void glmExpandMatrix24d(double result[16], const double m[4]) {
  result[0] = m[0];
  result[1] = m[1];
  result[2] = 0;
  result[3] = 0;
  result[4] = m[2];
  result[5] = m[3];
  result[6] = 0;
  result[7] = 0;
  result[8] = 0;
  result[9] = 0;
  result[10] = 0;
  result[11] = 0;
  result[12] = 0;
  result[13] = 0;
  result[14] = 0;
  result[15] = 1;
}


x86 assembly (clang, -O0):
<glmExpandMatrix24d>:
push   %rbp
mov    %rsp,%rbp
mov    %rdi,-0x8(%rbp)
mov    %rsi,-0x10(%rbp)
mov    -0x10(%rbp),%rax
movsd  (%rax),%xmm0
mov    -0x8(%rbp),%rax
movsd  %xmm0,(%rax)
mov    -0x10(%rbp),%rax
movsd  0x8(%rax),%xmm0
mov    -0x8(%rbp),%rax
movsd  %xmm0,0x8(%rax)
mov    -0x8(%rbp),%rax
xorps  %xmm0,%xmm0
movsd  %xmm0,0x10(%rax)
mov    -0x8(%rbp),%rax
xorps  %xmm0,%xmm0
movsd  %xmm0,0x18(%rax)
mov    -0x10(%rbp),%rax
movsd  0x10(%rax),%xmm0
mov    -0x8(%rbp),%rax
movsd  %xmm0,0x20(%rax)
mov    -0x10(%rbp),%rax
movsd  0x18(%rax),%xmm0
mov    -0x8(%rbp),%rax
movsd  %xmm0,0x28(%rax)
mov    -0x8(%rbp),%rax
xorps  %xmm0,%xmm0
movsd  %xmm0,0x30(%rax)
mov    -0x8(%rbp),%rax
xorps  %xmm0,%xmm0
movsd  %xmm0,0x38(%rax)
mov    -0x8(%rbp),%rax
xorps  %xmm0,%xmm0
movsd  %xmm0,0x40(%rax)
mov    -0x8(%rbp),%rax
xorps  %xmm0,%xmm0
movsd  %xmm0,0x48(%rax)
mov    -0x8(%rbp),%rax
xorps  %xmm0,%xmm0
movsd  %xmm0,0x50(%rax)
mov    -0x8(%rbp),%rax
xorps  %xmm0,%xmm0
movsd  %xmm0,0x58(%rax)
mov    -0x8(%rbp),%rax
xorps  %xmm0,%xmm0
movsd  %xmm0,0x60(%rax)
mov    -0x8(%rbp),%rax
xorps  %xmm0,%xmm0
movsd  %xmm0,0x68(%rax)
mov    -0x8(%rbp),%rax
xorps  %xmm0,%xmm0
movsd  %xmm0,0x70(%rax)
mov    -0x8(%rbp),%rax
movsd  0xe1e(%rip),%xmm0
movsd  %xmm0,0x78(%rax)
pop    %rbp
ret

x86 assembly (clang, -O2):
<glmExpandMatrix24d>:
movsd  (%rsi),%xmm0
movsd  %xmm0,(%rdi)
movsd  0x8(%rsi),%xmm0
movsd  %xmm0,0x8(%rdi)
xorps  %xmm0,%xmm0
movups %xmm0,0x10(%rdi)
movsd  0x10(%rsi),%xmm1
movsd  %xmm1,0x20(%rdi)
movsd  0x18(%rsi),%xmm1
movsd  %xmm1,0x28(%rdi)
movups %xmm0,0x30(%rdi)
movups %xmm0,0x40(%rdi)
movups %xmm0,0x50(%rdi)
movups %xmm0,0x60(%rdi)
movq   $0x0,0x70(%rdi)
movabs $0x3ff0000000000000,%rax
mov    %rax,0x78(%rdi)
ret

LLVM IR (-O0):
define void @glmExpandMatrix24d(double* %0, double* %1) {
%3 = alloca double*
%4 = alloca double*
store double* %0, double** %3
store double* %1, double** %4
%5 = load double*, double** %4
%6 = getelementptr inbounds double, double* %5, i64 0
%7 = load double, double* %6
%8 = load double*, double** %3
%9 = getelementptr inbounds double, double* %8, i64 0
store double %7, double* %9
%10 = load double*, double** %4
%11 = getelementptr inbounds double, double* %10, i64 1
%12 = load double, double* %11
%13 = load double*, double** %3
%14 = getelementptr inbounds double, double* %13, i64 1
store double %12, double* %14
%15 = load double*, double** %3
%16 = getelementptr inbounds double, double* %15, i64 2
store double 0.000000e+00, double* %16
%17 = load double*, double** %3
%18 = getelementptr inbounds double, double* %17, i64 3
store double 0.000000e+00, double* %18
%19 = load double*, double** %4
%20 = getelementptr inbounds double, double* %19, i64 2
%21 = load double, double* %20
%22 = load double*, double** %3
%23 = getelementptr inbounds double, double* %22, i64 4
store double %21, double* %23
%24 = load double*, double** %4
%25 = getelementptr inbounds double, double* %24, i64 3
%26 = load double, double* %25
%27 = load double*, double** %3
%28 = getelementptr inbounds double, double* %27, i64 5
store double %26, double* %28
%29 = load double*, double** %3
%30 = getelementptr inbounds double, double* %29, i64 6
store double 0.000000e+00, double* %30
%31 = load double*, double** %3
%32 = getelementptr inbounds double, double* %31, i64 7
store double 0.000000e+00, double* %32
%33 = load double*, double** %3
%34 = getelementptr inbounds double, double* %33, i64 8
store double 0.000000e+00, double* %34
%35 = load double*, double** %3
%36 = getelementptr inbounds double, double* %35, i64 9
store double 0.000000e+00, double* %36
%37 = load double*, double** %3
%38 = getelementptr inbounds double, double* %37, i64 10
store double 0.000000e+00, double* %38
%39 = load double*, double** %3
%40 = getelementptr inbounds double, double* %39, i64 11
store double 0.000000e+00, double* %40
%41 = load double*, double** %3
%42 = getelementptr inbounds double, double* %41, i64 12
store double 0.000000e+00, double* %42
%43 = load double*, double** %3
%44 = getelementptr inbounds double, double* %43, i64 13
store double 0.000000e+00, double* %44
%45 = load double*, double** %3
%46 = getelementptr inbounds double, double* %45, i64 14
store double 0.000000e+00, double* %46
%47 = load double*, double** %3
%48 = getelementptr inbounds double, double* %47, i64 15
store double 1.000000e+00, double* %48
ret void
}

LLVM IR (-O2):
define void @glmExpandMatrix24d(double* nocapture writeonly %0, double* nocapture %1) {
%3 = load double, double* %1
store double %3, double* %0
%4 = getelementptr inbounds double, double* %1, i64 1
%5 = load double, double* %4
%6 = getelementptr inbounds double, double* %0, i64 1
store double %5, double* %6
%7 = getelementptr inbounds double, double* %0, i64 2
%8 = getelementptr inbounds double, double* %1, i64 2
%9 = bitcast double* %7 to i8*
%10 = load double, double* %8
%11 = getelementptr inbounds double, double* %0, i64 4
store double %10, double* %11
%12 = getelementptr inbounds double, double* %1, i64 3
%13 = load double, double* %12
%14 = getelementptr inbounds double, double* %0, i64 5
store double %13, double* %14
%15 = getelementptr inbounds double, double* %0, i64 6
%16 = getelementptr inbounds double, double* %0, i64 15
%17 = bitcast double* %15 to i8*
store double 1.000000e+00, double* %16
ret void
}