Codegen insertelement with constant insertion points as scalar_to_vector

and a shuffle.  For this:

void %test2(<4 x float>* %F, float %f) {
        %tmp = load <4 x float>* %F             ; <<4 x float>> [#uses=2]
        %tmp3 = add <4 x float> %tmp, %tmp              ; <<4 x float>> [#uses=1]
        %tmp2 = insertelement <4 x float> %tmp3, float %f, uint 2               ; <<4 x float>> [#uses=2]
        %tmp6 = add <4 x float> %tmp2, %tmp2            ; <<4 x float>> [#uses=1]
        store <4 x float> %tmp6, <4 x float>* %F
        ret void
}

we now get this on X86 (which will get better):

_test2:
        movl 4(%esp), %eax
        movaps (%eax), %xmm0
        addps %xmm0, %xmm0
        movaps %xmm0, %xmm1
        shufps $3, %xmm1, %xmm1
        movaps %xmm0, %xmm2
        shufps $1, %xmm2, %xmm2
        unpcklps %xmm1, %xmm2
        movss 8(%esp), %xmm1
        unpcklps %xmm1, %xmm0
        unpcklps %xmm2, %xmm0
        addps %xmm0, %xmm0
        movaps %xmm0, (%eax)
        ret

instead of:

_test2:
        subl $28, %esp
        movl 32(%esp), %eax
        movaps (%eax), %xmm0
        addps %xmm0, %xmm0
        movaps %xmm0, (%esp)
        movss 36(%esp), %xmm0
        movss %xmm0, 8(%esp)
        movaps (%esp), %xmm0
        addps %xmm0, %xmm0
        movaps %xmm0, (%eax)
        addl $28, %esp
        ret

llvm-svn: 27765