void precess_fast(mjd1, mjd2, ra, dec) double mjd1, mjd2;
double *ra, *dec;
{
  double nyrs;
  *ra = ((*ra) * 3.141592653589793 / 180);
  *dec = ((*dec) * 3.141592653589793 / 180);
  nyrs = (mjd2 - mjd1) / 365.2425;
  *dec += ((20.0468 / 3600.0) * 3.141592653589793 / 180) * cos(*ra) * nyrs;
  *ra += (((((3.07234 / 3600.0) * 15.)) * 3.141592653589793 / 180) +
          (((20.0468 / 3600.0) * 3.141592653589793 / 180) * sin(*ra) *
           tan(*dec))) *
         nyrs;
  range(ra, 2.0 * 3.141592653589793);
  *ra = ((*ra) * 180 / 3.141592653589793);
  *dec = ((*dec) * 180 / 3.141592653589793);
}


x86 assembly (clang, -O0):
<precess_fast>:
push   %rbp
mov    %rsp,%rbp
sub    $0x30,%rsp
movsd  %xmm0,-0x8(%rbp)
movsd  %xmm1,-0x10(%rbp)
mov    %rdi,-0x18(%rbp)
mov    %rsi,-0x20(%rbp)
mov    -0x18(%rbp),%rax
movsd  0xe9a(%rip),%xmm0
mulsd  (%rax),%xmm0
movsd  0xe96(%rip),%xmm1
divsd  %xmm1,%xmm0
mov    -0x18(%rbp),%rax
movsd  %xmm0,(%rax)
mov    -0x20(%rbp),%rax
movsd  0xe76(%rip),%xmm0
mulsd  (%rax),%xmm0
movsd  0xe72(%rip),%xmm1
divsd  %xmm1,%xmm0
mov    -0x20(%rbp),%rax
movsd  %xmm0,(%rax)
movsd  -0x10(%rbp),%xmm0
subsd  -0x8(%rbp),%xmm0
movsd  0xe74(%rip),%xmm1
divsd  %xmm1,%xmm0
movsd  %xmm0,-0x28(%rbp)
mov    -0x18(%rbp),%rax
movsd  (%rax),%xmm0
call   1060 <cos@plt>
movaps %xmm0,%xmm1
movsd  0xe4b(%rip),%xmm0
mulsd  %xmm1,%xmm0
movsd  -0x28(%rbp),%xmm2
mov    -0x20(%rbp),%rax
movsd  (%rax),%xmm1
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
movsd  %xmm0,(%rax)
mov    -0x18(%rbp),%rax
movsd  (%rax),%xmm0
call   1030 <sin@plt>
movaps %xmm0,%xmm1
movsd  0xe16(%rip),%xmm0
mulsd  %xmm1,%xmm0
movsd  %xmm0,-0x30(%rbp)
mov    -0x20(%rbp),%rax
movsd  (%rax),%xmm0
call   1050 <tan@plt>
movaps %xmm0,%xmm1
movsd  -0x30(%rbp),%xmm0
mulsd  %xmm1,%xmm0
movsd  0xde4(%rip),%xmm1
addsd  %xmm1,%xmm0
movsd  -0x28(%rbp),%xmm2
mov    -0x18(%rbp),%rax
movsd  (%rax),%xmm1
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
movsd  %xmm0,(%rax)
mov    -0x18(%rbp),%rdi
movsd  0xdb3(%rip),%xmm0
mov    $0x1,%al
call   1040 <range@plt>
mov    -0x18(%rbp),%rax
movsd  0xd98(%rip),%xmm0
mulsd  (%rax),%xmm0
movsd  0xd84(%rip),%xmm1
divsd  %xmm1,%xmm0
mov    -0x18(%rbp),%rax
movsd  %xmm0,(%rax)
mov    -0x20(%rbp),%rax
movsd  0xd74(%rip),%xmm0
mulsd  (%rax),%xmm0
movsd  0xd60(%rip),%xmm1
divsd  %xmm1,%xmm0
mov    -0x20(%rbp),%rax
movsd  %xmm0,(%rax)
add    $0x30,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<precess_fast>:
push   %r14
push   %rbx
sub    $0x18,%rsp
mov    %rsi,%r14
mov    %rdi,%rbx
movsd  0xeab(%rip),%xmm2
movsd  (%rdi),%xmm4
mulsd  %xmm2,%xmm4
movsd  0xea3(%rip),%xmm3
divsd  %xmm3,%xmm4
movsd  %xmm4,(%rdi)
movsd  (%rsi),%xmm4
mulsd  %xmm2,%xmm4
divsd  %xmm3,%xmm4
movsd  %xmm4,(%rsi)
subsd  %xmm0,%xmm1
divsd  0xe87(%rip),%xmm1
movsd  %xmm1,0x8(%rsp)
movsd  (%rdi),%xmm0
call   1060 <cos@plt>
mulsd  0xe78(%rip),%xmm0
mulsd  0x8(%rsp),%xmm0
addsd  (%r14),%xmm0
movsd  %xmm0,(%r14)
movsd  (%rbx),%xmm0
call   1030 <sin@plt>
mulsd  0xe57(%rip),%xmm0
movsd  %xmm0,0x10(%rsp)
movsd  (%r14),%xmm0
call   1050 <tan@plt>
mulsd  0x10(%rsp),%xmm0
addsd  0xe41(%rip),%xmm0
mulsd  0x8(%rsp),%xmm0
addsd  (%rbx),%xmm0
movsd  %xmm0,(%rbx)
movsd  0xe33(%rip),%xmm0
mov    %rbx,%rdi
mov    $0x1,%al
call   1040 <range@plt>
movsd  (%rbx),%xmm0
movsd  0xdfd(%rip),%xmm1
mulsd  %xmm1,%xmm0
movsd  0xde9(%rip),%xmm2
divsd  %xmm2,%xmm0
movsd  %xmm0,(%rbx)
mulsd  (%r14),%xmm1
divsd  %xmm2,%xmm1
movsd  %xmm1,(%r14)
add    $0x18,%rsp
pop    %rbx
pop    %r14
ret

LLVM IR (-O0):
define void @precess_fast(double %0, double %1, double* %2, double* %3) {
%5 = alloca double
%6 = alloca double
%7 = alloca double*
%8 = alloca double*
%9 = alloca double
store double %0, double* %5
store double %1, double* %6
store double* %2, double** %7
store double* %3, double** %8
%10 = load double*, double** %7
%11 = load double, double* %10
%12 = fmul double %11, 0x400921FB54442D18
%13 = fdiv double %12, 1.800000e+02
%14 = load double*, double** %7
store double %13, double* %14
%15 = load double*, double** %8
%16 = load double, double* %15
%17 = fmul double %16, 0x400921FB54442D18
%18 = fdiv double %17, 1.800000e+02
%19 = load double*, double** %8
store double %18, double* %19
%20 = load double, double* %6
%21 = load double, double* %5
%22 = fsub double %20, %21
%23 = fdiv double %22, 0x4076D3E147AE147B
store double %23, double* %9
%24 = load double*, double** %7
%25 = load double, double* %24
%26 = call double @cos(double %25)
%27 = fmul double 0x3F197A491CD8F0EF, %26
%28 = load double, double* %9
%29 = load double*, double** %8
%30 = load double, double* %29
%31 = call double @llvm.fmuladd.f64(double %27, double %28, double %30)
store double %31, double* %29
%32 = load double*, double** %7
%33 = load double, double* %32
%34 = call double @sin(double %33)
%35 = fmul double 0x3F197A491CD8F0EF, %34
%36 = load double*, double** %8
%37 = load double, double* %36
%38 = call double @tan(double %37)
%39 = call double @llvm.fmuladd.f64(double %35, double %38, double 0x3F2D48F6328086E6)
%40 = load double, double* %9
%41 = load double*, double** %7
%42 = load double, double* %41
%43 = call double @llvm.fmuladd.f64(double %39, double %40, double %42)
store double %43, double* %41
%44 = load double*, double** %7
%45 = call i32 (double*, double, ...) bitcast (i32 (...)* @range to i32 (double*, double, ...)*)(double* %44, double 0x401921FB54442D18)
%46 = load double*, double** %7
%47 = load double, double* %46
%48 = fmul double %47, 1.800000e+02
%49 = fdiv double %48, 0x400921FB54442D18
%50 = load double*, double** %7
store double %49, double* %50
%51 = load double*, double** %8
%52 = load double, double* %51
%53 = fmul double %52, 1.800000e+02
%54 = fdiv double %53, 0x400921FB54442D18
%55 = load double*, double** %8
store double %54, double* %55
ret void
}

LLVM IR (-O2):
define void @precess_fast(double %0, double %1, double* %2, double* nocapture %3) {
%5 = load double, double* %2
%6 = fmul double %5, 0x400921FB54442D18
%7 = fdiv double %6, 1.800000e+02
store double %7, double* %2
%8 = load double, double* %3
%9 = fmul double %8, 0x400921FB54442D18
%10 = fdiv double %9, 1.800000e+02
store double %10, double* %3
%11 = fsub double %1, %0
%12 = fdiv double %11, 0x4076D3E147AE147B
%13 = load double, double* %2
%14 = tail call double @cos(double %13)
%15 = fmul double %14, 0x3F197A491CD8F0EF
%16 = load double, double* %3
%17 = tail call double @llvm.fmuladd.f64(double %15, double %12, double %16)
store double %17, double* %3
%18 = load double, double* %2
%19 = tail call double @sin(double %18)
%20 = fmul double %19, 0x3F197A491CD8F0EF
%21 = load double, double* %3
%22 = tail call double @tan(double %21)
%23 = tail call double @llvm.fmuladd.f64(double %20, double %22, double 0x3F2D48F6328086E6)
%24 = load double, double* %2
%25 = tail call double @llvm.fmuladd.f64(double %23, double %12, double %24)
store double %25, double* %2
%26 = tail call i32 (double*, double, ...) bitcast (i32 (...)* @range to i32 (double*, double, ...)*)(double* %2, double 0x401921FB54442D18)
%27 = load double, double* %2
%28 = fmul double %27, 1.800000e+02
%29 = fdiv double %28, 0x400921FB54442D18
store double %29, double* %2
%30 = load double, double* %3
%31 = fmul double %30, 1.800000e+02
%32 = fdiv double %31, 0x400921FB54442D18
store double %32, double* %3
ret void
}