Fix a fixme: allow memdep to see past read-only calls when doing load dependence queries.  This allows GVN to eliminate a few more instructions on 403.gcc:
Fix a fixme: allow memdep to see past read-only calls when doing
load dependence queries.  This allows GVN to eliminate a few more
instructions on 403.gcc:

 152598 gvn    - Number of instructions deleted
  49240 gvn    - Number of loads deleted
after:
 153986 gvn    - Number of instructions deleted
  50069 gvn    - Number of loads deleted



git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@60786 91177308-0d34-0410-b5e6-96231b3b80d8

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