Allow to fold vector load if there is more than one bitcast, so in the case:

%0 = load <8 x i16>* %dest
%1 = shufflevector <8 x i16> %0, <8 x i16> %in,
      <8 x i32> < i32 0, i32 1, i32 2, i32 3, i32 13, i32 undef, i32 14, i32 14>
store <8 x i16> %1, <8 x i16>* %dest

We get:
  vmovlpd (%eax), %xmm0, %xmm0

instead of:
  vmovaps (%eax), %xmm1
  vmovsd  %xmm1, %xmm0, %xmm0

No extra test-case is added. I just fixed the existing one
(also it uses FileCheck now).

llvm-svn: 166971