Add alignment value to allowsUnalignedMemoryAccess

Rename to allowsMisalignedMemoryAccess.

On R600, 8 and 16 byte accesses are mostly OK with 4-byte alignment,
and don't need to be split into multiple accesses. Vector loads with
an alignment of the element type are not uncommon in OpenCL code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214055 91177308-0d34-0410-b5e6-96231b3b80d8
ARM: convert loop to range based

Convert a loop to use range based iteration.  Rename structure members to help
naming, and make structure definition anonymous.  NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214056 91177308-0d34-0410-b5e6-96231b3b80d8
ARM: correct handling of features in arch_extension

The subtarget information is the ultimate source of truth for the feature set
that is enabled at this point.  We would previously not propagate the feature
information to the subtarget.  While this worked for the most part (features
would be enabled/disabled as requested), if another operation that changed the
feature bits was encountered (such as a mode switch via a .arm or .thumb
directive), we would end up resetting the behaviour of the architectural
extensions.

Handling this properly requires a slightly more complicated handling.  We need
to check if the feature is now being toggled.  If so, only then do we toggle the
features.  In return, we no longer have to calculate the feature bits ourselves.

The test changes are mostly to the diagnosis, which is now more uniform (a nice
side effect!).  Add an additional test to ensure that we handle this case
properly.

Thanks to Nico Weber for alerting me to this issue!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214057 91177308-0d34-0410-b5e6-96231b3b80d8
Start adding some tests for the gold plugin.

These are only used when the 'ld' in the path is gold and the plugin has
been built, but it is already a start to make sure we don't regress features
that cannot be tested with llvm-lto.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214058 91177308-0d34-0410-b5e6-96231b3b80d8