LoopVectorize: Fix a C++11 incompatibility.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172990 91177308-0d34-0410-b5e6-96231b3b80d8
[Support] Port ErrorOr<T> from lld to C++03.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172991 91177308-0d34-0410-b5e6-96231b3b80d8
Revert CostTable algorithm, will re-write

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172992 91177308-0d34-0410-b5e6-96231b3b80d8