crossSkew(const float *matA, float *matB) {
  (*(matB)) = 0;
  (*(matB + 1)) = -(*(matA + 2));
  (*(matB + 2)) = (*(matA + 1));
  (*(matB + 3)) = (*(matA + 2));
  (*(matB + 4)) = 0;
  (*(matB + 5)) = -(*(matA));
  (*(matB + 6)) = -(*(matA + 1));
  (*(matB + 7)) = (*(matA));
  (*(matB + 8)) = 0;
}


x86 assembly (clang, -O0):
<crossSkew>:
push   %rbp
mov    %rsp,%rbp
mov    %rdi,-0x10(%rbp)
mov    %rsi,-0x18(%rbp)
mov    -0x18(%rbp),%rax
xorps  %xmm0,%xmm0
movss  %xmm0,(%rax)
mov    -0x10(%rbp),%rax
movss  0x8(%rax),%xmm0
movd   %xmm0,%eax
xor    $0x80000000,%eax
movd   %eax,%xmm0
mov    -0x18(%rbp),%rax
movss  %xmm0,0x4(%rax)
mov    -0x10(%rbp),%rax
movss  0x4(%rax),%xmm0
mov    -0x18(%rbp),%rax
movss  %xmm0,0x8(%rax)
mov    -0x10(%rbp),%rax
movss  0x8(%rax),%xmm0
mov    -0x18(%rbp),%rax
movss  %xmm0,0xc(%rax)
mov    -0x18(%rbp),%rax
xorps  %xmm0,%xmm0
movss  %xmm0,0x10(%rax)
mov    -0x10(%rbp),%rax
movss  (%rax),%xmm0
movd   %xmm0,%eax
xor    $0x80000000,%eax
movd   %eax,%xmm0
mov    -0x18(%rbp),%rax
movss  %xmm0,0x14(%rax)
mov    -0x10(%rbp),%rax
movss  0x4(%rax),%xmm0
movd   %xmm0,%eax
xor    $0x80000000,%eax
movd   %eax,%xmm0
mov    -0x18(%rbp),%rax
movss  %xmm0,0x18(%rax)
mov    -0x10(%rbp),%rax
movss  (%rax),%xmm0
mov    -0x18(%rbp),%rax
movss  %xmm0,0x1c(%rax)
mov    -0x18(%rbp),%rax
xorps  %xmm0,%xmm0
movss  %xmm0,0x20(%rax)
mov    -0x4(%rbp),%eax
pop    %rbp
ret

x86 assembly (clang, -O2):
<crossSkew>:
movl   $0x0,(%rsi)
movss  0x8(%rdi),%xmm0
movaps 0xeee(%rip),%xmm1
xorps  %xmm1,%xmm0
movss  %xmm0,0x4(%rsi)
movss  0x4(%rdi),%xmm0
movss  %xmm0,0x8(%rsi)
movss  0x8(%rdi),%xmm0
movss  %xmm0,0xc(%rsi)
movl   $0x0,0x10(%rsi)
movss  (%rdi),%xmm0
xorps  %xmm1,%xmm0
movss  %xmm0,0x14(%rsi)
movss  0x4(%rdi),%xmm0
xorps  %xmm1,%xmm0
movss  %xmm0,0x18(%rsi)
movss  (%rdi),%xmm0
movss  %xmm0,0x1c(%rsi)
movl   $0x0,0x20(%rsi)
ret

LLVM IR (-O0):
define i32 @crossSkew(float* %0, float* %1) {
%3 = alloca i32
%4 = alloca float*
%5 = alloca float*
store float* %0, float** %4
store float* %1, float** %5
%6 = load float*, float** %5
store float 0.000000e+00, float* %6
%7 = load float*, float** %4
%8 = getelementptr inbounds float, float* %7, i64 2
%9 = load float, float* %8
%10 = fneg float %9
%11 = load float*, float** %5
%12 = getelementptr inbounds float, float* %11, i64 1
store float %10, float* %12
%13 = load float*, float** %4
%14 = getelementptr inbounds float, float* %13, i64 1
%15 = load float, float* %14
%16 = load float*, float** %5
%17 = getelementptr inbounds float, float* %16, i64 2
store float %15, float* %17
%18 = load float*, float** %4
%19 = getelementptr inbounds float, float* %18, i64 2
%20 = load float, float* %19
%21 = load float*, float** %5
%22 = getelementptr inbounds float, float* %21, i64 3
store float %20, float* %22
%23 = load float*, float** %5
%24 = getelementptr inbounds float, float* %23, i64 4
store float 0.000000e+00, float* %24
%25 = load float*, float** %4
%26 = load float, float* %25
%27 = fneg float %26
%28 = load float*, float** %5
%29 = getelementptr inbounds float, float* %28, i64 5
store float %27, float* %29
%30 = load float*, float** %4
%31 = getelementptr inbounds float, float* %30, i64 1
%32 = load float, float* %31
%33 = fneg float %32
%34 = load float*, float** %5
%35 = getelementptr inbounds float, float* %34, i64 6
store float %33, float* %35
%36 = load float*, float** %4
%37 = load float, float* %36
%38 = load float*, float** %5
%39 = getelementptr inbounds float, float* %38, i64 7
store float %37, float* %39
%40 = load float*, float** %5
%41 = getelementptr inbounds float, float* %40, i64 8
store float 0.000000e+00, float* %41
%42 = load i32, i32* %3
ret i32 %42
}

LLVM IR (-O2):
define i32 @crossSkew(float* nocapture %0, float* nocapture writeonly %1) {
store float 0.000000e+00, float* %1
%3 = getelementptr inbounds float, float* %0, i64 2
%4 = load float, float* %3
%5 = fneg float %4
%6 = getelementptr inbounds float, float* %1, i64 1
store float %5, float* %6
%7 = getelementptr inbounds float, float* %0, i64 1
%8 = load float, float* %7
%9 = getelementptr inbounds float, float* %1, i64 2
store float %8, float* %9
%10 = load float, float* %3
%11 = getelementptr inbounds float, float* %1, i64 3
store float %10, float* %11
%12 = getelementptr inbounds float, float* %1, i64 4
store float 0.000000e+00, float* %12
%13 = load float, float* %0
%14 = fneg float %13
%15 = getelementptr inbounds float, float* %1, i64 5
store float %14, float* %15
%16 = load float, float* %7
%17 = fneg float %16
%18 = getelementptr inbounds float, float* %1, i64 6
store float %17, float* %18
%19 = load float, float* %0
%20 = getelementptr inbounds float, float* %1, i64 7
store float %19, float* %20
%21 = getelementptr inbounds float, float* %1, i64 8
store float 0.000000e+00, float* %21
ret i32 undef
}