double a_Hp(t)
double t;
{
  if (t > 0.0) {
    return (8.40e-11 / sqrt(t)) * pow(t / 1e3, -0.2) /
           (1.0 + pow(t / 1e6, 0.7));
  }
  return 0.0;
}


x86 assembly (clang, -O0):
<a_Hp>:
push   %rbp
mov    %rsp,%rbp
sub    $0x20,%rsp
movsd  %xmm0,-0x10(%rbp)
movsd  -0x10(%rbp),%xmm0
xorps  %xmm1,%xmm1
ucomisd %xmm1,%xmm0
jbe    11cc <a_Hp+0xac>
movsd  -0x10(%rbp),%xmm0
call   1040 <sqrt@plt>
movaps %xmm0,%xmm1
movsd  0xed4(%rip),%xmm0
divsd  %xmm1,%xmm0
movsd  %xmm0,-0x20(%rbp)
movsd  -0x10(%rbp),%xmm0
movsd  0xeb6(%rip),%xmm1
divsd  %xmm1,%xmm0
movsd  0xea2(%rip),%xmm1
call   1030 <pow@plt>
movaps %xmm0,%xmm1
movsd  -0x20(%rbp),%xmm0
mulsd  %xmm1,%xmm0
movsd  %xmm0,-0x18(%rbp)
movsd  -0x10(%rbp),%xmm0
movsd  0xe77(%rip),%xmm1
divsd  %xmm1,%xmm0
movsd  0xe63(%rip),%xmm1
call   1030 <pow@plt>
movaps %xmm0,%xmm2
movsd  -0x18(%rbp),%xmm0
movsd  0xe46(%rip),%xmm1
addsd  %xmm2,%xmm1
divsd  %xmm1,%xmm0
movsd  %xmm0,-0x8(%rbp)
jmp    11d4 <a_Hp+0xb4>
xorps  %xmm0,%xmm0
movsd  %xmm0,-0x8(%rbp)
movsd  -0x8(%rbp),%xmm0
add    $0x20,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<a_Hp>:
movapd %xmm0,%xmm1
xorpd  %xmm0,%xmm0
ucomisd %xmm0,%xmm1
jbe    11ca <a_Hp+0xaa>
sub    $0x18,%rsp
xorpd  %xmm0,%xmm0
ucomisd %xmm0,%xmm1
movsd  %xmm1,0x10(%rsp)
jb     114f <a_Hp+0x2f>
xorps  %xmm0,%xmm0
sqrtsd %xmm1,%xmm0
jmp    115e <a_Hp+0x3e>
movapd %xmm1,%xmm0
call   1040 <sqrt@plt>
movsd  0x10(%rsp),%xmm1
movsd  0xe9a(%rip),%xmm2
divsd  %xmm0,%xmm2
movsd  %xmm2,0x8(%rsp)
movapd %xmm1,%xmm0
divsd  0xe8c(%rip),%xmm0
movsd  0xe8c(%rip),%xmm1
call   1030 <pow@plt>
mulsd  0x8(%rsp),%xmm0
movsd  %xmm0,0x8(%rsp)
movsd  0x10(%rsp),%xmm0
divsd  0xe75(%rip),%xmm0
movsd  0xe75(%rip),%xmm1
call   1030 <pow@plt>
addsd  0xe70(%rip),%xmm0
movsd  0x8(%rsp),%xmm1
divsd  %xmm0,%xmm1
movapd %xmm1,%xmm0
add    $0x18,%rsp
ret

LLVM IR (-O0):
define double @a_Hp(double %0) {
%2 = alloca double
%3 = alloca double
store double %0, double* %3
%4 = load double, double* %3
%5 = fcmp ogt double %4, 0.000000e+00
br i1 %5, label %6, label %19
6: ; preds = %1
%7 = load double, double* %3
%8 = call double @sqrt(double %7)
%9 = fdiv double 8.400000e-11, %8
%10 = load double, double* %3
%11 = fdiv double %10, 1.000000e+03
%12 = call double @pow(double %11, double -2.000000e-01)
%13 = fmul double %9, %12
%14 = load double, double* %3
%15 = fdiv double %14, 1.000000e+06
%16 = call double @pow(double %15, double 0x3FE6666666666666)
%17 = fadd double 1.000000e+00, %16
%18 = fdiv double %13, %17
store double %18, double* %2
br label %20
19: ; preds = %1
store double 0.000000e+00, double* %2
br label %20
20: ; preds = %19, %6
%21 = load double, double* %2
ret double %21
}

LLVM IR (-O2):
define double @a_Hp(double %0) {
%2 = fcmp ogt double %0, 0.000000e+00
br i1 %2, label %3, label %13
3: ; preds = %1
%4 = tail call double @sqrt(double %0)
%5 = fdiv double 8.400000e-11, %4
%6 = fdiv double %0, 1.000000e+03
%7 = tail call double @pow(double %6, double -2.000000e-01)
%8 = fmul double %5, %7
%9 = fdiv double %0, 1.000000e+06
%10 = tail call double @pow(double %9, double 0x3FE6666666666666)
%11 = fadd double %10, 1.000000e+00
%12 = fdiv double %8, %11
br label %13
13: ; preds = %1, %3
%14 = phi double [ %12, %3 ], [ 0.000000e+00, %1 ]
ret double %14
}