float xatan(float arg) {
  float argsq;
  float value;
  argsq = arg * arg;
  value = ((((0.161536412982230e2 * argsq + 0.268425481955040e3) * argsq +
             0.115302935154049e4) *
                argsq +
            0.178040631643320e4) *
               argsq +
           0.896785974036639e3);
  value =
      value /
      (((((argsq + 0.589569705084446e2) * argsq + 0.536265374031215e3) * argsq +
         0.166678381488163e4) *
            argsq +
        0.207933497444541e4) *
           argsq +
       0.896785974036639e3);
  return (value * arg);
}


x86 assembly (clang, -O0):
<xatan>:
push   %rbp
mov    %rsp,%rbp
movss  %xmm0,-0x4(%rbp)
movss  -0x4(%rbp),%xmm0
mulss  -0x4(%rbp),%xmm0
movss  %xmm0,-0x8(%rbp)
movss  -0x8(%rbp),%xmm0
cvtss2sd %xmm0,%xmm0
movsd  0xf0f(%rip),%xmm1
mulsd  %xmm1,%xmm0
movsd  0xf0b(%rip),%xmm1
addsd  %xmm1,%xmm0
movss  -0x8(%rbp),%xmm1
cvtss2sd %xmm1,%xmm1
mulsd  %xmm1,%xmm0
movsd  0xee2(%rip),%xmm1
addsd  %xmm1,%xmm0
movss  -0x8(%rbp),%xmm1
cvtss2sd %xmm1,%xmm1
mulsd  %xmm1,%xmm0
movsd  0xec1(%rip),%xmm1
addsd  %xmm1,%xmm0
movss  -0x8(%rbp),%xmm1
cvtss2sd %xmm1,%xmm1
mulsd  %xmm1,%xmm0
movsd  0xe80(%rip),%xmm1
addsd  %xmm1,%xmm0
cvtsd2ss %xmm0,%xmm0
movss  %xmm0,-0xc(%rbp)
movss  -0xc(%rbp),%xmm0
cvtss2sd %xmm0,%xmm0
movss  -0x8(%rbp),%xmm1
cvtss2sd %xmm1,%xmm1
movsd  0xe79(%rip),%xmm2
addsd  %xmm2,%xmm1
movss  -0x8(%rbp),%xmm2
cvtss2sd %xmm2,%xmm2
mulsd  %xmm2,%xmm1
movsd  0xe58(%rip),%xmm2
addsd  %xmm2,%xmm1
movss  -0x8(%rbp),%xmm2
cvtss2sd %xmm2,%xmm2
mulsd  %xmm2,%xmm1
movsd  0xe37(%rip),%xmm2
addsd  %xmm2,%xmm1
movss  -0x8(%rbp),%xmm2
cvtss2sd %xmm2,%xmm2
mulsd  %xmm2,%xmm1
movsd  0xe16(%rip),%xmm2
addsd  %xmm2,%xmm1
movss  -0x8(%rbp),%xmm2
cvtss2sd %xmm2,%xmm2
mulsd  %xmm2,%xmm1
movsd  0xdf5(%rip),%xmm2
addsd  %xmm2,%xmm1
divsd  %xmm1,%xmm0
cvtsd2ss %xmm0,%xmm0
movss  %xmm0,-0xc(%rbp)
movss  -0xc(%rbp),%xmm0
mulss  -0x4(%rbp),%xmm0
pop    %rbp
ret

x86 assembly (clang, -O2):
<xatan>:
movaps %xmm0,%xmm1
mulss  %xmm0,%xmm1
cvtss2sd %xmm1,%xmm1
movsd  0xeed(%rip),%xmm2
mulsd  %xmm1,%xmm2
addsd  0xee9(%rip),%xmm2
mulsd  %xmm1,%xmm2
addsd  0xee5(%rip),%xmm2
mulsd  %xmm1,%xmm2
addsd  0xee1(%rip),%xmm2
mulsd  %xmm1,%xmm2
movsd  0xedd(%rip),%xmm3
addsd  %xmm3,%xmm2
cvtsd2ss %xmm2,%xmm2
cvtss2sd %xmm2,%xmm2
movsd  0xed1(%rip),%xmm4
addsd  %xmm1,%xmm4
mulsd  %xmm1,%xmm4
addsd  0xec9(%rip),%xmm4
mulsd  %xmm1,%xmm4
addsd  0xec5(%rip),%xmm4
mulsd  %xmm1,%xmm4
addsd  0xec1(%rip),%xmm4
mulsd  %xmm1,%xmm4
addsd  %xmm3,%xmm4
divsd  %xmm4,%xmm2
xorps  %xmm1,%xmm1
cvtsd2ss %xmm2,%xmm1
mulss  %xmm1,%xmm0
ret

LLVM IR (-O0):
define float @xatan(float %0) {
%2 = alloca float
%3 = alloca float
%4 = alloca float
store float %0, float* %2
%5 = load float, float* %2
%6 = load float, float* %2
%7 = fmul float %5, %6
store float %7, float* %3
%8 = load float, float* %3
%9 = fpext float %8 to double
%10 = call double @llvm.fmuladd.f64(double 0x40302755093F2ECA, double %9, double 0x4070C6CEC62A9EF6)
%11 = load float, float* %3
%12 = fpext float %11 to double
%13 = call double @llvm.fmuladd.f64(double %10, double %12, double 0x4092041E0E5489F8)
%14 = load float, float* %3
%15 = fpext float %14 to double
%16 = call double @llvm.fmuladd.f64(double %13, double %15, double 0x409BD1A0116A41AF)
%17 = load float, float* %3
%18 = fpext float %17 to double
%19 = call double @llvm.fmuladd.f64(double %16, double %18, double 0x408C0649ACC176F5)
%20 = fptrunc double %19 to float
store float %20, float* %4
%21 = load float, float* %4
%22 = fpext float %21 to double
%23 = load float, float* %3
%24 = fpext float %23 to double
%25 = fadd double %24, 0x404D7A7E027680C6
%26 = load float, float* %3
%27 = fpext float %26 to double
%28 = call double @llvm.fmuladd.f64(double %25, double %27, double 0x4080C21F7C6B8A35)
%29 = load float, float* %3
%30 = fpext float %29 to double
%31 = call double @llvm.fmuladd.f64(double %28, double %30, double 0x409A0B22A05E4AE0)
%32 = load float, float* %3
%33 = fpext float %32 to double
%34 = call double @llvm.fmuladd.f64(double %31, double %33, double 0x40A03EAB81C54010)
%35 = load float, float* %3
%36 = fpext float %35 to double
%37 = call double @llvm.fmuladd.f64(double %34, double %36, double 0x408C0649ACC176F5)
%38 = fdiv double %22, %37
%39 = fptrunc double %38 to float
store float %39, float* %4
%40 = load float, float* %4
%41 = load float, float* %2
%42 = fmul float %40, %41
ret float %42
}

LLVM IR (-O2):
define float @xatan(float %0) {
%2 = fmul float %0, %0
%3 = fpext float %2 to double
%4 = tail call double @llvm.fmuladd.f64(double %3, double 0x40302755093F2ECA, double 0x4070C6CEC62A9EF6)
%5 = tail call double @llvm.fmuladd.f64(double %4, double %3, double 0x4092041E0E5489F8)
%6 = tail call double @llvm.fmuladd.f64(double %5, double %3, double 0x409BD1A0116A41AF)
%7 = tail call double @llvm.fmuladd.f64(double %6, double %3, double 0x408C0649ACC176F5)
%8 = fptrunc double %7 to float
%9 = fpext float %8 to double
%10 = fadd double %3, 0x404D7A7E027680C6
%11 = tail call double @llvm.fmuladd.f64(double %10, double %3, double 0x4080C21F7C6B8A35)
%12 = tail call double @llvm.fmuladd.f64(double %11, double %3, double 0x409A0B22A05E4AE0)
%13 = tail call double @llvm.fmuladd.f64(double %12, double %3, double 0x40A03EAB81C54010)
%14 = tail call double @llvm.fmuladd.f64(double %13, double %3, double 0x408C0649ACC176F5)
%15 = fdiv double %9, %14
%16 = fptrunc double %15 to float
%17 = fmul float %16, %0
ret float %17
}