Revert "[Reassociate] As the expression tree is rewritten make sure the operands are"

This reverts commit r222142.  This is causing/exposing an execution-time regression
in spec2006/gcc and coremark on AArch64/A57/Ofast.

Conflicts:

	test/Transforms/Reassociate/optional-flags.ll

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222398 91177308-0d34-0410-b5e6-96231b3b80d8
[Hexagon] Adding A2_xor instruction with IR selection pattern and test.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222399 91177308-0d34-0410-b5e6-96231b3b80d8