Import prebuilt clang toolchain for linux.
diff --git a/linux-x64/clang/include/llvm/CodeGen/PBQPRAConstraint.h b/linux-x64/clang/include/llvm/CodeGen/PBQPRAConstraint.h
new file mode 100644
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+++ b/linux-x64/clang/include/llvm/CodeGen/PBQPRAConstraint.h
@@ -0,0 +1,71 @@
+//===- RegAllocPBQP.h -------------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the PBQPBuilder interface, for classes which build PBQP
+// instances to represent register allocation problems, and the RegAllocPBQP
+// interface.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_PBQPRACONSTRAINT_H
+#define LLVM_CODEGEN_PBQPRACONSTRAINT_H
+
+#include <algorithm>
+#include <memory>
+#include <vector>
+
+namespace llvm {
+
+namespace PBQP {
+namespace RegAlloc {
+
+// Forward declare PBQP graph class.
+class PBQPRAGraph;
+
+} // end namespace RegAlloc
+} // end namespace PBQP
+
+using PBQPRAGraph = PBQP::RegAlloc::PBQPRAGraph;
+
+/// @brief Abstract base for classes implementing PBQP register allocation
+///        constraints (e.g. Spill-costs, interference, coalescing).
+class PBQPRAConstraint {
+public:
+  virtual ~PBQPRAConstraint() = 0;
+  virtual void apply(PBQPRAGraph &G) = 0;
+
+private:
+  virtual void anchor();
+};
+
+/// @brief PBQP register allocation constraint composer.
+///
+///   Constraints added to this list will be applied, in the order that they are
+/// added, to the PBQP graph.
+class PBQPRAConstraintList : public PBQPRAConstraint {
+public:
+  void apply(PBQPRAGraph &G) override {
+    for (auto &C : Constraints)
+      C->apply(G);
+  }
+
+  void addConstraint(std::unique_ptr<PBQPRAConstraint> C) {
+    if (C)
+      Constraints.push_back(std::move(C));
+  }
+
+private:
+  std::vector<std::unique_ptr<PBQPRAConstraint>> Constraints;
+
+  void anchor() override;
+};
+
+} // end namespace llvm
+
+#endif // LLVM_CODEGEN_PBQPRACONSTRAINT_H