//===---- LiveRangeCalc.h - Calculate live ranges ---------------*- C++ -*-===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // The LiveRangeCalc class can be used to compute live ranges from scratch. It // caches information about values in the CFG to speed up repeated operations // on the same live range. The cache can be shared by non-overlapping live // ranges. SplitKit uses that when computing the live range of split products. // // A low-level interface is available to clients that know where a variable is // live, but don't know which value it has as every point. LiveRangeCalc will // propagate values down the dominator tree, and even insert PHI-defs where // needed. SplitKit uses this faster interface when possible. // //===----------------------------------------------------------------------===// #ifndef LLVM_CODEGEN_LIVERANGECALC_H #define LLVM_CODEGEN_LIVERANGECALC_H #include "llvm/ADT/BitVector.h" #include "llvm/ADT/IndexedMap.h" #include "llvm/CodeGen/LiveInterval.h" namespace llvm { /// Forward declarations for MachineDominators.h: class MachineDominatorTree; template <class NodeT> class DomTreeNodeBase; typedef DomTreeNodeBase<MachineBasicBlock> MachineDomTreeNode; class LiveRangeCalc { const MachineRegisterInfo *MRI; SlotIndexes *Indexes; MachineDominatorTree *DomTree; VNInfo::Allocator *Alloc; /// Seen - Bit vector of active entries in LiveOut, also used as a visited /// set by findReachingDefs. One entry per basic block, indexed by block /// number. This is kept as a separate bit vector because it can be cleared /// quickly when switching live ranges. BitVector Seen; /// LiveOutPair - A value and the block that defined it. The domtree node is /// redundant, it can be computed as: MDT[Indexes.getMBBFromIndex(VNI->def)]. typedef std::pair<VNInfo*, MachineDomTreeNode*> LiveOutPair; /// LiveOutMap - Map basic blocks to the value leaving the block. typedef IndexedMap<LiveOutPair, MBB2NumberFunctor> LiveOutMap; /// LiveOut - Map each basic block where a live range is live out to the /// live-out value and its defining block. /// /// For every basic block, MBB, one of these conditions shall be true: /// /// 1. !Seen.count(MBB->getNumber()) /// Blocks without a Seen bit are ignored. /// 2. LiveOut[MBB].second.getNode() == MBB /// The live-out value is defined in MBB. /// 3. forall P in preds(MBB): LiveOut[P] == LiveOut[MBB] /// The live-out value passses through MBB. All predecessors must carry /// the same value. /// /// The domtree node may be null, it can be computed. /// /// The map can be shared by multiple live ranges as long as no two are /// live-out of the same block. LiveOutMap LiveOut; /// LiveInBlock - Information about a basic block where a live range is known /// to be live-in, but the value has not yet been determined. struct LiveInBlock { // LI - The live range that is live-in to this block. The algorithms can // handle multiple non-overlapping live ranges simultaneously. LiveInterval *LI; // DomNode - Dominator tree node for the block. // Cleared when the final value has been determined and LI has been updated. MachineDomTreeNode *DomNode; // Position in block where the live-in range ends, or SlotIndex() if the // range passes through the block. When the final value has been // determined, the range from the block start to Kill will be added to LI. SlotIndex Kill; // Live-in value filled in by updateSSA once it is known. VNInfo *Value; LiveInBlock(LiveInterval *li, MachineDomTreeNode *node, SlotIndex kill) : LI(li), DomNode(node), Kill(kill), Value(0) {} }; /// LiveIn - Work list of blocks where the live-in value has yet to be /// determined. This list is typically computed by findReachingDefs() and /// used as a work list by updateSSA(). The low-level interface may also be /// used to add entries directly. SmallVector<LiveInBlock, 16> LiveIn; /// findReachingDefs - Assuming that LI is live-in to KillMBB and killed at /// Kill, search for values that can reach KillMBB. All blocks that need LI /// to be live-in are added to LiveIn. If a unique reaching def is found, /// its value is returned, if Kill is jointly dominated by multiple values, /// NULL is returned. /// /// PhysReg, when set, is used to verify live-in lists on basic blocks. VNInfo *findReachingDefs(LiveInterval *LI, MachineBasicBlock *KillMBB, SlotIndex Kill, unsigned PhysReg); /// updateSSA - Compute the values that will be live in to all requested /// blocks in LiveIn. Create PHI-def values as required to preserve SSA form. /// /// Every live-in block must be jointly dominated by the added live-out /// blocks. No values are read from the live ranges. void updateSSA(); /// updateLiveIns - Add liveness as specified in the LiveIn vector, using VNI /// as a wildcard value for LiveIn entries without a value. void updateLiveIns(VNInfo *VNI); public: LiveRangeCalc() : MRI(0), Indexes(0), DomTree(0), Alloc(0) {} //===--------------------------------------------------------------------===// // High-level interface. //===--------------------------------------------------------------------===// // // Calculate live ranges from scratch. // /// reset - Prepare caches for a new set of non-overlapping live ranges. The /// caches must be reset before attempting calculations with a live range /// that may overlap a previously computed live range, and before the first /// live range in a function. If live ranges are not known to be /// non-overlapping, call reset before each. void reset(const MachineFunction *MF, SlotIndexes*, MachineDominatorTree*, VNInfo::Allocator*); /// calculate - Calculate the live range of a virtual register from its defs /// and uses. LI must be empty with no values. void calculate(LiveInterval *LI); //===--------------------------------------------------------------------===// // Mid-level interface. //===--------------------------------------------------------------------===// // // Modify existing live ranges. // /// extend - Extend the live range of LI to reach Kill. /// /// The existing values in LI must be live so they jointly dominate Kill. If /// Kill is not dominated by a single existing value, PHI-defs are inserted /// as required to preserve SSA form. If Kill is known to be dominated by a /// single existing value, Alloc may be null. /// /// PhysReg, when set, is used to verify live-in lists on basic blocks. void extend(LiveInterval *LI, SlotIndex Kill, unsigned PhysReg = 0); /// createDeadDefs - Create a dead def in LI for every def operand of Reg. /// Each instruction defining Reg gets a new VNInfo with a corresponding /// minimal live range. void createDeadDefs(LiveInterval *LI, unsigned Reg); /// createDeadDefs - Create a dead def in LI for every def of LI->reg. void createDeadDefs(LiveInterval *LI) { createDeadDefs(LI, LI->reg); } /// extendToUses - Extend the live range of LI to reach all uses of Reg. /// /// All uses must be jointly dominated by existing liveness. PHI-defs are /// inserted as needed to preserve SSA form. void extendToUses(LiveInterval *LI, unsigned Reg); /// extendToUses - Extend the live range of LI to reach all uses of LI->reg. void extendToUses(LiveInterval *LI) { extendToUses(LI, LI->reg); } //===--------------------------------------------------------------------===// // Low-level interface. //===--------------------------------------------------------------------===// // // These functions can be used to compute live ranges where the live-in and // live-out blocks are already known, but the SSA value in each block is // unknown. // // After calling reset(), add known live-out values and known live-in blocks. // Then call calculateValues() to compute the actual value that is // live-in to each block, and add liveness to the live ranges. // /// setLiveOutValue - Indicate that VNI is live out from MBB. The /// calculateValues() function will not add liveness for MBB, the caller /// should take care of that. /// /// VNI may be null only if MBB is a live-through block also passed to /// addLiveInBlock(). void setLiveOutValue(MachineBasicBlock *MBB, VNInfo *VNI) { Seen.set(MBB->getNumber()); LiveOut[MBB] = LiveOutPair(VNI, (MachineDomTreeNode *)0); } /// addLiveInBlock - Add a block with an unknown live-in value. This /// function can only be called once per basic block. Once the live-in value /// has been determined, calculateValues() will add liveness to LI. /// /// @param LI The live range that is live-in to the block. /// @param DomNode The domtree node for the block. /// @param Kill Index in block where LI is killed. If the value is /// live-through, set Kill = SLotIndex() and also call /// setLiveOutValue(MBB, 0). void addLiveInBlock(LiveInterval *LI, MachineDomTreeNode *DomNode, SlotIndex Kill = SlotIndex()) { LiveIn.push_back(LiveInBlock(LI, DomNode, Kill)); } /// calculateValues - Calculate the value that will be live-in to each block /// added with addLiveInBlock. Add PHI-def values as needed to preserve SSA /// form. Add liveness to all live-in blocks up to the Kill point, or the /// whole block for live-through blocks. /// /// Every predecessor of a live-in block must have been given a value with /// setLiveOutValue, the value may be null for live-trough blocks. void calculateValues(); }; } // end namespace llvm #endif