Log Message:
Changes 3.1:
* Major New Features
  - AddressSanitizer, a fast memory error detector.
  - MachineInstr Bundles, Support to model instruction bundling / packing.
  - ARM Integrated Assembler, A full featured assembler and direct-to-object
    support for ARM.
  - Basic Block Placement Probability driven basic block placement.
* LLVM IR and Core Improvements
  - A new type representing 16 bit half floating point values has been added.
  - IR now supports vectors of pointers, including vector GEPs.
  - Module flags have been introduced. They convey information about the module
    as a whole to LLVM subsystems. This is currently used to encode Objective C
    ABI information.
  - Loads can now have range metadata attached to them to describe the possible
    values being loaded.
  - The llvm.ctlz and llvm.cttz intrinsics now have an additional argument which
    indicates whether the behavior of the intrinsic is undefined on a zero
    input. This can be used to generate more efficient code on platforms that
    only have instructions which don't return the type size when counting bits
    in 0.
* Optimizer Improvements
  - The loop unroll pass now is able to unroll loops with run-time trip counts.
    This feature is turned off by default, and is enabled with the
    -unroll-runtime flag.
  - A new basic-block autovectorization pass is available. Pass -vectorize to
    run this pass along with some associated post-vectorization cleanup passes.
    For more information, see the EuroLLVM 2012 slides: Autovectorization with
    LLVM.
  - Inline cost heuristics have been completely overhauled and now closely model
    constant propagation through call sites, disregard trivially dead code
    costs, and can model C++ STL iterator patterns.