don't bother calling ConstantFoldInstruction unless there is a use of the instruction (which disqualifies stores, unreachable, etc) and at least the first operand is a constant.  This filters out a lot of obvious cases that can't be folded.  Also, switch the IRBuilder to a TargetFolder, which tries harder.
don't bother calling ConstantFoldInstruction unless there is a use of the
instruction (which disqualifies stores, unreachable, etc) and at least the
first operand is a constant.  This filters out a lot of obvious cases that
can't be folded.  Also, switch the IRBuilder to a TargetFolder, which tries
harder.



git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@84170 91177308-0d34-0410-b5e6-96231b3b80d8

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