Subzero: Initial O2 lowering

src/IceRegAlloc.h

+//===- subzero/src/IceRegAlloc.h - Linear-scan reg. allocation --*- C++ -*-===//
+//
+//                        The Subzero Code Generator
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares the data structures used during linear-scan
+// register allocation.  This includes LiveRangeWrapper which
+// encapsulates a variable and its live range, and LinearScan which
+// holds the various work queues for the linear-scan algorithm.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SUBZERO_SRC_ICEREGALLOC_H
+#define SUBZERO_SRC_ICEREGALLOC_H
+
+#include "IceDefs.h"
+#include "IceTypes.h"
+
+namespace Ice {
+
+// Currently this just wraps a Variable pointer, so in principle we
+// could use containers of Variable* instead of LiveRangeWrapper.  But
+// in the future, we may want to do more complex things such as live
+// range splitting, and keeping a wrapper should make that simpler.
+class LiveRangeWrapper {
+public:
+  LiveRangeWrapper(Variable *Var) : Var(Var) {}
+  const LiveRange &range() const { return Var->getLiveRange(); }
+  bool endsBefore(const LiveRangeWrapper &Other) const {
+    return range().endsBefore(Other.range());
+  }
+  bool overlaps(const LiveRangeWrapper &Other) const {
+    return range().overlaps(Other.range());
+  }
+  Variable *const Var;
+  void dump(const Cfg *Func) const;
+
+private:
+  // LiveRangeWrapper(const LiveRangeWrapper &) LLVM_DELETED_FUNCTION;
+  LiveRangeWrapper &operator=(const LiveRangeWrapper &) LLVM_DELETED_FUNCTION;
+};
+
+class LinearScan {
+public:
+  LinearScan(Cfg *Func) : Func(Func) {}
+  void scan(const llvm::SmallBitVector &RegMask);
+  void dump(Cfg *Func) const;
+
+private:
+  Cfg *const Func;
+  // RangeCompare is the comparator for sorting an LiveRangeWrapper
+  // by starting point in a std::set<>.  Ties are broken by variable
+  // number so that sorting is stable.
+  struct RangeCompare {
+    bool operator()(const LiveRangeWrapper &L,
+                    const LiveRangeWrapper &R) const {
+      int32_t Lstart = L.Var->getLiveRange().getStart();
+      int32_t Rstart = R.Var->getLiveRange().getStart();
+      if (Lstart == Rstart)
+        return L.Var->getIndex() < R.Var->getIndex();
+      return Lstart < Rstart;
+    }
+  };
+  typedef std::set<LiveRangeWrapper, RangeCompare> OrderedRanges;
+  typedef std::list<LiveRangeWrapper> UnorderedRanges;
+  OrderedRanges Unhandled;
+  UnorderedRanges Active, Inactive, Handled;
+  LinearScan(const LinearScan &) LLVM_DELETED_FUNCTION;
+  LinearScan &operator=(const LinearScan &) LLVM_DELETED_FUNCTION;
+};
+
+} // end of namespace Ice
+
+#endif // SUBZERO_SRC_ICEREGALLOC_H