Switch spill weights from a basic loop depth estimation to BlockFrequencyInfo.

The main advantages here are way better heuristics, taking into account not
just loop depth but also __builtin_expect and other static heuristics and will
eventually learn how to use profile info. Most of the work in this patch is
pushing the MachineBlockFrequencyInfo analysis into the right places.

This is good for a 5% speedup on zlib's deflate (x86_64), there were some very
unfortunate spilling decisions in its hottest loop in longest_match(). Other
benchmarks I tried were mostly neutral.

This changes register allocation in subtle ways, update the tests for it.
2012-02-20-MachineCPBug.ll was deleted as it's very fragile and the instruction
it looked for was gone already (but the FileCheck pattern picked up unrelated
stuff).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184105 91177308-0d34-0410-b5e6-96231b3b80d8
Remove CBE related code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184106 91177308-0d34-0410-b5e6-96231b3b80d8
Don't use PathV1.h in ToolRunner.h.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184107 91177308-0d34-0410-b5e6-96231b3b80d8
Don't use PathV1.h in CrashDebugger.cpp.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184109 91177308-0d34-0410-b5e6-96231b3b80d8
Revert "Remove a use of PathV1.h."

This reverts commit r183985.

We were missing the checks for not deleting things like /dev/null.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184111 91177308-0d34-0410-b5e6-96231b3b80d8