Add an option to enable the SSA based peephole optimizer.
Eventually this pass will provide substantially better code in the interim between when we
have a crappy isel and nice isel. Unfortunately doing so requires fixing the backend to
actually SUPPORT all of the fancy addressing modes that we now generate, and writing a DCE
pass for machine code. Each of these is a fairly substantial job, so this will remain disabled
for the immediate future. :(
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10276
91177308-0d34-0410-b5e6-
96231b3b80d8