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Diffstat (limited to 'contrib/llvm/lib/CodeGen/LiveRangeCalc.h')
| -rw-r--r-- | contrib/llvm/lib/CodeGen/LiveRangeCalc.h | 242 |
1 files changed, 242 insertions, 0 deletions
diff --git a/contrib/llvm/lib/CodeGen/LiveRangeCalc.h b/contrib/llvm/lib/CodeGen/LiveRangeCalc.h new file mode 100644 index 0000000..57cab7b --- /dev/null +++ b/contrib/llvm/lib/CodeGen/LiveRangeCalc.h @@ -0,0 +1,242 @@ +//===---- 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 MachineFunction *MF; + 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; + + /// Assuming that LI is live-in to KillMBB and killed at Kill, find the set + /// of defs that can reach it. + /// + /// If only one def can reach Kill, all paths from the def to kill are added + /// to LI, and the function returns true. + /// + /// If multiple values can reach Kill, the blocks that need LI to be live in + /// are added to the LiveIn array, and the function returns false. + /// + /// PhysReg, when set, is used to verify live-in lists on basic blocks. + bool 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(); + + /// Add liveness as specified in the LiveIn vector. + void updateLiveIns(); + +public: + LiveRangeCalc() : MF(0), 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 |
