user: What would the C source look like for the assembly code provided here:

```asm
<flip_A5>:
  endbr64
  push   %r12
  push   %rbp
  mov    %rdi,%rbp
  and    $0x3f000000,%edi
  lea    (%rsi,%rdi,2),%r12
  push   %rbx
  mov    %rsi,%rbx
  and    $0x80000000,%r12d
  jne    L9
L35:
  movabs $0x10204000000000,%rcx
  mov    %rbx,%rax
  movabs $0x7efdf8000000000,%rdx
  and    %rcx,%rax
  or     %rdx,%rax
  movabs $0x4000000000,%rdx
  add    %rdx,%rax
  movabs $0x810200000000000,%rdx
  and    %rbp,%rax
  and    %rdx,%rax
  je     L55
  sub    $0x1,%rax
  and    %rcx,%rax
  or     %rax,%r12
L55:
  mov    %rbp,%rdi
  mov    %rbx,%rax
  and    $0x2010,%edi
  and    $0x402000,%eax
  mov    %rdi,%rdx
  or     $0x7fbfc000,%rax
  shl    $0x9,%rdx
  add    %rdx,%rax
  test   $0x80000000,%eax
  jne    L0
L22:
  movabs $0x80808000000000,%rcx
  mov    %rbx,%rax
  movabs $0x7f7f7f0000000000,%rdx
  and    %rcx,%rax
  or     %rdx,%rax
  movabs $0x8000000000,%rdx
  add    %rdx,%rax
  movabs $0x8080800000000000,%rdx
  and    %rbp,%rax
  and    %rdx,%rax
  je     L57
  sub    $0x1,%rax
  and    %rcx,%rax
  or     %rax,%r12
L57:
  and    $0x8080,%ebp
  and    $0x808000,%ebx
  mov    %rbp,%rax
  or     $0x7f7f0000,%rbx
  shl    $0x8,%rax
  add    %rax,%rbx
  test   $0x80000000,%ebx
  jne    L29
  mov    %r12,%rax
  pop    %rbx
  pop    %rbp
  pop    %r12
  ret
  nopw   0x0(%rax,%rax,1)
L9:
  call   <last_bit@plt>
  mov    $0x2,%edx
  mov    $0x80000000,%r12d
  mov    %eax,%ecx
  shl    %cl,%rdx
  sub    %rdx,%r12
  jmp    L35
  nopl   (%rax)
L29:
  mov    %rbp,%rdi
  call   <last_bit@plt>
  mov    $0xfffffffffffffffe,%rdx
  pop    %rbx
  pop    %rbp
  mov    %eax,%ecx
  shl    %cl,%rdx
  and    $0x808000,%edx
  or     %rdx,%r12
  mov    %r12,%rax
  pop    %r12
  ret
  nopl   (%rax)
L0:
  call   <last_bit@plt>
  mov    $0xfffffffffffffffe,%rdx
  mov    %eax,%ecx
  shl    %cl,%rdx
  and    $0x402000,%edx
  or     %rdx,%r12
  jmp    L22
```

assistant: ```c
unsigned long long flip_A5(const unsigned long long discs_player, const unsigned long long discs_opponent) {
  unsigned long long my_discs, opp_discs, r, flipped = 0ULL;
  my_discs = discs_player & 0X000000003F000000ULL;
  r = ((my_discs << 1) + discs_opponent) & 0X0000000080000000ULL;
  if (r != 0) {
    flipped |= 0X0000000080000000ULL - (0X2ULL << last_bit(my_discs));
  }
  my_discs = discs_player & 0X0810200000000000ULL;
  opp_discs = (discs_opponent & 0X0010204000000000ULL) | 0X07EFDF8000000000ULL;
  r = (opp_discs + 0X0000004000000000ULL) & my_discs;
  if (r != 0) {
    flipped |= (r - 1) & 0X0010204000000000ULL;
  }
  my_discs = discs_player & 0X0000000000002010ULL;
  opp_discs = (discs_opponent & 0X0000000000402000ULL) | 0X000000007FBFC000ULL;
  r = ((my_discs << 9) + opp_discs) & 0X0000000080000000ULL;
  if (r != 0) {
    flipped |= (0X0000000080000000ULL - (0X2ULL << last_bit(my_discs))) & 0X0000000000402000ULL;
  }
  my_discs = discs_player & 0X8080800000000000ULL;
  opp_discs = (discs_opponent & 0X0080808000000000ULL) | 0X7F7F7F0000000000ULL;
  r = (opp_discs + 0X0000008000000000ULL) & my_discs;
  if (r != 0) {
    flipped |= (r - 1) & 0X0080808000000000ULL;
  }
  my_discs = discs_player & 0X0000000000008080ULL;
  opp_discs = (discs_opponent & 0X0000000000808000ULL) | 0X000000007F7F0000ULL;
  r = ((my_discs << 8) + opp_discs) & 0X0000000080000000ULL;
  if (r != 0) {
    flipped |= (0X0000000080000000ULL - (0X2ULL << last_bit(my_discs))) & 0X0000000000808000ULL;
  }
  return flipped;
}
```