From b5a457c4cbc71db6ae313ef1bf8eadac65767ab0 Mon Sep 17 00:00:00 2001 From: Jakob Stoklund Olesen Date: Tue, 13 Sep 2011 01:34:21 +0000 Subject: [PATCH] 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 --- lib/CodeGen/CMakeLists.txt | 1 + lib/CodeGen/LiveRangeCalc.cpp | 271 ++++++++++++++++++++++++++++++++++ lib/CodeGen/LiveRangeCalc.h | 226 ++++++++++++++++++++++++++++ lib/CodeGen/SplitKit.cpp | 251 ++----------------------------- lib/CodeGen/SplitKit.h | 73 +-------- 5 files changed, 516 insertions(+), 306 deletions(-) create mode 100644 lib/CodeGen/LiveRangeCalc.cpp create mode 100644 lib/CodeGen/LiveRangeCalc.h diff --git a/lib/CodeGen/CMakeLists.txt b/lib/CodeGen/CMakeLists.txt index af0f7f530c0..06fc3f32771 100644 --- a/lib/CodeGen/CMakeLists.txt +++ b/lib/CodeGen/CMakeLists.txt @@ -30,6 +30,7 @@ add_llvm_library(LLVMCodeGen LiveIntervalUnion.cpp LiveStackAnalysis.cpp LiveVariables.cpp + LiveRangeCalc.cpp LiveRangeEdit.cpp LocalStackSlotAllocation.cpp LowerSubregs.cpp diff --git a/lib/CodeGen/LiveRangeCalc.cpp b/lib/CodeGen/LiveRangeCalc.cpp new file mode 100644 index 00000000000..21eaa15d012 --- /dev/null +++ b/lib/CodeGen/LiveRangeCalc.cpp @@ -0,0 +1,271 @@ +//===---- LiveRangeCalc.cpp - Calculate live ranges -----------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// Implementation of the LiveRangeCalc class. +// +//===----------------------------------------------------------------------===// + +#define DEBUG_TYPE "regalloc" +#include "LiveRangeCalc.h" +#include "llvm/CodeGen/MachineDominators.h" + +using namespace llvm; + +void LiveRangeCalc::reset(const MachineFunction *MF) { + unsigned N = MF->getNumBlockIDs(); + Seen.clear(); + Seen.resize(N); + LiveOut.resize(N); + LiveIn.clear(); +} + + +// Transfer information from the LiveIn vector to the live ranges. +void LiveRangeCalc::updateLiveIns(VNInfo *OverrideVNI, SlotIndexes *Indexes) { + for (SmallVectorImpl::iterator I = LiveIn.begin(), + E = LiveIn.end(); I != E; ++I) { + if (!I->DomNode) + continue; + MachineBasicBlock *MBB = I->DomNode->getBlock(); + + VNInfo *VNI = OverrideVNI ? OverrideVNI : I->Value; + assert(VNI && "No live-in value found"); + + SlotIndex Start, End; + tie(Start, End) = Indexes->getMBBRange(MBB); + + if (I->Kill.isValid()) + I->LI->addRange(LiveRange(Start, I->Kill, VNI)); + else { + I->LI->addRange(LiveRange(Start, End, VNI)); + // The value is live-through, update LiveOut as well. Defer the Domtree + // lookup until it is needed. + assert(Seen.test(MBB->getNumber())); + LiveOut[MBB] = LiveOutPair(VNI, 0); + } + } + LiveIn.clear(); +} + + +void LiveRangeCalc::extend(LiveInterval *LI, + SlotIndex Kill, + SlotIndexes *Indexes, + MachineDominatorTree *DomTree, + VNInfo::Allocator *Alloc) { + assert(LI && "Missing live range"); + assert(Kill.isValid() && "Invalid SlotIndex"); + assert(Indexes && "Missing SlotIndexes"); + assert(DomTree && "Missing dominator tree"); + SlotIndex LastUse = Kill.getPrevSlot(); + + MachineBasicBlock *KillMBB = Indexes->getMBBFromIndex(LastUse); + assert(Kill && "No MBB at Kill"); + + // Is there a def in the same MBB we can extend? + if (LI->extendInBlock(Indexes->getMBBStartIdx(KillMBB), LastUse)) + return; + + // Find the single reaching def, or determine if Kill is jointly dominated by + // multiple values, and we may need to create even more phi-defs to preserve + // VNInfo SSA form. Perform a search for all predecessor blocks where we + // know the dominating VNInfo. + VNInfo *VNI = findReachingDefs(LI, KillMBB, Kill, Indexes, DomTree); + + // When there were multiple different values, we may need new PHIs. + if (!VNI) + updateSSA(Indexes, DomTree, Alloc); + + updateLiveIns(VNI, Indexes); +} + + +// This function is called by a client after using the low-level API to add +// live-out and live-in blocks. The unique value optimization is not +// available, SplitEditor::transferValues handles that case directly anyway. +void LiveRangeCalc::calculateValues(SlotIndexes *Indexes, + MachineDominatorTree *DomTree, + VNInfo::Allocator *Alloc) { + assert(Indexes && "Missing SlotIndexes"); + assert(DomTree && "Missing dominator tree"); + updateSSA(Indexes, DomTree, Alloc); + updateLiveIns(0, Indexes); +} + + +VNInfo *LiveRangeCalc::findReachingDefs(LiveInterval *LI, + MachineBasicBlock *KillMBB, + SlotIndex Kill, + SlotIndexes *Indexes, + MachineDominatorTree *DomTree) { + // Blocks where LI should be live-in. + SmallVector WorkList(1, KillMBB); + + // Remember if we have seen more than one value. + bool UniqueVNI = true; + VNInfo *TheVNI = 0; + + // Using Seen as a visited set, perform a BFS for all reaching defs. + for (unsigned i = 0; i != WorkList.size(); ++i) { + MachineBasicBlock *MBB = WorkList[i]; + assert(!MBB->pred_empty() && "Value live-in to entry block?"); + for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(), + PE = MBB->pred_end(); PI != PE; ++PI) { + MachineBasicBlock *Pred = *PI; + + // Is this a known live-out block? + if (Seen.test(Pred->getNumber())) { + if (VNInfo *VNI = LiveOut[Pred].first) { + if (TheVNI && TheVNI != VNI) + UniqueVNI = false; + TheVNI = VNI; + } + continue; + } + + SlotIndex Start, End; + tie(Start, End) = Indexes->getMBBRange(Pred); + + // First time we see Pred. Try to determine the live-out value, but set + // it as null if Pred is live-through with an unknown value. + VNInfo *VNI = LI->extendInBlock(Start, End.getPrevSlot()); + setLiveOutValue(Pred, VNI); + if (VNI) { + if (TheVNI && TheVNI != VNI) + UniqueVNI = false; + TheVNI = VNI; + continue; + } + + // No, we need a live-in value for Pred as well + if (Pred != KillMBB) + WorkList.push_back(Pred); + else + // Loopback to KillMBB, so value is really live through. + Kill = SlotIndex(); + } + } + + // Transfer WorkList to LiveInBlocks in reverse order. + // This ordering works best with updateSSA(). + LiveIn.clear(); + LiveIn.reserve(WorkList.size()); + while(!WorkList.empty()) + addLiveInBlock(LI, DomTree->getNode(WorkList.pop_back_val())); + + // The kill block may not be live-through. + assert(LiveIn.back().DomNode->getBlock() == KillMBB); + LiveIn.back().Kill = Kill; + + return UniqueVNI ? TheVNI : 0; +} + + +// This is essentially the same iterative algorithm that SSAUpdater uses, +// except we already have a dominator tree, so we don't have to recompute it. +void LiveRangeCalc::updateSSA(SlotIndexes *Indexes, + MachineDominatorTree *DomTree, + VNInfo::Allocator *Alloc) { + assert(Indexes && "Missing SlotIndexes"); + assert(DomTree && "Missing dominator tree"); + + // Interate until convergence. + unsigned Changes; + do { + Changes = 0; + // Propagate live-out values down the dominator tree, inserting phi-defs + // when necessary. + for (SmallVectorImpl::iterator I = LiveIn.begin(), + E = LiveIn.end(); I != E; ++I) { + MachineDomTreeNode *Node = I->DomNode; + // Skip block if the live-in value has already been determined. + if (!Node) + continue; + MachineBasicBlock *MBB = Node->getBlock(); + MachineDomTreeNode *IDom = Node->getIDom(); + LiveOutPair IDomValue; + + // We need a live-in value to a block with no immediate dominator? + // This is probably an unreachable block that has survived somehow. + bool needPHI = !IDom || !Seen.test(IDom->getBlock()->getNumber()); + + // IDom dominates all of our predecessors, but it may not be their + // immediate dominator. Check if any of them have live-out values that are + // properly dominated by IDom. If so, we need a phi-def here. + if (!needPHI) { + IDomValue = LiveOut[IDom->getBlock()]; + + // Cache the DomTree node that defined the value. + if (IDomValue.first && !IDomValue.second) + LiveOut[IDom->getBlock()].second = IDomValue.second = + DomTree->getNode(Indexes->getMBBFromIndex(IDomValue.first->def)); + + for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(), + PE = MBB->pred_end(); PI != PE; ++PI) { + LiveOutPair &Value = LiveOut[*PI]; + if (!Value.first || Value.first == IDomValue.first) + continue; + + // Cache the DomTree node that defined the value. + if (!Value.second) + Value.second = + DomTree->getNode(Indexes->getMBBFromIndex(Value.first->def)); + + // This predecessor is carrying something other than IDomValue. + // It could be because IDomValue hasn't propagated yet, or it could be + // because MBB is in the dominance frontier of that value. + if (DomTree->dominates(IDom, Value.second)) { + needPHI = true; + break; + } + } + } + + // The value may be live-through even if Kill is set, as can happen when + // we are called from extendRange. In that case LiveOutSeen is true, and + // LiveOut indicates a foreign or missing value. + LiveOutPair &LOP = LiveOut[MBB]; + + // Create a phi-def if required. + if (needPHI) { + ++Changes; + assert(Alloc && "Need VNInfo allocator to create PHI-defs"); + SlotIndex Start, End; + tie(Start, End) = Indexes->getMBBRange(MBB); + VNInfo *VNI = I->LI->getNextValue(Start, 0, *Alloc); + VNI->setIsPHIDef(true); + I->Value = VNI; + // This block is done, we know the final value. + I->DomNode = 0; + + // Add liveness since updateLiveIns now skips this node. + if (I->Kill.isValid()) + I->LI->addRange(LiveRange(Start, I->Kill, VNI)); + else { + I->LI->addRange(LiveRange(Start, End, VNI)); + LOP = LiveOutPair(VNI, Node); + } + } else if (IDomValue.first) { + // No phi-def here. Remember incoming value. + I->Value = IDomValue.first; + + // If the IDomValue is killed in the block, don't propagate through. + if (I->Kill.isValid()) + continue; + + // Propagate IDomValue if it isn't killed: + // MBB is live-out and doesn't define its own value. + if (LOP.first == IDomValue.first) + continue; + ++Changes; + LOP = IDomValue; + } + } + } while (Changes); +} diff --git a/lib/CodeGen/LiveRangeCalc.h b/lib/CodeGen/LiveRangeCalc.h new file mode 100644 index 00000000000..55e67bb1445 --- /dev/null +++ b/lib/CodeGen/LiveRangeCalc.h @@ -0,0 +1,226 @@ +//===---- 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 DomTreeNodeBase; +typedef DomTreeNodeBase 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 LiveOutPair; + + /// LiveOutMap - Map basic blocks to the value leaving the block. + typedef IndexedMap 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 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 diff --git a/lib/CodeGen/SplitKit.cpp b/lib/CodeGen/SplitKit.cpp index 67a722e143c..b1416cc17e5 100644 --- a/lib/CodeGen/SplitKit.cpp +++ b/lib/CodeGen/SplitKit.cpp @@ -319,9 +319,7 @@ void SplitEditor::reset(LiveRangeEdit &LRE, ComplementSpillMode SM) { OpenIdx = 0; RegAssign.clear(); Values.clear(); - - // We don't need to clear LiveOutCache, only LiveOutSeen entries are read. - LiveOutSeen.clear(); + LRCalc.reset(&VRM.getMachineFunction()); // We don't need an AliasAnalysis since we will only be performing // cheap-as-a-copy remats anyway. @@ -392,212 +390,8 @@ void SplitEditor::markComplexMapped(unsigned RegIdx, const VNInfo *ParentVNI) { // extendRange - Extend the live range to reach Idx. // Potentially create phi-def values. void SplitEditor::extendRange(unsigned RegIdx, SlotIndex Idx) { - assert(Idx.isValid() && "Invalid SlotIndex"); - MachineBasicBlock *IdxMBB = LIS.getMBBFromIndex(Idx); - assert(IdxMBB && "No MBB at Idx"); - LiveInterval *LI = Edit->get(RegIdx); - - // Is there a def in the same MBB we can extend? - if (LI->extendInBlock(LIS.getMBBStartIdx(IdxMBB), Idx)) - return; - - // Now for the fun part. We know that ParentVNI potentially has multiple defs, - // and we may need to create even more phi-defs to preserve VNInfo SSA form. - // Perform a search for all predecessor blocks where we know the dominating - // VNInfo. - VNInfo *VNI = findReachingDefs(LI, IdxMBB, Idx.getNextSlot()); - - // When there were multiple different values, we may need new PHIs. - if (!VNI) - return updateSSA(); - - // Poor man's SSA update for the single-value case. - LiveOutPair LOP(VNI, MDT[LIS.getMBBFromIndex(VNI->def)]); - for (SmallVectorImpl::iterator I = LiveInBlocks.begin(), - E = LiveInBlocks.end(); I != E; ++I) { - MachineBasicBlock *MBB = I->DomNode->getBlock(); - SlotIndex Start = LIS.getMBBStartIdx(MBB); - if (I->Kill.isValid()) - LI->addRange(LiveRange(Start, I->Kill, VNI)); - else { - LiveOutCache[MBB] = LOP; - LI->addRange(LiveRange(Start, LIS.getMBBEndIdx(MBB), VNI)); - } - } -} - -/// findReachingDefs - Search the CFG for known live-out values. -/// Add required live-in blocks to LiveInBlocks. -VNInfo *SplitEditor::findReachingDefs(LiveInterval *LI, - MachineBasicBlock *KillMBB, - SlotIndex Kill) { - // Initialize the live-out cache the first time it is needed. - if (LiveOutSeen.empty()) { - unsigned N = VRM.getMachineFunction().getNumBlockIDs(); - LiveOutSeen.resize(N); - LiveOutCache.resize(N); - } - - // Blocks where LI should be live-in. - SmallVector WorkList(1, KillMBB); - - // Remember if we have seen more than one value. - bool UniqueVNI = true; - VNInfo *TheVNI = 0; - - // Using LiveOutCache as a visited set, perform a BFS for all reaching defs. - for (unsigned i = 0; i != WorkList.size(); ++i) { - MachineBasicBlock *MBB = WorkList[i]; - assert(!MBB->pred_empty() && "Value live-in to entry block?"); - for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(), - PE = MBB->pred_end(); PI != PE; ++PI) { - MachineBasicBlock *Pred = *PI; - LiveOutPair &LOP = LiveOutCache[Pred]; - - // Is this a known live-out block? - if (LiveOutSeen.test(Pred->getNumber())) { - if (VNInfo *VNI = LOP.first) { - if (TheVNI && TheVNI != VNI) - UniqueVNI = false; - TheVNI = VNI; - } - continue; - } - - // First time. LOP is garbage and must be cleared below. - LiveOutSeen.set(Pred->getNumber()); - - // Does Pred provide a live-out value? - SlotIndex Start, Last; - tie(Start, Last) = LIS.getSlotIndexes()->getMBBRange(Pred); - Last = Last.getPrevSlot(); - VNInfo *VNI = LI->extendInBlock(Start, Last); - LOP.first = VNI; - if (VNI) { - LOP.second = MDT[LIS.getMBBFromIndex(VNI->def)]; - if (TheVNI && TheVNI != VNI) - UniqueVNI = false; - TheVNI = VNI; - continue; - } - LOP.second = 0; - - // No, we need a live-in value for Pred as well - if (Pred != KillMBB) - WorkList.push_back(Pred); - else - // Loopback to KillMBB, so value is really live through. - Kill = SlotIndex(); - } - } - - // Transfer WorkList to LiveInBlocks in reverse order. - // This ordering works best with updateSSA(). - LiveInBlocks.clear(); - LiveInBlocks.reserve(WorkList.size()); - while(!WorkList.empty()) - LiveInBlocks.push_back(MDT[WorkList.pop_back_val()]); - - // The kill block may not be live-through. - assert(LiveInBlocks.back().DomNode->getBlock() == KillMBB); - LiveInBlocks.back().Kill = Kill; - - return UniqueVNI ? TheVNI : 0; -} - -void SplitEditor::updateSSA() { - // This is essentially the same iterative algorithm that SSAUpdater uses, - // except we already have a dominator tree, so we don't have to recompute it. - unsigned Changes; - do { - Changes = 0; - // Propagate live-out values down the dominator tree, inserting phi-defs - // when necessary. - for (SmallVectorImpl::iterator I = LiveInBlocks.begin(), - E = LiveInBlocks.end(); I != E; ++I) { - MachineDomTreeNode *Node = I->DomNode; - // Skip block if the live-in value has already been determined. - if (!Node) - continue; - MachineBasicBlock *MBB = Node->getBlock(); - MachineDomTreeNode *IDom = Node->getIDom(); - LiveOutPair IDomValue; - - // We need a live-in value to a block with no immediate dominator? - // This is probably an unreachable block that has survived somehow. - bool needPHI = !IDom || !LiveOutSeen.test(IDom->getBlock()->getNumber()); - - // IDom dominates all of our predecessors, but it may not be their - // immediate dominator. Check if any of them have live-out values that are - // properly dominated by IDom. If so, we need a phi-def here. - if (!needPHI) { - IDomValue = LiveOutCache[IDom->getBlock()]; - for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(), - PE = MBB->pred_end(); PI != PE; ++PI) { - LiveOutPair Value = LiveOutCache[*PI]; - if (!Value.first || Value.first == IDomValue.first) - continue; - // This predecessor is carrying something other than IDomValue. - // It could be because IDomValue hasn't propagated yet, or it could be - // because MBB is in the dominance frontier of that value. - if (MDT.dominates(IDom, Value.second)) { - needPHI = true; - break; - } - } - } - - // The value may be live-through even if Kill is set, as can happen when - // we are called from extendRange. In that case LiveOutSeen is true, and - // LiveOutCache indicates a foreign or missing value. - LiveOutPair &LOP = LiveOutCache[MBB]; - - // Create a phi-def if required. - if (needPHI) { - ++Changes; - SlotIndex Start = LIS.getMBBStartIdx(MBB); - unsigned RegIdx = RegAssign.lookup(Start); - LiveInterval *LI = Edit->get(RegIdx); - VNInfo *VNI = LI->getNextValue(Start, 0, LIS.getVNInfoAllocator()); - VNI->setIsPHIDef(true); - I->Value = VNI; - // This block is done, we know the final value. - I->DomNode = 0; - if (I->Kill.isValid()) - LI->addRange(LiveRange(Start, I->Kill, VNI)); - else { - LI->addRange(LiveRange(Start, LIS.getMBBEndIdx(MBB), VNI)); - LOP = LiveOutPair(VNI, Node); - } - } else if (IDomValue.first) { - // No phi-def here. Remember incoming value. - I->Value = IDomValue.first; - if (I->Kill.isValid()) - continue; - // Propagate IDomValue if needed: - // MBB is live-out and doesn't define its own value. - if (LOP.second != Node && LOP.first != IDomValue.first) { - ++Changes; - LOP = IDomValue; - } - } - } - } while (Changes); - - // The values in LiveInBlocks are now accurate. No more phi-defs are needed - // for these blocks, so we can color the live ranges. - for (SmallVectorImpl::iterator I = LiveInBlocks.begin(), - E = LiveInBlocks.end(); I != E; ++I) { - if (!I->DomNode) - continue; - assert(I->Value && "No live-in value found"); - MachineBasicBlock *MBB = I->DomNode->getBlock(); - SlotIndex Start = LIS.getMBBStartIdx(MBB); - unsigned RegIdx = RegAssign.lookup(Start); - LiveInterval *LI = Edit->get(RegIdx); - LI->addRange(LiveRange(Start, I->Kill.isValid() ? - I->Kill : LIS.getMBBEndIdx(MBB), I->Value)); - } + LRCalc.extend(Edit->get(RegIdx), Idx.getNextSlot(), + LIS.getSlotIndexes(), &MDT, &LIS.getVNInfoAllocator()); } VNInfo *SplitEditor::defFromParent(unsigned RegIdx, @@ -794,7 +588,6 @@ void SplitEditor::overlapIntv(SlotIndex Start, SlotIndex End) { /// Values that were rematerialized are left alone, they need extendRange(). bool SplitEditor::transferValues() { bool Skipped = false; - LiveInBlocks.clear(); RegAssignMap::const_iterator AssignI = RegAssign.begin(); for (LiveInterval::const_iterator ParentI = Edit->getParent().begin(), ParentE = Edit->getParent().end(); ParentI != ParentE; ++ParentI) { @@ -840,13 +633,6 @@ bool SplitEditor::transferValues() { continue; } - // Initialize the live-out cache the first time it is needed. - if (LiveOutSeen.empty()) { - unsigned N = VRM.getMachineFunction().getNumBlockIDs(); - LiveOutSeen.resize(N); - LiveOutCache.resize(N); - } - // This value has multiple defs in RegIdx, but it wasn't rematerialized, // so the live range is accurate. Add live-in blocks in [Start;End) to the // LiveInBlocks. @@ -861,10 +647,9 @@ bool SplitEditor::transferValues() { assert(VNI && "Missing def for complex mapped value"); DEBUG(dbgs() << ':' << VNI->id << "*BB#" << MBB->getNumber()); // MBB has its own def. Is it also live-out? - if (BlockEnd <= End) { - LiveOutSeen.set(MBB->getNumber()); - LiveOutCache[MBB] = LiveOutPair(VNI, MDT[MBB]); - } + if (BlockEnd <= End) + LRCalc.setLiveOutValue(MBB, VNI); + // Skip to the next block for live-in. ++MBB; BlockStart = BlockEnd; @@ -881,22 +666,17 @@ bool SplitEditor::transferValues() { VNInfo *VNI = LI->extendInBlock(BlockStart, std::min(BlockEnd, End).getPrevSlot()); assert(VNI && "Missing def for complex mapped parent PHI"); - if (End >= BlockEnd) { - // Live-out as well. - LiveOutSeen.set(MBB->getNumber()); - LiveOutCache[MBB] = LiveOutPair(VNI, MDT[MBB]); - } + if (End >= BlockEnd) + LRCalc.setLiveOutValue(MBB, VNI); // Live-out as well. } else { - // This block needs a live-in value. - LiveInBlocks.push_back(MDT[MBB]); - // The last block covered may not be live-out. + // This block needs a live-in value. The last block covered may not + // be live-out. if (End < BlockEnd) - LiveInBlocks.back().Kill = End; + LRCalc.addLiveInBlock(LI, MDT[MBB], End); else { - // Live-out, but we need updateSSA to tell us the value. - LiveOutSeen.set(MBB->getNumber()); - LiveOutCache[MBB] = LiveOutPair((VNInfo*)0, - (MachineDomTreeNode*)0); + // Live-through, and we don't know the value. + LRCalc.addLiveInBlock(LI, MDT[MBB]); + LRCalc.setLiveOutValue(MBB, 0); } } BlockStart = BlockEnd; @@ -907,8 +687,7 @@ bool SplitEditor::transferValues() { DEBUG(dbgs() << '\n'); } - if (!LiveInBlocks.empty()) - updateSSA(); + LRCalc.calculateValues(LIS.getSlotIndexes(), &MDT, &LIS.getVNInfoAllocator()); return Skipped; } diff --git a/lib/CodeGen/SplitKit.h b/lib/CodeGen/SplitKit.h index 7f74d3acf6e..c00b8d366a2 100644 --- a/lib/CodeGen/SplitKit.h +++ b/lib/CodeGen/SplitKit.h @@ -15,13 +15,11 @@ #ifndef LLVM_CODEGEN_SPLITKIT_H #define LLVM_CODEGEN_SPLITKIT_H +#include "LiveRangeCalc.h" #include "llvm/ADT/ArrayRef.h" -#include "llvm/ADT/BitVector.h" #include "llvm/ADT/DenseMap.h" -#include "llvm/ADT/IndexedMap.h" #include "llvm/ADT/IntervalMap.h" #include "llvm/ADT/SmallPtrSet.h" -#include "llvm/CodeGen/SlotIndexes.h" namespace llvm { @@ -38,12 +36,6 @@ class VirtRegMap; class VNInfo; class raw_ostream; -/// At some point we should just include MachineDominators.h: -class MachineDominatorTree; -template class DomTreeNodeBase; -typedef DomTreeNodeBase MachineDomTreeNode; - - /// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting /// opportunities. class SplitAnalysis { @@ -281,54 +273,8 @@ private: /// The new value has no live ranges anywhere. ValueMap Values; - typedef std::pair LiveOutPair; - typedef IndexedMap LiveOutMap; - - // LiveOutCache - Map each basic block where a new register is live out to the - // live-out value and its defining block. - // One of these conditions shall be true: - // - // 1. !LiveOutSeen.count(MBB->getNumber()) - // 2. LiveOutCache[MBB].second.getNode() == MBB - // 3. forall P in preds(MBB): LiveOutCache[P] == LiveOutCache[MBB] - // - // This is only a cache, the values can be computed as: - // - // VNI = Edit.get(RegIdx)->getVNInfoAt(LIS.getMBBEndIdx(MBB)) - // Node = mbt_[LIS.getMBBFromIndex(VNI->def)] - // - // The cache can be shared by all the new registers because at most one is - // live out of each block. - LiveOutMap LiveOutCache; - - // LiveOutSeen - Indexed by MBB->getNumber(), a bit is set for each valid - // entry in LiveOutCache. This is also used as a visited set for - // findReachingDefs(). - BitVector LiveOutSeen; - - /// LiveInBlock - Info for updateSSA() about a block where a register is - /// live-in. - /// The updateSSA caller provides DomNode and Kill inside MBB, updateSSA() - /// adds the computed live-in value. - struct LiveInBlock { - // Dominator tree node for the block. - // Cleared by updateSSA when the final value has been determined. - MachineDomTreeNode *DomNode; - - // Live-in value filled in by updateSSA once it is known. - VNInfo *Value; - - // Position in block where the live-in range ends, or SlotIndex() if the - // range passes through the block. - SlotIndex Kill; - - LiveInBlock(MachineDomTreeNode *node) : DomNode(node), Value(0) {} - }; - - /// LiveInBlocks - List of live-in blocks used by findReachingDefs() and - /// updateSSA(). This list is usually empty, it exists here to avoid frequent - /// reallocations. - SmallVector LiveInBlocks; + /// LRCalc - Cache for computing live ranges and SSA update. + LiveRangeCalc LRCalc; /// defValue - define a value in RegIdx from ParentVNI at Idx. /// Idx does not have to be ParentVNI->def, but it must be contained within @@ -353,19 +299,6 @@ private: /// Insert PHIDefs as needed to preserve SSA form. void extendRange(unsigned RegIdx, SlotIndex Idx); - /// findReachingDefs - Starting from MBB, add blocks to LiveInBlocks until all - /// reaching defs for LI are found. - /// @param LI Live interval whose value is needed. - /// @param MBB Block where LI should be live-in. - /// @param Kill Kill point in MBB. - /// @return Unique value seen, or NULL. - VNInfo *findReachingDefs(LiveInterval *LI, MachineBasicBlock *MBB, - SlotIndex Kill); - - /// updateSSA - Compute and insert PHIDefs such that all blocks in - // LiveInBlocks get a known live-in value. Add live ranges to the blocks. - void updateSSA(); - /// transferValues - Transfer values to the new ranges. /// Return true if any ranges were skipped. bool transferValues();