[turbofan] Greedy allocator refactoring.

src/compiler/coalesced-live-ranges.h

+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef V8_COALESCED_LIVE_RANGES_H_
+#define V8_COALESCED_LIVE_RANGES_H_
+
+#include "src/compiler/register-allocator.h"
+#include "src/zone-containers.h"
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+
+class AllocationScheduler;
+
+
+// Collection of live ranges allocated to the same register.
+// It supports efficiently finding all conflicts for a given, non-allocated
+// range. See AllocatedInterval.
+// Allocated live ranges do not intersect. At most, individual use intervals
+// touch. We store, for a live range, an AllocatedInterval corresponding to each
+// of that range's UseIntervals. We keep the list of AllocatedIntervals sorted
+// by starts. Then, given the non-intersecting property, we know that
+// consecutive AllocatedIntervals have the property that the "smaller"'s end is
+// less or equal to the "larger"'s start.
+// This allows for quick (logarithmic complexity) identification of the first
+// AllocatedInterval to conflict with a given LiveRange, and then for efficient
+// traversal of conflicts.
+class CoalescedLiveRanges : public ZoneObject {
+ public:
+  explicit CoalescedLiveRanges(Zone* zone) : storage_(zone) {}
+  void clear() { storage_.clear(); }
+
+  bool empty() const { return storage_.empty(); }
+
+  // Returns kInvalidWeight if there are no conflicts, or the largest weight of
+  // a range conflicting with the given range.
+  float GetMaximumConflictingWeight(const LiveRange* range) const;
+
+  // Evicts all conflicts of the given range, and reschedules them with the
+  // provided scheduler.
+  void EvictAndRescheduleConflicts(LiveRange* range,
+                                   AllocationScheduler* scheduler);
+
+  // Allocates a range with a pre-calculated candidate weight.
+  void AllocateRange(LiveRange* range);
+
+  // TODO(mtrofin): remove this in favor of comprehensive unit tests.
+  bool VerifyAllocationsAreValid() const;
+
+ private:
+  static const float kAllocatedRangeMultiplier;
+  // Storage detail for CoalescedLiveRanges.
+  struct AllocatedInterval {
+    LifetimePosition start;
+    LifetimePosition end;
+    LiveRange* range;
+    bool operator<(const AllocatedInterval& other) const {
+      return start < other.start;
+    }
+    bool operator>(const AllocatedInterval& other) const {
+      return start > other.start;
+    }
+  };
+  typedef ZoneSet<AllocatedInterval> IntervalStore;
+  typedef IntervalStore::const_iterator interval_iterator;
+
+  IntervalStore& storage() { return storage_; }
+  const IntervalStore& storage() const { return storage_; }
+
+  // Augment the weight of a range that is about to be allocated.
+  static void UpdateWeightAtAllocation(LiveRange* range);
+
+  // Reduce the weight of a range that has lost allocation.
+  static void UpdateWeightAtEviction(LiveRange* range);
+
+  // Intersection utilities.
+  static bool Intersects(LifetimePosition a_start, LifetimePosition a_end,
+                         LifetimePosition b_start, LifetimePosition b_end) {
+    return a_start < b_end && b_start < a_end;
+  }
+  static AllocatedInterval AsAllocatedInterval(LifetimePosition pos) {
+    return {pos, LifetimePosition::Invalid(), nullptr};
+  }
+
+  bool QueryIntersectsAllocatedInterval(const UseInterval* query,
+                                        interval_iterator& pos) const {
+    DCHECK(query != nullptr);
+    return pos != storage().end() &&
+           Intersects(query->start(), query->end(), pos->start, pos->end);
+  }
+
+  void Remove(LiveRange* range);
+
+  // Get the first interval intersecting query. Since the intervals are sorted,
+  // subsequent intervals intersecting query follow.
+  interval_iterator GetFirstConflict(const UseInterval* query) const;
+
+  IntervalStore storage_;
+  DISALLOW_COPY_AND_ASSIGN(CoalescedLiveRanges);
+};
+
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8
+#endif  // V8_COALESCED_LIVE_RANGES_H_