[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.

llvm-svn: 219421

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64Subtarget.h b/llvm/lib/Target/AArch64/AArch64Subtarget.h
index b2cd0cd5738..06bd3698c6a 100644
--- a/llvm/lib/Target/AArch64/AArch64Subtarget.h
+++ b/llvm/lib/Target/AArch64/AArch64Subtarget.h
@@ -142,6 +142,8 @@ public:
                            unsigned NumRegionInstrs) const override;
 
   bool enableEarlyIfConversion() const override;
+
+  std::unique_ptr<PBQPRAConstraint> getCustomPBQPConstraints() const override;
 };
 } // End llvm namespace