Revert "[ConstHoist] Do not rebase single (or few) dependent constant"

This caused a couple test failures on a bot:

CodeGen/X86/constant-hoisting-bfi.ll
Transforms/ConstantHoisting/X86/ehpad.ll

Example:

http://green.lab.llvm.org/green/job/clang-stage1-cmake-RA-incremental/53575/

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@343005 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed