Mips: Silence a -Wcovered-switch-default

Remove a default label which covered no enumerators, replace it with a
llvm_unreachable.

No functionality changed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212729 91177308-0d34-0410-b5e6-96231b3b80d8
Feeding isSafeToSpeculativelyExecute its DataLayout pointer (in Sink)

This is the one remaining place I see where passing
isSafeToSpeculativelyExecute a DataLayout pointer might matter (at least for
loads) -- I think I got the others in r212720. Most of the other remaining
callers of isSafeToSpeculativelyExecute only use it for call sites (or
otherwise exclude loads).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212730 91177308-0d34-0410-b5e6-96231b3b80d8
IR: Aliases don't belong to an explicit comdat

Aliases inherit their comdat from their aliasee, they don't have an
explicit comdat.

This fixes PR20279.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212732 91177308-0d34-0410-b5e6-96231b3b80d8