[X86] Fix a couple isel patterns to not shrink a volatile load.
[X86] Fix a couple isel patterns to not shrink a volatile load.

Also add a FIXME because I'm not sure why these patterns exist. Looks like a missing combine.

And another FIXME because the AVX512 equivalent one of the patterns is missing.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@370276 91177308-0d34-0410-b5e6-96231b3b80d8

GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm