Why does gcc add this movss command only with _mm_set_ss?

Consider these two functions using SSE:

#include <xmmintrin.h>

int ftrunc1(float f) {
    return _mm_cvttss_si32(_mm_set1_ps(f));
}

int ftrunc2(float f) {
    return _mm_cvttss_si32(_mm_set_ss(f));
}

Both are the same in behavior for any input. But assembler output is different:

ftrunc1:
    pushl   %ebp
    movl    %esp, %ebp
    cvttss2si   8(%ebp), %eax
    leave
    ret

ftrunc2:
    pushl   %ebp
    movl    %esp, %ebp
    movss   8(%ebp), %xmm0
    cvttss2si   %xmm0, %eax
    leave
    ret

That is, it ftrunc2uses one movssextra command !

This is normal? Does it matter? If _mm_set1_psalways preferred _mm_set_ss, when you only need to set the bottom element?

The compiler used was GCC 4.5.2 s -O3 -msse.