[ARM] Fix for PR39060

[ARM] Fix for PR39060

When calculating whether a value can safely overflow for use by an
icmp, we weren't checking that the value couldn't wrap around. To do
this we need the icmp to be using a constant, as well as the incoming
add or sub.

bugzilla report: https://bugs.llvm.org/show_bug.cgi?id=39060

Differential Revision: https://reviews.llvm.org/D52463

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@343092 91177308-0d34-0410-b5e6-96231b3b80d8