void to_xyz(double r, double g, double b, double *restrict x,
            double *restrict y, double *restrict z) {
  *x = 0.412391 * r + 0.357584 * g + 0.180481 * b;
  *y = 0.212639 * r + 0.715169 * g + 0.072192 * b;
  *z = 0.019331 * r + 0.119195 * g + 0.950532 * b;
}


x86 assembly (clang, -O0):
<to_xyz>:
push   %rbp
mov    %rsp,%rbp
movsd  %xmm0,-0x8(%rbp)
movsd  %xmm1,-0x10(%rbp)
movsd  %xmm2,-0x18(%rbp)
mov    %rdi,-0x20(%rbp)
mov    %rsi,-0x28(%rbp)
mov    %rdx,-0x30(%rbp)
movsd  -0x8(%rbp),%xmm1
movsd  0xf14(%rip),%xmm0
mulsd  -0x10(%rbp),%xmm0
movsd  0xeff(%rip),%xmm2
mulsd  %xmm2,%xmm1
addsd  %xmm0,%xmm1
movsd  -0x18(%rbp),%xmm0
movsd  0xee2(%rip),%xmm2
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
mov    -0x20(%rbp),%rax
movsd  %xmm0,(%rax)
movsd  -0x8(%rbp),%xmm1
movsd  0xebd(%rip),%xmm0
mulsd  -0x10(%rbp),%xmm0
movsd  0xea8(%rip),%xmm2
mulsd  %xmm2,%xmm1
addsd  %xmm0,%xmm1
movsd  -0x18(%rbp),%xmm0
movsd  0xe8b(%rip),%xmm2
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
mov    -0x28(%rbp),%rax
movsd  %xmm0,(%rax)
movsd  -0x8(%rbp),%xmm1
movsd  0xe66(%rip),%xmm0
mulsd  -0x10(%rbp),%xmm0
movsd  0xe51(%rip),%xmm2
mulsd  %xmm2,%xmm1
addsd  %xmm0,%xmm1
movsd  -0x18(%rbp),%xmm0
movsd  0xe34(%rip),%xmm2
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
mov    -0x30(%rbp),%rax
movsd  %xmm0,(%rax)
pop    %rbp
ret

x86 assembly (clang, -O2):
<to_xyz>:
movsd  0xef8(%rip),%xmm3
mulsd  %xmm1,%xmm3
movsd  0xef4(%rip),%xmm4
mulsd  %xmm0,%xmm4
addsd  %xmm3,%xmm4
movsd  0xeec(%rip),%xmm3
mulsd  %xmm2,%xmm3
addsd  %xmm4,%xmm3
movsd  %xmm3,(%rdi)
movsd  0xee0(%rip),%xmm3
mulsd  %xmm1,%xmm3
movsd  0xedc(%rip),%xmm4
mulsd  %xmm0,%xmm4
addsd  %xmm3,%xmm4
movsd  0xed4(%rip),%xmm3
mulsd  %xmm2,%xmm3
addsd  %xmm4,%xmm3
mulsd  0xecc(%rip),%xmm1
movsd  %xmm3,(%rsi)
mulsd  0xec8(%rip),%xmm0
addsd  %xmm1,%xmm0
mulsd  0xec4(%rip),%xmm2
addsd  %xmm0,%xmm2
movsd  %xmm2,(%rdx)
ret

LLVM IR (-O0):
define void @to_xyz(double %0, double %1, double %2, double* noalias %3, double* noalias %4, double* noalias %5) {
%7 = alloca double
%8 = alloca double
%9 = alloca double
%10 = alloca double*
%11 = alloca double*
%12 = alloca double*
store double %0, double* %7
store double %1, double* %8
store double %2, double* %9
store double* %3, double** %10
store double* %4, double** %11
store double* %5, double** %12
%13 = load double, double* %7
%14 = load double, double* %8
%15 = fmul double 3.575840e-01, %14
%16 = call double @llvm.fmuladd.f64(double 4.123910e-01, double %13, double %15)
%17 = load double, double* %9
%18 = call double @llvm.fmuladd.f64(double 1.804810e-01, double %17, double %16)
%19 = load double*, double** %10
store double %18, double* %19
%20 = load double, double* %7
%21 = load double, double* %8
%22 = fmul double 7.151690e-01, %21
%23 = call double @llvm.fmuladd.f64(double 2.126390e-01, double %20, double %22)
%24 = load double, double* %9
%25 = call double @llvm.fmuladd.f64(double 7.219200e-02, double %24, double %23)
%26 = load double*, double** %11
store double %25, double* %26
%27 = load double, double* %7
%28 = load double, double* %8
%29 = fmul double 1.191950e-01, %28
%30 = call double @llvm.fmuladd.f64(double 1.933100e-02, double %27, double %29)
%31 = load double, double* %9
%32 = call double @llvm.fmuladd.f64(double 9.505320e-01, double %31, double %30)
%33 = load double*, double** %12
store double %32, double* %33
ret void
}

LLVM IR (-O2):
define void @to_xyz(double %0, double %1, double %2, double* noalias nocapture writeonly %3, double* noalias nocapture writeonly %4, double* noalias nocapture writeonly %5) {
%7 = fmul double %1, 3.575840e-01
%8 = tail call double @llvm.fmuladd.f64(double %0, double 4.123910e-01, double %7)
%9 = tail call double @llvm.fmuladd.f64(double %2, double 1.804810e-01, double %8)
store double %9, double* %3
%10 = fmul double %1, 7.151690e-01
%11 = tail call double @llvm.fmuladd.f64(double %0, double 2.126390e-01, double %10)
%12 = tail call double @llvm.fmuladd.f64(double %2, double 7.219200e-02, double %11)
store double %12, double* %4
%13 = fmul double %1, 1.191950e-01
%14 = tail call double @llvm.fmuladd.f64(double %0, double 1.933100e-02, double %13)
%15 = tail call double @llvm.fmuladd.f64(double %2, double 9.505320e-01, double %14)
store double %15, double* %5
ret void
}