[DAGCombiner] Add an option to control whether or not to enable store merging.
[DAGCombiner] Add an option to control whether or not to enable store merging.

Add an option to control whether or not to enable store merging in dag combiner
so we can workaround some bugs more easily.

Differential Revision: https://reviews.llvm.org/D65482


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@367365 91177308-0d34-0410-b5e6-96231b3b80d8

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