[PATCH] [InstCombine][x86] Constant fold pslld.

[Andrea Di Biagio]

  I agree with Jim.
  You can also do something similar to simplify packed logical shift right instructions ( psrlw/ psrld/ psrlq/vpsrlw/ vpsrld/ vpsrlq  ).
  SSE2/AVX2 packed logical shift right instructions also evaluate to 0 if the shift count is greater than or equal to the element size.

http://reviews.llvm.org/D3359