[CodeGenPrepare] Undo changes that happened for the profitability check.

The addressing mode matcher checks at some point the profitability of folding an
instruction into the addressing mode. When the instruction to be folded has
several uses, it checks that the instruction can be folded in each use.
To do so, it creates a new matcher for each use and check if the instruction is
in the list of the matched instructions of this new matcher.

The new matchers may promote some instructions and this has to be undone to keep
the state of the original matcher consistent.

A test case will follow.

<rdar://problem/16020230>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201121 91177308-0d34-0410-b5e6-96231b3b80d8