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//===-- llvm/CodeGen/MachineBasicBlock.cpp ----------------------*- C++ -*-===//
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// The LLVM Compiler Infrastructure
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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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// Collect the sequence of machine instructions for a basic block.
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/MachineBasicBlock.h"
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#include "llvm/BasicBlock.h"
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#include "llvm/CodeGen/LiveVariables.h"
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#include "llvm/CodeGen/MachineDominators.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/CodeGen/MachineLoopInfo.h"
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#include "llvm/MC/MCAsmInfo.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/Target/TargetRegisterInfo.h"
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#include "llvm/Target/TargetData.h"
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#include "llvm/Target/TargetInstrDesc.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Assembly/Writer.h"
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#include "llvm/ADT/SmallString.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/LeakDetector.h"
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#include "llvm/Support/raw_ostream.h"
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MachineBasicBlock::MachineBasicBlock(MachineFunction &mf, const BasicBlock *bb)
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: BB(bb), Number(-1), xParent(&mf), Alignment(0), IsLandingPad(false),
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MachineBasicBlock::~MachineBasicBlock() {
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LeakDetector::removeGarbageObject(this);
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/// getSymbol - Return the MCSymbol for this basic block.
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MCSymbol *MachineBasicBlock::getSymbol() const {
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const MachineFunction *MF = getParent();
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MCContext &Ctx = MF->getContext();
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const char *Prefix = Ctx.getAsmInfo().getPrivateGlobalPrefix();
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return Ctx.GetOrCreateSymbol(Twine(Prefix) + "BB" +
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Twine(MF->getFunctionNumber()) + "_" +
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raw_ostream &llvm::operator<<(raw_ostream &OS, const MachineBasicBlock &MBB) {
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/// addNodeToList (MBB) - When an MBB is added to an MF, we need to update the
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/// parent pointer of the MBB, the MBB numbering, and any instructions in the
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/// MBB to be on the right operand list for registers.
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/// MBBs start out as #-1. When a MBB is added to a MachineFunction, it
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/// gets the next available unique MBB number. If it is removed from a
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/// MachineFunction, it goes back to being #-1.
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void ilist_traits<MachineBasicBlock>::addNodeToList(MachineBasicBlock *N) {
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MachineFunction &MF = *N->getParent();
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N->Number = MF.addToMBBNumbering(N);
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// Make sure the instructions have their operands in the reginfo lists.
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MachineRegisterInfo &RegInfo = MF.getRegInfo();
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for (MachineBasicBlock::iterator I = N->begin(), E = N->end(); I != E; ++I)
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I->AddRegOperandsToUseLists(RegInfo);
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LeakDetector::removeGarbageObject(N);
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void ilist_traits<MachineBasicBlock>::removeNodeFromList(MachineBasicBlock *N) {
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N->getParent()->removeFromMBBNumbering(N->Number);
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LeakDetector::addGarbageObject(N);
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/// addNodeToList (MI) - When we add an instruction to a basic block
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/// list, we update its parent pointer and add its operands from reg use/def
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/// lists if appropriate.
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void ilist_traits<MachineInstr>::addNodeToList(MachineInstr *N) {
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assert(N->getParent() == 0 && "machine instruction already in a basic block");
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// Add the instruction's register operands to their corresponding
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MachineFunction *MF = Parent->getParent();
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N->AddRegOperandsToUseLists(MF->getRegInfo());
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LeakDetector::removeGarbageObject(N);
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/// removeNodeFromList (MI) - When we remove an instruction from a basic block
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/// list, we update its parent pointer and remove its operands from reg use/def
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/// lists if appropriate.
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void ilist_traits<MachineInstr>::removeNodeFromList(MachineInstr *N) {
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assert(N->getParent() != 0 && "machine instruction not in a basic block");
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// Remove from the use/def lists.
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N->RemoveRegOperandsFromUseLists();
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LeakDetector::addGarbageObject(N);
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/// transferNodesFromList (MI) - When moving a range of instructions from one
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/// MBB list to another, we need to update the parent pointers and the use/def
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void ilist_traits<MachineInstr>::
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transferNodesFromList(ilist_traits<MachineInstr> &fromList,
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MachineBasicBlock::iterator first,
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MachineBasicBlock::iterator last) {
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assert(Parent->getParent() == fromList.Parent->getParent() &&
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"MachineInstr parent mismatch!");
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// Splice within the same MBB -> no change.
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if (Parent == fromList.Parent) return;
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// If splicing between two blocks within the same function, just update the
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for (; first != last; ++first)
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first->setParent(Parent);
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void ilist_traits<MachineInstr>::deleteNode(MachineInstr* MI) {
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assert(!MI->getParent() && "MI is still in a block!");
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Parent->getParent()->DeleteMachineInstr(MI);
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MachineBasicBlock::iterator MachineBasicBlock::getFirstNonPHI() {
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iterator I = begin();
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while (I != end() && I->isPHI())
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MachineBasicBlock::iterator MachineBasicBlock::getFirstTerminator() {
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while (I != begin() && (--I)->getDesc().isTerminator())
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if (I != end() && !I->getDesc().isTerminator()) ++I;
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void MachineBasicBlock::dump() const {
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static inline void OutputReg(raw_ostream &os, unsigned RegNo,
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const TargetRegisterInfo *TRI = 0) {
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if (RegNo != 0 && TargetRegisterInfo::isPhysicalRegister(RegNo)) {
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os << " %" << TRI->get(RegNo).Name;
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os << " %physreg" << RegNo;
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os << " %reg" << RegNo;
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StringRef MachineBasicBlock::getName() const {
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if (const BasicBlock *LBB = getBasicBlock())
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return LBB->getName();
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void MachineBasicBlock::print(raw_ostream &OS) const {
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const MachineFunction *MF = getParent();
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OS << "Can't print out MachineBasicBlock because parent MachineFunction"
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if (Alignment) { OS << "Alignment " << Alignment << "\n"; }
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OS << "BB#" << getNumber() << ": ";
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const char *Comma = "";
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if (const BasicBlock *LBB = getBasicBlock()) {
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OS << Comma << "derived from LLVM BB ";
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WriteAsOperand(OS, LBB, /*PrintType=*/false);
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if (isLandingPad()) { OS << Comma << "EH LANDING PAD"; Comma = ", "; }
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if (hasAddressTaken()) { OS << Comma << "ADDRESS TAKEN"; Comma = ", "; }
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const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo();
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if (!livein_empty()) {
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for (livein_iterator I = livein_begin(),E = livein_end(); I != E; ++I)
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OutputReg(OS, *I, TRI);
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// Print the preds of this block according to the CFG.
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OS << " Predecessors according to CFG:";
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for (const_pred_iterator PI = pred_begin(), E = pred_end(); PI != E; ++PI)
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OS << " BB#" << (*PI)->getNumber();
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for (const_iterator I = begin(); I != end(); ++I) {
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I->print(OS, &getParent()->getTarget());
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// Print the successors of this block according to the CFG.
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OS << " Successors according to CFG:";
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for (const_succ_iterator SI = succ_begin(), E = succ_end(); SI != E; ++SI)
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OS << " BB#" << (*SI)->getNumber();
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void MachineBasicBlock::removeLiveIn(unsigned Reg) {
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std::vector<unsigned>::iterator I =
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std::find(LiveIns.begin(), LiveIns.end(), Reg);
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assert(I != LiveIns.end() && "Not a live in!");
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bool MachineBasicBlock::isLiveIn(unsigned Reg) const {
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livein_iterator I = std::find(livein_begin(), livein_end(), Reg);
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return I != livein_end();
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void MachineBasicBlock::moveBefore(MachineBasicBlock *NewAfter) {
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getParent()->splice(NewAfter, this);
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void MachineBasicBlock::moveAfter(MachineBasicBlock *NewBefore) {
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MachineFunction::iterator BBI = NewBefore;
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getParent()->splice(++BBI, this);
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void MachineBasicBlock::updateTerminator() {
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const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo();
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// A block with no successors has no concerns with fall-through edges.
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if (this->succ_empty()) return;
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MachineBasicBlock *TBB = 0, *FBB = 0;
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SmallVector<MachineOperand, 4> Cond;
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DebugLoc dl; // FIXME: this is nowhere
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bool B = TII->AnalyzeBranch(*this, TBB, FBB, Cond);
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assert(!B && "UpdateTerminators requires analyzable predecessors!");
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// The block has an unconditional branch. If its successor is now
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// its layout successor, delete the branch.
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if (isLayoutSuccessor(TBB))
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TII->RemoveBranch(*this);
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// The block has an unconditional fallthrough. If its successor is not
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// its layout successor, insert a branch.
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if (!isLayoutSuccessor(TBB))
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TII->InsertBranch(*this, TBB, 0, Cond, dl);
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// The block has a non-fallthrough conditional branch. If one of its
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// successors is its layout successor, rewrite it to a fallthrough
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// conditional branch.
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if (isLayoutSuccessor(TBB)) {
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if (TII->ReverseBranchCondition(Cond))
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TII->RemoveBranch(*this);
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TII->InsertBranch(*this, FBB, 0, Cond, dl);
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} else if (isLayoutSuccessor(FBB)) {
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TII->RemoveBranch(*this);
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TII->InsertBranch(*this, TBB, 0, Cond, dl);
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// The block has a fallthrough conditional branch.
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MachineBasicBlock *MBBA = *succ_begin();
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MachineBasicBlock *MBBB = *llvm::next(succ_begin());
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if (MBBA == TBB) std::swap(MBBB, MBBA);
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if (isLayoutSuccessor(TBB)) {
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if (TII->ReverseBranchCondition(Cond)) {
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// We can't reverse the condition, add an unconditional branch.
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TII->InsertBranch(*this, MBBA, 0, Cond, dl);
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TII->RemoveBranch(*this);
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TII->InsertBranch(*this, MBBA, 0, Cond, dl);
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} else if (!isLayoutSuccessor(MBBA)) {
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TII->RemoveBranch(*this);
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TII->InsertBranch(*this, TBB, MBBA, Cond, dl);
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void MachineBasicBlock::addSuccessor(MachineBasicBlock *succ) {
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Successors.push_back(succ);
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succ->addPredecessor(this);
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void MachineBasicBlock::removeSuccessor(MachineBasicBlock *succ) {
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succ->removePredecessor(this);
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succ_iterator I = std::find(Successors.begin(), Successors.end(), succ);
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assert(I != Successors.end() && "Not a current successor!");
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MachineBasicBlock::succ_iterator
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MachineBasicBlock::removeSuccessor(succ_iterator I) {
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assert(I != Successors.end() && "Not a current successor!");
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(*I)->removePredecessor(this);
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return Successors.erase(I);
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void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) {
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Predecessors.push_back(pred);
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void MachineBasicBlock::removePredecessor(MachineBasicBlock *pred) {
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std::vector<MachineBasicBlock *>::iterator I =
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std::find(Predecessors.begin(), Predecessors.end(), pred);
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assert(I != Predecessors.end() && "Pred is not a predecessor of this block!");
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Predecessors.erase(I);
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void MachineBasicBlock::transferSuccessors(MachineBasicBlock *fromMBB) {
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while (!fromMBB->succ_empty()) {
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MachineBasicBlock *Succ = *fromMBB->succ_begin();
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fromMBB->removeSuccessor(Succ);
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MachineBasicBlock::transferSuccessorsAndUpdatePHIs(MachineBasicBlock *fromMBB) {
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while (!fromMBB->succ_empty()) {
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MachineBasicBlock *Succ = *fromMBB->succ_begin();
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fromMBB->removeSuccessor(Succ);
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// Fix up any PHI nodes in the successor.
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for (MachineBasicBlock::iterator MI = Succ->begin(), ME = Succ->end();
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MI != ME && MI->isPHI(); ++MI)
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for (unsigned i = 2, e = MI->getNumOperands()+1; i != e; i += 2) {
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MachineOperand &MO = MI->getOperand(i);
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if (MO.getMBB() == fromMBB)
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bool MachineBasicBlock::isSuccessor(const MachineBasicBlock *MBB) const {
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std::vector<MachineBasicBlock *>::const_iterator I =
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std::find(Successors.begin(), Successors.end(), MBB);
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return I != Successors.end();
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bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const {
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MachineFunction::const_iterator I(this);
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return llvm::next(I) == MachineFunction::const_iterator(MBB);
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bool MachineBasicBlock::canFallThrough() {
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MachineFunction::iterator Fallthrough = this;
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// If FallthroughBlock is off the end of the function, it can't fall through.
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if (Fallthrough == getParent()->end())
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// If FallthroughBlock isn't a successor, no fallthrough is possible.
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if (!isSuccessor(Fallthrough))
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// Analyze the branches, if any, at the end of the block.
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MachineBasicBlock *TBB = 0, *FBB = 0;
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SmallVector<MachineOperand, 4> Cond;
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const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo();
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if (TII->AnalyzeBranch(*this, TBB, FBB, Cond)) {
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// If we couldn't analyze the branch, examine the last instruction.
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// If the block doesn't end in a known control barrier, assume fallthrough
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// is possible. The isPredicable check is needed because this code can be
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// called during IfConversion, where an instruction which is normally a
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// Barrier is predicated and thus no longer an actual control barrier. This
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// is over-conservative though, because if an instruction isn't actually
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// predicated we could still treat it like a barrier.
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return empty() || !back().getDesc().isBarrier() ||
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back().getDesc().isPredicable();
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// If there is no branch, control always falls through.
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if (TBB == 0) return true;
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// If there is some explicit branch to the fallthrough block, it can obviously
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// reach, even though the branch should get folded to fall through implicitly.
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if (MachineFunction::iterator(TBB) == Fallthrough ||
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MachineFunction::iterator(FBB) == Fallthrough)
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// If it's an unconditional branch to some block not the fall through, it
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// doesn't fall through.
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if (Cond.empty()) return false;
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// Otherwise, if it is conditional and has no explicit false block, it falls
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MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) {
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MachineFunction *MF = getParent();
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DebugLoc dl; // FIXME: this is nowhere
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// We may need to update this's terminator, but we can't do that if AnalyzeBranch
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// fails. If this uses a jump table, we won't touch it.
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const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
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MachineBasicBlock *TBB = 0, *FBB = 0;
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SmallVector<MachineOperand, 4> Cond;
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if (TII->AnalyzeBranch(*this, TBB, FBB, Cond))
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MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock();
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MF->insert(llvm::next(MachineFunction::iterator(this)), NMBB);
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DEBUG(dbgs() << "Splitting critical edge:"
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" BB#" << getNumber()
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<< " -- BB#" << NMBB->getNumber()
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<< " -- BB#" << Succ->getNumber() << '\n');
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ReplaceUsesOfBlockWith(Succ, NMBB);
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// Insert unconditional "jump Succ" instruction in NMBB if necessary.
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NMBB->addSuccessor(Succ);
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if (!NMBB->isLayoutSuccessor(Succ)) {
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MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, Succ, NULL, Cond, dl);
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// Fix PHI nodes in Succ so they refer to NMBB instead of this
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for (MachineBasicBlock::iterator i = Succ->begin(), e = Succ->end();
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i != e && i->isPHI(); ++i)
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for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2)
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if (i->getOperand(ni+1).getMBB() == this)
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i->getOperand(ni+1).setMBB(NMBB);
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if (LiveVariables *LV =
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P->getAnalysisIfAvailable<LiveVariables>())
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LV->addNewBlock(NMBB, this, Succ);
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if (MachineDominatorTree *MDT =
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P->getAnalysisIfAvailable<MachineDominatorTree>()) {
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// Update dominator information.
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MachineDomTreeNode *SucccDTNode = MDT->getNode(Succ);
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bool IsNewIDom = true;
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for (const_pred_iterator PI = Succ->pred_begin(), E = Succ->pred_end();
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MachineBasicBlock *PredBB = *PI;
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if (!MDT->dominates(SucccDTNode, MDT->getNode(PredBB))) {
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// We know "this" dominates the newly created basic block.
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MachineDomTreeNode *NewDTNode = MDT->addNewBlock(NMBB, this);
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// If all the other predecessors of "Succ" are dominated by "Succ" itself
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// then the new block is the new immediate dominator of "Succ". Otherwise,
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// the new block doesn't dominate anything.
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MDT->changeImmediateDominator(SucccDTNode, NewDTNode);
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if (MachineLoopInfo *MLI = P->getAnalysisIfAvailable<MachineLoopInfo>())
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if (MachineLoop *TIL = MLI->getLoopFor(this)) {
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// If one or the other blocks were not in a loop, the new block is not
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// either, and thus LI doesn't need to be updated.
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if (MachineLoop *DestLoop = MLI->getLoopFor(Succ)) {
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if (TIL == DestLoop) {
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// Both in the same loop, the NMBB joins loop.
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DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase());
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} else if (TIL->contains(DestLoop)) {
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// Edge from an outer loop to an inner loop. Add to the outer loop.
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TIL->addBasicBlockToLoop(NMBB, MLI->getBase());
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} else if (DestLoop->contains(TIL)) {
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// Edge from an inner loop to an outer loop. Add to the outer loop.
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DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase());
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// Edge from two loops with no containment relation. Because these
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// are natural loops, we know that the destination block must be the
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// header of its loop (adding a branch into a loop elsewhere would
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// create an irreducible loop).
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assert(DestLoop->getHeader() == Succ &&
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"Should not create irreducible loops!");
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if (MachineLoop *P = DestLoop->getParentLoop())
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P->addBasicBlockToLoop(NMBB, MLI->getBase());
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/// removeFromParent - This method unlinks 'this' from the containing function,
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/// and returns it, but does not delete it.
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MachineBasicBlock *MachineBasicBlock::removeFromParent() {
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assert(getParent() && "Not embedded in a function!");
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getParent()->remove(this);
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/// eraseFromParent - This method unlinks 'this' from the containing function,
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void MachineBasicBlock::eraseFromParent() {
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assert(getParent() && "Not embedded in a function!");
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getParent()->erase(this);
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/// ReplaceUsesOfBlockWith - Given a machine basic block that branched to
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/// 'Old', change the code and CFG so that it branches to 'New' instead.
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void MachineBasicBlock::ReplaceUsesOfBlockWith(MachineBasicBlock *Old,
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MachineBasicBlock *New) {
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assert(Old != New && "Cannot replace self with self!");
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MachineBasicBlock::iterator I = end();
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while (I != begin()) {
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if (!I->getDesc().isTerminator()) break;
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// Scan the operands of this machine instruction, replacing any uses of Old
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for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
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if (I->getOperand(i).isMBB() &&
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I->getOperand(i).getMBB() == Old)
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I->getOperand(i).setMBB(New);
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// Update the successor information.
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removeSuccessor(Old);
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/// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in the
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/// CFG to be inserted. If we have proven that MBB can only branch to DestA and
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/// DestB, remove any other MBB successors from the CFG. DestA and DestB can be
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/// Besides DestA and DestB, retain other edges leading to LandingPads
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/// (currently there can be only one; we don't check or require that here).
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/// Note it is possible that DestA and/or DestB are LandingPads.
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bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA,
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MachineBasicBlock *DestB,
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// The values of DestA and DestB frequently come from a call to the
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// 'TargetInstrInfo::AnalyzeBranch' method. We take our meaning of the initial
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// values from there.
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// 1. If both DestA and DestB are null, then the block ends with no branches
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// (it falls through to its successor).
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// 2. If DestA is set, DestB is null, and isCond is false, then the block ends
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// with only an unconditional branch.
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// 3. If DestA is set, DestB is null, and isCond is true, then the block ends
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// with a conditional branch that falls through to a successor (DestB).
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// 4. If DestA and DestB is set and isCond is true, then the block ends with a
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// conditional branch followed by an unconditional branch. DestA is the
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// 'true' destination and DestB is the 'false' destination.
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bool Changed = false;
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MachineFunction::iterator FallThru =
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llvm::next(MachineFunction::iterator(this));
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if (DestA == 0 && DestB == 0) {
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// Block falls through to successor.
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} else if (DestA != 0 && DestB == 0) {
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// Block ends in conditional jump that falls through to successor.
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assert(DestA && DestB && isCond &&
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"CFG in a bad state. Cannot correct CFG edges");
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// Remove superfluous edges. I.e., those which aren't destinations of this
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// basic block, duplicate edges, or landing pads.
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SmallPtrSet<const MachineBasicBlock*, 8> SeenMBBs;
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MachineBasicBlock::succ_iterator SI = succ_begin();
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while (SI != succ_end()) {
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const MachineBasicBlock *MBB = *SI;
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if (!SeenMBBs.insert(MBB) ||
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(MBB != DestA && MBB != DestB && !MBB->isLandingPad())) {
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// This is a superfluous edge, remove it.
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SI = removeSuccessor(SI);
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/// findDebugLoc - find the next valid DebugLoc starting at MBBI, skipping
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/// any DBG_VALUE instructions. Return UnknownLoc if there is none.
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MachineBasicBlock::findDebugLoc(MachineBasicBlock::iterator &MBBI) {
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MachineBasicBlock::iterator E = end();
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// Skip debug declarations, we don't want a DebugLoc from them.
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MachineBasicBlock::iterator MBBI2 = MBBI;
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while (MBBI2 != E && MBBI2->isDebugValue())
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DL = MBBI2->getDebugLoc();
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void llvm::WriteAsOperand(raw_ostream &OS, const MachineBasicBlock *MBB,
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OS << "BB#" << MBB->getNumber();
added
removed
libclamav/c++/llvm/lib/CodeGen/MachineBasicBlock.cpp
