user: 请将这段汇编代码片段转换成等效的C代码:

```asm
<packforblock20_64>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  mov    %edi,%eax
  mov    %rsi,%r14
  mov    %rdx,%r15
  mov    (%rdx),%rcx
  mov    (%rsi),%rdx
  mov    (%rdx),%ebx
  sub    %edi,%ebx
  mov    %ebx,-0x4(%rsp)
  mov    0xc(%rdx),%esi
  sub    %edi,%esi
  sar    $0x4,%esi
  mov    0x10(%rdx),%r12d
  sub    %edi,%r12d
  shl    $0x10,%r12d
  or     %esi,%r12d
  mov    0x18(%rdx),%esi
  sub    %edi,%esi
  sar    $0x8,%esi
  mov    0x1c(%rdx),%ebp
  sub    %edi,%ebp
  shl    $0xc,%ebp
  or     %esi,%ebp
  mov    0x24(%rdx),%edi
  sub    %eax,%edi
  sar    $0xc,%edi
  mov    0x28(%rdx),%esi
  sub    %eax,%esi
  shl    $0x8,%esi
  or     %edi,%esi
  mov    0x2c(%rdx),%ebx
  sub    %eax,%ebx
  shl    $0x1c,%ebx
  or     %esi,%ebx
  mov    0x30(%rdx),%edi
  sub    %eax,%edi
  sar    $0x10,%edi
  mov    0x34(%rdx),%esi
  sub    %eax,%esi
  shl    $0x4,%esi
  or     %edi,%esi
  mov    0x38(%rdx),%r11d
  sub    %eax,%r11d
  shl    $0x18,%r11d
  or     %esi,%r11d
  mov    0x40(%rdx),%esi
  sub    %eax,%esi
  mov    0x44(%rdx),%r10d
  sub    %eax,%r10d
  shl    $0x14,%r10d
  or     %esi,%r10d
  mov    0x4c(%rdx),%esi
  sub    %eax,%esi
  sar    $0x4,%esi
  mov    0x50(%rdx),%r9d
  sub    %eax,%r9d
  shl    $0x10,%r9d
  or     %esi,%r9d
  mov    0x58(%rdx),%esi
  sub    %eax,%esi
  sar    $0x8,%esi
  mov    0x5c(%rdx),%r8d
  sub    %eax,%r8d
  shl    $0xc,%r8d
  or     %esi,%r8d
  mov    0x64(%rdx),%edi
  sub    %eax,%edi
  sar    $0xc,%edi
  mov    0x68(%rdx),%esi
  sub    %eax,%esi
  shl    $0x8,%esi
  or     %edi,%esi
  mov    0x6c(%rdx),%edi
  sub    %eax,%edi
  shl    $0x1c,%edi
  or     %esi,%edi
  mov    0x70(%rdx),%esi
  sub    %eax,%esi
  sar    $0x10,%esi
  mov    0x74(%rdx),%r13d
  sub    %eax,%r13d
  shl    $0x4,%r13d
  or     %esi,%r13d
  mov    0x78(%rdx),%esi
  sub    %eax,%esi
  shl    $0x18,%esi
  or     %r13d,%esi
  mov    0x4(%rdx),%edx
  sub    %eax,%edx
  mov    %edx,%eax
  shl    $0x14,%eax
  or     -0x4(%rsp),%eax
  mov    %eax,(%rcx)
  mov    %r12d,0x4(%rcx)
  mov    %ebp,0x8(%rcx)
  mov    %ebx,0xc(%rcx)
  mov    %r11d,0x10(%rcx)
  mov    %r10d,0x14(%rcx)
  mov    %r9d,0x18(%rcx)
  mov    %r8d,0x1c(%rcx)
  mov    %edi,0x20(%rcx)
  mov    %esi,0x24(%rcx)
  subq   $0xffffffffffffff80,(%r14)
  addq   $0x140,(%r15)
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
```

assistant: ```c
void packforblock20_64(const uint64_t base, const uint64_t **pin, uint8_t **pw) {
  uint64_t *pw64 = *(uint64_t **)pw;
  const uint64_t *in = *pin;
  uint64_t w0;
  uint64_t w1;
  uint64_t w2;
  uint64_t w3;
  uint64_t w4;
  uint64_t w5;
  uint64_t w6;
  uint64_t w7;
  uint64_t w8;
  uint64_t w9;
  w0 = (in[0] - base);
  w0 |= (in[1] - base) << 20;
  w0 |= (in[2] - base) << 40;
  w0 |= (in[3] - base) << 60;
  w1 = (in[3] - base) >> 4;
  w1 |= (in[4] - base) << 16;
  w1 |= (in[5] - base) << 36;
  w1 |= (in[6] - base) << 56;
  w2 = (in[6] - base) >> 8;
  w2 |= (in[7] - base) << 12;
  w2 |= (in[8] - base) << 32;
  w2 |= (in[9] - base) << 52;
  w3 = (in[9] - base) >> 12;
  w3 |= (in[10] - base) << 8;
  w3 |= (in[11] - base) << 28;
  w3 |= (in[12] - base) << 48;
  w4 = (in[12] - base) >> 16;
  w4 |= (in[13] - base) << 4;
  w4 |= (in[14] - base) << 24;
  w4 |= (in[15] - base) << 44;
  w5 = (in[16] - base);
  w5 |= (in[17] - base) << 20;
  w5 |= (in[18] - base) << 40;
  w5 |= (in[19] - base) << 60;
  w6 = (in[19] - base) >> 4;
  w6 |= (in[20] - base) << 16;
  w6 |= (in[21] - base) << 36;
  w6 |= (in[22] - base) << 56;
  w7 = (in[22] - base) >> 8;
  w7 |= (in[23] - base) << 12;
  w7 |= (in[24] - base) << 32;
  w7 |= (in[25] - base) << 52;
  w8 = (in[25] - base) >> 12;
  w8 |= (in[26] - base) << 8;
  w8 |= (in[27] - base) << 28;
  w8 |= (in[28] - base) << 48;
  w9 = (in[28] - base) >> 16;
  w9 |= (in[29] - base) << 4;
  w9 |= (in[30] - base) << 24;
  w9 |= (in[31] - base) << 44;
  pw64[0] = w0;
  pw64[1] = w1;
  pw64[2] = w2;
  pw64[3] = w3;
  pw64[4] = w4;
  pw64[5] = w5;
  pw64[6] = w6;
  pw64[7] = w7;
  pw64[8] = w8;
  pw64[9] = w9;
  *pin += 32;
  *pw += 80;
}
```