I basically copied this patch from here: https://reviews.llvm.org/D1251
But I skipped some of the refactoring to make the patch more clean.
The new outer3/inner3 test case in ptr-diff.ll triggers the following assert without this patch:
lib/IR/Constants.cpp:1834: static llvm::Constant *llvm::ConstantExpr::getCompare(unsigned short, llvm::Constant *, llvm::Constant *, bool): Assertion `C1->getType() == C2->getType() && "Op types should be identical!"' failed.
The other new test cases makes sure that there is code coverage for all modifications in InlineCost.cpp (getting different values due to not fetching sizes for address space zero). I only guarantee code coverage for those tests. The tests are not written in a way that they would break if not having the corrections in InlineCost.cpp. I found it quite hard to fine tune the tests into getting different results based on the pointer sizes (except for the test case where we hit an assert if not teaching InlineCost about address spaces).