XCore target: fix weak linkage attribute handling

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190298 91177308-0d34-0410-b5e6-96231b3b80d8
XCore target: change to Sched::Source

This sidesteps a bug in PrescheduleNodesWithMultipleUses() which
does not check if callResources will be affected by the transformation.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190299 91177308-0d34-0410-b5e6-96231b3b80d8
XCore handling of thread local lowering

Fix XCoreLowerThreadLocal trying to initialise globals
which have no initializer.

Add handling of const expressions containing thread local variables.
These need to be replaced with instructions, as the thread ID is
used to access the thread local variable.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190300 91177308-0d34-0410-b5e6-96231b3b80d8