//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "regalloc"
#include "LiveRangeCalc.h"
#include "llvm/CodeGen/MachineDominators.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
using namespace llvm;
-void LiveRangeCalc::reset(const MachineFunction *MF) {
+#define DEBUG_TYPE "regalloc"
+
+void LiveRangeCalc::reset(const MachineFunction *mf,
+ SlotIndexes *SI,
+ MachineDominatorTree *MDT,
+ VNInfo::Allocator *VNIA) {
+ MF = mf;
+ MRI = &MF->getRegInfo();
+ Indexes = SI;
+ DomTree = MDT;
+ Alloc = VNIA;
+
unsigned N = MF->getNumBlockIDs();
Seen.clear();
Seen.resize(N);
}
+void LiveRangeCalc::createDeadDefs(LiveRange &LR, unsigned Reg) {
+ assert(MRI && Indexes && "call reset() first");
+
+ // Visit all def operands. If the same instruction has multiple defs of Reg,
+ // LR.createDeadDef() will deduplicate.
+ for (MachineOperand &MO : MRI->def_operands(Reg)) {
+ const MachineInstr *MI = MO.getParent();
+ // Find the corresponding slot index.
+ SlotIndex Idx;
+ if (MI->isPHI())
+ // PHI defs begin at the basic block start index.
+ Idx = Indexes->getMBBStartIdx(MI->getParent());
+ else
+ // Instructions are either normal 'r', or early clobber 'e'.
+ Idx = Indexes->getInstructionIndex(MI)
+ .getRegSlot(MO.isEarlyClobber());
+
+ // Create the def in LR. This may find an existing def.
+ LR.createDeadDef(Idx, *Alloc);
+ }
+}
+
+
+void LiveRangeCalc::extendToUses(LiveRange &LR, unsigned Reg) {
+ assert(MRI && Indexes && "call reset() first");
+
+ // Visit all operands that read Reg. This may include partial defs.
+ for (MachineOperand &MO : MRI->reg_nodbg_operands(Reg)) {
+ // Clear all kill flags. They will be reinserted after register allocation
+ // by LiveIntervalAnalysis::addKillFlags().
+ if (MO.isUse())
+ MO.setIsKill(false);
+ if (!MO.readsReg())
+ continue;
+ // MI is reading Reg. We may have visited MI before if it happens to be
+ // reading Reg multiple times. That is OK, extend() is idempotent.
+ const MachineInstr *MI = MO.getParent();
+ unsigned OpNo = (&MO - &MI->getOperand(0));
+
+ // Find the SlotIndex being read.
+ SlotIndex Idx;
+ if (MI->isPHI()) {
+ assert(!MO.isDef() && "Cannot handle PHI def of partial register.");
+ // PHI operands are paired: (Reg, PredMBB).
+ // Extend the live range to be live-out from PredMBB.
+ Idx = Indexes->getMBBEndIdx(MI->getOperand(OpNo+1).getMBB());
+ } else {
+ // This is a normal instruction.
+ Idx = Indexes->getInstructionIndex(MI).getRegSlot();
+ // Check for early-clobber redefs.
+ unsigned DefIdx;
+ if (MO.isDef()) {
+ if (MO.isEarlyClobber())
+ Idx = Idx.getRegSlot(true);
+ } else if (MI->isRegTiedToDefOperand(OpNo, &DefIdx)) {
+ // FIXME: This would be a lot easier if tied early-clobber uses also
+ // had an early-clobber flag.
+ if (MI->getOperand(DefIdx).isEarlyClobber())
+ Idx = Idx.getRegSlot(true);
+ }
+ }
+ extend(LR, Idx, Reg);
+ }
+}
+
+
// Transfer information from the LiveIn vector to the live ranges.
-void LiveRangeCalc::updateLiveIns(VNInfo *OverrideVNI, SlotIndexes *Indexes) {
+void LiveRangeCalc::updateLiveIns() {
+ LiveRangeUpdater Updater;
for (SmallVectorImpl<LiveInBlock>::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");
-
+ assert(I->Value && "No live-in value found");
SlotIndex Start, End;
- tie(Start, End) = Indexes->getMBBRange(MBB);
+ std::tie(Start, End) = Indexes->getMBBRange(MBB);
if (I->Kill.isValid())
- I->LI->addRange(LiveRange(Start, I->Kill, VNI));
+ // Value is killed inside this block.
+ End = I->Kill;
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.
+ // 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, (MachineDomTreeNode *)0);
+ LiveOut[MBB] = LiveOutPair(I->Value, (MachineDomTreeNode *)nullptr);
}
+ Updater.setDest(&I->LR);
+ Updater.add(Start, End, I->Value);
}
LiveIn.clear();
}
-void LiveRangeCalc::extend(LiveInterval *LI,
- SlotIndex Kill,
- SlotIndexes *Indexes,
- MachineDominatorTree *DomTree,
- VNInfo::Allocator *Alloc) {
- assert(LI && "Missing live range");
+void LiveRangeCalc::extend(LiveRange &LR, SlotIndex Kill, unsigned PhysReg) {
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");
+ MachineBasicBlock *KillMBB = Indexes->getMBBFromIndex(Kill.getPrevSlot());
+ assert(KillMBB && "No MBB at Kill");
// Is there a def in the same MBB we can extend?
- if (LI->extendInBlock(Indexes->getMBBStartIdx(KillMBB), LastUse))
+ if (LR.extendInBlock(Indexes->getMBBStartIdx(KillMBB), Kill))
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);
+ if (findReachingDefs(LR, *KillMBB, Kill, PhysReg))
+ return;
// When there were multiple different values, we may need new PHIs.
- if (!VNI)
- updateSSA(Indexes, DomTree, Alloc);
-
- updateLiveIns(VNI, Indexes);
+ calculateValues();
}
// 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) {
+void LiveRangeCalc::calculateValues() {
assert(Indexes && "Missing SlotIndexes");
assert(DomTree && "Missing dominator tree");
- updateSSA(Indexes, DomTree, Alloc);
- updateLiveIns(0, Indexes);
+ updateSSA();
+ updateLiveIns();
}
-VNInfo *LiveRangeCalc::findReachingDefs(LiveInterval *LI,
- MachineBasicBlock *KillMBB,
- SlotIndex Kill,
- SlotIndexes *Indexes,
- MachineDominatorTree *DomTree) {
- // Blocks where LI should be live-in.
- SmallVector<MachineBasicBlock*, 16> WorkList(1, KillMBB);
+bool LiveRangeCalc::findReachingDefs(LiveRange &LR, MachineBasicBlock &KillMBB,
+ SlotIndex Kill, unsigned PhysReg) {
+ unsigned KillMBBNum = KillMBB.getNumber();
+
+ // Block numbers where LR should be live-in.
+ SmallVector<unsigned, 16> WorkList(1, KillMBBNum);
// Remember if we have seen more than one value.
bool UniqueVNI = true;
- VNInfo *TheVNI = 0;
+ VNInfo *TheVNI = nullptr;
// 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?");
+ MachineBasicBlock *MBB = MF->getBlockNumbered(WorkList[i]);
+
+#ifndef NDEBUG
+ if (MBB->pred_empty()) {
+ MBB->getParent()->verify();
+ llvm_unreachable("Use not jointly dominated by defs.");
+ }
+
+ if (TargetRegisterInfo::isPhysicalRegister(PhysReg) &&
+ !MBB->isLiveIn(PhysReg)) {
+ MBB->getParent()->verify();
+ errs() << "The register needs to be live in to BB#" << MBB->getNumber()
+ << ", but is missing from the live-in list.\n";
+ llvm_unreachable("Invalid global physical register");
+ }
+#endif
+
for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
- PE = MBB->pred_end(); PI != PE; ++PI) {
+ PE = MBB->pred_end(); PI != PE; ++PI) {
MachineBasicBlock *Pred = *PI;
// Is this a known live-out block?
}
SlotIndex Start, End;
- tie(Start, End) = Indexes->getMBBRange(Pred);
+ std::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());
+ VNInfo *VNI = LR.extendInBlock(Start, End);
setLiveOutValue(Pred, VNI);
if (VNI) {
if (TheVNI && TheVNI != VNI)
}
// No, we need a live-in value for Pred as well
- if (Pred != KillMBB)
- WorkList.push_back(Pred);
+ if (Pred != &KillMBB)
+ WorkList.push_back(Pred->getNumber());
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;
+ // Both updateSSA() and LiveRangeUpdater benefit from ordered blocks, but
+ // neither require it. Skip the sorting overhead for small updates.
+ if (WorkList.size() > 4)
+ array_pod_sort(WorkList.begin(), WorkList.end());
+
+ // If a unique reaching def was found, blit in the live ranges immediately.
+ if (UniqueVNI) {
+ LiveRangeUpdater Updater(&LR);
+ for (SmallVectorImpl<unsigned>::const_iterator I = WorkList.begin(),
+ E = WorkList.end(); I != E; ++I) {
+ SlotIndex Start, End;
+ std::tie(Start, End) = Indexes->getMBBRange(*I);
+ // Trim the live range in KillMBB.
+ if (*I == KillMBBNum && Kill.isValid())
+ End = Kill;
+ else
+ LiveOut[MF->getBlockNumbered(*I)] =
+ LiveOutPair(TheVNI, nullptr);
+ Updater.add(Start, End, TheVNI);
+ }
+ return true;
+ }
+
+ // Multiple values were found, so transfer the work list to the LiveIn array
+ // where UpdateSSA will use it as a work list.
+ LiveIn.reserve(WorkList.size());
+ for (SmallVectorImpl<unsigned>::const_iterator
+ I = WorkList.begin(), E = WorkList.end(); I != E; ++I) {
+ MachineBasicBlock *MBB = MF->getBlockNumbered(*I);
+ addLiveInBlock(LR, DomTree->getNode(MBB));
+ if (MBB == &KillMBB)
+ LiveIn.back().Kill = Kill;
+ }
- return UniqueVNI ? TheVNI : 0;
+ return false;
}
// 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) {
+void LiveRangeCalc::updateSSA() {
assert(Indexes && "Missing SlotIndexes");
assert(DomTree && "Missing dominator tree");
++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);
+ std::tie(Start, End) = Indexes->getMBBRange(MBB);
+ LiveRange &LR = I->LR;
+ VNInfo *VNI = LR.getNextValue(Start, *Alloc);
I->Value = VNI;
// This block is done, we know the final value.
- I->DomNode = 0;
+ I->DomNode = nullptr;
// Add liveness since updateLiveIns now skips this node.
if (I->Kill.isValid())
- I->LI->addRange(LiveRange(Start, I->Kill, VNI));
+ LR.addSegment(LiveInterval::Segment(Start, I->Kill, VNI));
else {
- I->LI->addRange(LiveRange(Start, End, VNI));
+ LR.addSegment(LiveInterval::Segment(Start, End, VNI));
LOP = LiveOutPair(VNI, Node);
}
} else if (IDomValue.first) {
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