Revert "[SimplifyCFG] Followup fix to r280790"
Revert "[SimplifyCFG] Followup fix to r280790"

This reverts commit e50466a8d1bca43d0e453b07f3011399eac18494.
It's a follow-up to r280351, which caused PR31928, where the
improved SimplifyCFG exposed deeper strict-aliasing issues.

rdar://30408338

apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm