user: Demonstrate the C code that generates the assembly output below:

```asm
<dtrans_mat_mat_mult>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbx
  mov    %rdi,-0x40(%rbp)
  mov    %rsi,-0x48(%rbp)
  mov    %edx,-0x4c(%rbp)
  mov    %ecx,-0x50(%rbp)
  movl   $0x20,-0x2c(%rbp)
  mov    $0x0,%r13d
  jmp    L91
L139:
  mov    $0x0,%ebx
  jmp    L20
L171:
  mov    %ebx,%eax
  imul   -0x50(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x48(%rbp),%rax
  add    %rdx,%rax
  mov    %rax,%rcx
  cmp    %ebx,%r13d
  mov    %ebx,%r12d
  cmovge %r13d,%r12d
  jmp    L63
L144:
  movslq %r12d,%rax
  shl    $0x3,%rax
  add    %rcx,%rax
  pxor   %xmm0,%xmm0
  movsd  %xmm0,(%rax)
  add    $0x1,%r12d
L63:
  mov    -0x2c(%rbp),%eax
  lea    0x0(%r13,%rax,1),%edx
  mov    -0x50(%rbp),%eax
  cmp    %eax,%edx
  cmovle %edx,%eax
  cmp    %eax,%r12d
  jl     L144
  add    $0x1,%ebx
L20:
  cmp    -0x50(%rbp),%ebx
  jl     L171
  mov    $0x0,%r15d
  jmp    L159
L136:
  mov    $0x0,%ebx
  jmp    L106
L77:
  mov    %ebx,%eax
  imul   -0x50(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x48(%rbp),%rax
  add    %rdx,%rax
  mov    %rax,%rcx
  cmp    %ebx,%r13d
  mov    %ebx,%r12d
  cmovge %r13d,%r12d
  jmp    L108
L114:
  pxor   %xmm2,%xmm2
  movapd %xmm2,%xmm5
  mov    %r15d,%r14d
  jmp    L27
L121:
  mov    %r14d,%eax
  imul   -0x50(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x40(%rbp),%rax
  lea    (%rdx,%rax,1),%rsi
  movslq %ebx,%rax
  shl    $0x3,%rax
  add    %rsi,%rax
  movsd  (%rax),%xmm1
  movslq %r12d,%rax
  shl    $0x3,%rax
  add    %rsi,%rax
  movsd  (%rax),%xmm0
  mulsd  %xmm1,%xmm0
  movapd %xmm5,%xmm3
  addsd  %xmm3,%xmm0
  movapd %xmm0,%xmm5
  add    $0x1,%r14d
L27:
  mov    -0x2c(%rbp),%eax
  lea    (%r15,%rax,1),%edx
  mov    -0x4c(%rbp),%eax
  cmp    %eax,%edx
  cmovle %edx,%eax
  cmp    %eax,%r14d
  jl     L121
  movslq %r12d,%rax
  shl    $0x3,%rax
  mov    %rcx,%rdi
  add    %rdi,%rax
  movsd  (%rax),%xmm0
  movslq %r12d,%rax
  shl    $0x3,%rax
  add    %rdi,%rax
  movapd %xmm5,%xmm4
  addsd  %xmm4,%xmm0
  movsd  %xmm0,(%rax)
  add    $0x1,%r12d
L108:
  mov    -0x2c(%rbp),%eax
  lea    0x0(%r13,%rax,1),%edx
  mov    -0x50(%rbp),%eax
  cmp    %eax,%edx
  cmovle %edx,%eax
  cmp    %eax,%r12d
  jl     L114
  add    $0x1,%ebx
L106:
  cmp    -0x50(%rbp),%ebx
  jl     L77
  mov    -0x2c(%rbp),%eax
  add    %r15d,%eax
  mov    %eax,%r15d
L159:
  cmp    -0x4c(%rbp),%r15d
  jl     L136
  mov    -0x2c(%rbp),%eax
  add    %r13d,%eax
  mov    %eax,%r13d
L91:
  cmp    -0x50(%rbp),%r13d
  jl     L139
  mov    $0x0,%ebx
  jmp    L65
L50:
  mov    $0x0,%r12d
  jmp    L129
L153:
  mov    %r12d,%eax
  imul   -0x50(%rbp),%eax
  add    %ebx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x48(%rbp),%rax
  add    %rax,%rdx
  mov    %ebx,%eax
  imul   -0x50(%rbp),%eax
  add    %r12d,%eax
  cltq
  lea    0x0(,%rax,8),%rcx
  mov    -0x48(%rbp),%rax
  add    %rcx,%rax
  movsd  (%rdx),%xmm0
  movsd  %xmm0,(%rax)
  add    $0x1,%r12d
L129:
  cmp    %ebx,%r12d
  jl     L153
  add    $0x1,%ebx
L65:
  cmp    -0x50(%rbp),%ebx
  jl     L50
  nop
  nop
  pop    %rbx
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  pop    %rbp
  ret
```

assistant: ```c
void dtrans_mat_mat_mult(double *a, double *b, int n, int m) {
  register int i, j, k, jj, kk;
  register double sum, *bim, *akm;
  const int bsize = 32;
  for (jj = 0; jj < m; jj += bsize) {
    for (i = 0; i < m; ++i) {
      bim = b + i * m;
      for (j = (((jj) >= (i)) ? (jj) : (i)); j < (((jj + bsize) <= (m)) ? (jj + bsize) : (m)); ++j)
        bim[j] = 0.0;
    }
    for (kk = 0; kk < n; kk += bsize) {
      for (i = 0; i < m; ++i) {
        bim = b + i * m;
        for (j = (((jj) >= (i)) ? (jj) : (i)); j < (((jj + bsize) <= (m)) ? (jj + bsize) : (m)); ++j) {
          sum = 0.0;
          for (k = kk; k < (((kk + bsize) <= (n)) ? (kk + bsize) : (n)); ++k) {
            akm = a + k * m;
            sum += akm[i] * akm[j];
          }
          bim[j] += sum;
        }
      }
    }
  }
  for (i = 0; i < m; ++i)
    for (j = 0; j < i; ++j)
      b[i * m + j] = b[j * m + i];
}
```