void transform44d3f(double *m1, float *m2, float *m3) {
  register double m2r0 = m2[0];
  register double m2r1 = m2[1];
  register double m2r2 = m2[2];
  m3[0] = (float)(m1[0] * m2r0 + m1[1] * m2r1 + m1[2] * m2r2 + m1[3]);
  m3[1] = (float)(m1[4] * m2r0 + m1[5] * m2r1 + m1[6] * m2r2 + m1[7]);
  m3[2] = (float)(m1[8] * m2r0 + m1[9] * m2r1 + m1[10] * m2r2 + m1[11]);
}


x86 assembly (clang, -O0):
<transform44d3f>:
push   %rbp
mov    %rsp,%rbp
mov    %rdi,-0x8(%rbp)
mov    %rsi,-0x10(%rbp)
mov    %rdx,-0x18(%rbp)
mov    -0x10(%rbp),%rax
movss  (%rax),%xmm0
cvtss2sd %xmm0,%xmm0
movsd  %xmm0,-0x20(%rbp)
mov    -0x10(%rbp),%rax
movss  0x4(%rax),%xmm0
cvtss2sd %xmm0,%xmm0
movsd  %xmm0,-0x28(%rbp)
mov    -0x10(%rbp),%rax
movss  0x8(%rax),%xmm0
cvtss2sd %xmm0,%xmm0
movsd  %xmm0,-0x30(%rbp)
mov    -0x8(%rbp),%rax
movsd  (%rax),%xmm1
movsd  -0x20(%rbp),%xmm2
mov    -0x8(%rbp),%rax
movsd  0x8(%rax),%xmm0
mulsd  -0x28(%rbp),%xmm0
mulsd  %xmm2,%xmm1
addsd  %xmm0,%xmm1
mov    -0x8(%rbp),%rax
movsd  0x10(%rax),%xmm0
movsd  -0x30(%rbp),%xmm2
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
mov    -0x8(%rbp),%rax
addsd  0x18(%rax),%xmm0
cvtsd2ss %xmm0,%xmm0
mov    -0x18(%rbp),%rax
movss  %xmm0,(%rax)
mov    -0x8(%rbp),%rax
movsd  0x20(%rax),%xmm1
movsd  -0x20(%rbp),%xmm2
mov    -0x8(%rbp),%rax
movsd  0x28(%rax),%xmm0
mulsd  -0x28(%rbp),%xmm0
mulsd  %xmm2,%xmm1
addsd  %xmm0,%xmm1
mov    -0x8(%rbp),%rax
movsd  0x30(%rax),%xmm0
movsd  -0x30(%rbp),%xmm2
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
mov    -0x8(%rbp),%rax
addsd  0x38(%rax),%xmm0
cvtsd2ss %xmm0,%xmm0
mov    -0x18(%rbp),%rax
movss  %xmm0,0x4(%rax)
mov    -0x8(%rbp),%rax
movsd  0x40(%rax),%xmm1
movsd  -0x20(%rbp),%xmm2
mov    -0x8(%rbp),%rax
movsd  0x48(%rax),%xmm0
mulsd  -0x28(%rbp),%xmm0
mulsd  %xmm2,%xmm1
addsd  %xmm0,%xmm1
mov    -0x8(%rbp),%rax
movsd  0x50(%rax),%xmm0
movsd  -0x30(%rbp),%xmm2
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
mov    -0x8(%rbp),%rax
addsd  0x58(%rax),%xmm0
cvtsd2ss %xmm0,%xmm0
mov    -0x18(%rbp),%rax
movss  %xmm0,0x8(%rax)
pop    %rbp
ret

x86 assembly (clang, -O2):
<transform44d3f>:
movss  (%rsi),%xmm0
movss  0x4(%rsi),%xmm1
cvtss2sd %xmm0,%xmm0
cvtss2sd %xmm1,%xmm2
movss  0x8(%rsi),%xmm1
cvtss2sd %xmm1,%xmm1
movsd  0x8(%rdi),%xmm3
mulsd  %xmm2,%xmm3
movsd  (%rdi),%xmm4
mulsd  %xmm0,%xmm4
addsd  %xmm3,%xmm4
movsd  0x10(%rdi),%xmm3
mulsd  %xmm1,%xmm3
addsd  %xmm4,%xmm3
addsd  0x18(%rdi),%xmm3
cvtsd2ss %xmm3,%xmm3
movss  %xmm3,(%rdx)
movsd  0x28(%rdi),%xmm3
mulsd  %xmm2,%xmm3
movsd  0x20(%rdi),%xmm4
mulsd  %xmm0,%xmm4
addsd  %xmm3,%xmm4
movsd  0x30(%rdi),%xmm3
mulsd  %xmm1,%xmm3
addsd  %xmm4,%xmm3
addsd  0x38(%rdi),%xmm3
cvtsd2ss %xmm3,%xmm3
movss  %xmm3,0x4(%rdx)
mulsd  0x48(%rdi),%xmm2
mulsd  0x40(%rdi),%xmm0
mulsd  0x50(%rdi),%xmm1
addsd  %xmm2,%xmm0
addsd  %xmm0,%xmm1
addsd  0x58(%rdi),%xmm1
xorps  %xmm0,%xmm0
cvtsd2ss %xmm1,%xmm0
movss  %xmm0,0x8(%rdx)
ret

LLVM IR (-O0):
define void @transform44d3f(double* %0, float* %1, float* %2) {
%4 = alloca double*
%5 = alloca float*
%6 = alloca float*
%7 = alloca double
%8 = alloca double
%9 = alloca double
store double* %0, double** %4
store float* %1, float** %5
store float* %2, float** %6
%10 = load float*, float** %5
%11 = getelementptr inbounds float, float* %10, i64 0
%12 = load float, float* %11
%13 = fpext float %12 to double
store double %13, double* %7
%14 = load float*, float** %5
%15 = getelementptr inbounds float, float* %14, i64 1
%16 = load float, float* %15
%17 = fpext float %16 to double
store double %17, double* %8
%18 = load float*, float** %5
%19 = getelementptr inbounds float, float* %18, i64 2
%20 = load float, float* %19
%21 = fpext float %20 to double
store double %21, double* %9
%22 = load double*, double** %4
%23 = getelementptr inbounds double, double* %22, i64 0
%24 = load double, double* %23
%25 = load double, double* %7
%26 = load double*, double** %4
%27 = getelementptr inbounds double, double* %26, i64 1
%28 = load double, double* %27
%29 = load double, double* %8
%30 = fmul double %28, %29
%31 = call double @llvm.fmuladd.f64(double %24, double %25, double %30)
%32 = load double*, double** %4
%33 = getelementptr inbounds double, double* %32, i64 2
%34 = load double, double* %33
%35 = load double, double* %9
%36 = call double @llvm.fmuladd.f64(double %34, double %35, double %31)
%37 = load double*, double** %4
%38 = getelementptr inbounds double, double* %37, i64 3
%39 = load double, double* %38
%40 = fadd double %36, %39
%41 = fptrunc double %40 to float
%42 = load float*, float** %6
%43 = getelementptr inbounds float, float* %42, i64 0
store float %41, float* %43
%44 = load double*, double** %4
%45 = getelementptr inbounds double, double* %44, i64 4
%46 = load double, double* %45
%47 = load double, double* %7
%48 = load double*, double** %4
%49 = getelementptr inbounds double, double* %48, i64 5
%50 = load double, double* %49
%51 = load double, double* %8
%52 = fmul double %50, %51
%53 = call double @llvm.fmuladd.f64(double %46, double %47, double %52)
%54 = load double*, double** %4
%55 = getelementptr inbounds double, double* %54, i64 6
%56 = load double, double* %55
%57 = load double, double* %9
%58 = call double @llvm.fmuladd.f64(double %56, double %57, double %53)
%59 = load double*, double** %4
%60 = getelementptr inbounds double, double* %59, i64 7
%61 = load double, double* %60
%62 = fadd double %58, %61
%63 = fptrunc double %62 to float
%64 = load float*, float** %6
%65 = getelementptr inbounds float, float* %64, i64 1
store float %63, float* %65
%66 = load double*, double** %4
%67 = getelementptr inbounds double, double* %66, i64 8
%68 = load double, double* %67
%69 = load double, double* %7
%70 = load double*, double** %4
%71 = getelementptr inbounds double, double* %70, i64 9
%72 = load double, double* %71
%73 = load double, double* %8
%74 = fmul double %72, %73
%75 = call double @llvm.fmuladd.f64(double %68, double %69, double %74)
%76 = load double*, double** %4
%77 = getelementptr inbounds double, double* %76, i64 10
%78 = load double, double* %77
%79 = load double, double* %9
%80 = call double @llvm.fmuladd.f64(double %78, double %79, double %75)
%81 = load double*, double** %4
%82 = getelementptr inbounds double, double* %81, i64 11
%83 = load double, double* %82
%84 = fadd double %80, %83
%85 = fptrunc double %84 to float
%86 = load float*, float** %6
%87 = getelementptr inbounds float, float* %86, i64 2
store float %85, float* %87
ret void
}

LLVM IR (-O2):
define void @transform44d3f(double* nocapture %0, float* nocapture %1, float* nocapture writeonly %2) {
%4 = load float, float* %1
%5 = fpext float %4 to double
%6 = getelementptr inbounds float, float* %1, i64 1
%7 = load float, float* %6
%8 = fpext float %7 to double
%9 = getelementptr inbounds float, float* %1, i64 2
%10 = load float, float* %9
%11 = fpext float %10 to double
%12 = load double, double* %0
%13 = getelementptr inbounds double, double* %0, i64 1
%14 = load double, double* %13
%15 = fmul double %14, %8
%16 = tail call double @llvm.fmuladd.f64(double %12, double %5, double %15)
%17 = getelementptr inbounds double, double* %0, i64 2
%18 = load double, double* %17
%19 = tail call double @llvm.fmuladd.f64(double %18, double %11, double %16)
%20 = getelementptr inbounds double, double* %0, i64 3
%21 = load double, double* %20
%22 = fadd double %21, %19
%23 = fptrunc double %22 to float
store float %23, float* %2
%24 = getelementptr inbounds double, double* %0, i64 4
%25 = load double, double* %24
%26 = getelementptr inbounds double, double* %0, i64 5
%27 = load double, double* %26
%28 = fmul double %27, %8
%29 = tail call double @llvm.fmuladd.f64(double %25, double %5, double %28)
%30 = getelementptr inbounds double, double* %0, i64 6
%31 = load double, double* %30
%32 = tail call double @llvm.fmuladd.f64(double %31, double %11, double %29)
%33 = getelementptr inbounds double, double* %0, i64 7
%34 = load double, double* %33
%35 = fadd double %34, %32
%36 = fptrunc double %35 to float
%37 = getelementptr inbounds float, float* %2, i64 1
store float %36, float* %37
%38 = getelementptr inbounds double, double* %0, i64 8
%39 = load double, double* %38
%40 = getelementptr inbounds double, double* %0, i64 9
%41 = load double, double* %40
%42 = fmul double %41, %8
%43 = tail call double @llvm.fmuladd.f64(double %39, double %5, double %42)
%44 = getelementptr inbounds double, double* %0, i64 10
%45 = load double, double* %44
%46 = tail call double @llvm.fmuladd.f64(double %45, double %11, double %43)
%47 = getelementptr inbounds double, double* %0, i64 11
%48 = load double, double* %47
%49 = fadd double %48, %46
%50 = fptrunc double %49 to float
%51 = getelementptr inbounds float, float* %2, i64 2
store float %50, float* %51
ret void
}