void glmGenerateScaleMatrix3d(double m[9], const double s[3]) {
  m[0] = s[0];
  m[3] = 0;
  m[6] = 0;
  m[1] = 0;
  m[4] = s[1];
  m[7] = 0;
  m[2] = 0;
  m[5] = 0;
  m[8] = s[2];
}


x86 assembly (clang, -O0):
<glmGenerateScaleMatrix3d>:
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    -0x8(%rbp),%rax
xorps  %xmm0,%xmm0
movsd  %xmm0,0x18(%rax)
mov    -0x8(%rbp),%rax
xorps  %xmm0,%xmm0
movsd  %xmm0,0x30(%rax)
mov    -0x8(%rbp),%rax
xorps  %xmm0,%xmm0
movsd  %xmm0,0x8(%rax)
mov    -0x10(%rbp),%rax
movsd  0x8(%rax),%xmm0
mov    -0x8(%rbp),%rax
movsd  %xmm0,0x20(%rax)
mov    -0x8(%rbp),%rax
xorps  %xmm0,%xmm0
movsd  %xmm0,0x38(%rax)
mov    -0x8(%rbp),%rax
xorps  %xmm0,%xmm0
movsd  %xmm0,0x10(%rax)
mov    -0x8(%rbp),%rax
xorps  %xmm0,%xmm0
movsd  %xmm0,0x28(%rax)
mov    -0x10(%rbp),%rax
movsd  0x10(%rax),%xmm0
mov    -0x8(%rbp),%rax
movsd  %xmm0,0x40(%rax)
pop    %rbp
ret

x86 assembly (clang, -O2):
<glmGenerateScaleMatrix3d>:
movsd  (%rsi),%xmm0
movsd  %xmm0,(%rdi)
movq   $0x0,0x18(%rdi)
movq   $0x0,0x30(%rdi)
movq   $0x0,0x8(%rdi)
movsd  0x8(%rsi),%xmm0
movsd  %xmm0,0x20(%rdi)
movq   $0x0,0x38(%rdi)
movq   $0x0,0x10(%rdi)
movq   $0x0,0x28(%rdi)
movsd  0x10(%rsi),%xmm0
movsd  %xmm0,0x40(%rdi)
ret

LLVM IR (-O0):
define void @glmGenerateScaleMatrix3d(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** %3
%11 = getelementptr inbounds double, double* %10, i64 3
store double 0.000000e+00, double* %11
%12 = load double*, double** %3
%13 = getelementptr inbounds double, double* %12, i64 6
store double 0.000000e+00, double* %13
%14 = load double*, double** %3
%15 = getelementptr inbounds double, double* %14, i64 1
store double 0.000000e+00, double* %15
%16 = load double*, double** %4
%17 = getelementptr inbounds double, double* %16, i64 1
%18 = load double, double* %17
%19 = load double*, double** %3
%20 = getelementptr inbounds double, double* %19, i64 4
store double %18, double* %20
%21 = load double*, double** %3
%22 = getelementptr inbounds double, double* %21, i64 7
store double 0.000000e+00, double* %22
%23 = load double*, double** %3
%24 = getelementptr inbounds double, double* %23, i64 2
store double 0.000000e+00, double* %24
%25 = load double*, double** %3
%26 = getelementptr inbounds double, double* %25, i64 5
store double 0.000000e+00, double* %26
%27 = load double*, double** %4
%28 = getelementptr inbounds double, double* %27, i64 2
%29 = load double, double* %28
%30 = load double*, double** %3
%31 = getelementptr inbounds double, double* %30, i64 8
store double %29, double* %31
ret void
}

LLVM IR (-O2):
define void @glmGenerateScaleMatrix3d(double* nocapture writeonly %0, double* nocapture %1) {
%3 = load double, double* %1
store double %3, double* %0
%4 = getelementptr inbounds double, double* %0, i64 3
store double 0.000000e+00, double* %4
%5 = getelementptr inbounds double, double* %0, i64 6
store double 0.000000e+00, double* %5
%6 = getelementptr inbounds double, double* %0, i64 1
store double 0.000000e+00, double* %6
%7 = getelementptr inbounds double, double* %1, i64 1
%8 = load double, double* %7
%9 = getelementptr inbounds double, double* %0, i64 4
store double %8, double* %9
%10 = getelementptr inbounds double, double* %0, i64 7
store double 0.000000e+00, double* %10
%11 = getelementptr inbounds double, double* %0, i64 2
store double 0.000000e+00, double* %11
%12 = getelementptr inbounds double, double* %0, i64 5
store double 0.000000e+00, double* %12
%13 = getelementptr inbounds double, double* %1, i64 2
%14 = load double, double* %13
%15 = getelementptr inbounds double, double* %0, i64 8
store double %14, double* %15
ret void
}