[AArch64][NEON] Added UXTL and UXTL2 instruction aliases



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198791 91177308-0d34-0410-b5e6-96231b3b80d8
Add get and getError methods to ErrorOr.

ErrorOr is modeled after boost::optional which has a get method.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198792 91177308-0d34-0410-b5e6-96231b3b80d8
Add missing definitions of key_type and value_type to DenseSet.

This matches std::set and allows using DenseSet with the functions
in SetOperations.h

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198793 91177308-0d34-0410-b5e6-96231b3b80d8
Move declaration of variables down to first use.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198794 91177308-0d34-0410-b5e6-96231b3b80d8
Conservatively handle multiple MMOs in MIsNeedChainEdge

MIsNeedChainEdge, which is used by -enable-aa-sched-mi (AA in misched), had an
llvm_unreachable when -enable-aa-sched-mi is enabled and we reach an
instruction with multiple MMOs. Instead, return a conservative answer. This
allows testing -enable-aa-sched-mi on x86.

Also, this moves the check above the isUnsafeMemoryObject checks.
isUnsafeMemoryObject is currently correct only for instructions with one MMO
(as noted in the comment in isUnsafeMemoryObject):

  // We purposefully do no check for hasOneMemOperand() here
  // in hope to trigger an assert downstream in order to
  // finish implementation.

The problem with this is that, had the candidate edge passed the
"!MIa->mayStore() && !MIb->mayStore()" check, the hoped-for assert would never
happen (which could, in theory, lead to incorrect behavior if one of these
secondary MMOs was volatile, for example).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198795 91177308-0d34-0410-b5e6-96231b3b80d8