user: 请从给定的汇编指令推导出C源代码：

```asm
<matrix_mult>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  mov    %edi,-0x24(%rbp)
  mov    %rsi,-0x30(%rbp)
  mov    %rdx,-0x38(%rbp)
  mov    %rcx,-0x40(%rbp)
  mov    -0x24(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x24(%rbp),%eax
  cltq
  imul   %rax,%rdx
  mov    -0x24(%rbp),%eax
  cltq
  imul   %rdx,%rax
  add    %rax,%rax
  mov    %rax,-0x10(%rbp)
  movl   $0x0,-0x1c(%rbp)
  jmp    L4
L54:
  movl   $0x0,-0x18(%rbp)
  jmp    L73
L64:
  mov    -0x1c(%rbp),%eax
  imul   -0x24(%rbp),%eax
  mov    %eax,%edx
  mov    -0x18(%rbp),%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x38(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  movsd  %xmm0,-0x8(%rbp)
  mov    -0x18(%rbp),%eax
  imul   -0x24(%rbp),%eax
  mov    %eax,%edx
  mov    -0x1c(%rbp),%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x38(%rbp),%rax
  add    %rax,%rdx
  mov    -0x1c(%rbp),%eax
  imul   -0x24(%rbp),%eax
  mov    %eax,%ecx
  mov    -0x18(%rbp),%eax
  add    %ecx,%eax
  cltq
  lea    0x0(,%rax,8),%rcx
  mov    -0x38(%rbp),%rax
  add    %rcx,%rax
  movsd  (%rdx),%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x18(%rbp),%eax
  imul   -0x24(%rbp),%eax
  mov    %eax,%edx
  mov    -0x1c(%rbp),%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x38(%rbp),%rax
  add    %rdx,%rax
  movsd  -0x8(%rbp),%xmm0
  movsd  %xmm0,(%rax)
  addl   $0x1,-0x18(%rbp)
L73:
  mov    -0x18(%rbp),%eax
  cmp    -0x24(%rbp),%eax
  jl     L64
  addl   $0x1,-0x1c(%rbp)
L4:
  mov    -0x1c(%rbp),%eax
  cmp    -0x24(%rbp),%eax
  jl     L54
  movl   $0x0,-0x1c(%rbp)
  jmp    L99
L95:
  movl   $0x0,-0x18(%rbp)
  jmp    L27
L59:
  movl   $0x0,-0x14(%rbp)
  jmp    L7
L71:
  mov    -0x1c(%rbp),%eax
  imul   -0x24(%rbp),%eax
  mov    %eax,%edx
  mov    -0x18(%rbp),%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x30(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm1
  mov    -0x1c(%rbp),%eax
  imul   -0x24(%rbp),%eax
  mov    %eax,%edx
  mov    -0x14(%rbp),%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x38(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm2
  mov    -0x18(%rbp),%eax
  imul   -0x24(%rbp),%eax
  mov    %eax,%edx
  mov    -0x14(%rbp),%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x40(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mulsd  %xmm2,%xmm0
  mov    -0x1c(%rbp),%eax
  imul   -0x24(%rbp),%eax
  mov    %eax,%edx
  mov    -0x18(%rbp),%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x30(%rbp),%rax
  add    %rdx,%rax
  addsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x1c(%rbp),%eax
  add    $0x1,%eax
  imul   -0x24(%rbp),%eax
  mov    %eax,%edx
  mov    -0x18(%rbp),%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x30(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm1
  mov    -0x1c(%rbp),%eax
  add    $0x1,%eax
  imul   -0x24(%rbp),%eax
  mov    %eax,%edx
  mov    -0x14(%rbp),%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x38(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm2
  mov    -0x18(%rbp),%eax
  imul   -0x24(%rbp),%eax
  mov    %eax,%edx
  mov    -0x14(%rbp),%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x40(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mulsd  %xmm2,%xmm0
  mov    -0x1c(%rbp),%eax
  add    $0x1,%eax
  imul   -0x24(%rbp),%eax
  mov    %eax,%edx
  mov    -0x18(%rbp),%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x30(%rbp),%rax
  add    %rdx,%rax
  addsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x1c(%rbp),%eax
  imul   -0x24(%rbp),%eax
  mov    %eax,%edx
  mov    -0x18(%rbp),%eax
  add    $0x1,%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x30(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm1
  mov    -0x1c(%rbp),%eax
  imul   -0x24(%rbp),%eax
  mov    %eax,%edx
  mov    -0x14(%rbp),%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x38(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm2
  mov    -0x18(%rbp),%eax
  add    $0x1,%eax
  imul   -0x24(%rbp),%eax
  mov    %eax,%edx
  mov    -0x14(%rbp),%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x40(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mulsd  %xmm2,%xmm0
  mov    -0x1c(%rbp),%eax
  imul   -0x24(%rbp),%eax
  mov    %eax,%edx
  mov    -0x18(%rbp),%eax
  add    $0x1,%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x30(%rbp),%rax
  add    %rdx,%rax
  addsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x1c(%rbp),%eax
  add    $0x1,%eax
  imul   -0x24(%rbp),%eax
  mov    %eax,%edx
  mov    -0x18(%rbp),%eax
  add    $0x1,%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x30(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm1
  mov    -0x1c(%rbp),%eax
  add    $0x1,%eax
  imul   -0x24(%rbp),%eax
  mov    %eax,%edx
  mov    -0x14(%rbp),%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x38(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm2
  mov    -0x18(%rbp),%eax
  add    $0x1,%eax
  imul   -0x24(%rbp),%eax
  mov    %eax,%edx
  mov    -0x14(%rbp),%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x40(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mulsd  %xmm2,%xmm0
  mov    -0x1c(%rbp),%eax
  add    $0x1,%eax
  imul   -0x24(%rbp),%eax
  mov    %eax,%edx
  mov    -0x18(%rbp),%eax
  add    $0x1,%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x30(%rbp),%rax
  add    %rdx,%rax
  addsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  addl   $0x1,-0x14(%rbp)
L7:
  mov    -0x14(%rbp),%eax
  cmp    -0x24(%rbp),%eax
  jl     L71
  addl   $0x2,-0x18(%rbp)
L27:
  mov    -0x18(%rbp),%eax
  cmp    -0x24(%rbp),%eax
  jl     L59
  addl   $0x2,-0x1c(%rbp)
L99:
  mov    -0x1c(%rbp),%eax
  cmp    -0x24(%rbp),%eax
  jl     L95
  mov    -0x10(%rbp),%rax
  pop    %rbp
  ret
```

assistant: ```c
size_t matrix_mult(int len, double *restrict a, double *restrict b, double *restrict c) {
  int i, j, k, l, m;
  size_t fpops;
  double temp;
  fpops = (size_t)2 * len * len * len;
  for (i = 0; i < len; i++) {
    for (j = 0; j < len; j++) {
      temp = b[i * len + j];
      b[i * len + j] = b[j * len + i];
      b[j * len + i] = temp;
    }
  }
  for (i = 0; i < len; i += 2) {
    for (j = 0; j < len; j += 2) {
      for (k = 0; k < len; k++) {
        a[i * len + j] += b[i * len + k] * c[j * len + k];
        a[(i + 1) * len + j] += b[(i + 1) * len + k] * c[j * len + k];
        a[i * len + (j + 1)] += b[i * len + k] * c[(j + 1) * len + k];
        a[(i + 1) * len + (j + 1)] += b[(i + 1) * len + k] * c[(j + 1) * len + k];
      }
    }
  }
  return fpops;
}
```