Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 1 | // Copyright 2015 the V8 project authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #ifndef V8_COALESCED_LIVE_RANGES_H_ |
| 6 | #define V8_COALESCED_LIVE_RANGES_H_ |
| 7 | |
| 8 | #include "src/compiler/register-allocator.h" |
| 9 | #include "src/zone-containers.h" |
| 10 | |
| 11 | namespace v8 { |
| 12 | namespace internal { |
| 13 | namespace compiler { |
| 14 | |
| 15 | |
| 16 | // Implementation detail for CoalescedLiveRanges. |
| 17 | struct AllocatedInterval { |
| 18 | AllocatedInterval(LifetimePosition start, LifetimePosition end, |
| 19 | LiveRange* range) |
| 20 | : start_(start), end_(end), range_(range) {} |
| 21 | |
| 22 | LifetimePosition start_; |
| 23 | LifetimePosition end_; |
| 24 | LiveRange* range_; |
| 25 | bool operator<(const AllocatedInterval& other) const { |
| 26 | return start_ < other.start_; |
| 27 | } |
| 28 | bool operator>(const AllocatedInterval& other) const { |
| 29 | return start_ > other.start_; |
| 30 | } |
| 31 | }; |
| 32 | typedef ZoneSet<AllocatedInterval> IntervalStore; |
| 33 | |
| 34 | |
| 35 | // An iterator over conflicts of a live range, obtained from CoalescedLiveRanges |
| 36 | // The design supports two main scenarios (see GreedyAllocator): |
| 37 | // (1) observing each conflicting range, without mutating the allocations, and |
| 38 | // (2) observing each conflicting range, and then moving to the next, after |
| 39 | // removing the current conflict. |
| 40 | class LiveRangeConflictIterator { |
| 41 | public: |
| 42 | // Current conflict. nullptr if no conflicts, or if we reached the end of |
| 43 | // conflicts. |
| 44 | LiveRange* Current() const; |
| 45 | |
| 46 | // Get the next conflict. Caller should handle non-consecutive repetitions of |
| 47 | // the same range. |
| 48 | LiveRange* GetNext() { return InternalGetNext(false); } |
| 49 | |
| 50 | // Get the next conflict, after evicting the current one. Caller may expect |
| 51 | // to never observe the same live range more than once. |
| 52 | LiveRange* RemoveCurrentAndGetNext() { return InternalGetNext(true); } |
| 53 | |
| 54 | private: |
| 55 | friend class CoalescedLiveRanges; |
| 56 | |
| 57 | typedef IntervalStore::const_iterator interval_iterator; |
| 58 | LiveRangeConflictIterator(const LiveRange* range, IntervalStore* store); |
| 59 | |
| 60 | // Move the store iterator to first interval intersecting query. Since the |
| 61 | // intervals are sorted, subsequent intervals intersecting query follow. May |
| 62 | // leave the store iterator at "end", meaning that the current query does not |
| 63 | // have an intersection. |
| 64 | void MovePosToFirstConflictForQuery(); |
| 65 | |
| 66 | // Move both query and store iterator to the first intersection, if any. If |
| 67 | // none, then it invalidates the iterator (IsFinished() == true) |
| 68 | void MovePosAndQueryToFirstConflict(); |
| 69 | |
| 70 | // Increment pos and skip over intervals belonging to the same range we |
| 71 | // started with (i.e. Current() before the call). It is possible that range |
| 72 | // will be seen again, but not consecutively. |
| 73 | void IncrementPosAndSkipOverRepetitions(); |
| 74 | |
| 75 | // Common implementation used by both GetNext as well as |
| 76 | // ClearCurrentAndGetNext. |
| 77 | LiveRange* InternalGetNext(bool clean_behind); |
| 78 | |
| 79 | bool IsFinished() const { return query_ == nullptr; } |
| 80 | |
| 81 | static AllocatedInterval AsAllocatedInterval(LifetimePosition pos) { |
| 82 | return AllocatedInterval(pos, LifetimePosition::Invalid(), nullptr); |
| 83 | } |
| 84 | |
| 85 | // Intersection utilities. |
| 86 | static bool Intersects(LifetimePosition a_start, LifetimePosition a_end, |
| 87 | LifetimePosition b_start, LifetimePosition b_end) { |
| 88 | return a_start < b_end && b_start < a_end; |
| 89 | } |
| 90 | |
| 91 | bool QueryIntersectsAllocatedInterval() const { |
| 92 | DCHECK_NOT_NULL(query_); |
| 93 | return pos_ != intervals_->end() && |
| 94 | Intersects(query_->start(), query_->end(), pos_->start_, pos_->end_); |
| 95 | } |
| 96 | |
| 97 | void Invalidate() { |
| 98 | query_ = nullptr; |
| 99 | pos_ = intervals_->end(); |
| 100 | } |
| 101 | |
| 102 | const UseInterval* query_; |
| 103 | interval_iterator pos_; |
| 104 | IntervalStore* intervals_; |
| 105 | }; |
| 106 | |
| 107 | // Collection of live ranges allocated to the same register. |
| 108 | // It supports efficiently finding all conflicts for a given, non-allocated |
| 109 | // range. See AllocatedInterval. |
| 110 | // Allocated live ranges do not intersect. At most, individual use intervals |
| 111 | // touch. We store, for a live range, an AllocatedInterval corresponding to each |
| 112 | // of that range's UseIntervals. We keep the list of AllocatedIntervals sorted |
| 113 | // by starts. Then, given the non-intersecting property, we know that |
| 114 | // consecutive AllocatedIntervals have the property that the "smaller"'s end is |
| 115 | // less or equal to the "larger"'s start. |
| 116 | // This allows for quick (logarithmic complexity) identification of the first |
| 117 | // AllocatedInterval to conflict with a given LiveRange, and then for efficient |
| 118 | // traversal of conflicts. |
| 119 | class CoalescedLiveRanges : public ZoneObject { |
| 120 | public: |
| 121 | explicit CoalescedLiveRanges(Zone* zone) : intervals_(zone) {} |
| 122 | void clear() { intervals_.clear(); } |
| 123 | |
| 124 | bool empty() const { return intervals_.empty(); } |
| 125 | |
| 126 | // Iterate over each live range conflicting with the provided one. |
| 127 | // The same live range may be observed multiple, but non-consecutive times. |
| 128 | LiveRangeConflictIterator GetConflicts(const LiveRange* range); |
| 129 | |
| 130 | |
| 131 | // Allocates a range with a pre-calculated candidate weight. |
| 132 | void AllocateRange(LiveRange* range); |
| 133 | |
| 134 | // Unit testing API, verifying that allocated intervals do not overlap. |
| 135 | bool VerifyAllocationsAreValidForTesting() const; |
| 136 | |
| 137 | private: |
| 138 | static const float kAllocatedRangeMultiplier; |
| 139 | |
| 140 | IntervalStore& intervals() { return intervals_; } |
| 141 | const IntervalStore& intervals() const { return intervals_; } |
| 142 | |
| 143 | // Augment the weight of a range that is about to be allocated. |
| 144 | static void UpdateWeightAtAllocation(LiveRange* range); |
| 145 | |
| 146 | // Reduce the weight of a range that has lost allocation. |
| 147 | static void UpdateWeightAtEviction(LiveRange* range); |
| 148 | |
| 149 | |
| 150 | IntervalStore intervals_; |
| 151 | DISALLOW_COPY_AND_ASSIGN(CoalescedLiveRanges); |
| 152 | }; |
| 153 | |
| 154 | |
| 155 | } // namespace compiler |
| 156 | } // namespace internal |
| 157 | } // namespace v8 |
| 158 | #endif // V8_COALESCED_LIVE_RANGES_H_ |