[x86/SLH] Extract the logic to trace predicate state through calls to a helper function with a nice overview comment. NFC.
[x86/SLH] Extract the logic to trace predicate state through calls to
a helper function with a nice overview comment. NFC.

This is a preperatory refactoring to implementing another component of
mitigation here that was descibed in the design document but hadn't been
implemented yet.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@338016 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm