user: What would the C source look like for the assembly code provided here:

```asm
<echelonform>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x58,%rsp
  mov    %rdi,0x10(%rsp)
  mov    %esi,0x24(%rsp)
  test   %esi,%esi
  jle    L10
  mov    %edx,%r14d
  test   %edx,%edx
  jle    L214
  lea    -0x1(%rdx),%eax
  movl   $0x0,0x20(%rsp)
  mov    %eax,0x38(%rsp)
  mov    %edx,%eax
  shr    $0x4,%eax
  movl   $0x0,0x18(%rsp)
  mov    0x18(%rsp),%esi
  sub    $0x1,%eax
  add    $0x1,%rax
  shl    $0x4,%rax
  mov    %rax,0x40(%rsp)
  mov    %edx,%eax
  and    $0xfffffff0,%eax
  mov    %eax,0x3c(%rsp)
  movslq %edx,%rax
  mov    %rax,0x30(%rsp)
  mov    0x10(%rsp),%rax
  add    $0x1,%rax
  mov    %rax,0x28(%rsp)
  mov    %edx,%eax
  and    $0xf,%eax
  mov    %eax,0x48(%rsp)
  sub    $0x1,%eax
  mov    %eax,0x4c(%rsp)
  nopl   (%rax)
L168:
  imul   %r14d,%esi
  movslq 0x20(%rsp),%rdi
  mov    0x24(%rsp),%r8d
  mov    0x30(%rsp),%r9
  mov    %rdi,%r10
  movslq %esi,%r12
  add    %r12,%rdi
  add    0x10(%rsp),%rdi
L17:
  mov    0x18(%rsp),%edx
  mov    %rdi,%rax
  mov    %esi,%ecx
  jmp    L191
  nopl   0x0(%rax)
L139:
  add    $0x1,%edx
  add    %r14d,%ecx
  add    %r9,%rax
  cmp    %edx,%r8d
  je     L245
L191:
  cmpb   $0x0,(%rax)
  je     L139
  movslq %ecx,%r8
  lea    0x10(%r12),%rdx
  mov    %r10d,0x20(%rsp)
  lea    0x10(%r8),%rax
  cmp    %rax,%r12
  setge  %al
  cmp    %rdx,%r8
  setge  %dl
  or     %dl,%al
  je     L11
  mov    0x38(%rsp),%eax
  cmp    $0x6,%eax
  jbe    L11
  cmp    $0xe,%eax
  jbe    L124
  mov    0x10(%rsp),%rax
  mov    0x40(%rsp),%r9
  lea    (%rax,%r12,1),%rdi
  lea    (%rax,%r8,1),%rdx
  xor    %eax,%eax
  cs nopw 0x0(%rax,%rax,1)
L286:
  movdqu (%rdi,%rax,1),%xmm0
  movdqu (%rdx,%rax,1),%xmm1
  movups %xmm1,(%rdi,%rax,1)
  movups %xmm0,(%rdx,%rax,1)
  add    $0x10,%rax
  cmp    %r9,%rax
  jne    L286
  mov    0x3c(%rsp),%eax
  cmp    %r14d,%eax
  je     L267
  cmpl   $0x6,0x4c(%rsp)
  mov    0x48(%rsp),%edx
  jbe    L244
  mov    %eax,%edi
L72:
  mov    0x10(%rsp),%rbx
  lea    (%rax,%r12,1),%r9
  add    %r8,%rax
  add    %rbx,%rax
  add    %rbx,%r9
  mov    (%r9),%r8
  mov    (%rax),%r10
  mov    %r10,(%r9)
  mov    %r8,(%rax)
  mov    %edx,%r8d
  and    $0xfffffff8,%r8d
  lea    (%r8,%rdi,1),%eax
  cmp    %edx,%r8d
  je     L267
L244:
  mov    0x10(%rsp),%rbx
  lea    (%rax,%rsi,1),%edi
  lea    (%rcx,%rax,1),%edx
  movslq %edi,%rdi
  movslq %edx,%rdx
  add    %rbx,%rdx
  add    %rbx,%rdi
  movzbl (%rdx),%r9d
  movzbl (%rdi),%r8d
  mov    %r9b,(%rdi)
  mov    %r8b,(%rdx)
  lea    0x1(%rax),%edx
  cmp    %edx,%r14d
  jle    L267
  lea    (%rdx,%rsi,1),%edi
  add    %ecx,%edx
  movslq %edi,%rdi
  movslq %edx,%rdx
  add    %rbx,%rdx
  add    %rbx,%rdi
  movzbl (%rdx),%r9d
  movzbl (%rdi),%r8d
  mov    %r9b,(%rdi)
  mov    %r8b,(%rdx)
  lea    0x2(%rax),%edx
  cmp    %edx,%r14d
  jle    L267
  lea    (%rdx,%rsi,1),%edi
  add    %ecx,%edx
  movslq %edi,%rdi
  movslq %edx,%rdx
  add    %rbx,%rdx
  add    %rbx,%rdi
  movzbl (%rdx),%r9d
  movzbl (%rdi),%r8d
  mov    %r9b,(%rdi)
  mov    %r8b,(%rdx)
  lea    0x3(%rax),%edx
  cmp    %edx,%r14d
  jle    L267
  lea    (%rdx,%rsi,1),%edi
  add    %ecx,%edx
  movslq %edi,%rdi
  movslq %edx,%rdx
  add    %rbx,%rdx
  add    %rbx,%rdi
  movzbl (%rdx),%r9d
  movzbl (%rdi),%r8d
  mov    %r9b,(%rdi)
  mov    %r8b,(%rdx)
  lea    0x4(%rax),%edx
  cmp    %edx,%r14d
  jle    L267
  lea    (%rdx,%rsi,1),%edi
  add    %ecx,%edx
  movslq %edi,%rdi
  movslq %edx,%rdx
  add    %rbx,%rdx
  add    %rbx,%rdi
  movzbl (%rdx),%r9d
  movzbl (%rdi),%r8d
  mov    %r9b,(%rdi)
  mov    %r8b,(%rdx)
  lea    0x5(%rax),%edx
  cmp    %edx,%r14d
  jle    L267
  lea    (%rdx,%rsi,1),%edi
  add    %ecx,%edx
  add    $0x6,%eax
  movslq %edi,%rdi
  movslq %edx,%rdx
  add    %rbx,%rdi
  add    %rbx,%rdx
  movzbl (%rdi),%r8d
  movzbl (%rdx),%r9d
  mov    %r9b,(%rdi)
  mov    %r8b,(%rdx)
  cmp    %eax,%r14d
  jle    L267
  lea    (%rax,%rsi,1),%edx
  add    %ecx,%eax
  movslq %edx,%rdx
  cltq
  add    %rbx,%rdx
  add    %rbx,%rax
  movzbl (%rdx),%edi
  movzbl (%rax),%ecx
  mov    %cl,(%rdx)
  mov    %dil,(%rax)
L267:
  mov    0x10(%rsp),%rax
  add    0x20(%rsp),%esi
  movslq %esi,%rsi
  movzbl (%rax,%rsi,1),%ebx
  test   %bl,%bl
  jne    L16
L274:
  movl   $0x0,0xc(%rsp)
  xor    %eax,%eax
  mov    0xc(%rsp),%ecx
  mov    %r14d,0x1c(%rsp)
  mov    %eax,%r14d
  nopl   0x0(%rax)
L266:
  cmp    %ecx,0x18(%rsp)
  je     L167
  mov    0x20(%rsp),%eax
  mov    0x10(%rsp),%rcx
  movslq %r14d,%rbp
  mov    0x38(%rsp),%ebx
  add    0x28(%rsp),%rbx
  add    %r14d,%eax
  lea    (%rcx,%rbp,1),%r15
  add    %rbp,%rbx
  cltq
  movzbl (%rcx,%rax,1),%r13d
  nopl   0x0(%rax)
L229:
  mov    %r15,%rax
  mov    %r13d,%edi
  add    $0x1,%r15
  sub    %rbp,%rax
  movzbl (%rax,%r12,1),%esi
  call   <mul@plt>
  movzbl -0x1(%r15),%edi
  mov    %eax,%esi
  call   <sub@plt>
  mov    %al,-0x1(%r15)
  cmp    %rbx,%r15
  jne    L229
L167:
  mov    0xc(%rsp),%eax
  add    0x1c(%rsp),%r14d
  add    $0x1,%eax
  cmp    %eax,0x24(%rsp)
  je     L217
  mov    %eax,0xc(%rsp)
  mov    %eax,%ecx
  jmp    L266
  cs nopw 0x0(%rax,%rax,1)
L245:
  add    $0x1,%r10d
  add    $0x1,%rdi
  cmp    %r10d,%r14d
  jne    L17
L214:
  add    $0x58,%rsp
  xor    %eax,%eax
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
  nopw   0x0(%rax,%rax,1)
L217:
  mov    0x18(%rsp),%ebx
  addl   $0x1,0x20(%rsp)
  mov    0x1c(%rsp),%r14d
  lea    0x1(%rbx),%eax
  cmp    0xc(%rsp),%ebx
  jge    L10
  cmp    0x20(%rsp),%r14d
  jle    L214
  mov    %eax,0x18(%rsp)
  mov    %eax,%esi
  jmp    L168
L16:
  mov    0x38(%rsp),%ebp
  add    0x28(%rsp),%rbp
  lea    (%rax,%r12,1),%r13
  add    %r12,%rbp
  nopl   (%rax)
L108:
  movzbl 0x0(%r13),%edi
  mov    %ebx,%esi
  add    $0x1,%r13
  call   <divs@plt>
  mov    %al,-0x1(%r13)
  cmp    %rbp,%r13
  jne    L108
  jmp    L274
L11:
  mov    0x10(%rsp),%rax
  mov    0x38(%rsp),%r9d
  add    0x28(%rsp),%r9
  add    %r12,%rax
  add    %r12,%r9
  nopl   0x0(%rax,%rax,1)
L215:
  mov    %rax,%rdx
  movzbl (%rax),%ecx
  add    $0x1,%rax
  sub    %r12,%rdx
  movzbl (%rdx,%r8,1),%edi
  mov    %dil,-0x1(%rax)
  mov    %cl,(%rdx,%r8,1)
  cmp    %r9,%rax
  jne    L215
  jmp    L267
L124:
  mov    %r14d,%edx
  xor    %edi,%edi
  xor    %eax,%eax
  jmp    L72
L10:
  add    $0x58,%rsp
  mov    $0x1,%eax
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
```

assistant: ```c
int echelonform(unsigned char M[], int nrows, int ncols) {
  int lead = 0, rix = 0, iix = 0, j, k;
  unsigned char temp, de, sb;
  for (rix = 0; rix < nrows; rix++) {
    if (lead >= ncols) {
      return 0;
    }
    iix = rix;
    while (M[iix * ncols + lead] == 0) {
      iix++;
      if (iix == nrows) {
        iix = rix;
        lead++;
        if (ncols == lead) {
          return 0;
        }
      }
    }
    for (j = 0; j < ncols; j++) {
      temp = M[rix * ncols + j];
      M[rix * ncols + j] = M[iix * ncols + j];
      M[iix * ncols + j] = temp;
    }
    de = M[rix * ncols + lead];
    if (de != 0) {
      for (j = 0; j < ncols; j++) {
        M[rix * ncols + j] = divs(M[rix * ncols + j], de);
      }
    }
    for (j = 0; j < nrows; j++) {
      if (j != rix) {
        sb = M[j * ncols + lead];
        for (k = 0; k < ncols; k++) {
          M[j * ncols + k] = sub(M[j * ncols + k], mul(sb, M[rix * ncols + k]));
        }
      }
    }
    lead++;
  }
  return 1;
}
```