Normally an 'optnone' function goes through fast-isel, which does not
call DAGCombiner. But we ran into a case (on Windows) where the
calling convention causes argument lowering to bail out of fast-isel,
and we end up in CodeGenAndEmitDAG() which does run DAGCombiner.
So, we need to make DAGCombiner check for 'optnone' after all.

Commit includes the test that found this, plus another one that got
missed in the original optnone work.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221168 91177308-0d34-0410-b5e6-96231b3b80d8
Relax the LLVM_NOEXCEPT _MSC_VER version check back to 1900

Unconditional noexcept support was added in the VS 2013 Nov CTP. Given
that there have been three CTPs since then, I don't think we need
careful macro magic to target that specific tech preview. Instead,
target the major release version number of 1900, which corresponds to
the as-yet unreleased VS "14".

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221169 91177308-0d34-0410-b5e6-96231b3b80d8
[Reassociate] Canonicalize negative constants out of expressions.

This gives CSE/GVN more options to eliminate duplicate expressions.
This is a follow up patch to http://reviews.llvm.org/D4904.

http://reviews.llvm.org/D5363

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221171 91177308-0d34-0410-b5e6-96231b3b80d8