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in SSAUpdaterImpl.h Verifying live intervals revealed that the old method was completely wrong, and we need an iterative approach to calculating PHI placemant. Fortunately, we have MachineDominators available, so we don't have to compute that over and over like SSAUpdaterImpl.h must. Live-out values are cached between calls to mapValue() and computed in a greedy way, so most calls will be working with very small block sets. Thanks to Bob for explaining how this should work. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@117599 91177308-0d34-0410-b5e6-96231b3b80d8
365 lines
14 KiB
C++
365 lines
14 KiB
C++
//===-------- SplitKit.cpp - Toolkit for splitting live ranges --*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file contains the SplitAnalysis class as well as mutator functions for
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// live range splitting.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/CodeGen/SlotIndexes.h"
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namespace llvm {
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class LiveInterval;
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class LiveIntervals;
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class LiveRangeEdit;
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class MachineInstr;
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class MachineLoop;
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class MachineLoopInfo;
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class MachineRegisterInfo;
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class TargetInstrInfo;
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class VirtRegMap;
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class VNInfo;
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class raw_ostream;
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/// At some point we should just include MachineDominators.h:
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class MachineDominatorTree;
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template <class NodeT> class DomTreeNodeBase;
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typedef DomTreeNodeBase<MachineBasicBlock> MachineDomTreeNode;
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/// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting
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/// opportunities.
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class SplitAnalysis {
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public:
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const MachineFunction &mf_;
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const LiveIntervals &lis_;
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const MachineLoopInfo &loops_;
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const TargetInstrInfo &tii_;
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// Instructions using the the current register.
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typedef SmallPtrSet<const MachineInstr*, 16> InstrPtrSet;
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InstrPtrSet usingInstrs_;
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// The number of instructions using curli in each basic block.
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typedef DenseMap<const MachineBasicBlock*, unsigned> BlockCountMap;
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BlockCountMap usingBlocks_;
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// The number of basic block using curli in each loop.
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typedef DenseMap<const MachineLoop*, unsigned> LoopCountMap;
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LoopCountMap usingLoops_;
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private:
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// Current live interval.
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const LiveInterval *curli_;
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// Sumarize statistics by counting instructions using curli_.
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void analyzeUses();
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/// canAnalyzeBranch - Return true if MBB ends in a branch that can be
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/// analyzed.
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bool canAnalyzeBranch(const MachineBasicBlock *MBB);
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public:
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SplitAnalysis(const MachineFunction &mf, const LiveIntervals &lis,
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const MachineLoopInfo &mli);
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/// analyze - set curli to the specified interval, and analyze how it may be
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/// split.
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void analyze(const LiveInterval *li);
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/// clear - clear all data structures so SplitAnalysis is ready to analyze a
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/// new interval.
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void clear();
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typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet;
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typedef SmallPtrSet<const MachineLoop*, 16> LoopPtrSet;
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// Print a set of blocks with use counts.
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void print(const BlockPtrSet&, raw_ostream&) const;
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// Sets of basic blocks surrounding a machine loop.
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struct LoopBlocks {
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BlockPtrSet Loop; // Blocks in the loop.
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BlockPtrSet Preds; // Loop predecessor blocks.
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BlockPtrSet Exits; // Loop exit blocks.
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void clear() {
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Loop.clear();
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Preds.clear();
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Exits.clear();
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}
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};
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// Print loop blocks with use counts.
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void print(const LoopBlocks&, raw_ostream&) const;
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// Calculate the block sets surrounding the loop.
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void getLoopBlocks(const MachineLoop *Loop, LoopBlocks &Blocks);
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/// LoopPeripheralUse - how is a variable used in and around a loop?
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/// Peripheral blocks are the loop predecessors and exit blocks.
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enum LoopPeripheralUse {
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ContainedInLoop, // All uses are inside the loop.
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SinglePeripheral, // At most one instruction per peripheral block.
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MultiPeripheral, // Multiple instructions in some peripheral blocks.
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OutsideLoop // Uses outside loop periphery.
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};
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/// analyzeLoopPeripheralUse - Return an enum describing how curli_ is used in
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/// and around the Loop.
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LoopPeripheralUse analyzeLoopPeripheralUse(const LoopBlocks&);
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/// getCriticalExits - It may be necessary to partially break critical edges
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/// leaving the loop if an exit block has phi uses of curli. Collect the exit
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/// blocks that need special treatment into CriticalExits.
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void getCriticalExits(const LoopBlocks &Blocks, BlockPtrSet &CriticalExits);
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/// canSplitCriticalExits - Return true if it is possible to insert new exit
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/// blocks before the blocks in CriticalExits.
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bool canSplitCriticalExits(const LoopBlocks &Blocks,
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BlockPtrSet &CriticalExits);
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/// getCriticalPreds - Get the set of loop predecessors with critical edges to
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/// blocks outside the loop that have curli live in. We don't have to break
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/// these edges, but they do require special treatment.
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void getCriticalPreds(const LoopBlocks &Blocks, BlockPtrSet &CriticalPreds);
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/// getBestSplitLoop - Return the loop where curli may best be split to a
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/// separate register, or NULL.
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const MachineLoop *getBestSplitLoop();
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/// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from
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/// having curli split to a new live interval. Return true if Blocks can be
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/// passed to SplitEditor::splitSingleBlocks.
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bool getMultiUseBlocks(BlockPtrSet &Blocks);
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/// getBlockForInsideSplit - If curli is contained inside a single basic block,
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/// and it wou pay to subdivide the interval inside that block, return it.
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/// Otherwise return NULL. The returned block can be passed to
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/// SplitEditor::splitInsideBlock.
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const MachineBasicBlock *getBlockForInsideSplit();
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};
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/// LiveIntervalMap - Map values from a large LiveInterval into a small
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/// interval that is a subset. Insert phi-def values as needed. This class is
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/// used by SplitEditor to create new smaller LiveIntervals.
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///
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/// parentli_ is the larger interval, li_ is the subset interval. Every value
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/// in li_ corresponds to exactly one value in parentli_, and the live range
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/// of the value is contained within the live range of the parentli_ value.
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/// Values in parentli_ may map to any number of openli_ values, including 0.
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class LiveIntervalMap {
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LiveIntervals &lis_;
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MachineDominatorTree &mdt_;
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// The parent interval is never changed.
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const LiveInterval &parentli_;
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// The child interval's values are fully contained inside parentli_ values.
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LiveInterval *li_;
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typedef DenseMap<const VNInfo*, VNInfo*> ValueMap;
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// Map parentli_ values to simple values in li_ that are defined at the same
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// SlotIndex, or NULL for parentli_ values that have complex li_ defs.
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// Note there is a difference between values mapping to NULL (complex), and
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// values not present (unknown/unmapped).
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ValueMap valueMap_;
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typedef std::pair<VNInfo*, MachineDomTreeNode*> LiveOutPair;
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typedef DenseMap<MachineBasicBlock*,LiveOutPair> LiveOutMap;
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// liveOutCache_ - Map each basic block where li_ is live out to the live-out
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// value and its defining block. One of these conditions shall be true:
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//
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// 1. !liveOutCache_.count(MBB)
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// 2. liveOutCache_[MBB].second.getNode() == MBB
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// 3. forall P in preds(MBB): liveOutCache_[P] == liveOutCache_[MBB]
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//
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// This is only a cache, the values can be computed as:
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//
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// VNI = li_->getVNInfoAt(lis_.getMBBEndIdx(MBB))
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// Node = mbt_[lis_.getMBBFromIndex(VNI->def)]
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//
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// The cache is also used as a visiteed set by mapValue().
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LiveOutMap liveOutCache_;
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public:
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LiveIntervalMap(LiveIntervals &lis,
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MachineDominatorTree &mdt,
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const LiveInterval &parentli)
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: lis_(lis), mdt_(mdt), parentli_(parentli), li_(0) {}
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/// reset - clear all data structures and start a new live interval.
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void reset(LiveInterval *);
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/// getLI - return the current live interval.
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LiveInterval *getLI() const { return li_; }
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/// defValue - define a value in li_ from the parentli_ value VNI and Idx.
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/// Idx does not have to be ParentVNI->def, but it must be contained within
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/// ParentVNI's live range in parentli_.
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/// Return the new li_ value.
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VNInfo *defValue(const VNInfo *ParentVNI, SlotIndex Idx);
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/// mapValue - map ParentVNI to the corresponding li_ value at Idx. It is
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/// assumed that ParentVNI is live at Idx.
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/// If ParentVNI has not been defined by defValue, it is assumed that
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/// ParentVNI->def dominates Idx.
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/// If ParentVNI has been defined by defValue one or more times, a value that
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/// dominates Idx will be returned. This may require creating extra phi-def
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/// values and adding live ranges to li_.
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/// If simple is not NULL, *simple will indicate if ParentVNI is a simply
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/// mapped value.
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VNInfo *mapValue(const VNInfo *ParentVNI, SlotIndex Idx, bool *simple = 0);
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// extendTo - Find the last li_ value defined in MBB at or before Idx. The
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// parentli is assumed to be live at Idx. Extend the live range to include
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// Idx. Return the found VNInfo, or NULL.
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VNInfo *extendTo(const MachineBasicBlock *MBB, SlotIndex Idx);
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/// isMapped - Return true is ParentVNI is a known mapped value. It may be a
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/// simple 1-1 mapping or a complex mapping to later defs.
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bool isMapped(const VNInfo *ParentVNI) const {
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return valueMap_.count(ParentVNI);
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}
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/// isComplexMapped - Return true if ParentVNI has received new definitions
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/// with defValue.
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bool isComplexMapped(const VNInfo *ParentVNI) const;
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// addSimpleRange - Add a simple range from parentli_ to li_.
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// ParentVNI must be live in the [Start;End) interval.
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void addSimpleRange(SlotIndex Start, SlotIndex End, const VNInfo *ParentVNI);
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/// addRange - Add live ranges to li_ where [Start;End) intersects parentli_.
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/// All needed values whose def is not inside [Start;End) must be defined
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/// beforehand so mapValue will work.
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void addRange(SlotIndex Start, SlotIndex End);
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/// defByCopyFrom - Insert a copy from Reg to li, assuming that Reg carries
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/// ParentVNI. Add a minimal live range for the new value and return it.
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VNInfo *defByCopyFrom(unsigned Reg,
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const VNInfo *ParentVNI,
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MachineBasicBlock &MBB,
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MachineBasicBlock::iterator I);
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};
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/// SplitEditor - Edit machine code and LiveIntervals for live range
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/// splitting.
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///
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/// - Create a SplitEditor from a SplitAnalysis.
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/// - Start a new live interval with openIntv.
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/// - Mark the places where the new interval is entered using enterIntv*
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/// - Mark the ranges where the new interval is used with useIntv*
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/// - Mark the places where the interval is exited with exitIntv*.
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/// - Finish the current interval with closeIntv and repeat from 2.
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/// - Rewrite instructions with finish().
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///
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class SplitEditor {
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SplitAnalysis &sa_;
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LiveIntervals &lis_;
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VirtRegMap &vrm_;
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MachineRegisterInfo &mri_;
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const TargetInstrInfo &tii_;
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/// edit_ - The current parent register and new intervals created.
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LiveRangeEdit &edit_;
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/// dupli_ - Created as a copy of curli_, ranges are carved out as new
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/// intervals get added through openIntv / closeIntv. This is used to avoid
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/// editing curli_.
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LiveIntervalMap dupli_;
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/// Currently open LiveInterval.
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LiveIntervalMap openli_;
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/// intervalsLiveAt - Return true if any member of intervals_ is live at Idx.
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bool intervalsLiveAt(SlotIndex Idx) const;
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/// Values in curli whose live range has been truncated when entering an open
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/// li.
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SmallPtrSet<const VNInfo*, 8> truncatedValues;
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/// addTruncSimpleRange - Add the given simple range to dupli_ after
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/// truncating any overlap with intervals_.
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void addTruncSimpleRange(SlotIndex Start, SlotIndex End, VNInfo *VNI);
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/// criticalPreds_ - Set of basic blocks where both dupli and openli should be
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/// live out because of a critical edge.
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SplitAnalysis::BlockPtrSet criticalPreds_;
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/// computeRemainder - Compute the dupli liveness as the complement of all the
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/// new intervals.
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void computeRemainder();
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/// rewrite - Rewrite all uses of reg to use the new registers.
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void rewrite(unsigned reg);
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public:
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/// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
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/// Newly created intervals will be appended to newIntervals.
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SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&,
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MachineDominatorTree&, LiveRangeEdit&);
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/// getAnalysis - Get the corresponding analysis.
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SplitAnalysis &getAnalysis() { return sa_; }
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/// Create a new virtual register and live interval.
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void openIntv();
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/// enterIntvBefore - Enter openli before the instruction at Idx. If curli is
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/// not live before Idx, a COPY is not inserted.
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void enterIntvBefore(SlotIndex Idx);
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/// enterIntvAtEnd - Enter openli at the end of MBB.
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void enterIntvAtEnd(MachineBasicBlock &MBB);
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/// useIntv - indicate that all instructions in MBB should use openli.
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void useIntv(const MachineBasicBlock &MBB);
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/// useIntv - indicate that all instructions in range should use openli.
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void useIntv(SlotIndex Start, SlotIndex End);
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/// leaveIntvAfter - Leave openli after the instruction at Idx.
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void leaveIntvAfter(SlotIndex Idx);
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/// leaveIntvAtTop - Leave the interval at the top of MBB.
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/// Currently, only one value can leave the interval.
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void leaveIntvAtTop(MachineBasicBlock &MBB);
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/// closeIntv - Indicate that we are done editing the currently open
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/// LiveInterval, and ranges can be trimmed.
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void closeIntv();
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/// finish - after all the new live ranges have been created, compute the
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/// remaining live range, and rewrite instructions to use the new registers.
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void finish();
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// ===--- High level methods ---===
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/// splitAroundLoop - Split curli into a separate live interval inside
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/// the loop.
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void splitAroundLoop(const MachineLoop*);
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/// splitSingleBlocks - Split curli into a separate live interval inside each
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/// basic block in Blocks.
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void splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks);
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/// splitInsideBlock - Split curli into multiple intervals inside MBB.
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void splitInsideBlock(const MachineBasicBlock *);
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};
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}
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