X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FMachineBasicBlock.cpp;h=31d12ebdc479b24aa41698c826caaf339d6c5c29;hb=caebdd44f3a2c89457f09d0fa45a998c912235d2;hp=7ec9aab8c2cc39c7c2e476de32d9a11e2f1dfe97;hpb=2d8e3d20be377112999670f210200b3658762571;p=oota-llvm.git diff --git a/lib/CodeGen/MachineBasicBlock.cpp b/lib/CodeGen/MachineBasicBlock.cpp index 7ec9aab8c2c..31d12ebdc47 100644 --- a/lib/CodeGen/MachineBasicBlock.cpp +++ b/lib/CodeGen/MachineBasicBlock.cpp @@ -13,18 +13,30 @@ #include "llvm/CodeGen/MachineBasicBlock.h" #include "llvm/BasicBlock.h" +#include "llvm/CodeGen/LiveVariables.h" +#include "llvm/CodeGen/MachineDominators.h" #include "llvm/CodeGen/MachineFunction.h" +#include "llvm/CodeGen/MachineLoopInfo.h" +#include "llvm/CodeGen/SlotIndexes.h" +#include "llvm/MC/MCAsmInfo.h" +#include "llvm/MC/MCContext.h" #include "llvm/Target/TargetRegisterInfo.h" #include "llvm/Target/TargetData.h" #include "llvm/Target/TargetInstrDesc.h" +#include "llvm/Target/TargetInstrInfo.h" #include "llvm/Target/TargetMachine.h" +#include "llvm/Assembly/Writer.h" +#include "llvm/ADT/SmallString.h" +#include "llvm/ADT/SmallPtrSet.h" +#include "llvm/Support/Debug.h" #include "llvm/Support/LeakDetector.h" #include "llvm/Support/raw_ostream.h" #include using namespace llvm; MachineBasicBlock::MachineBasicBlock(MachineFunction &mf, const BasicBlock *bb) - : BB(bb), Number(-1), xParent(&mf), Alignment(0), IsLandingPad(false) { + : BB(bb), Number(-1), xParent(&mf), Alignment(0), IsLandingPad(false), + AddressTaken(false) { Insts.Parent = this; } @@ -32,10 +44,18 @@ MachineBasicBlock::~MachineBasicBlock() { LeakDetector::removeGarbageObject(this); } -std::ostream &llvm::operator<<(std::ostream &OS, const MachineBasicBlock &MBB) { - MBB.print(OS); - return OS; +/// getSymbol - Return the MCSymbol for this basic block. +/// +MCSymbol *MachineBasicBlock::getSymbol() const { + const MachineFunction *MF = getParent(); + MCContext &Ctx = MF->getContext(); + const char *Prefix = Ctx.getAsmInfo().getPrivateGlobalPrefix(); + return Ctx.GetOrCreateSymbol(Twine(Prefix) + "BB" + + Twine(MF->getFunctionNumber()) + "_" + + Twine(getNumber())); } + + raw_ostream &llvm::operator<<(raw_ostream &OS, const MachineBasicBlock &MBB) { MBB.print(OS); return OS; @@ -120,6 +140,20 @@ void ilist_traits::deleteNode(MachineInstr* MI) { Parent->getParent()->DeleteMachineInstr(MI); } +MachineBasicBlock::iterator MachineBasicBlock::getFirstNonPHI() { + iterator I = begin(); + while (I != end() && I->isPHI()) + ++I; + return I; +} + +MachineBasicBlock::iterator +MachineBasicBlock::SkipPHIsAndLabels(MachineBasicBlock::iterator I) { + while (I != end() && (I->isPHI() || I->isLabel() || I->isDebugValue())) + ++I; + return I; +} + MachineBasicBlock::iterator MachineBasicBlock::getFirstTerminator() { iterator I = end(); while (I != begin() && (--I)->getDesc().isTerminator()) @@ -128,57 +162,29 @@ MachineBasicBlock::iterator MachineBasicBlock::getFirstTerminator() { return I; } -/// isOnlyReachableViaFallthough - Return true if this basic block has -/// exactly one predecessor and the control transfer mechanism between -/// the predecessor and this block is a fall-through. -bool MachineBasicBlock::isOnlyReachableByFallthrough() const { - // If this is a landing pad, it isn't a fall through. If it has no preds, - // then nothing falls through to it. - if (isLandingPad() || pred_empty()) - return false; - - // If there isn't exactly one predecessor, it can't be a fall through. - const_pred_iterator PI = pred_begin(), PI2 = PI; - ++PI2; - if (PI2 != pred_end()) - return false; - - // The predecessor has to be immediately before this block. - const MachineBasicBlock *Pred = *PI; - - if (!Pred->isLayoutSuccessor(this)) - return false; - - // If the block is completely empty, then it definitely does fall through. - if (Pred->empty()) - return true; - - // Otherwise, check the last instruction. - const MachineInstr &LastInst = Pred->back(); - return !LastInst.getDesc().isBarrier(); -} - void MachineBasicBlock::dump() const { - print(*cerr.stream()); + print(dbgs()); } static inline void OutputReg(raw_ostream &os, unsigned RegNo, const TargetRegisterInfo *TRI = 0) { - if (!RegNo || TargetRegisterInfo::isPhysicalRegister(RegNo)) { + if (RegNo != 0 && TargetRegisterInfo::isPhysicalRegister(RegNo)) { if (TRI) os << " %" << TRI->get(RegNo).Name; else - os << " %mreg(" << RegNo << ")"; + os << " %physreg" << RegNo; } else os << " %reg" << RegNo; } -void MachineBasicBlock::print(std::ostream &OS) const { - raw_os_ostream RawOS(OS); - print(RawOS); +StringRef MachineBasicBlock::getName() const { + if (const BasicBlock *LBB = getBasicBlock()) + return LBB->getName(); + else + return "(null)"; } -void MachineBasicBlock::print(raw_ostream &OS) const { +void MachineBasicBlock::print(raw_ostream &OS, SlotIndexes *Indexes) const { const MachineFunction *MF = getParent(); if (!MF) { OS << "Can't print out MachineBasicBlock because parent MachineFunction" @@ -186,52 +192,69 @@ void MachineBasicBlock::print(raw_ostream &OS) const { return; } - const BasicBlock *LBB = getBasicBlock(); + if (Alignment) { OS << "Alignment " << Alignment << "\n"; } + + if (Indexes) + OS << Indexes->getMBBStartIdx(this) << '\t'; + + OS << "BB#" << getNumber() << ": "; + + const char *Comma = ""; + if (const BasicBlock *LBB = getBasicBlock()) { + OS << Comma << "derived from LLVM BB "; + WriteAsOperand(OS, LBB, /*PrintType=*/false); + Comma = ", "; + } + if (isLandingPad()) { OS << Comma << "EH LANDING PAD"; Comma = ", "; } + if (hasAddressTaken()) { OS << Comma << "ADDRESS TAKEN"; Comma = ", "; } OS << '\n'; - if (LBB) OS << LBB->getName() << ": "; - OS << (const void*)this - << ", LLVM BB @" << (const void*) LBB << ", ID#" << getNumber(); - if (Alignment) OS << ", Alignment " << Alignment; - if (isLandingPad()) OS << ", EH LANDING PAD"; - OS << ":\n"; - - const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo(); + + const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo(); if (!livein_empty()) { - OS << "Live Ins:"; - for (const_livein_iterator I = livein_begin(),E = livein_end(); I != E; ++I) + if (Indexes) OS << '\t'; + OS << " Live Ins:"; + for (livein_iterator I = livein_begin(),E = livein_end(); I != E; ++I) OutputReg(OS, *I, TRI); OS << '\n'; } // Print the preds of this block according to the CFG. if (!pred_empty()) { + if (Indexes) OS << '\t'; OS << " Predecessors according to CFG:"; for (const_pred_iterator PI = pred_begin(), E = pred_end(); PI != E; ++PI) - OS << ' ' << *PI << " (#" << (*PI)->getNumber() << ')'; + OS << " BB#" << (*PI)->getNumber(); OS << '\n'; } - + for (const_iterator I = begin(); I != end(); ++I) { + if (Indexes) { + if (Indexes->hasIndex(I)) + OS << Indexes->getInstructionIndex(I); + OS << '\t'; + } OS << '\t'; I->print(OS, &getParent()->getTarget()); } // Print the successors of this block according to the CFG. if (!succ_empty()) { + if (Indexes) OS << '\t'; OS << " Successors according to CFG:"; for (const_succ_iterator SI = succ_begin(), E = succ_end(); SI != E; ++SI) - OS << ' ' << *SI << " (#" << (*SI)->getNumber() << ')'; + OS << " BB#" << (*SI)->getNumber(); OS << '\n'; } } void MachineBasicBlock::removeLiveIn(unsigned Reg) { - livein_iterator I = std::find(livein_begin(), livein_end(), Reg); - assert(I != livein_end() && "Not a live in!"); + std::vector::iterator I = + std::find(LiveIns.begin(), LiveIns.end(), Reg); + assert(I != LiveIns.end() && "Not a live in!"); LiveIns.erase(I); } bool MachineBasicBlock::isLiveIn(unsigned Reg) const { - const_livein_iterator I = std::find(livein_begin(), livein_end(), Reg); + livein_iterator I = std::find(livein_begin(), livein_end(), Reg); return I != livein_end(); } @@ -244,6 +267,65 @@ void MachineBasicBlock::moveAfter(MachineBasicBlock *NewBefore) { getParent()->splice(++BBI, this); } +void MachineBasicBlock::updateTerminator() { + const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo(); + // A block with no successors has no concerns with fall-through edges. + if (this->succ_empty()) return; + + MachineBasicBlock *TBB = 0, *FBB = 0; + SmallVector Cond; + DebugLoc dl; // FIXME: this is nowhere + bool B = TII->AnalyzeBranch(*this, TBB, FBB, Cond); + (void) B; + assert(!B && "UpdateTerminators requires analyzable predecessors!"); + if (Cond.empty()) { + if (TBB) { + // The block has an unconditional branch. If its successor is now + // its layout successor, delete the branch. + if (isLayoutSuccessor(TBB)) + TII->RemoveBranch(*this); + } else { + // The block has an unconditional fallthrough. If its successor is not + // its layout successor, insert a branch. + TBB = *succ_begin(); + if (!isLayoutSuccessor(TBB)) + TII->InsertBranch(*this, TBB, 0, Cond, dl); + } + } else { + if (FBB) { + // The block has a non-fallthrough conditional branch. If one of its + // successors is its layout successor, rewrite it to a fallthrough + // conditional branch. + if (isLayoutSuccessor(TBB)) { + if (TII->ReverseBranchCondition(Cond)) + return; + TII->RemoveBranch(*this); + TII->InsertBranch(*this, FBB, 0, Cond, dl); + } else if (isLayoutSuccessor(FBB)) { + TII->RemoveBranch(*this); + TII->InsertBranch(*this, TBB, 0, Cond, dl); + } + } else { + // The block has a fallthrough conditional branch. + MachineBasicBlock *MBBA = *succ_begin(); + MachineBasicBlock *MBBB = *llvm::next(succ_begin()); + if (MBBA == TBB) std::swap(MBBB, MBBA); + if (isLayoutSuccessor(TBB)) { + if (TII->ReverseBranchCondition(Cond)) { + // We can't reverse the condition, add an unconditional branch. + Cond.clear(); + TII->InsertBranch(*this, MBBA, 0, Cond, dl); + return; + } + TII->RemoveBranch(*this); + TII->InsertBranch(*this, MBBA, 0, Cond, dl); + } else if (!isLayoutSuccessor(MBBA)) { + TII->RemoveBranch(*this); + TII->InsertBranch(*this, TBB, MBBA, Cond, dl); + } + } + } +} void MachineBasicBlock::addSuccessor(MachineBasicBlock *succ) { Successors.push_back(succ); @@ -279,12 +361,32 @@ void MachineBasicBlock::transferSuccessors(MachineBasicBlock *fromMBB) { if (this == fromMBB) return; - for (MachineBasicBlock::succ_iterator I = fromMBB->succ_begin(), - E = fromMBB->succ_end(); I != E; ++I) - addSuccessor(*I); + while (!fromMBB->succ_empty()) { + MachineBasicBlock *Succ = *fromMBB->succ_begin(); + addSuccessor(Succ); + fromMBB->removeSuccessor(Succ); + } +} + +void +MachineBasicBlock::transferSuccessorsAndUpdatePHIs(MachineBasicBlock *fromMBB) { + if (this == fromMBB) + return; - while (!fromMBB->succ_empty()) - fromMBB->removeSuccessor(fromMBB->succ_begin()); + while (!fromMBB->succ_empty()) { + MachineBasicBlock *Succ = *fromMBB->succ_begin(); + addSuccessor(Succ); + fromMBB->removeSuccessor(Succ); + + // Fix up any PHI nodes in the successor. + for (MachineBasicBlock::iterator MI = Succ->begin(), ME = Succ->end(); + MI != ME && MI->isPHI(); ++MI) + for (unsigned i = 2, e = MI->getNumOperands()+1; i != e; i += 2) { + MachineOperand &MO = MI->getOperand(i); + if (MO.getMBB() == fromMBB) + MO.setMBB(this); + } + } } bool MachineBasicBlock::isSuccessor(const MachineBasicBlock *MBB) const { @@ -295,7 +397,160 @@ bool MachineBasicBlock::isSuccessor(const MachineBasicBlock *MBB) const { bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const { MachineFunction::const_iterator I(this); - return next(I) == MachineFunction::const_iterator(MBB); + return llvm::next(I) == MachineFunction::const_iterator(MBB); +} + +bool MachineBasicBlock::canFallThrough() { + MachineFunction::iterator Fallthrough = this; + ++Fallthrough; + // If FallthroughBlock is off the end of the function, it can't fall through. + if (Fallthrough == getParent()->end()) + return false; + + // If FallthroughBlock isn't a successor, no fallthrough is possible. + if (!isSuccessor(Fallthrough)) + return false; + + // Analyze the branches, if any, at the end of the block. + MachineBasicBlock *TBB = 0, *FBB = 0; + SmallVector Cond; + const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo(); + if (TII->AnalyzeBranch(*this, TBB, FBB, Cond)) { + // If we couldn't analyze the branch, examine the last instruction. + // If the block doesn't end in a known control barrier, assume fallthrough + // is possible. The isPredicable check is needed because this code can be + // called during IfConversion, where an instruction which is normally a + // Barrier is predicated and thus no longer an actual control barrier. This + // is over-conservative though, because if an instruction isn't actually + // predicated we could still treat it like a barrier. + return empty() || !back().getDesc().isBarrier() || + back().getDesc().isPredicable(); + } + + // If there is no branch, control always falls through. + if (TBB == 0) return true; + + // If there is some explicit branch to the fallthrough block, it can obviously + // reach, even though the branch should get folded to fall through implicitly. + if (MachineFunction::iterator(TBB) == Fallthrough || + MachineFunction::iterator(FBB) == Fallthrough) + return true; + + // If it's an unconditional branch to some block not the fall through, it + // doesn't fall through. + if (Cond.empty()) return false; + + // Otherwise, if it is conditional and has no explicit false block, it falls + // through. + return FBB == 0; +} + +MachineBasicBlock * +MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) { + MachineFunction *MF = getParent(); + DebugLoc dl; // FIXME: this is nowhere + + // We may need to update this's terminator, but we can't do that if + // AnalyzeBranch fails. If this uses a jump table, we won't touch it. + const TargetInstrInfo *TII = MF->getTarget().getInstrInfo(); + MachineBasicBlock *TBB = 0, *FBB = 0; + SmallVector Cond; + if (TII->AnalyzeBranch(*this, TBB, FBB, Cond)) + return NULL; + + // Avoid bugpoint weirdness: A block may end with a conditional branch but + // jumps to the same MBB is either case. We have duplicate CFG edges in that + // case that we can't handle. Since this never happens in properly optimized + // code, just skip those edges. + if (TBB && TBB == FBB) { + DEBUG(dbgs() << "Won't split critical edge after degenerate BB#" + << getNumber() << '\n'); + return NULL; + } + + MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock(); + MF->insert(llvm::next(MachineFunction::iterator(this)), NMBB); + DEBUG(dbgs() << "Splitting critical edge:" + " BB#" << getNumber() + << " -- BB#" << NMBB->getNumber() + << " -- BB#" << Succ->getNumber() << '\n'); + + ReplaceUsesOfBlockWith(Succ, NMBB); + updateTerminator(); + + // Insert unconditional "jump Succ" instruction in NMBB if necessary. + NMBB->addSuccessor(Succ); + if (!NMBB->isLayoutSuccessor(Succ)) { + Cond.clear(); + MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, Succ, NULL, Cond, dl); + } + + // Fix PHI nodes in Succ so they refer to NMBB instead of this + for (MachineBasicBlock::iterator i = Succ->begin(), e = Succ->end(); + i != e && i->isPHI(); ++i) + for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2) + if (i->getOperand(ni+1).getMBB() == this) + i->getOperand(ni+1).setMBB(NMBB); + + if (LiveVariables *LV = + P->getAnalysisIfAvailable()) + LV->addNewBlock(NMBB, this, Succ); + + if (MachineDominatorTree *MDT = + P->getAnalysisIfAvailable()) { + // Update dominator information. + MachineDomTreeNode *SucccDTNode = MDT->getNode(Succ); + + bool IsNewIDom = true; + for (const_pred_iterator PI = Succ->pred_begin(), E = Succ->pred_end(); + PI != E; ++PI) { + MachineBasicBlock *PredBB = *PI; + if (PredBB == NMBB) + continue; + if (!MDT->dominates(SucccDTNode, MDT->getNode(PredBB))) { + IsNewIDom = false; + break; + } + } + + // We know "this" dominates the newly created basic block. + MachineDomTreeNode *NewDTNode = MDT->addNewBlock(NMBB, this); + + // If all the other predecessors of "Succ" are dominated by "Succ" itself + // then the new block is the new immediate dominator of "Succ". Otherwise, + // the new block doesn't dominate anything. + if (IsNewIDom) + MDT->changeImmediateDominator(SucccDTNode, NewDTNode); + } + + if (MachineLoopInfo *MLI = P->getAnalysisIfAvailable()) + if (MachineLoop *TIL = MLI->getLoopFor(this)) { + // If one or the other blocks were not in a loop, the new block is not + // either, and thus LI doesn't need to be updated. + if (MachineLoop *DestLoop = MLI->getLoopFor(Succ)) { + if (TIL == DestLoop) { + // Both in the same loop, the NMBB joins loop. + DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase()); + } else if (TIL->contains(DestLoop)) { + // Edge from an outer loop to an inner loop. Add to the outer loop. + TIL->addBasicBlockToLoop(NMBB, MLI->getBase()); + } else if (DestLoop->contains(TIL)) { + // Edge from an inner loop to an outer loop. Add to the outer loop. + DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase()); + } else { + // Edge from two loops with no containment relation. Because these + // are natural loops, we know that the destination block must be the + // header of its loop (adding a branch into a loop elsewhere would + // create an irreducible loop). + assert(DestLoop->getHeader() == Succ && + "Should not create irreducible loops!"); + if (MachineLoop *P = DestLoop->getParentLoop()) + P->addBasicBlockToLoop(NMBB, MLI->getBase()); + } + } + } + + return NMBB; } /// removeFromParent - This method unlinks 'this' from the containing function, @@ -341,61 +596,85 @@ void MachineBasicBlock::ReplaceUsesOfBlockWith(MachineBasicBlock *Old, /// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in the /// CFG to be inserted. If we have proven that MBB can only branch to DestA and -/// DestB, remove any other MBB successors from the CFG. DestA and DestB can -/// be null. +/// DestB, remove any other MBB successors from the CFG. DestA and DestB can be +/// null. +/// /// Besides DestA and DestB, retain other edges leading to LandingPads /// (currently there can be only one; we don't check or require that here). /// Note it is possible that DestA and/or DestB are LandingPads. bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA, MachineBasicBlock *DestB, bool isCond) { - bool MadeChange = false; - bool AddedFallThrough = false; - - MachineFunction::iterator FallThru = next(MachineFunction::iterator(this)); - - // If this block ends with a conditional branch that falls through to its - // successor, set DestB as the successor. - if (isCond) { - if (DestB == 0 && FallThru != getParent()->end()) { + // The values of DestA and DestB frequently come from a call to the + // 'TargetInstrInfo::AnalyzeBranch' method. We take our meaning of the initial + // values from there. + // + // 1. If both DestA and DestB are null, then the block ends with no branches + // (it falls through to its successor). + // 2. If DestA is set, DestB is null, and isCond is false, then the block ends + // with only an unconditional branch. + // 3. If DestA is set, DestB is null, and isCond is true, then the block ends + // with a conditional branch that falls through to a successor (DestB). + // 4. If DestA and DestB is set and isCond is true, then the block ends with a + // conditional branch followed by an unconditional branch. DestA is the + // 'true' destination and DestB is the 'false' destination. + + bool Changed = false; + + MachineFunction::iterator FallThru = + llvm::next(MachineFunction::iterator(this)); + + if (DestA == 0 && DestB == 0) { + // Block falls through to successor. + DestA = FallThru; + DestB = FallThru; + } else if (DestA != 0 && DestB == 0) { + if (isCond) + // Block ends in conditional jump that falls through to successor. DestB = FallThru; - AddedFallThrough = true; - } } else { - // If this is an unconditional branch with no explicit dest, it must just be - // a fallthrough into DestB. - if (DestA == 0 && FallThru != getParent()->end()) { - DestA = FallThru; - AddedFallThrough = true; - } + assert(DestA && DestB && isCond && + "CFG in a bad state. Cannot correct CFG edges"); } - + + // Remove superfluous edges. I.e., those which aren't destinations of this + // basic block, duplicate edges, or landing pads. + SmallPtrSet SeenMBBs; MachineBasicBlock::succ_iterator SI = succ_begin(); - MachineBasicBlock *OrigDestA = DestA, *OrigDestB = DestB; while (SI != succ_end()) { - if (*SI == DestA && DestA == DestB) { - DestA = DestB = 0; - ++SI; - } else if (*SI == DestA) { - DestA = 0; - ++SI; - } else if (*SI == DestB) { - DestB = 0; - ++SI; - } else if ((*SI)->isLandingPad() && - *SI!=OrigDestA && *SI!=OrigDestB) { - ++SI; - } else { - // Otherwise, this is a superfluous edge, remove it. + const MachineBasicBlock *MBB = *SI; + if (!SeenMBBs.insert(MBB) || + (MBB != DestA && MBB != DestB && !MBB->isLandingPad())) { + // This is a superfluous edge, remove it. SI = removeSuccessor(SI); - MadeChange = true; + Changed = true; + } else { + ++SI; } } - if (!AddedFallThrough) { - assert(DestA == 0 && DestB == 0 && - "MachineCFG is missing edges!"); - } else if (isCond) { - assert(DestA == 0 && "MachineCFG is missing edges!"); + + return Changed; +} + +/// findDebugLoc - find the next valid DebugLoc starting at MBBI, skipping +/// any DBG_VALUE instructions. Return UnknownLoc if there is none. +DebugLoc +MachineBasicBlock::findDebugLoc(MachineBasicBlock::iterator &MBBI) { + DebugLoc DL; + MachineBasicBlock::iterator E = end(); + if (MBBI != E) { + // Skip debug declarations, we don't want a DebugLoc from them. + MachineBasicBlock::iterator MBBI2 = MBBI; + while (MBBI2 != E && MBBI2->isDebugValue()) + MBBI2++; + if (MBBI2 != E) + DL = MBBI2->getDebugLoc(); } - return MadeChange; + return DL; } + +void llvm::WriteAsOperand(raw_ostream &OS, const MachineBasicBlock *MBB, + bool t) { + OS << "BB#" << MBB->getNumber(); +} +