void gcf(gammcf, a, x, gln) float a, x, *gammcf, *gln;
{
  int n;
  float gold = 0.0, g, fac = 1.0, b1 = 1.0;
  float b0 = 0.0, anf, ana, an, a1, a0 = 1.0;
  float gammln();
  void nrerror();
  *gln = gammln(a);
  a1 = x;
  for (n = 1; n <= 100; n++) {
    an = (float)n;
    ana = an - a;
    a0 = (a1 + a0 * ana) * fac;
    b0 = (b1 + b0 * ana) * fac;
    anf = an * fac;
    a1 = x * a0 + anf * a1;
    b1 = x * b0 + anf * b1;
    if (a1) {
      fac = 1.0 / a1;
      g = b1 * fac;
      if (fabs((g - gold) / g) < 3.0e-7) {
        *gammcf = exp(-x + a * log(x) - (*gln)) * g;
        return;
      }
      gold = g;
    }
  }
  nrerror("a too large, ITMAX too small in routine GCF");
}


x86 assembly (clang, -O0):
<gcf>:
push   %rbp
mov    %rsp,%rbp
sub    $0x60,%rsp
movsd  %xmm1,-0x50(%rbp)
movaps %xmm0,%xmm1
movsd  -0x50(%rbp),%xmm0
cvtsd2ss %xmm1,%xmm1
cvtsd2ss %xmm0,%xmm0
mov    %rdi,-0x8(%rbp)
movss  %xmm1,-0xc(%rbp)
movss  %xmm0,-0x10(%rbp)
mov    %rsi,-0x18(%rbp)
xorps  %xmm0,%xmm0
movss  %xmm0,-0x20(%rbp)
movss  0xe81(%rip),%xmm0
movss  %xmm0,-0x28(%rbp)
movss  0xe74(%rip),%xmm0
movss  %xmm0,-0x2c(%rbp)
xorps  %xmm0,%xmm0
movss  %xmm0,-0x30(%rbp)
movss  0xe5f(%rip),%xmm0
movss  %xmm0,-0x44(%rbp)
movss  -0xc(%rbp),%xmm0
cvtss2sd %xmm0,%xmm0
mov    $0x1,%al
call   1060 <gammln@plt>
mov    -0x18(%rbp),%rax
movss  %xmm0,(%rax)
movss  -0x10(%rbp),%xmm0
movss  %xmm0,-0x40(%rbp)
movl   $0x1,-0x1c(%rbp)
cmpl   $0x64,-0x1c(%rbp)
jg     139a <gcf+0x25a>
cvtsi2ssl -0x1c(%rbp),%xmm0
movss  %xmm0,-0x3c(%rbp)
movss  -0x3c(%rbp),%xmm0
subss  -0xc(%rbp),%xmm0
movss  %xmm0,-0x38(%rbp)
movss  -0x40(%rbp),%xmm1
movss  -0x44(%rbp),%xmm0
movss  -0x38(%rbp),%xmm2
mulss  %xmm2,%xmm0
addss  %xmm1,%xmm0
mulss  -0x28(%rbp),%xmm0
movss  %xmm0,-0x44(%rbp)
movss  -0x2c(%rbp),%xmm1
movss  -0x30(%rbp),%xmm0
movss  -0x38(%rbp),%xmm2
mulss  %xmm2,%xmm0
addss  %xmm1,%xmm0
mulss  -0x28(%rbp),%xmm0
movss  %xmm0,-0x30(%rbp)
movss  -0x3c(%rbp),%xmm0
mulss  -0x28(%rbp),%xmm0
movss  %xmm0,-0x34(%rbp)
movss  -0x10(%rbp),%xmm0
movss  -0x44(%rbp),%xmm2
movss  -0x34(%rbp),%xmm1
mulss  -0x40(%rbp),%xmm1
mulss  %xmm2,%xmm0
addss  %xmm1,%xmm0
movss  %xmm0,-0x40(%rbp)
movss  -0x10(%rbp),%xmm0
movss  -0x30(%rbp),%xmm2
movss  -0x34(%rbp),%xmm1
mulss  -0x2c(%rbp),%xmm1
mulss  %xmm2,%xmm0
addss  %xmm1,%xmm0
movss  %xmm0,-0x2c(%rbp)
movss  -0x40(%rbp),%xmm0
xorps  %xmm1,%xmm1
ucomiss %xmm1,%xmm0
jne    12a1 <gcf+0x161>
jp     12a1 <gcf+0x161>
jmp    1387 <gcf+0x247>
movss  -0x40(%rbp),%xmm0
cvtss2sd %xmm0,%xmm1
movsd  0xd5e(%rip),%xmm0
divsd  %xmm1,%xmm0
cvtsd2ss %xmm0,%xmm0
movss  %xmm0,-0x28(%rbp)
movss  -0x2c(%rbp),%xmm0
mulss  -0x28(%rbp),%xmm0
movss  %xmm0,-0x24(%rbp)
movss  -0x24(%rbp),%xmm0
subss  -0x20(%rbp),%xmm0
divss  -0x24(%rbp),%xmm0
cvtss2sd %xmm0,%xmm1
movaps 0xd38(%rip),%xmm0
pand   %xmm0,%xmm1
movsd  0xd14(%rip),%xmm0
ucomisd %xmm1,%xmm0
jbe    137d <gcf+0x23d>
movss  -0x10(%rbp),%xmm0
movd   %xmm0,%eax
xor    $0x80000000,%eax
movd   %eax,%xmm0
cvtss2sd %xmm0,%xmm0
movsd  %xmm0,-0x60(%rbp)
movss  -0xc(%rbp),%xmm0
cvtss2sd %xmm0,%xmm0
movsd  %xmm0,-0x58(%rbp)
movss  -0x10(%rbp),%xmm0
cvtss2sd %xmm0,%xmm0
call   1050 <log@plt>
movsd  -0x60(%rbp),%xmm1
movaps %xmm0,%xmm2
movsd  -0x58(%rbp),%xmm0
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
mov    -0x18(%rbp),%rax
movss  (%rax),%xmm1
cvtss2sd %xmm1,%xmm1
subsd  %xmm1,%xmm0
call   1040 <exp@plt>
movss  -0x24(%rbp),%xmm1
cvtss2sd %xmm1,%xmm1
mulsd  %xmm1,%xmm0
cvtsd2ss %xmm0,%xmm0
mov    -0x8(%rbp),%rax
movss  %xmm0,(%rax)
jmp    13a8 <gcf+0x268>
movss  -0x24(%rbp),%xmm0
movss  %xmm0,-0x20(%rbp)
jmp    138c <gcf+0x24c>
mov    -0x1c(%rbp),%eax
add    $0x1,%eax
mov    %eax,-0x1c(%rbp)
jmp    11cf <gcf+0x8f>
lea    0xc8f(%rip),%rdi
mov    $0x0,%al
call   1030 <nrerror@plt>
add    $0x60,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<gcf>:
push   %r14
push   %rbx
sub    $0x28,%rsp
cvtsd2ss %xmm0,%xmm2
movss  %xmm2,0x8(%rsp)
mov    %rsi,%rbx
mov    %rdi,%r14
xorps  %xmm0,%xmm0
cvtsd2ss %xmm1,%xmm0
movaps %xmm0,0x10(%rsp)
xorps  %xmm0,%xmm0
cvtss2sd %xmm2,%xmm0
movsd  %xmm0,0x20(%rsp)
mov    $0x1,%al
call   1060 <gammln@plt>
movaps 0x10(%rsp),%xmm12
movss  0x8(%rsp),%xmm3
movss  %xmm0,(%rbx)
movaps 0xe72(%rip),%xmm0
movss  %xmm12,%xmm0
movaps %xmm12,%xmm1
shufps $0x0,%xmm12,%xmm1
movss  0xe7c(%rip),%xmm4
movss  0xe73(%rip),%xmm10
xorps  %xmm11,%xmm11
mov    $0x1,%eax
movaps 0xe52(%rip),%xmm8
movsd  0xe61(%rip),%xmm9
xorps  %xmm5,%xmm5
movaps %xmm10,%xmm2
jmp    11d8 <gcf+0x98>
add    $0x1,%eax
cmp    $0x65,%eax
je     124b <gcf+0x10b>
xorps  %xmm6,%xmm6
cvtsi2ss %eax,%xmm6
movaps %xmm2,%xmm7
mulss  %xmm6,%xmm7
subss  %xmm3,%xmm6
shufps $0x0,%xmm6,%xmm6
mulps  %xmm4,%xmm6
addps  %xmm0,%xmm6
movaps %xmm2,%xmm4
shufps $0x0,%xmm2,%xmm4
mulps  %xmm6,%xmm4
shufps $0x0,%xmm7,%xmm7
mulps  %xmm0,%xmm7
movaps %xmm1,%xmm0
mulps  %xmm4,%xmm0
addps  %xmm7,%xmm0
ucomiss %xmm11,%xmm0
jne    1216 <gcf+0xd6>
jnp    11d0 <gcf+0x90>
movaps %xmm10,%xmm2
divss  %xmm0,%xmm2
movaps %xmm0,%xmm7
shufps $0x55,%xmm0,%xmm7
mulss  %xmm2,%xmm7
movaps %xmm7,%xmm6
subss  %xmm5,%xmm6
divss  %xmm7,%xmm6
andps  %xmm8,%xmm6
xorps  %xmm5,%xmm5
cvtss2sd %xmm6,%xmm5
ucomisd %xmm5,%xmm9
ja     1260 <gcf+0x120>
movaps %xmm7,%xmm5
jmp    11d0 <gcf+0x90>
lea    0xdde(%rip),%rdi
xor    %eax,%eax
add    $0x28,%rsp
pop    %rbx
pop    %r14
jmp    1030 <nrerror@plt>
xorps  %xmm0,%xmm0
cvtss2sd %xmm12,%xmm0
movsd  %xmm0,0x8(%rsp)
movaps %xmm7,0x10(%rsp)
call   1050 <log@plt>
mulsd  0x20(%rsp),%xmm0
subsd  0x8(%rsp),%xmm0
movss  (%rbx),%xmm1
cvtss2sd %xmm1,%xmm1
subsd  %xmm1,%xmm0
call   1040 <exp@plt>
movaps 0x10(%rsp),%xmm1
cvtss2sd %xmm1,%xmm1
mulsd  %xmm0,%xmm1
xorps  %xmm0,%xmm0
cvtsd2ss %xmm1,%xmm0
movss  %xmm0,(%r14)
add    $0x28,%rsp
pop    %rbx
pop    %r14
ret

LLVM IR (-O0):
@.str = [44 x i8] c"a too large, ITMAX too small in routine GCF\00"
define void @gcf(float* %0, double %1, double %2, float* %3) {
%5 = alloca float*
%6 = alloca float
%7 = alloca float
%8 = alloca float*
%9 = alloca i32
%10 = alloca float
%11 = alloca float
%12 = alloca float
%13 = alloca float
%14 = alloca float
%15 = alloca float
%16 = alloca float
%17 = alloca float
%18 = alloca float
%19 = alloca float
%20 = fptrunc double %1 to float
%21 = fptrunc double %2 to float
store float* %0, float** %5
store float %20, float* %6
store float %21, float* %7
store float* %3, float** %8
store float 0.000000e+00, float* %10
store float 1.000000e+00, float* %12
store float 1.000000e+00, float* %13
store float 0.000000e+00, float* %14
store float 1.000000e+00, float* %19
%22 = load float, float* %6
%23 = fpext float %22 to double
%24 = call float (double, ...) bitcast (float (...)* @gammln to float (double, ...)*)(double %23)
%25 = load float*, float** %8
store float %24, float* %25
%26 = load float, float* %7
store float %26, float* %18
store i32 1, i32* %9
br label %27
27: ; preds = %104, %4
%28 = load i32, i32* %9
%29 = icmp sle i32 %28, 100
br i1 %29, label %30, label %107
30: ; preds = %27
%31 = load i32, i32* %9
%32 = sitofp i32 %31 to float
store float %32, float* %17
%33 = load float, float* %17
%34 = load float, float* %6
%35 = fsub float %33, %34
store float %35, float* %16
%36 = load float, float* %18
%37 = load float, float* %19
%38 = load float, float* %16
%39 = call float @llvm.fmuladd.f32(float %37, float %38, float %36)
%40 = load float, float* %12
%41 = fmul float %39, %40
store float %41, float* %19
%42 = load float, float* %13
%43 = load float, float* %14
%44 = load float, float* %16
%45 = call float @llvm.fmuladd.f32(float %43, float %44, float %42)
%46 = load float, float* %12
%47 = fmul float %45, %46
store float %47, float* %14
%48 = load float, float* %17
%49 = load float, float* %12
%50 = fmul float %48, %49
store float %50, float* %15
%51 = load float, float* %7
%52 = load float, float* %19
%53 = load float, float* %15
%54 = load float, float* %18
%55 = fmul float %53, %54
%56 = call float @llvm.fmuladd.f32(float %51, float %52, float %55)
store float %56, float* %18
%57 = load float, float* %7
%58 = load float, float* %14
%59 = load float, float* %15
%60 = load float, float* %13
%61 = fmul float %59, %60
%62 = call float @llvm.fmuladd.f32(float %57, float %58, float %61)
store float %62, float* %13
%63 = load float, float* %18
%64 = fcmp une float %63, 0.000000e+00
br i1 %64, label %65, label %103
65: ; preds = %30
%66 = load float, float* %18
%67 = fpext float %66 to double
%68 = fdiv double 1.000000e+00, %67
%69 = fptrunc double %68 to float
store float %69, float* %12
%70 = load float, float* %13
%71 = load float, float* %12
%72 = fmul float %70, %71
store float %72, float* %11
%73 = load float, float* %11
%74 = load float, float* %10
%75 = fsub float %73, %74
%76 = load float, float* %11
%77 = fdiv float %75, %76
%78 = fpext float %77 to double
%79 = call double @llvm.fabs.f64(double %78)
%80 = fcmp olt double %79, 3.000000e-07
br i1 %80, label %81, label %101
81: ; preds = %65
%82 = load float, float* %7
%83 = fneg float %82
%84 = fpext float %83 to double
%85 = load float, float* %6
%86 = fpext float %85 to double
%87 = load float, float* %7
%88 = fpext float %87 to double
%89 = call double @log(double %88)
%90 = call double @llvm.fmuladd.f64(double %86, double %89, double %84)
%91 = load float*, float** %8
%92 = load float, float* %91
%93 = fpext float %92 to double
%94 = fsub double %90, %93
%95 = call double @exp(double %94)
%96 = load float, float* %11
%97 = fpext float %96 to double
%98 = fmul double %95, %97
%99 = fptrunc double %98 to float
%100 = load float*, float** %5
store float %99, float* %100
br label %108
101: ; preds = %65
%102 = load float, float* %11
store float %102, float* %10
br label %103
103: ; preds = %101, %30
br label %104
104: ; preds = %103
%105 = load i32, i32* %9
%106 = add nsw i32 %105, 1
store i32 %106, i32* %9
br label %27
107: ; preds = %27
br label %108
108: ; preds = %107, %81
ret void
}

LLVM IR (-O2):
@.str = [44 x i8] c"a too large, ITMAX too small in routine GCF\00"
define void @gcf(float* nocapture writeonly %0, double %1, double %2, float* nocapture %3) {
%5 = fptrunc double %1 to float
%6 = fptrunc double %2 to float
%7 = fpext float %5 to double
%8 = tail call float (double, ...) bitcast (float (...)* @gammln to float (double, ...)*)(double %7)
store float %8, float* %3
%9 = insertelement <2 x float> <float poison, float 1.000000e+00>, float %6, i64 0
%10 = insertelement <2 x float> poison, float %6, i64 0
%11 = shufflevector <2 x float> %10, <2 x float> poison, <2 x i32> zeroinitializer
br label %12
12: ; preds = %4, %55
%13 = phi i32 [ 1, %4 ], [ %58, %55 ]
%14 = phi float [ 0.000000e+00, %4 ], [ %57, %55 ]
%15 = phi float [ 1.000000e+00, %4 ], [ %56, %55 ]
%16 = phi <2 x float> [ <float 1.000000e+00, float 0.000000e+00>, %4 ], [ %25, %55 ]
%17 = phi <2 x float> [ %9, %4 ], [ %30, %55 ]
%18 = sitofp i32 %13 to float
%19 = fsub float %18, %5
%20 = insertelement <2 x float> poison, float %19, i64 0
%21 = shufflevector <2 x float> %20, <2 x float> poison, <2 x i32> zeroinitializer
%22 = call <2 x float> @llvm.fmuladd.v2f32(<2 x float> %16, <2 x float> %21, <2 x float> %17)
%23 = insertelement <2 x float> poison, float %15, i64 0
%24 = shufflevector <2 x float> %23, <2 x float> poison, <2 x i32> zeroinitializer
%25 = fmul <2 x float> %24, %22
%26 = fmul float %15, %18
%27 = insertelement <2 x float> poison, float %26, i64 0
%28 = shufflevector <2 x float> %27, <2 x float> poison, <2 x i32> zeroinitializer
%29 = fmul <2 x float> %17, %28
%30 = call <2 x float> @llvm.fmuladd.v2f32(<2 x float> %11, <2 x float> %25, <2 x float> %29)
%31 = extractelement <2 x float> %30, i64 0
%32 = fcmp une float %31, 0.000000e+00
br i1 %32, label %33, label %55
33: ; preds = %12
%34 = fdiv float 1.000000e+00, %31
%35 = extractelement <2 x float> %30, i64 1
%36 = fmul float %35, %34
%37 = fsub float %36, %14
%38 = fdiv float %37, %36
%39 = tail call float @llvm.fabs.f32(float %38)
%40 = fpext float %39 to double
%41 = fcmp olt double %40, 3.000000e-07
br i1 %41, label %42, label %55
42: ; preds = %33
%43 = fneg float %6
%44 = fpext float %43 to double
%45 = fpext float %6 to double
%46 = tail call double @log(double %45)
%47 = tail call double @llvm.fmuladd.f64(double %7, double %46, double %44)
%48 = load float, float* %3
%49 = fpext float %48 to double
%50 = fsub double %47, %49
%51 = tail call double @exp(double %50)
%52 = fpext float %36 to double
%53 = fmul double %51, %52
%54 = fptrunc double %53 to float
store float %54, float* %0
br label %61
55: ; preds = %33, %12
%56 = phi float [ %15, %12 ], [ %34, %33 ]
%57 = phi float [ %14, %12 ], [ %36, %33 ]
%58 = add nuw nsw i32 %13, 1
%59 = icmp eq i32 %58, 101
br i1 %59, label %60, label %12
60: ; preds = %55
tail call void (i8*, ...) bitcast (void (...)* @nrerror to void (i8*, ...)*)(i8* getelementptr inbounds ([44 x i8], [44 x i8]* @.str, i64 0, i64 0))
br label %61
61: ; preds = %60, %42
ret void
}