void copy44f44d(float *src, double *dst) {
  *(dst++) = (double)*(src++);
  *(dst++) = (double)*(src++);
  *(dst++) = (double)*(src++);
  *(dst++) = (double)*(src++);
  *(dst++) = (double)*(src++);
  *(dst++) = (double)*(src++);
  *(dst++) = (double)*(src++);
  *(dst++) = (double)*(src++);
  *(dst++) = (double)*(src++);
  *(dst++) = (double)*(src++);
  *(dst++) = (double)*(src++);
  *(dst++) = (double)*(src++);
  *(dst++) = (double)*(src++);
  *(dst++) = (double)*(src++);
  *(dst++) = (double)*(src++);
  *(dst++) = (double)*(src++);
}


x86 assembly (clang, -O0):
<copy44f44d>:
push   %rbp
mov    %rsp,%rbp
mov    %rdi,-0x8(%rbp)
mov    %rsi,-0x10(%rbp)
mov    -0x8(%rbp),%rax
mov    %rax,%rcx
add    $0x4,%rcx
mov    %rcx,-0x8(%rbp)
movss  (%rax),%xmm0
cvtss2sd %xmm0,%xmm0
mov    -0x10(%rbp),%rax
mov    %rax,%rcx
add    $0x8,%rcx
mov    %rcx,-0x10(%rbp)
movsd  %xmm0,(%rax)
mov    -0x8(%rbp),%rax
mov    %rax,%rcx
add    $0x4,%rcx
mov    %rcx,-0x8(%rbp)
movss  (%rax),%xmm0
cvtss2sd %xmm0,%xmm0
mov    -0x10(%rbp),%rax
mov    %rax,%rcx
add    $0x8,%rcx
mov    %rcx,-0x10(%rbp)
movsd  %xmm0,(%rax)
mov    -0x8(%rbp),%rax
mov    %rax,%rcx
add    $0x4,%rcx
mov    %rcx,-0x8(%rbp)
movss  (%rax),%xmm0
cvtss2sd %xmm0,%xmm0
mov    -0x10(%rbp),%rax
mov    %rax,%rcx
add    $0x8,%rcx
mov    %rcx,-0x10(%rbp)
movsd  %xmm0,(%rax)
mov    -0x8(%rbp),%rax
mov    %rax,%rcx
add    $0x4,%rcx
mov    %rcx,-0x8(%rbp)
movss  (%rax),%xmm0
cvtss2sd %xmm0,%xmm0
mov    -0x10(%rbp),%rax
mov    %rax,%rcx
add    $0x8,%rcx
mov    %rcx,-0x10(%rbp)
movsd  %xmm0,(%rax)
mov    -0x8(%rbp),%rax
mov    %rax,%rcx
add    $0x4,%rcx
mov    %rcx,-0x8(%rbp)
movss  (%rax),%xmm0
cvtss2sd %xmm0,%xmm0
mov    -0x10(%rbp),%rax
mov    %rax,%rcx
add    $0x8,%rcx
mov    %rcx,-0x10(%rbp)
movsd  %xmm0,(%rax)
mov    -0x8(%rbp),%rax
mov    %rax,%rcx
add    $0x4,%rcx
mov    %rcx,-0x8(%rbp)
movss  (%rax),%xmm0
cvtss2sd %xmm0,%xmm0
mov    -0x10(%rbp),%rax
mov    %rax,%rcx
add    $0x8,%rcx
mov    %rcx,-0x10(%rbp)
movsd  %xmm0,(%rax)
mov    -0x8(%rbp),%rax
mov    %rax,%rcx
add    $0x4,%rcx
mov    %rcx,-0x8(%rbp)
movss  (%rax),%xmm0
cvtss2sd %xmm0,%xmm0
mov    -0x10(%rbp),%rax
mov    %rax,%rcx
add    $0x8,%rcx
mov    %rcx,-0x10(%rbp)
movsd  %xmm0,(%rax)
mov    -0x8(%rbp),%rax
mov    %rax,%rcx
add    $0x4,%rcx
mov    %rcx,-0x8(%rbp)
movss  (%rax),%xmm0
cvtss2sd %xmm0,%xmm0
mov    -0x10(%rbp),%rax
mov    %rax,%rcx
add    $0x8,%rcx
mov    %rcx,-0x10(%rbp)
movsd  %xmm0,(%rax)
mov    -0x8(%rbp),%rax
mov    %rax,%rcx
add    $0x4,%rcx
mov    %rcx,-0x8(%rbp)
movss  (%rax),%xmm0
cvtss2sd %xmm0,%xmm0
mov    -0x10(%rbp),%rax
mov    %rax,%rcx
add    $0x8,%rcx
mov    %rcx,-0x10(%rbp)
movsd  %xmm0,(%rax)
mov    -0x8(%rbp),%rax
mov    %rax,%rcx
add    $0x4,%rcx
mov    %rcx,-0x8(%rbp)
movss  (%rax),%xmm0
cvtss2sd %xmm0,%xmm0
mov    -0x10(%rbp),%rax
mov    %rax,%rcx
add    $0x8,%rcx
mov    %rcx,-0x10(%rbp)
movsd  %xmm0,(%rax)
mov    -0x8(%rbp),%rax
mov    %rax,%rcx
add    $0x4,%rcx
mov    %rcx,-0x8(%rbp)
movss  (%rax),%xmm0
cvtss2sd %xmm0,%xmm0
mov    -0x10(%rbp),%rax
mov    %rax,%rcx
add    $0x8,%rcx
mov    %rcx,-0x10(%rbp)
movsd  %xmm0,(%rax)
mov    -0x8(%rbp),%rax
mov    %rax,%rcx
add    $0x4,%rcx
mov    %rcx,-0x8(%rbp)
movss  (%rax),%xmm0
cvtss2sd %xmm0,%xmm0
mov    -0x10(%rbp),%rax
mov    %rax,%rcx
add    $0x8,%rcx
mov    %rcx,-0x10(%rbp)
movsd  %xmm0,(%rax)
mov    -0x8(%rbp),%rax
mov    %rax,%rcx
add    $0x4,%rcx
mov    %rcx,-0x8(%rbp)
movss  (%rax),%xmm0
cvtss2sd %xmm0,%xmm0
mov    -0x10(%rbp),%rax
mov    %rax,%rcx
add    $0x8,%rcx
mov    %rcx,-0x10(%rbp)
movsd  %xmm0,(%rax)
mov    -0x8(%rbp),%rax
mov    %rax,%rcx
add    $0x4,%rcx
mov    %rcx,-0x8(%rbp)
movss  (%rax),%xmm0
cvtss2sd %xmm0,%xmm0
mov    -0x10(%rbp),%rax
mov    %rax,%rcx
add    $0x8,%rcx
mov    %rcx,-0x10(%rbp)
movsd  %xmm0,(%rax)
mov    -0x8(%rbp),%rax
mov    %rax,%rcx
add    $0x4,%rcx
mov    %rcx,-0x8(%rbp)
movss  (%rax),%xmm0
cvtss2sd %xmm0,%xmm0
mov    -0x10(%rbp),%rax
mov    %rax,%rcx
add    $0x8,%rcx
mov    %rcx,-0x10(%rbp)
movsd  %xmm0,(%rax)
mov    -0x8(%rbp),%rax
mov    %rax,%rcx
add    $0x4,%rcx
mov    %rcx,-0x8(%rbp)
movss  (%rax),%xmm0
cvtss2sd %xmm0,%xmm0
mov    -0x10(%rbp),%rax
mov    %rax,%rcx
add    $0x8,%rcx
mov    %rcx,-0x10(%rbp)
movsd  %xmm0,(%rax)
pop    %rbp
ret

x86 assembly (clang, -O2):
<copy44f44d>:
cvtps2pd (%rdi),%xmm0
movups %xmm0,(%rsi)
cvtps2pd 0x8(%rdi),%xmm0
movups %xmm0,0x10(%rsi)
cvtps2pd 0x10(%rdi),%xmm0
movups %xmm0,0x20(%rsi)
cvtps2pd 0x18(%rdi),%xmm0
movups %xmm0,0x30(%rsi)
cvtps2pd 0x20(%rdi),%xmm0
movups %xmm0,0x40(%rsi)
cvtps2pd 0x28(%rdi),%xmm0
movups %xmm0,0x50(%rsi)
cvtps2pd 0x30(%rdi),%xmm0
movups %xmm0,0x60(%rsi)
cvtps2pd 0x38(%rdi),%xmm0
movups %xmm0,0x70(%rsi)
ret

LLVM IR (-O0):
define void @copy44f44d(float* %0, double* %1) {
%3 = alloca float*
%4 = alloca double*
store float* %0, float** %3
store double* %1, double** %4
%5 = load float*, float** %3
%6 = getelementptr inbounds float, float* %5, i32 1
store float* %6, float** %3
%7 = load float, float* %5
%8 = fpext float %7 to double
%9 = load double*, double** %4
%10 = getelementptr inbounds double, double* %9, i32 1
store double* %10, double** %4
store double %8, double* %9
%11 = load float*, float** %3
%12 = getelementptr inbounds float, float* %11, i32 1
store float* %12, float** %3
%13 = load float, float* %11
%14 = fpext float %13 to double
%15 = load double*, double** %4
%16 = getelementptr inbounds double, double* %15, i32 1
store double* %16, double** %4
store double %14, double* %15
%17 = load float*, float** %3
%18 = getelementptr inbounds float, float* %17, i32 1
store float* %18, float** %3
%19 = load float, float* %17
%20 = fpext float %19 to double
%21 = load double*, double** %4
%22 = getelementptr inbounds double, double* %21, i32 1
store double* %22, double** %4
store double %20, double* %21
%23 = load float*, float** %3
%24 = getelementptr inbounds float, float* %23, i32 1
store float* %24, float** %3
%25 = load float, float* %23
%26 = fpext float %25 to double
%27 = load double*, double** %4
%28 = getelementptr inbounds double, double* %27, i32 1
store double* %28, double** %4
store double %26, double* %27
%29 = load float*, float** %3
%30 = getelementptr inbounds float, float* %29, i32 1
store float* %30, float** %3
%31 = load float, float* %29
%32 = fpext float %31 to double
%33 = load double*, double** %4
%34 = getelementptr inbounds double, double* %33, i32 1
store double* %34, double** %4
store double %32, double* %33
%35 = load float*, float** %3
%36 = getelementptr inbounds float, float* %35, i32 1
store float* %36, float** %3
%37 = load float, float* %35
%38 = fpext float %37 to double
%39 = load double*, double** %4
%40 = getelementptr inbounds double, double* %39, i32 1
store double* %40, double** %4
store double %38, double* %39
%41 = load float*, float** %3
%42 = getelementptr inbounds float, float* %41, i32 1
store float* %42, float** %3
%43 = load float, float* %41
%44 = fpext float %43 to double
%45 = load double*, double** %4
%46 = getelementptr inbounds double, double* %45, i32 1
store double* %46, double** %4
store double %44, double* %45
%47 = load float*, float** %3
%48 = getelementptr inbounds float, float* %47, i32 1
store float* %48, float** %3
%49 = load float, float* %47
%50 = fpext float %49 to double
%51 = load double*, double** %4
%52 = getelementptr inbounds double, double* %51, i32 1
store double* %52, double** %4
store double %50, double* %51
%53 = load float*, float** %3
%54 = getelementptr inbounds float, float* %53, i32 1
store float* %54, float** %3
%55 = load float, float* %53
%56 = fpext float %55 to double
%57 = load double*, double** %4
%58 = getelementptr inbounds double, double* %57, i32 1
store double* %58, double** %4
store double %56, double* %57
%59 = load float*, float** %3
%60 = getelementptr inbounds float, float* %59, i32 1
store float* %60, float** %3
%61 = load float, float* %59
%62 = fpext float %61 to double
%63 = load double*, double** %4
%64 = getelementptr inbounds double, double* %63, i32 1
store double* %64, double** %4
store double %62, double* %63
%65 = load float*, float** %3
%66 = getelementptr inbounds float, float* %65, i32 1
store float* %66, float** %3
%67 = load float, float* %65
%68 = fpext float %67 to double
%69 = load double*, double** %4
%70 = getelementptr inbounds double, double* %69, i32 1
store double* %70, double** %4
store double %68, double* %69
%71 = load float*, float** %3
%72 = getelementptr inbounds float, float* %71, i32 1
store float* %72, float** %3
%73 = load float, float* %71
%74 = fpext float %73 to double
%75 = load double*, double** %4
%76 = getelementptr inbounds double, double* %75, i32 1
store double* %76, double** %4
store double %74, double* %75
%77 = load float*, float** %3
%78 = getelementptr inbounds float, float* %77, i32 1
store float* %78, float** %3
%79 = load float, float* %77
%80 = fpext float %79 to double
%81 = load double*, double** %4
%82 = getelementptr inbounds double, double* %81, i32 1
store double* %82, double** %4
store double %80, double* %81
%83 = load float*, float** %3
%84 = getelementptr inbounds float, float* %83, i32 1
store float* %84, float** %3
%85 = load float, float* %83
%86 = fpext float %85 to double
%87 = load double*, double** %4
%88 = getelementptr inbounds double, double* %87, i32 1
store double* %88, double** %4
store double %86, double* %87
%89 = load float*, float** %3
%90 = getelementptr inbounds float, float* %89, i32 1
store float* %90, float** %3
%91 = load float, float* %89
%92 = fpext float %91 to double
%93 = load double*, double** %4
%94 = getelementptr inbounds double, double* %93, i32 1
store double* %94, double** %4
store double %92, double* %93
%95 = load float*, float** %3
%96 = getelementptr inbounds float, float* %95, i32 1
store float* %96, float** %3
%97 = load float, float* %95
%98 = fpext float %97 to double
%99 = load double*, double** %4
%100 = getelementptr inbounds double, double* %99, i32 1
store double* %100, double** %4
store double %98, double* %99
ret void
}

LLVM IR (-O2):
define void @copy44f44d(float* nocapture %0, double* nocapture writeonly %1) {
%3 = getelementptr inbounds float, float* %0, i64 2
%4 = bitcast float* %0 to <2 x float>*
%5 = load <2 x float>, <2 x float>* %4
%6 = fpext <2 x float> %5 to <2 x double>
%7 = getelementptr inbounds double, double* %1, i64 2
%8 = bitcast double* %1 to <2 x double>*
store <2 x double> %6, <2 x double>* %8
%9 = getelementptr inbounds float, float* %0, i64 4
%10 = bitcast float* %3 to <2 x float>*
%11 = load <2 x float>, <2 x float>* %10
%12 = fpext <2 x float> %11 to <2 x double>
%13 = getelementptr inbounds double, double* %1, i64 4
%14 = bitcast double* %7 to <2 x double>*
store <2 x double> %12, <2 x double>* %14
%15 = getelementptr inbounds float, float* %0, i64 6
%16 = bitcast float* %9 to <2 x float>*
%17 = load <2 x float>, <2 x float>* %16
%18 = fpext <2 x float> %17 to <2 x double>
%19 = getelementptr inbounds double, double* %1, i64 6
%20 = bitcast double* %13 to <2 x double>*
store <2 x double> %18, <2 x double>* %20
%21 = getelementptr inbounds float, float* %0, i64 8
%22 = bitcast float* %15 to <2 x float>*
%23 = load <2 x float>, <2 x float>* %22
%24 = fpext <2 x float> %23 to <2 x double>
%25 = getelementptr inbounds double, double* %1, i64 8
%26 = bitcast double* %19 to <2 x double>*
store <2 x double> %24, <2 x double>* %26
%27 = getelementptr inbounds float, float* %0, i64 10
%28 = bitcast float* %21 to <2 x float>*
%29 = load <2 x float>, <2 x float>* %28
%30 = fpext <2 x float> %29 to <2 x double>
%31 = getelementptr inbounds double, double* %1, i64 10
%32 = bitcast double* %25 to <2 x double>*
store <2 x double> %30, <2 x double>* %32
%33 = getelementptr inbounds float, float* %0, i64 12
%34 = bitcast float* %27 to <2 x float>*
%35 = load <2 x float>, <2 x float>* %34
%36 = fpext <2 x float> %35 to <2 x double>
%37 = getelementptr inbounds double, double* %1, i64 12
%38 = bitcast double* %31 to <2 x double>*
store <2 x double> %36, <2 x double>* %38
%39 = getelementptr inbounds float, float* %0, i64 14
%40 = bitcast float* %33 to <2 x float>*
%41 = load <2 x float>, <2 x float>* %40
%42 = fpext <2 x float> %41 to <2 x double>
%43 = getelementptr inbounds double, double* %1, i64 14
%44 = bitcast double* %37 to <2 x double>*
store <2 x double> %42, <2 x double>* %44
%45 = bitcast float* %39 to <2 x float>*
%46 = load <2 x float>, <2 x float>* %45
%47 = fpext <2 x float> %46 to <2 x double>
%48 = bitcast double* %43 to <2 x double>*
store <2 x double> %47, <2 x double>* %48
ret void
}