user: Please show me the C implementation that matches the assembly code listed below:

```asm
<flip_E6>:
  endbr64
  push   %r12
  push   %rbp
  push   %rbx
  mov    %rdi,%r12
  mov    %rsi,%rbx
  mov    %rdi,%rdx
  shl    $0x9,%rdx
  and    %rsi,%rdx
  and    $0x400,%edx
  mov    %rdi,%rax
  shl    $0x8,%rax
  and    %rsi,%rax
  and    $0x800,%eax
  or     %rdx,%rax
  mov    %rdi,%rbp
  shl    $0x7,%rbp
  and    %rsi,%rbp
  and    $0x1000,%ebp
  or     %rax,%rbp
  and    $0x30000,%edi
  lea    (%rsi,%rdi,2),%rax
  test   $0x80000,%eax
  jne    L19
L37:
  movabs $0x204000000,%rax
  and    %rbx,%rax
  movabs $0xfdf8000000,%rdx
  or     %rdx,%rax
  add    $0x4000000,%rax
  and    %r12,%rax
  movabs $0x10200000000,%rdx
  and    %rdx,%rax
  je     L29
  sub    $0x1,%rax
  movabs $0x204000000,%rdx
  and    %rdx,%rax
  or     %rax,%rbp
L29:
  movabs $0x8080808000000,%rax
  and    %rbx,%rax
  movabs $0x7f7f7f7f0000000,%rdx
  or     %rdx,%rax
  add    $0x8000000,%rax
  and    %r12,%rax
  movabs $0x808080800000000,%rdx
  and    %rdx,%rax
  je     L43
  sub    $0x1,%rax
  movabs $0x8080808000000,%rdx
  and    %rdx,%rax
  or     %rax,%rbp
L43:
  movabs $0x402010000000,%rax
  and    %rbx,%rax
  movabs $0x7fbfdfe0000000,%rdx
  or     %rdx,%rax
  add    $0x10000000,%rax
  and    %r12,%rax
  movabs $0x80402000000000,%rdx
  and    %rdx,%rax
  je     L31
  sub    $0x1,%rax
  movabs $0x402010000000,%rdx
  and    %rdx,%rax
  or     %rax,%rbp
L31:
  add    $0x100000,%rbx
  and    %r12,%rbx
  and    $0xe00000,%ebx
  je     L44
  sub    $0x1,%rbx
  and    $0xf00000,%ebx
  or     %rbx,%rbp
L44:
  mov    %rbp,%rax
  pop    %rbx
  pop    %rbp
  pop    %r12
  ret
L19:
  call   <last_bit@plt>
  mov    $0x2,%edx
  mov    %eax,%ecx
  shl    %cl,%rdx
  mov    $0x80000,%eax
  sub    %rdx,%rax
  or     %rax,%rbp
  jmp    L37
```

assistant: ```c
unsigned long long flip_E6(const unsigned long long discs_player, const unsigned long long discs_opponent) {
  unsigned long long my_discs, opp_discs, r;
  unsigned long long flipped = (discs_opponent & 0X0000000000000400ULL) & (discs_player << 9);
  flipped |= (discs_opponent & 0X0000000000000800ULL) & (discs_player << 8);
  flipped |= (discs_opponent & 0X0000000000001000ULL) & (discs_player << 7);
  my_discs = discs_player & 0X0000000000030000ULL;
  r = ((my_discs << 1) + discs_opponent) & 0X0000000000080000ULL;
  if (r != 0) {
    flipped |= 0X0000000000080000ULL - (0X2ULL << last_bit(my_discs));
  }
  my_discs = discs_player & 0X0000010200000000ULL;
  opp_discs = (discs_opponent & 0X0000000204000000ULL) | 0X000000FDF8000000ULL;
  r = (opp_discs + 0X0000000004000000ULL) & my_discs;
  if (r != 0) {
    flipped |= (r - 1) & 0X0000000204000000ULL;
  }
  my_discs = discs_player & 0X0808080800000000ULL;
  opp_discs = (discs_opponent & 0X0008080808000000ULL) | 0X07F7F7F7F0000000ULL;
  r = (opp_discs + 0X0000000008000000ULL) & my_discs;
  if (r != 0) {
    flipped |= (r - 1) & 0X0008080808000000ULL;
  }
  my_discs = discs_player & 0X0080402000000000ULL;
  opp_discs = (discs_opponent & 0X0000402010000000ULL) | 0X007FBFDFE0000000ULL;
  r = (opp_discs + 0X0000000010000000ULL) & my_discs;
  if (r != 0) {
    flipped |= (r - 1) & 0X0000402010000000ULL;
  }
  my_discs = discs_player & 0X0000000000E00000ULL;
  r = (discs_opponent + 0X0000000000100000ULL) & my_discs;
  if (r != 0) {
    flipped |= (r - 1) & 0X0000000000F00000ULL;
  }
  return flipped;
}
```