use v8i32 as optimal mem type over v8f32 if AVX2 is enabled. Similar to SSE2 vs SSE1.
use v8i32 as optimal mem type over v8f32 if AVX2 is enabled. Similar to SSE2 vs SSE1.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@148109 91177308-0d34-0410-b5e6-96231b3b80d8

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