double rate_H(t)
double t;
{
  if (t == 0.0)
    return 0.0;
  return 1.27e-21 * sqrt(t) * exp(-157809.1 / t) / (1.0 + sqrt(t / 1e5)) +
         7.5e-19 * exp(-118348.0 / t) / (1.0 + sqrt(t / 1e5));
}


x86 assembly (clang, -O0):
<rate_H>:
push   %rbp
mov    %rsp,%rbp
sub    $0x30,%rsp
movsd  %xmm0,-0x10(%rbp)
movsd  -0x10(%rbp),%xmm0
xorps  %xmm1,%xmm1
ucomisd %xmm1,%xmm0
jne    1152 <rate_H+0x32>
jp     1152 <rate_H+0x32>
xorps  %xmm0,%xmm0
movsd  %xmm0,-0x8(%rbp)
jmp    1228 <rate_H+0x108>
movsd  -0x10(%rbp),%xmm0
call   1040 <sqrt@plt>
movaps %xmm0,%xmm1
movsd  0xec1(%rip),%xmm0
mulsd  %xmm1,%xmm0
movsd  %xmm0,-0x30(%rbp)
movsd  0xea8(%rip),%xmm0
divsd  -0x10(%rbp),%xmm0
call   1030 <exp@plt>
movaps %xmm0,%xmm1
movsd  -0x30(%rbp),%xmm0
mulsd  %xmm1,%xmm0
movsd  %xmm0,-0x28(%rbp)
movsd  -0x10(%rbp),%xmm0
movsd  0xe68(%rip),%xmm1
divsd  %xmm1,%xmm0
call   1040 <sqrt@plt>
movaps %xmm0,%xmm2
movsd  -0x28(%rbp),%xmm0
movsd  0xe47(%rip),%xmm1
addsd  %xmm2,%xmm1
divsd  %xmm1,%xmm0
movsd  %xmm0,-0x18(%rbp)
movsd  0xe4a(%rip),%xmm0
divsd  -0x10(%rbp),%xmm0
call   1030 <exp@plt>
movaps %xmm0,%xmm1
movsd  0xe2d(%rip),%xmm0
mulsd  %xmm1,%xmm0
movsd  %xmm0,-0x20(%rbp)
movsd  -0x10(%rbp),%xmm0
movsd  0xe0f(%rip),%xmm1
divsd  %xmm1,%xmm0
call   1040 <sqrt@plt>
movsd  -0x20(%rbp),%xmm1
movaps %xmm0,%xmm3
movsd  -0x18(%rbp),%xmm0
movsd  0xde9(%rip),%xmm2
addsd  %xmm3,%xmm2
divsd  %xmm2,%xmm1
addsd  %xmm1,%xmm0
movsd  %xmm0,-0x8(%rbp)
movsd  -0x8(%rbp),%xmm0
add    $0x30,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<rate_H>:
movapd %xmm0,%xmm1
xorpd  %xmm0,%xmm0
ucomisd %xmm0,%xmm1
jne    1131 <rate_H+0x11>
jp     1131 <rate_H+0x11>
ret
sub    $0x58,%rsp
xorpd  %xmm0,%xmm0
ucomisd %xmm0,%xmm1
movsd  %xmm1,0x10(%rsp)
jb     114e <rate_H+0x2e>
xorps  %xmm0,%xmm0
sqrtsd %xmm1,%xmm0
jmp    115d <rate_H+0x3d>
movapd %xmm1,%xmm0
call   1040 <sqrt@plt>
movsd  0x10(%rsp),%xmm1
mulsd  0xe9b(%rip),%xmm0
movapd %xmm0,0x40(%rsp)
movsd  0xe95(%rip),%xmm0
divsd  %xmm1,%xmm0
call   1030 <exp@plt>
movsd  0x10(%rsp),%xmm1
movapd %xmm1,%xmm2
divsd  0xe82(%rip),%xmm2
movapd %xmm0,0x20(%rsp)
xorps  %xmm0,%xmm0
sqrtsd %xmm2,%xmm0
movsd  %xmm2,0x8(%rsp)
ucomisd 0xe77(%rip),%xmm2
movapd %xmm0,0x30(%rsp)
jae    11c2 <rate_H+0xa2>
movsd  0x8(%rsp),%xmm0
call   1040 <sqrt@plt>
movsd  0x10(%rsp),%xmm1
movapd %xmm0,0x10(%rsp)
movsd  0xe48(%rip),%xmm0
divsd  %xmm1,%xmm0
call   1030 <exp@plt>
movapd 0x40(%rsp),%xmm2
shufpd $0x2,0xe48(%rip),%xmm2
movapd 0x20(%rsp),%xmm1
unpcklpd %xmm0,%xmm1
mulpd  %xmm2,%xmm1
xorpd  %xmm0,%xmm0
movsd  0x8(%rsp),%xmm2
ucomisd %xmm0,%xmm2
movapd 0x30(%rsp),%xmm0
jae    1223 <rate_H+0x103>
movsd  0x8(%rsp),%xmm0
movapd %xmm1,0x20(%rsp)
call   1040 <sqrt@plt>
movapd 0x20(%rsp),%xmm1
movapd 0x10(%rsp),%xmm2
unpcklpd %xmm0,%xmm2
addpd  0xe0b(%rip),%xmm2
divpd  %xmm2,%xmm1
movapd %xmm1,%xmm0
unpckhpd %xmm1,%xmm0
addsd  %xmm1,%xmm0
add    $0x58,%rsp
ret

LLVM IR (-O0):
define double @rate_H(double %0) {
%2 = alloca double
%3 = alloca double
store double %0, double* %3
%4 = load double, double* %3
%5 = fcmp oeq double %4, 0.000000e+00
br i1 %5, label %6, label %7
6: ; preds = %1
store double 0.000000e+00, double* %2
br label %30
7: ; preds = %1
%8 = load double, double* %3
%9 = call double @sqrt(double %8)
%10 = fmul double 1.270000e-21, %9
%11 = load double, double* %3
%12 = fdiv double 0xC1034388CCCCCCCD, %11
%13 = call double @exp(double %12)
%14 = fmul double %10, %13
%15 = load double, double* %3
%16 = fdiv double %15, 1.000000e+05
%17 = call double @sqrt(double %16)
%18 = fadd double 1.000000e+00, %17
%19 = fdiv double %14, %18
%20 = load double, double* %3
%21 = fdiv double -1.183480e+05, %20
%22 = call double @exp(double %21)
%23 = fmul double 0x3C2BAB8CBABB6581, %22
%24 = load double, double* %3
%25 = fdiv double %24, 1.000000e+05
%26 = call double @sqrt(double %25)
%27 = fadd double 1.000000e+00, %26
%28 = fdiv double %23, %27
%29 = fadd double %19, %28
store double %29, double* %2
br label %30
30: ; preds = %7, %6
%31 = load double, double* %2
ret double %31
}

LLVM IR (-O2):
define double @rate_H(double %0) {
%2 = fcmp oeq double %0, 0.000000e+00
br i1 %2, label %24, label %3
3: ; preds = %1
%4 = tail call double @sqrt(double %0)
%5 = fmul double %4, 1.270000e-21
%6 = fdiv double 0xC1034388CCCCCCCD, %0
%7 = tail call double @exp(double %6)
%8 = fdiv double %0, 1.000000e+05
%9 = tail call double @sqrt(double %8)
%10 = fdiv double -1.183480e+05, %0
%11 = tail call double @exp(double %10)
%12 = insertelement <2 x double> <double poison, double 0x3C2BAB8CBABB6581>, double %5, i64 0
%13 = insertelement <2 x double> poison, double %7, i64 0
%14 = insertelement <2 x double> %13, double %11, i64 1
%15 = fmul <2 x double> %12, %14
%16 = tail call double @sqrt(double %8)
%17 = insertelement <2 x double> poison, double %9, i64 0
%18 = insertelement <2 x double> %17, double %16, i64 1
%19 = fadd <2 x double> %18, <double 1.000000e+00, double 1.000000e+00>
%20 = fdiv <2 x double> %15, %19
%21 = shufflevector <2 x double> %20, <2 x double> poison, <2 x i32> <i32 1, i32 undef>
%22 = fadd <2 x double> %20, %21
%23 = extractelement <2 x double> %22, i64 0
br label %24
24: ; preds = %1, %3
%25 = phi double [ %23, %3 ], [ 0.000000e+00, %1 ]
ret double %25
}