1226584Sdim//===---- LiveRangeCalc.h - Calculate live ranges ---------------*- C++ -*-===// 2226584Sdim// 3226584Sdim// The LLVM Compiler Infrastructure 4226584Sdim// 5226584Sdim// This file is distributed under the University of Illinois Open Source 6226584Sdim// License. See LICENSE.TXT for details. 7226584Sdim// 8226584Sdim//===----------------------------------------------------------------------===// 9226584Sdim// 10226584Sdim// The LiveRangeCalc class can be used to compute live ranges from scratch. It 11226584Sdim// caches information about values in the CFG to speed up repeated operations 12226584Sdim// on the same live range. The cache can be shared by non-overlapping live 13226584Sdim// ranges. SplitKit uses that when computing the live range of split products. 14226584Sdim// 15226584Sdim// A low-level interface is available to clients that know where a variable is 16226584Sdim// live, but don't know which value it has as every point. LiveRangeCalc will 17226584Sdim// propagate values down the dominator tree, and even insert PHI-defs where 18226584Sdim// needed. SplitKit uses this faster interface when possible. 19226584Sdim// 20226584Sdim//===----------------------------------------------------------------------===// 21226584Sdim 22226584Sdim#ifndef LLVM_CODEGEN_LIVERANGECALC_H 23226584Sdim#define LLVM_CODEGEN_LIVERANGECALC_H 24226584Sdim 25226584Sdim#include "llvm/ADT/BitVector.h" 26226584Sdim#include "llvm/ADT/IndexedMap.h" 27226584Sdim#include "llvm/CodeGen/LiveInterval.h" 28226584Sdim 29226584Sdimnamespace llvm { 30226584Sdim 31226584Sdim/// Forward declarations for MachineDominators.h: 32226584Sdimclass MachineDominatorTree; 33226584Sdimtemplate <class NodeT> class DomTreeNodeBase; 34226584Sdimtypedef DomTreeNodeBase<MachineBasicBlock> MachineDomTreeNode; 35226584Sdim 36226584Sdimclass LiveRangeCalc { 37249423Sdim const MachineFunction *MF; 38239462Sdim const MachineRegisterInfo *MRI; 39239462Sdim SlotIndexes *Indexes; 40239462Sdim MachineDominatorTree *DomTree; 41239462Sdim VNInfo::Allocator *Alloc; 42239462Sdim 43226584Sdim /// Seen - Bit vector of active entries in LiveOut, also used as a visited 44226584Sdim /// set by findReachingDefs. One entry per basic block, indexed by block 45226584Sdim /// number. This is kept as a separate bit vector because it can be cleared 46226584Sdim /// quickly when switching live ranges. 47226584Sdim BitVector Seen; 48226584Sdim 49226584Sdim /// LiveOutPair - A value and the block that defined it. The domtree node is 50226584Sdim /// redundant, it can be computed as: MDT[Indexes.getMBBFromIndex(VNI->def)]. 51226584Sdim typedef std::pair<VNInfo*, MachineDomTreeNode*> LiveOutPair; 52226584Sdim 53226584Sdim /// LiveOutMap - Map basic blocks to the value leaving the block. 54226584Sdim typedef IndexedMap<LiveOutPair, MBB2NumberFunctor> LiveOutMap; 55226584Sdim 56226584Sdim /// LiveOut - Map each basic block where a live range is live out to the 57226584Sdim /// live-out value and its defining block. 58226584Sdim /// 59226584Sdim /// For every basic block, MBB, one of these conditions shall be true: 60226584Sdim /// 61226584Sdim /// 1. !Seen.count(MBB->getNumber()) 62226584Sdim /// Blocks without a Seen bit are ignored. 63226584Sdim /// 2. LiveOut[MBB].second.getNode() == MBB 64226584Sdim /// The live-out value is defined in MBB. 65226584Sdim /// 3. forall P in preds(MBB): LiveOut[P] == LiveOut[MBB] 66226584Sdim /// The live-out value passses through MBB. All predecessors must carry 67226584Sdim /// the same value. 68226584Sdim /// 69226584Sdim /// The domtree node may be null, it can be computed. 70226584Sdim /// 71226584Sdim /// The map can be shared by multiple live ranges as long as no two are 72226584Sdim /// live-out of the same block. 73226584Sdim LiveOutMap LiveOut; 74226584Sdim 75226584Sdim /// LiveInBlock - Information about a basic block where a live range is known 76226584Sdim /// to be live-in, but the value has not yet been determined. 77226584Sdim struct LiveInBlock { 78263508Sdim // The live range set that is live-in to this block. The algorithms can 79226584Sdim // handle multiple non-overlapping live ranges simultaneously. 80263508Sdim LiveRange &LR; 81226584Sdim 82226584Sdim // DomNode - Dominator tree node for the block. 83226584Sdim // Cleared when the final value has been determined and LI has been updated. 84226584Sdim MachineDomTreeNode *DomNode; 85226584Sdim 86226584Sdim // Position in block where the live-in range ends, or SlotIndex() if the 87226584Sdim // range passes through the block. When the final value has been 88226584Sdim // determined, the range from the block start to Kill will be added to LI. 89226584Sdim SlotIndex Kill; 90226584Sdim 91226584Sdim // Live-in value filled in by updateSSA once it is known. 92226584Sdim VNInfo *Value; 93226584Sdim 94263508Sdim LiveInBlock(LiveRange &LR, MachineDomTreeNode *node, SlotIndex kill) 95263508Sdim : LR(LR), DomNode(node), Kill(kill), Value(0) {} 96226584Sdim }; 97226584Sdim 98226584Sdim /// LiveIn - Work list of blocks where the live-in value has yet to be 99226584Sdim /// determined. This list is typically computed by findReachingDefs() and 100226584Sdim /// used as a work list by updateSSA(). The low-level interface may also be 101226584Sdim /// used to add entries directly. 102226584Sdim SmallVector<LiveInBlock, 16> LiveIn; 103226584Sdim 104249423Sdim /// Assuming that LI is live-in to KillMBB and killed at Kill, find the set 105249423Sdim /// of defs that can reach it. 106239462Sdim /// 107249423Sdim /// If only one def can reach Kill, all paths from the def to kill are added 108249423Sdim /// to LI, and the function returns true. 109249423Sdim /// 110249423Sdim /// If multiple values can reach Kill, the blocks that need LI to be live in 111249423Sdim /// are added to the LiveIn array, and the function returns false. 112249423Sdim /// 113239462Sdim /// PhysReg, when set, is used to verify live-in lists on basic blocks. 114263508Sdim bool findReachingDefs(LiveRange &LR, MachineBasicBlock &KillMBB, 115263508Sdim SlotIndex Kill, unsigned PhysReg); 116226584Sdim 117226584Sdim /// updateSSA - Compute the values that will be live in to all requested 118226584Sdim /// blocks in LiveIn. Create PHI-def values as required to preserve SSA form. 119226584Sdim /// 120226584Sdim /// Every live-in block must be jointly dominated by the added live-out 121226584Sdim /// blocks. No values are read from the live ranges. 122239462Sdim void updateSSA(); 123226584Sdim 124249423Sdim /// Add liveness as specified in the LiveIn vector. 125249423Sdim void updateLiveIns(); 126226584Sdim 127226584Sdimpublic: 128249423Sdim LiveRangeCalc() : MF(0), MRI(0), Indexes(0), DomTree(0), Alloc(0) {} 129239462Sdim 130226584Sdim //===--------------------------------------------------------------------===// 131226584Sdim // High-level interface. 132226584Sdim //===--------------------------------------------------------------------===// 133226584Sdim // 134226584Sdim // Calculate live ranges from scratch. 135226584Sdim // 136226584Sdim 137226584Sdim /// reset - Prepare caches for a new set of non-overlapping live ranges. The 138226584Sdim /// caches must be reset before attempting calculations with a live range 139226584Sdim /// that may overlap a previously computed live range, and before the first 140226584Sdim /// live range in a function. If live ranges are not known to be 141226584Sdim /// non-overlapping, call reset before each. 142239462Sdim void reset(const MachineFunction *MF, 143239462Sdim SlotIndexes*, 144239462Sdim MachineDominatorTree*, 145239462Sdim VNInfo::Allocator*); 146226584Sdim 147226584Sdim //===--------------------------------------------------------------------===// 148226584Sdim // Mid-level interface. 149226584Sdim //===--------------------------------------------------------------------===// 150226584Sdim // 151226584Sdim // Modify existing live ranges. 152226584Sdim // 153226584Sdim 154226584Sdim /// extend - Extend the live range of LI to reach Kill. 155226584Sdim /// 156226584Sdim /// The existing values in LI must be live so they jointly dominate Kill. If 157226584Sdim /// Kill is not dominated by a single existing value, PHI-defs are inserted 158226584Sdim /// as required to preserve SSA form. If Kill is known to be dominated by a 159226584Sdim /// single existing value, Alloc may be null. 160239462Sdim /// 161239462Sdim /// PhysReg, when set, is used to verify live-in lists on basic blocks. 162263508Sdim void extend(LiveRange &LR, SlotIndex Kill, unsigned PhysReg = 0); 163226584Sdim 164239462Sdim /// createDeadDefs - Create a dead def in LI for every def operand of Reg. 165239462Sdim /// Each instruction defining Reg gets a new VNInfo with a corresponding 166239462Sdim /// minimal live range. 167263508Sdim void createDeadDefs(LiveRange &LR, unsigned Reg); 168239462Sdim 169239462Sdim /// createDeadDefs - Create a dead def in LI for every def of LI->reg. 170263508Sdim void createDeadDefs(LiveInterval &LI) { 171263508Sdim createDeadDefs(LI, LI.reg); 172239462Sdim } 173239462Sdim 174239462Sdim /// extendToUses - Extend the live range of LI to reach all uses of Reg. 175226584Sdim /// 176226584Sdim /// All uses must be jointly dominated by existing liveness. PHI-defs are 177226584Sdim /// inserted as needed to preserve SSA form. 178263508Sdim void extendToUses(LiveRange &LR, unsigned Reg); 179226584Sdim 180239462Sdim /// extendToUses - Extend the live range of LI to reach all uses of LI->reg. 181263508Sdim void extendToUses(LiveInterval &LI) { 182263508Sdim extendToUses(LI, LI.reg); 183239462Sdim } 184239462Sdim 185226584Sdim //===--------------------------------------------------------------------===// 186226584Sdim // Low-level interface. 187226584Sdim //===--------------------------------------------------------------------===// 188226584Sdim // 189226584Sdim // These functions can be used to compute live ranges where the live-in and 190226584Sdim // live-out blocks are already known, but the SSA value in each block is 191226584Sdim // unknown. 192226584Sdim // 193226584Sdim // After calling reset(), add known live-out values and known live-in blocks. 194226584Sdim // Then call calculateValues() to compute the actual value that is 195226584Sdim // live-in to each block, and add liveness to the live ranges. 196226584Sdim // 197226584Sdim 198226584Sdim /// setLiveOutValue - Indicate that VNI is live out from MBB. The 199226584Sdim /// calculateValues() function will not add liveness for MBB, the caller 200226584Sdim /// should take care of that. 201226584Sdim /// 202226584Sdim /// VNI may be null only if MBB is a live-through block also passed to 203226584Sdim /// addLiveInBlock(). 204226584Sdim void setLiveOutValue(MachineBasicBlock *MBB, VNInfo *VNI) { 205226584Sdim Seen.set(MBB->getNumber()); 206226584Sdim LiveOut[MBB] = LiveOutPair(VNI, (MachineDomTreeNode *)0); 207226584Sdim } 208226584Sdim 209226584Sdim /// addLiveInBlock - Add a block with an unknown live-in value. This 210226584Sdim /// function can only be called once per basic block. Once the live-in value 211226584Sdim /// has been determined, calculateValues() will add liveness to LI. 212226584Sdim /// 213263508Sdim /// @param LR The live range that is live-in to the block. 214226584Sdim /// @param DomNode The domtree node for the block. 215226584Sdim /// @param Kill Index in block where LI is killed. If the value is 216226584Sdim /// live-through, set Kill = SLotIndex() and also call 217226584Sdim /// setLiveOutValue(MBB, 0). 218263508Sdim void addLiveInBlock(LiveRange &LR, 219226584Sdim MachineDomTreeNode *DomNode, 220226584Sdim SlotIndex Kill = SlotIndex()) { 221263508Sdim LiveIn.push_back(LiveInBlock(LR, DomNode, Kill)); 222226584Sdim } 223226584Sdim 224226584Sdim /// calculateValues - Calculate the value that will be live-in to each block 225226584Sdim /// added with addLiveInBlock. Add PHI-def values as needed to preserve SSA 226226584Sdim /// form. Add liveness to all live-in blocks up to the Kill point, or the 227226584Sdim /// whole block for live-through blocks. 228226584Sdim /// 229226584Sdim /// Every predecessor of a live-in block must have been given a value with 230226584Sdim /// setLiveOutValue, the value may be null for live-trough blocks. 231239462Sdim void calculateValues(); 232226584Sdim}; 233226584Sdim 234226584Sdim} // end namespace llvm 235226584Sdim 236226584Sdim#endif 237