void glmMultVectorByMatrix32d(double result[2], const double v[2],
                              const double m[9]) {
  result[0] = m[0] * v[0] + m[3] * v[1] + m[6];
  result[1] = m[1] * v[0] + m[4] * v[1] + m[7];
}


x86 assembly (clang, -O0):
<glmMultVectorByMatrix32d>:
push   %rbp
mov    %rsp,%rbp
mov    %rdi,-0x8(%rbp)
mov    %rsi,-0x10(%rbp)
mov    %rdx,-0x18(%rbp)
mov    -0x18(%rbp),%rax
movsd  (%rax),%xmm0
mov    -0x10(%rbp),%rax
movsd  (%rax),%xmm2
mov    -0x18(%rbp),%rax
movsd  0x18(%rax),%xmm1
mov    -0x10(%rbp),%rax
mulsd  0x8(%rax),%xmm1
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
mov    -0x18(%rbp),%rax
addsd  0x30(%rax),%xmm0
mov    -0x8(%rbp),%rax
movsd  %xmm0,(%rax)
mov    -0x18(%rbp),%rax
movsd  0x8(%rax),%xmm0
mov    -0x10(%rbp),%rax
movsd  (%rax),%xmm2
mov    -0x18(%rbp),%rax
movsd  0x20(%rax),%xmm1
mov    -0x10(%rbp),%rax
mulsd  0x8(%rax),%xmm1
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
mov    -0x18(%rbp),%rax
addsd  0x38(%rax),%xmm0
mov    -0x8(%rbp),%rax
movsd  %xmm0,0x8(%rax)
pop    %rbp
ret

x86 assembly (clang, -O2):
<glmMultVectorByMatrix32d>:
movsd  (%rdx),%xmm0
movsd  0x18(%rdx),%xmm1
mulsd  0x8(%rsi),%xmm1
mulsd  (%rsi),%xmm0
addsd  %xmm1,%xmm0
addsd  0x30(%rdx),%xmm0
movsd  %xmm0,(%rdi)
movsd  0x8(%rdx),%xmm0
movsd  0x20(%rdx),%xmm1
mulsd  0x8(%rsi),%xmm1
mulsd  (%rsi),%xmm0
addsd  %xmm1,%xmm0
addsd  0x38(%rdx),%xmm0
movsd  %xmm0,0x8(%rdi)
ret

LLVM IR (-O0):
define void @glmMultVectorByMatrix32d(double* %0, double* %1, double* %2) {
%4 = alloca double*
%5 = alloca double*
%6 = alloca double*
store double* %0, double** %4
store double* %1, double** %5
store double* %2, double** %6
%7 = load double*, double** %6
%8 = getelementptr inbounds double, double* %7, i64 0
%9 = load double, double* %8
%10 = load double*, double** %5
%11 = getelementptr inbounds double, double* %10, i64 0
%12 = load double, double* %11
%13 = load double*, double** %6
%14 = getelementptr inbounds double, double* %13, i64 3
%15 = load double, double* %14
%16 = load double*, double** %5
%17 = getelementptr inbounds double, double* %16, i64 1
%18 = load double, double* %17
%19 = fmul double %15, %18
%20 = call double @llvm.fmuladd.f64(double %9, double %12, double %19)
%21 = load double*, double** %6
%22 = getelementptr inbounds double, double* %21, i64 6
%23 = load double, double* %22
%24 = fadd double %20, %23
%25 = load double*, double** %4
%26 = getelementptr inbounds double, double* %25, i64 0
store double %24, double* %26
%27 = load double*, double** %6
%28 = getelementptr inbounds double, double* %27, i64 1
%29 = load double, double* %28
%30 = load double*, double** %5
%31 = getelementptr inbounds double, double* %30, i64 0
%32 = load double, double* %31
%33 = load double*, double** %6
%34 = getelementptr inbounds double, double* %33, i64 4
%35 = load double, double* %34
%36 = load double*, double** %5
%37 = getelementptr inbounds double, double* %36, i64 1
%38 = load double, double* %37
%39 = fmul double %35, %38
%40 = call double @llvm.fmuladd.f64(double %29, double %32, double %39)
%41 = load double*, double** %6
%42 = getelementptr inbounds double, double* %41, i64 7
%43 = load double, double* %42
%44 = fadd double %40, %43
%45 = load double*, double** %4
%46 = getelementptr inbounds double, double* %45, i64 1
store double %44, double* %46
ret void
}

LLVM IR (-O2):
define void @glmMultVectorByMatrix32d(double* nocapture writeonly %0, double* nocapture %1, double* nocapture %2) {
%4 = load double, double* %2
%5 = load double, double* %1
%6 = getelementptr inbounds double, double* %2, i64 3
%7 = load double, double* %6
%8 = getelementptr inbounds double, double* %1, i64 1
%9 = load double, double* %8
%10 = fmul double %7, %9
%11 = tail call double @llvm.fmuladd.f64(double %4, double %5, double %10)
%12 = getelementptr inbounds double, double* %2, i64 6
%13 = load double, double* %12
%14 = fadd double %13, %11
store double %14, double* %0
%15 = getelementptr inbounds double, double* %2, i64 1
%16 = load double, double* %15
%17 = load double, double* %1
%18 = getelementptr inbounds double, double* %2, i64 4
%19 = load double, double* %18
%20 = load double, double* %8
%21 = fmul double %19, %20
%22 = tail call double @llvm.fmuladd.f64(double %16, double %17, double %21)
%23 = getelementptr inbounds double, double* %2, i64 7
%24 = load double, double* %23
%25 = fadd double %24, %22
%26 = getelementptr inbounds double, double* %0, i64 1
store double %25, double* %26
ret void
}