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