Using target specific nodes for shuffle nodes makes the mask

check more strict, breaking some cases not checked in the
testsuite, but also exposes some foldings not done before,
as this example:

  movaps  (%rdi), %xmm0
  movaps  (%rax), %xmm1
  movaps  %xmm0, %xmm2
  movss %xmm1, %xmm2
  shufps  $36, %xmm2, %xmm0

now is generated as:

  movaps  (%rdi), %xmm0
  movaps  %xmm0, %xmm1
  movlps  (%rax), %xmm1
  shufps  $36, %xmm1, %xmm0

llvm-svn: 112753