Add a new function attribute 'cold' to functions.

Other than recognizing the attribute, the patch does little else.
It changes the branch probability analyzer so that edges into
blocks postdominated by a cold function are given low weight.

Added analysis and code generation tests.  Added documentation for the
new attribute.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182638 91177308-0d34-0410-b5e6-96231b3b80d8
scalarizePHI needs to insert the next ExtractElement in the same block
as the BinaryOperator, *not* in the block where the IRBuilder is currently
inserting into. Fixes a bug where scalarizePHI would create instructions
that would not dominate all uses.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182639 91177308-0d34-0410-b5e6-96231b3b80d8
Run clang-format over the scalarizePHI function.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182640 91177308-0d34-0410-b5e6-96231b3b80d8