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

```asm
<sc_atan2_s16>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  mov    %rdi,%r12
  push   %rbp
  push   %rbx
  sub    $0x8,%rsp
  or     %rsi,%r12
  jne    L15
L127:
  add    $0x8,%rsp
  mov    %r12,%rax
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
  nopl   0x0(%rax)
L15:
  mov    %rsi,%rbp
  mov    %edx,%ecx
  mov    $0x1,%r13d
  mov    %edx,%r15d
  shl    %cl,%r13d
  mov    %rdi,%rbx
  call   <abs@plt>
  mov    %rbp,%rdi
  movslq %r13d,%r13
  mov    %rax,%r12
  call   <abs@plt>
  mov    %r15d,%esi
  cmp    %rax,%r12
  jge    L99
  mov    %rbp,%rdi
  call   <sc_sqr_s16@plt>
  mov    $0xc,%edx
  mov    $0x3244,%edi
  mov    %rax,%rsi
  call   <sc_mul_s16@plt>
  mov    %r15d,%esi
  mov    %rbx,%rdi
  mov    %rax,%r12
  call   <sc_sqr_s16@plt>
  mov    $0xc,%edx
  mov    $0xe23,%edi
  mov    %rax,%rsi
  call   <sc_mul_s16@plt>
  add    %rax,%r12
  jne    L120
L19:
  test   %rbp,%rbp
  jg     L127
  lea    (%r12,%r13,1),%rax
  sub    %r13,%r12
  test   %rbx,%rbx
  cmovns %rax,%r12
  jmp    L127
  xchg   %ax,%ax
L99:
  mov    %rbx,%rdi
  call   <sc_sqr_s16@plt>
  mov    $0xc,%edx
  mov    $0x3244,%edi
  mov    %rax,%rsi
  call   <sc_mul_s16@plt>
  mov    %r15d,%esi
  mov    %rbp,%rdi
  mov    %rax,%r14
  call   <sc_sqr_s16@plt>
  mov    $0xc,%edx
  mov    $0xe23,%edi
  mov    %rax,%rsi
  call   <sc_mul_s16@plt>
  add    %rax,%r14
  jne    L129
L113:
  mov    %r13,%r12
  test   %rbx,%rbx
  jle    L67
  shr    $0x3f,%r12
  add    %r13,%r12
  sar    %r12
  sub    %r14,%r12
  jmp    L127
  nopl   0x0(%rax)
L67:
  jne    L22
  shr    $0x3f,%r12
  add    %r13,%r12
  sar    %r12
  test   %rbp,%rbp
  jg     L127
  neg    %r12
  jmp    L127
  nopl   (%rax)
L129:
  mov    %r15d,%edx
  mov    %rbx,%rsi
  mov    %rbp,%rdi
  call   <sc_mul_s16@plt>
  mov    %r14,%rsi
  mov    %r15d,%edx
  mov    %rax,%rdi
  call   <sc_div_s16@plt>
  mov    %rax,%r14
  jmp    L113
  nopl   0x0(%rax)
L120:
  mov    %r15d,%edx
  mov    %rbx,%rsi
  mov    %rbp,%rdi
  call   <sc_mul_s16@plt>
  mov    %r12,%rsi
  mov    %r15d,%edx
  mov    %rax,%rdi
  call   <sc_div_s16@plt>
  mov    %rax,%r12
  jmp    L19
  nopl   0x0(%rax)
L22:
  shr    $0x3f,%r12
  add    %r13,%r12
  sar    %r12
  neg    %r12
  sub    %r14,%r12
  jmp    L127
```

assistant: ```c
int16_t sc_atan2_s16(int16_t y, int16_t x, int radix) {
  int16_t tmp, c28_m_pi, one;
  int16_t arctantent = 0;
  if ((y != 0) || (x != 0)) {
    c28_m_pi = ((int16_t)((((0.28125 * (3.141592653590)) * ((int16_t)1 << ((12)))) < 0) ? (((0.28125 * (3.141592653590)) * ((int16_t)1 << ((12)))) - 0.5) : (((0.28125 * (3.141592653590)) * ((int16_t)1 << ((12)))) + 0.5)));
    one = (1 << (radix));
    if (abs(y) < abs(x)) {
      tmp = sc_mul_s16(((int16_t)(((((3.141592653590)) * ((int16_t)1 << ((12)))) < 0) ? ((((3.141592653590)) * ((int16_t)1 << ((12)))) - 0.5) : ((((3.141592653590)) * ((int16_t)1 << ((12)))) + 0.5))), sc_sqr_s16(x, radix), (12));
      tmp += sc_mul_s16(c28_m_pi, sc_sqr_s16(y, radix), (12));
      if (tmp != 0) {
        arctantent = sc_div_s16(sc_mul_s16(x, y, radix), tmp, radix);
      } else {
        arctantent = 0;
      }
      if (x <= 0) {
        if (y >= 0) {
          arctantent = one + arctantent;
        } else {
          arctantent = -one + arctantent;
        }
      }
    } else {
      tmp = sc_mul_s16(((int16_t)(((((3.141592653590)) * ((int16_t)1 << ((12)))) < 0) ? ((((3.141592653590)) * ((int16_t)1 << ((12)))) - 0.5) : ((((3.141592653590)) * ((int16_t)1 << ((12)))) + 0.5))), sc_sqr_s16(y, radix), (12));
      tmp += sc_mul_s16(c28_m_pi, sc_sqr_s16(x, radix), (12));
      if (tmp != 0) {
        arctantent = sc_div_s16(sc_mul_s16(x, y, radix), tmp, radix);
      } else {
        arctantent = 0;
      }
      if (y > 0) {
        arctantent = one / 2 - arctantent;
      } else {
        if (y < 0) {
          arctantent = -one / 2 - arctantent;
        } else {
          if (x > 0) {
            arctantent = one / 2;
          } else {
            arctantent = -one / 2;
          }
        }
      }
    }
  }
  return arctantent;
}
```