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

```asm
<rec_matmul>:
  endbr64
  push   %r15
  lea    (%rcx,%r8,1),%r15d
  mov    %r9d,%eax
  push   %r14
  push   %r13
  mov    %rdx,%r13
  lea    (%r15,%r9,1),%edx
  push   %r12
  mov    %rdi,%r12
  push   %rbp
  mov    %ecx,%ebp
  push   %rbx
  mov    %r8d,%ebx
  sub    $0x28,%rsp
  mov    %rsi,0x8(%rsp)
  mov    0x68(%rsp),%r14d
  cmp    $0x40,%edx
  jle    L87
  mov    %r13,%rdx
  mov    0x8(%rsp),%r13
  mov    %r14d,%r10d
  mov    %r15d,%r12d
  mov    %rdi,%r14
  mov    %r9d,%r15d
L113:
  cmp    %ebx,%ebp
  jl     L167
  cmp    %r15d,%ebx
  jl     L167
  push   %r10
  mov    0x68(%rsp),%eax
  mov    %ebp,%r12d
  mov    %r15d,%r9d
  sar    %r12d
  mov    %ebx,%r8d
  mov    %r14,%rdi
  mov    %r13,%rsi
  mov    %r12d,%ecx
  sub    %r12d,%ebp
  mov    %r10d,0x70(%rsp)
  push   %rax
  mov    %rdx,0x18(%rsp)
  call   <rec_matmul>
  imul   0x70(%rsp),%r12d
  mov    0x18(%rsp),%rdx
  pop    %r8
  pop    %r9
  mov    0x68(%rsp),%r10d
  movslq %r12d,%rax
  lea    0x0(%rbp,%rbx,1),%r12d
  shl    $0x2,%rax
  add    %rax,%rdx
  add    %rax,%r14
L149:
  lea    (%r12,%r15,1),%eax
  cmp    $0x40,%eax
  jg     L113
  mov    %r13,0x8(%rsp)
  mov    %r14,%r12
  mov    %rdx,%r13
  mov    %r15d,%eax
  mov    %r10d,%r14d
L87:
  test   %r14d,%r14d
  jne    L166
  test   %ebp,%ebp
  jle    L193
  test   %eax,%eax
  jle    L193
  movslq %eax,%r8
  lea    0x4(%r12),%rax
  movslq 0x60(%rsp),%rsi
  xor    %r15d,%r15d
  mov    %rax,0x10(%rsp)
  lea    -0x1(%rbx),%eax
  pxor   %xmm2,%xmm2
  mov    %rax,0x18(%rsp)
  shl    $0x2,%rsi
  nopl   0x0(%rax)
L186:
  mov    0x10(%rsp),%rdi
  movslq %r15d,%rax
  mov    0x8(%rsp),%r9
  lea    0x0(,%rax,4),%r10
  add    0x18(%rsp),%rax
  lea    (%r12,%r10,1),%r11
  lea    (%rdi,%rax,4),%rcx
  add    %r13,%r10
  xor    %edi,%edi
  nopw   0x0(%rax,%rax,1)
L105:
  mov    %r9,%rdx
  mov    %r11,%rax
  movaps %xmm2,%xmm1
  test   %ebx,%ebx
  jle    L21
  nopl   (%rax)
L12:
  movss  (%rax),%xmm0
  mulss  (%rdx),%xmm0
  add    $0x4,%rax
  add    %rsi,%rdx
  addss  %xmm0,%xmm1
  cmp    %rax,%rcx
  jne    L12
L21:
  movss  %xmm1,(%r10,%rdi,4)
  add    $0x1,%rdi
  add    $0x4,%r9
  cmp    %rdi,%r8
  jne    L105
  add    $0x1,%r14d
  add    0x60(%rsp),%r15d
  cmp    %ebp,%r14d
  jne    L186
L193:
  add    $0x28,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
L167:
  cmp    %r15d,%ebp
  mov    %r15d,%eax
  cmovge %ebp,%eax
  cmp    %ebx,%eax
  jg     L116
  push   %r10
  mov    0x68(%rsp),%eax
  mov    %ebx,%r12d
  mov    %r13,%rsi
  sar    %r12d
  mov    %r14,%rdi
  mov    %r15d,%r9d
  mov    %ebp,%ecx
  push   %rax
  mov    %r12d,%r8d
  sub    %r12d,%ebx
  mov    %rdx,0x18(%rsp)
  call   <rec_matmul>
  mov    0x70(%rsp),%eax
  mov    $0x1,%r10d
  pop    %rsi
  pop    %rdi
  mov    0x8(%rsp),%rdx
  imul   %r12d,%eax
  movslq %r12d,%r12
  lea    (%r14,%r12,4),%r14
  lea    0x0(%rbp,%rbx,1),%r12d
  cltq
  lea    0x0(%r13,%rax,4),%r13
  jmp    L149
L116:
  push   %r10
  mov    0x68(%rsp),%eax
  mov    %r15d,%r9d
  mov    %ebp,%ecx
  sar    %r9d
  mov    %r13,%rsi
  mov    %ebx,%r8d
  mov    %r14,%rdi
  mov    %r10d,0x70(%rsp)
  push   %rax
  mov    %rdx,0x18(%rsp)
  mov    %r9d,0x20(%rsp)
  call   <rec_matmul>
  movslq 0x20(%rsp),%rax
  mov    0x18(%rsp),%rdx
  sub    %eax,%r15d
  shl    $0x2,%rax
  add    %rax,%rdx
  add    %rax,%r13
  pop    %rax
  pop    %rcx
  mov    0x68(%rsp),%r10d
  jmp    L149
L166:
  test   %ebp,%ebp
  jle    L193
  test   %eax,%eax
  jle    L193
  movslq %eax,%r8
  lea    0x4(%r12),%rax
  movslq 0x60(%rsp),%rsi
  xor    %r14d,%r14d
  mov    %rax,0x10(%rsp)
  lea    -0x1(%rbx),%eax
  xor    %r11d,%r11d
  pxor   %xmm2,%xmm2
  mov    %rax,0x18(%rsp)
  shl    $0x2,%rsi
  nopl   0x0(%rax)
L126:
  mov    0x10(%rsp),%rdi
  movslq %r14d,%rax
  mov    0x8(%rsp),%r9
  lea    0x0(,%rax,4),%r10
  add    0x18(%rsp),%rax
  lea    (%r12,%r10,1),%r15
  lea    (%rdi,%rax,4),%rcx
  add    %r13,%r10
  xor    %edi,%edi
  nop
L188:
  mov    %r9,%rdx
  mov    %r15,%rax
  movaps %xmm2,%xmm1
  test   %ebx,%ebx
  jle    L115
  nopl   (%rax)
L44:
  movss  (%rax),%xmm0
  mulss  (%rdx),%xmm0
  add    $0x4,%rax
  add    %rsi,%rdx
  addss  %xmm0,%xmm1
  cmp    %rax,%rcx
  jne    L44
L115:
  addss  (%r10,%rdi,4),%xmm1
  add    $0x4,%r9
  movss  %xmm1,(%r10,%rdi,4)
  add    $0x1,%rdi
  cmp    %rdi,%r8
  jne    L188
  add    $0x1,%r11d
  add    0x60(%rsp),%r14d
  cmp    %ebp,%r11d
  jne    L126
  add    $0x28,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
```

assistant: ```c
void rec_matmul(float *A, float *B, float *C, int m, int n, int p, int ld, int add) {
  if ((m + n + p) <= 64) {
    int i, j, k;
    if (add) {
      for (i = 0; i < m; i++)
        for (k = 0; k < p; k++) {
          float c = 0.0;
          for (j = 0; j < n; j++)
            c += A[i * ld + j] * B[j * ld + k];
          C[i * ld + k] += c;
        }
    } else {
      for (i = 0; i < m; i++)
        for (k = 0; k < p; k++) {
          float c = 0.0;
          for (j = 0; j < n; j++)
            c += A[i * ld + j] * B[j * ld + k];
          C[i * ld + k] = c;
        }
    }
  } else if (m >= n && n >= p) {
    int m1 = m >> 1;
    rec_matmul(A, B, C, m1, n, p, ld, add);
    rec_matmul(A + m1 * ld, B, C + m1 * ld, m - m1, n, p, ld, add);
  } else if (n >= m && n >= p) {
    int n1 = n >> 1;
    rec_matmul(A, B, C, m, n1, p, ld, add);
    rec_matmul(A + n1, B + n1 * ld, C, m, n - n1, p, ld, 1);
  } else {
    int p1 = p >> 1;
    rec_matmul(A, B, C, m, n, p1, ld, add);
    rec_matmul(A, B + p1, C + p1, m, n, p - p1, ld, add);
  }
}
```