[LV] Tail-folding, runtime scev checks
[LV] Tail-folding, runtime scev checks

Now that we allow tail-folding, not only when we optimise for size, make
sure we do not run in this assert.

Differential revision: https://reviews.llvm.org/D66932

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@370711 91177308-0d34-0410-b5e6-96231b3b80d8

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