Mostly finish up constant islands port for Mips for load constants.
Still need to finish the branch part. Still lots more review of the code,
clean up and testing. 



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194337 91177308-0d34-0410-b5e6-96231b3b80d8
Use variable for register name in test

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194338 91177308-0d34-0410-b5e6-96231b3b80d8
Fix missing C++ mode comment

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194339 91177308-0d34-0410-b5e6-96231b3b80d8
Make method static

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194340 91177308-0d34-0410-b5e6-96231b3b80d8
IR: Refactor GEP range checks, reuse them for other parts of folding


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194341 91177308-0d34-0410-b5e6-96231b3b80d8