Avoid creating a SlotIndex from the end() iterator.

No test case, spotted by inspection.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176705 91177308-0d34-0410-b5e6-96231b3b80d8
Rewrite the physreg part of findLastUseBefore().

To find the last use of a register unit, start from the bottom and scan
upwards until a user is found.

<rdar://problem/13353090>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176706 91177308-0d34-0410-b5e6-96231b3b80d8
Remove -print-dbginfo as it is unused & bitrotten.

This pass hasn't been touched in two years & would fail with assertions against
the current debug info metadata format (the only test case for it still uses a
many-versions old debug info metadata format)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176707 91177308-0d34-0410-b5e6-96231b3b80d8
No really, don't use end().

Clearly, this function is never actually called with the last
instruction in the function.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176708 91177308-0d34-0410-b5e6-96231b3b80d8