[PBQP] Replace PBQPBuilder with composable constraints (PBQPRAConstraint).

This patch removes the PBQPBuilder class and its subclasses and replaces them
with a composable constraints class: PBQPRAConstraint. This allows constraints
that are only required for optimisation (e.g. coalescing, soft pairing) to be
mixed and matched.

This patch also introduces support for target writers to supply custom
constraints for their targets by overriding a TargetSubtargetInfo method:

std::unique_ptr<PBQPRAConstraints> getCustomPBQPConstraints() const;

This patch should have no effect on allocations.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219421 91177308-0d34-0410-b5e6-96231b3b80d8
Sink DwarfDebug::createScopeChildrenDIE down into DwarfCompileUnit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219422 91177308-0d34-0410-b5e6-96231b3b80d8
[PBQP] Add missing headers from r219421.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219425 91177308-0d34-0410-b5e6-96231b3b80d8
R600/SI: Legalize CopyToReg during instruction selection

The instruction emitter will crash if it encounters a CopyToReg
node with a non-register operand like FrameIndex.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219428 91177308-0d34-0410-b5e6-96231b3b80d8
Fix typo

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219429 91177308-0d34-0410-b5e6-96231b3b80d8
Remove unused field from Operand

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219430 91177308-0d34-0410-b5e6-96231b3b80d8