(1) Major bug fix: DecomposeArrayRef() replaces its argument instr. and

    deletes it, but we were merrily trying to fix the operands of that
    instruction anyway!  Instead, fix the replacement instruction.

(2) An Improvement: Check for and extract global values in all operands,
    not just in known pointer operands.  For example, they can occur in
    call arguments, and probably other unforeseeable places as well.
    This also eliminates the special-case handling of Load and Store.

llvm-svn: 7053