Add the -disable-opt option to LTO. This adds:

- Consistency with opt (which supports the same option with the same meaning and
  description).
- Debugging gold plugin-based linking without optimizations getting in the way.
- Debugging programs linked with the gold plugin while preserving the original
  debug info.
- Fine-grained control over LTO passes using the gold plugin in combination with
  opt (or clang/dragonegg).

Patch by Cristiano Giuffrida!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176257 91177308-0d34-0410-b5e6-96231b3b80d8
AArch64: don't drop GlobalAddress offset when handling extern_weak decls.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176258 91177308-0d34-0410-b5e6-96231b3b80d8
AArch64: be more careful resorting to inefficient addressing for weak vars.

If an otherwise weak var is actually defined in this unit, it can't be
undefined at runtime so we can use normal global variable sequences (ADRP/ADD)
to access it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176259 91177308-0d34-0410-b5e6-96231b3b80d8
AArch64: remove post-encoder method from FCMP (immediate) instructions.

The work done by the post-encoder (setting architecturally unused bits to 0 as
required) can be done by the existing operand that covers the "#0.0". This
removes at least one use of the discouraged PostEncoderMethod uses.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176261 91177308-0d34-0410-b5e6-96231b3b80d8