >> (32 - (18))));
    x[9] ^= (((x[5] + x[1]) << (7)) | ((x[5] + x[1]) >> (32 - (7))));
    x[13] ^= (((x[9] + x[5]) << (9)) | ((x[9] + x[5]) >> (32 - (9))));
    x[1] ^= (((x[13] + x[9]) << (13)) | ((x[13] + x[9]) >> (32 - (13))));
    x[5] ^= (((x[1] + x[13]) << (18)) | ((x[1] + x[13]) >> (32 - (18))));
    x[14] ^= (((x[10] + x[6]) << (7)) | ((x[10] + x[6]) >> (32 - (7))));
    x[2] ^= (((x[14] + x[10]) << (9)) | ((x[14] + x[10]) >> (32 - (9))));
    x[6] ^= (((x[2] + x[14]) << (13)) | ((x[2] + x[14]) >> (32 - (13))));
    x[10] ^= (((x[6] + x[2]) << (18)) | ((x[6] + x[2]) >> (32 - (18))));
    x[3] ^= (((x[15] + x[11]) << (7)) | ((x[15] + x[11]) >> (32 - (7))));
    x[7] ^= (((x[3] + x[15]) << (9)) | ((x[3] + x[15]) >> (32 - (9))));
    x[11] ^= (((x[7] + x[3]) << (13)) | ((x[7] + x[3]) >> (32 - (13))));
    x[15] ^= (((x[11] + x[7]) << (18)) | ((x[11] + x[7]) >> (32 - (18))));
    x[1] ^= (((x[0] + x[3]) << (7)) | ((x[0] + x[3]) >> (32 - (7))));
    x[2] ^= (((x[1] + x[0]) << (9)) | ((x[1] + x[0]) >> (32 - (9))));
    x[3] ^= (((x[2] + x[1]) << (13)) | ((x[2] + x[1]) >> (32 - (13))));
    x[0] ^= (((x[3] + x[2]) << (18)) | ((x[3] + x[2]) >> (32 - (18))));
    x[6] ^= (((x[5] + x[4]) << (7)) | ((x[5] + x[4]) >> (32 - (7))));
    x[7] ^= (((x[6] + x[5]) << (9)) | ((x[6] + x[5]) >> (32 - (9))));
    x[4] ^= (((x[7] + x[6]) << (13)) | ((x[7] + x[6]) >> (32 - (13))));
    x[5] ^= (((x[4] + x[7]) << (18)) | ((x[4] + x[7]) >> (32 - (18))));
    x[11] ^= (((x[10] + x[9]) << (7)) | ((x[10] + x[9]) >> (32 - (7))));
    x[8] ^= (((x[11] + x[10]) << (9)) | ((x[11] + x[10]) >> (32 - (9))));
    x[9] ^= (((x[8] + x[11]) << (13)) | ((x[8] + x[11]) >> (32 - (13))));
    x[10] ^= (((x[9] + x[8]) << (18)) | ((x[9] + x[8]) >> (32 - (18))));
    x[12] ^= (((x[15] + x[14]) << (7)) | ((x[15] + x[14]) >> (32 - (7))));
    x[13] ^= (((x[12] + x[15]) << (9)) | ((x[12] + x[15]) >> (32 - (9))));
    x[14] ^= (((x[13] + x[12]) << (13)) | ((x[13] + x[12]) >> (32 - (13))));
    x[15] ^= (((x[14] + x[13]) << (18)) | ((x[14] + x[13]) >> (32 - (18))));
  }
  for (i = 0; i < 16; i++)
    B[i] += x[i];
}
```