Only emit implicit constant conversion truncation warnings in reachable code.  Apparently this is what GCC does, and some code depends on this.  Fixes <rdar://problem/10321089>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@142716 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed