Implement four-wide shuffle with 2 shufps if no more than two elements come from each vector. e.g.         shuffle(G1, G2, 7, 1, 5, 2) ==>         movaps _G2, %xmm0         shufps $151, _G1, %xmm0         shufps $216, %xmm0, %xmm0
Implement four-wide shuffle with 2 shufps if no more than two elements come
from each vector. e.g.
        shuffle(G1, G2, 7, 1, 5, 2)
==>
        movaps _G2, %xmm0
        shufps $151, _G1, %xmm0
        shufps $216, %xmm0, %xmm0


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@28011 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-llvm,dslab-epfl/asap,llvm-mirror/llvm,dslab-epfl/asap,chubbymaggie/asap,GPUOpen-Drivers/llvm,apple/swift-llvm,chubbymaggie/asap,chubbymaggie/asap,llvm-mirror/llvm,chubbymaggie/asap,chubbymaggie/asap,GPUOpen-Drivers/llvm,dslab-epfl/asap,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,dslab-epfl/asap,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,chubbymaggie/asap,dslab-epfl/asap,apple/swift-llvm,dslab-epfl/asap,apple/swift-llvm,llvm-mirror/llvm,dslab-epfl/asap,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm