void crossabc(double a[3], double b[3], double c[3], double n[3]) {
  double t;
  n[0] = (b[1] - a[1]) * (c[2] - a[2]) - (b[2] - a[2]) * (c[1] - a[1]);
  n[1] = (b[2] - a[2]) * (c[0] - a[0]) - (b[0] - a[0]) * (c[2] - a[2]);
  n[2] = (a[0] - b[0]) * (a[1] - c[1]) - (a[1] - b[1]) * (a[0] - c[0]);
  t = ((n[0]) * (n[0])) + ((n[1]) * (n[1])) + ((n[2]) * (n[2]));
  t = sqrt(t);
  n[0] = n[0] / t;
  n[2] = n[2] / t;
  n[1] = n[1] / t;
}


x86 assembly (clang, -O0):
<crossabc>:
push   %rbp
mov    %rsp,%rbp
sub    $0x30,%rsp
mov    %rdi,-0x8(%rbp)
mov    %rsi,-0x10(%rbp)
mov    %rdx,-0x18(%rbp)
mov    %rcx,-0x20(%rbp)
mov    -0x10(%rbp),%rax
movsd  0x8(%rax),%xmm0
mov    -0x8(%rbp),%rax
subsd  0x8(%rax),%xmm0
mov    -0x18(%rbp),%rax
movsd  0x10(%rax),%xmm2
mov    -0x8(%rbp),%rax
subsd  0x10(%rax),%xmm2
mov    -0x10(%rbp),%rax
movsd  0x10(%rax),%xmm1
mov    -0x8(%rbp),%rax
subsd  0x10(%rax),%xmm1
mov    -0x18(%rbp),%rax
movsd  0x8(%rax),%xmm3
mov    -0x8(%rbp),%rax
subsd  0x8(%rax),%xmm3
mulsd  %xmm3,%xmm1
movq   %xmm1,%rax
movabs $0x8000000000000000,%rcx
xor    %rcx,%rax
movq   %rax,%xmm1
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
mov    -0x20(%rbp),%rax
movsd  %xmm0,(%rax)
mov    -0x10(%rbp),%rax
movsd  0x10(%rax),%xmm0
mov    -0x8(%rbp),%rax
subsd  0x10(%rax),%xmm0
mov    -0x18(%rbp),%rax
movsd  (%rax),%xmm2
mov    -0x8(%rbp),%rax
subsd  (%rax),%xmm2
mov    -0x10(%rbp),%rax
movsd  (%rax),%xmm1
mov    -0x8(%rbp),%rax
subsd  (%rax),%xmm1
mov    -0x18(%rbp),%rax
movsd  0x10(%rax),%xmm3
mov    -0x8(%rbp),%rax
subsd  0x10(%rax),%xmm3
mulsd  %xmm3,%xmm1
movq   %xmm1,%rax
movabs $0x8000000000000000,%rcx
xor    %rcx,%rax
movq   %rax,%xmm1
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
mov    -0x20(%rbp),%rax
movsd  %xmm0,0x8(%rax)
mov    -0x8(%rbp),%rax
movsd  (%rax),%xmm0
mov    -0x10(%rbp),%rax
subsd  (%rax),%xmm0
mov    -0x8(%rbp),%rax
movsd  0x8(%rax),%xmm2
mov    -0x18(%rbp),%rax
subsd  0x8(%rax),%xmm2
mov    -0x8(%rbp),%rax
movsd  0x8(%rax),%xmm1
mov    -0x10(%rbp),%rax
subsd  0x8(%rax),%xmm1
mov    -0x8(%rbp),%rax
movsd  (%rax),%xmm3
mov    -0x18(%rbp),%rax
subsd  (%rax),%xmm3
mulsd  %xmm3,%xmm1
movq   %xmm1,%rax
movabs $0x8000000000000000,%rcx
xor    %rcx,%rax
movq   %rax,%xmm1
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
mov    -0x20(%rbp),%rax
movsd  %xmm0,0x10(%rax)
mov    -0x20(%rbp),%rax
movsd  (%rax),%xmm1
mov    -0x20(%rbp),%rax
movsd  (%rax),%xmm2
mov    -0x20(%rbp),%rax
movsd  0x8(%rax),%xmm0
mov    -0x20(%rbp),%rax
mulsd  0x8(%rax),%xmm0
mulsd  %xmm2,%xmm1
addsd  %xmm0,%xmm1
mov    -0x20(%rbp),%rax
movsd  0x10(%rax),%xmm0
mov    -0x20(%rbp),%rax
movsd  0x10(%rax),%xmm2
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
movsd  %xmm0,-0x28(%rbp)
movsd  -0x28(%rbp),%xmm0
call   1030 <sqrt@plt>
movsd  %xmm0,-0x28(%rbp)
mov    -0x20(%rbp),%rax
movsd  (%rax),%xmm0
divsd  -0x28(%rbp),%xmm0
mov    -0x20(%rbp),%rax
movsd  %xmm0,(%rax)
mov    -0x20(%rbp),%rax
movsd  0x10(%rax),%xmm0
divsd  -0x28(%rbp),%xmm0
mov    -0x20(%rbp),%rax
movsd  %xmm0,0x10(%rax)
mov    -0x20(%rbp),%rax
movsd  0x8(%rax),%xmm0
divsd  -0x28(%rbp),%xmm0
mov    -0x20(%rbp),%rax
movsd  %xmm0,0x8(%rax)
add    $0x30,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<crossabc>:
push   %rbx
mov    %rcx,%rbx
movsd  0x8(%rdi),%xmm0
movsd  0x10(%rdi),%xmm2
movsd  0x8(%rsi),%xmm3
movsd  0x10(%rsi),%xmm4
subsd  %xmm0,%xmm3
movsd  0x8(%rdx),%xmm5
movsd  0x10(%rdx),%xmm1
subsd  %xmm2,%xmm1
mulsd  %xmm3,%xmm1
subsd  %xmm2,%xmm4
subsd  %xmm0,%xmm5
mulsd  %xmm4,%xmm5
subsd  %xmm5,%xmm1
movsd  %xmm1,(%rcx)
movsd  (%rsi),%xmm0
movsd  0x10(%rsi),%xmm3
movsd  (%rdi),%xmm4
movsd  0x10(%rdi),%xmm5
subsd  %xmm5,%xmm3
movsd  (%rdx),%xmm2
movsd  0x10(%rdx),%xmm6
subsd  %xmm4,%xmm2
mulsd  %xmm3,%xmm2
subsd  %xmm4,%xmm0
subsd  %xmm5,%xmm6
mulsd  %xmm0,%xmm6
subsd  %xmm6,%xmm2
movsd  %xmm2,0x8(%rcx)
movsd  (%rdi),%xmm3
movsd  0x8(%rdi),%xmm4
movapd %xmm3,%xmm5
subsd  (%rsi),%xmm5
movapd %xmm4,%xmm0
subsd  0x8(%rdx),%xmm0
subsd  0x8(%rsi),%xmm4
subsd  (%rdx),%xmm3
mulsd  %xmm5,%xmm0
mulsd  %xmm4,%xmm3
subsd  %xmm3,%xmm0
movsd  %xmm0,0x10(%rcx)
mulsd  %xmm2,%xmm2
mulsd  %xmm1,%xmm1
addsd  %xmm2,%xmm1
mulsd  %xmm0,%xmm0
addsd  %xmm1,%xmm0
xorpd  %xmm1,%xmm1
ucomisd %xmm1,%xmm0
jb     11e6 <crossabc+0xd6>
sqrtsd %xmm0,%xmm0
jmp    11eb <crossabc+0xdb>
call   1030 <sqrt@plt>
movsd  0x10(%rbx),%xmm1
divsd  %xmm0,%xmm1
movsd  %xmm1,0x10(%rbx)
movupd (%rbx),%xmm1
unpcklpd %xmm0,%xmm0
divpd  %xmm0,%xmm1
movupd %xmm1,(%rbx)
pop    %rbx
ret

LLVM IR (-O0):
define void @crossabc(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** %6
%11 = getelementptr inbounds double, double* %10, i64 1
%12 = load double, double* %11
%13 = load double*, double** %5
%14 = getelementptr inbounds double, double* %13, i64 1
%15 = load double, double* %14
%16 = fsub double %12, %15
%17 = load double*, double** %7
%18 = getelementptr inbounds double, double* %17, i64 2
%19 = load double, double* %18
%20 = load double*, double** %5
%21 = getelementptr inbounds double, double* %20, i64 2
%22 = load double, double* %21
%23 = fsub double %19, %22
%24 = load double*, double** %6
%25 = getelementptr inbounds double, double* %24, i64 2
%26 = load double, double* %25
%27 = load double*, double** %5
%28 = getelementptr inbounds double, double* %27, i64 2
%29 = load double, double* %28
%30 = fsub double %26, %29
%31 = load double*, double** %7
%32 = getelementptr inbounds double, double* %31, i64 1
%33 = load double, double* %32
%34 = load double*, double** %5
%35 = getelementptr inbounds double, double* %34, i64 1
%36 = load double, double* %35
%37 = fsub double %33, %36
%38 = fmul double %30, %37
%39 = fneg double %38
%40 = call double @llvm.fmuladd.f64(double %16, double %23, double %39)
%41 = load double*, double** %8
%42 = getelementptr inbounds double, double* %41, i64 0
store double %40, double* %42
%43 = load double*, double** %6
%44 = getelementptr inbounds double, double* %43, i64 2
%45 = load double, double* %44
%46 = load double*, double** %5
%47 = getelementptr inbounds double, double* %46, i64 2
%48 = load double, double* %47
%49 = fsub double %45, %48
%50 = load double*, double** %7
%51 = getelementptr inbounds double, double* %50, i64 0
%52 = load double, double* %51
%53 = load double*, double** %5
%54 = getelementptr inbounds double, double* %53, i64 0
%55 = load double, double* %54
%56 = fsub double %52, %55
%57 = load double*, double** %6
%58 = getelementptr inbounds double, double* %57, i64 0
%59 = load double, double* %58
%60 = load double*, double** %5
%61 = getelementptr inbounds double, double* %60, i64 0
%62 = load double, double* %61
%63 = fsub double %59, %62
%64 = load double*, double** %7
%65 = getelementptr inbounds double, double* %64, i64 2
%66 = load double, double* %65
%67 = load double*, double** %5
%68 = getelementptr inbounds double, double* %67, i64 2
%69 = load double, double* %68
%70 = fsub double %66, %69
%71 = fmul double %63, %70
%72 = fneg double %71
%73 = call double @llvm.fmuladd.f64(double %49, double %56, double %72)
%74 = load double*, double** %8
%75 = getelementptr inbounds double, double* %74, i64 1
store double %73, double* %75
%76 = load double*, double** %5
%77 = getelementptr inbounds double, double* %76, i64 0
%78 = load double, double* %77
%79 = load double*, double** %6
%80 = getelementptr inbounds double, double* %79, i64 0
%81 = load double, double* %80
%82 = fsub double %78, %81
%83 = load double*, double** %5
%84 = getelementptr inbounds double, double* %83, i64 1
%85 = load double, double* %84
%86 = load double*, double** %7
%87 = getelementptr inbounds double, double* %86, i64 1
%88 = load double, double* %87
%89 = fsub double %85, %88
%90 = load double*, double** %5
%91 = getelementptr inbounds double, double* %90, i64 1
%92 = load double, double* %91
%93 = load double*, double** %6
%94 = getelementptr inbounds double, double* %93, i64 1
%95 = load double, double* %94
%96 = fsub double %92, %95
%97 = load double*, double** %5
%98 = getelementptr inbounds double, double* %97, i64 0
%99 = load double, double* %98
%100 = load double*, double** %7
%101 = getelementptr inbounds double, double* %100, i64 0
%102 = load double, double* %101
%103 = fsub double %99, %102
%104 = fmul double %96, %103
%105 = fneg double %104
%106 = call double @llvm.fmuladd.f64(double %82, double %89, double %105)
%107 = load double*, double** %8
%108 = getelementptr inbounds double, double* %107, i64 2
store double %106, double* %108
%109 = load double*, double** %8
%110 = getelementptr inbounds double, double* %109, i64 0
%111 = load double, double* %110
%112 = load double*, double** %8
%113 = getelementptr inbounds double, double* %112, i64 0
%114 = load double, double* %113
%115 = load double*, double** %8
%116 = getelementptr inbounds double, double* %115, i64 1
%117 = load double, double* %116
%118 = load double*, double** %8
%119 = getelementptr inbounds double, double* %118, i64 1
%120 = load double, double* %119
%121 = fmul double %117, %120
%122 = call double @llvm.fmuladd.f64(double %111, double %114, double %121)
%123 = load double*, double** %8
%124 = getelementptr inbounds double, double* %123, i64 2
%125 = load double, double* %124
%126 = load double*, double** %8
%127 = getelementptr inbounds double, double* %126, i64 2
%128 = load double, double* %127
%129 = call double @llvm.fmuladd.f64(double %125, double %128, double %122)
store double %129, double* %9
%130 = load double, double* %9
%131 = call double @sqrt(double %130)
store double %131, double* %9
%132 = load double*, double** %8
%133 = getelementptr inbounds double, double* %132, i64 0
%134 = load double, double* %133
%135 = load double, double* %9
%136 = fdiv double %134, %135
%137 = load double*, double** %8
%138 = getelementptr inbounds double, double* %137, i64 0
store double %136, double* %138
%139 = load double*, double** %8
%140 = getelementptr inbounds double, double* %139, i64 2
%141 = load double, double* %140
%142 = load double, double* %9
%143 = fdiv double %141, %142
%144 = load double*, double** %8
%145 = getelementptr inbounds double, double* %144, i64 2
store double %143, double* %145
%146 = load double*, double** %8
%147 = getelementptr inbounds double, double* %146, i64 1
%148 = load double, double* %147
%149 = load double, double* %9
%150 = fdiv double %148, %149
%151 = load double*, double** %8
%152 = getelementptr inbounds double, double* %151, i64 1
store double %150, double* %152
ret void
}

LLVM IR (-O2):
define void @crossabc(double* nocapture %0, double* nocapture %1, double* nocapture %2, double* nocapture %3) {
%5 = getelementptr inbounds double, double* %1, i64 1
%6 = load double, double* %5
%7 = getelementptr inbounds double, double* %0, i64 1
%8 = load double, double* %7
%9 = fsub double %6, %8
%10 = getelementptr inbounds double, double* %2, i64 2
%11 = load double, double* %10
%12 = getelementptr inbounds double, double* %0, i64 2
%13 = load double, double* %12
%14 = fsub double %11, %13
%15 = getelementptr inbounds double, double* %1, i64 2
%16 = load double, double* %15
%17 = fsub double %16, %13
%18 = getelementptr inbounds double, double* %2, i64 1
%19 = load double, double* %18
%20 = fsub double %19, %8
%21 = fneg double %17
%22 = fmul double %20, %21
%23 = tail call double @llvm.fmuladd.f64(double %9, double %14, double %22)
store double %23, double* %3
%24 = load double, double* %15
%25 = load double, double* %12
%26 = fsub double %24, %25
%27 = load double, double* %2
%28 = load double, double* %0
%29 = fsub double %27, %28
%30 = load double, double* %1
%31 = fsub double %30, %28
%32 = load double, double* %10
%33 = fsub double %32, %25
%34 = fneg double %31
%35 = fmul double %33, %34
%36 = tail call double @llvm.fmuladd.f64(double %26, double %29, double %35)
%37 = getelementptr inbounds double, double* %3, i64 1
store double %36, double* %37
%38 = load double, double* %0
%39 = load double, double* %1
%40 = fsub double %38, %39
%41 = load double, double* %7
%42 = load double, double* %18
%43 = fsub double %41, %42
%44 = load double, double* %5
%45 = fsub double %41, %44
%46 = load double, double* %2
%47 = fsub double %38, %46
%48 = fneg double %45
%49 = fmul double %47, %48
%50 = tail call double @llvm.fmuladd.f64(double %40, double %43, double %49)
%51 = getelementptr inbounds double, double* %3, i64 2
store double %50, double* %51
%52 = fmul double %36, %36
%53 = tail call double @llvm.fmuladd.f64(double %23, double %23, double %52)
%54 = tail call double @llvm.fmuladd.f64(double %50, double %50, double %53)
%55 = tail call double @sqrt(double %54)
%56 = load double, double* %51
%57 = fdiv double %56, %55
store double %57, double* %51
%58 = bitcast double* %3 to <2 x double>*
%59 = load <2 x double>, <2 x double>* %58
%60 = insertelement <2 x double> poison, double %55, i64 0
%61 = shufflevector <2 x double> %60, <2 x double> poison, <2 x i32> zeroinitializer
%62 = fdiv <2 x double> %59, %61
%63 = bitcast double* %3 to <2 x double>*
store <2 x double> %62, <2 x double>* %63
ret void
}