Extract live range calculations from SplitKit.
SplitKit will soon need two copies of these data structures, and the
algorithms will also be useful when LiveIntervalAnalysis becomes
independent of LiveVariables.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@139572 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveRangeCalc.h b/lib/CodeGen/LiveRangeCalc.h
new file mode 100644
index 0000000..55e67bb
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+++ b/lib/CodeGen/LiveRangeCalc.h
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+//===---- 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 {
+ /// 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.
+ VNInfo *findReachingDefs(LiveInterval *LI,
+ MachineBasicBlock *KillMBB,
+ SlotIndex Kill,
+ SlotIndexes *Indexes,
+ MachineDominatorTree *DomTree);
+
+ /// 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(SlotIndexes *Indexes,
+ MachineDominatorTree *DomTree,
+ VNInfo::Allocator *Alloc);
+
+ /// 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, SlotIndexes*);
+
+public:
+ //===--------------------------------------------------------------------===//
+ // 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);
+
+ /// 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,
+ MachineRegisterInfo *MRI,
+ SlotIndexes *Indexes,
+ VNInfo::Allocator *Alloc);
+
+ //===--------------------------------------------------------------------===//
+ // 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.
+ void extend(LiveInterval *LI,
+ SlotIndex Kill,
+ SlotIndexes *Indexes,
+ MachineDominatorTree *DomTree,
+ VNInfo::Allocator *Alloc);
+
+ /// extendToUses - Extend the live range of LI to reach all uses.
+ ///
+ /// All uses must be jointly dominated by existing liveness. PHI-defs are
+ /// inserted as needed to preserve SSA form.
+ void extendToUses(LiveInterval *LI,
+ MachineRegisterInfo *MRI,
+ SlotIndexes *Indexes,
+ MachineDominatorTree *DomTree,
+ VNInfo::Allocator *Alloc);
+
+ //===--------------------------------------------------------------------===//
+ // 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, 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(SlotIndexes *Indexes,
+ MachineDominatorTree *DomTree,
+ VNInfo::Allocator *Alloc);
+};
+
+} // end namespace llvm
+
+#endif