400 lines
13 KiB
C++
400 lines
13 KiB
C++
//===-- llvm/CodeGen/MachineBasicBlock.cpp ----------------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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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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//===----------------------------------------------------------------------===//
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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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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/MachineBasicBlock.h"
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#include "llvm/BasicBlock.h"
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#include "llvm/CodeGen/MachineFunction.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/TargetMachine.h"
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#include "llvm/Support/LeakDetector.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Assembly/Writer.h"
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#include <algorithm>
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using namespace llvm;
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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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AddressTaken(false) {
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Insts.Parent = this;
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}
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MachineBasicBlock::~MachineBasicBlock() {
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LeakDetector::removeGarbageObject(this);
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}
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raw_ostream &llvm::operator<<(raw_ostream &OS, const MachineBasicBlock &MBB) {
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MBB.print(OS);
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return OS;
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}
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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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///
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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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}
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void ilist_traits<MachineBasicBlock>::removeNodeFromList(MachineBasicBlock *N) {
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N->getParent()->removeFromMBBNumbering(N->Number);
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N->Number = -1;
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LeakDetector::addGarbageObject(N);
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}
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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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N->setParent(Parent);
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// Add the instruction's register operands to their corresponding
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// use/def lists.
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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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}
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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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N->setParent(0);
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LeakDetector::addGarbageObject(N);
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}
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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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/// lists.
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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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// parent pointers.
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for (; first != last; ++first)
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first->setParent(Parent);
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}
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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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}
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MachineBasicBlock::iterator MachineBasicBlock::getFirstTerminator() {
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iterator I = end();
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while (I != begin() && (--I)->getDesc().isTerminator())
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; /*noop */
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if (I != end() && !I->getDesc().isTerminator()) ++I;
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return I;
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}
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/// isOnlyReachableViaFallthough - Return true if this basic block has
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/// exactly one predecessor and the control transfer mechanism between
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/// the predecessor and this block is a fall-through.
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bool MachineBasicBlock::isOnlyReachableByFallthrough() const {
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// If this is a landing pad, it isn't a fall through. If it has no preds,
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// then nothing falls through to it.
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if (isLandingPad() || pred_empty())
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return false;
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// If there isn't exactly one predecessor, it can't be a fall through.
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const_pred_iterator PI = pred_begin(), PI2 = PI;
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++PI2;
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if (PI2 != pred_end())
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return false;
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// The predecessor has to be immediately before this block.
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const MachineBasicBlock *Pred = *PI;
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if (!Pred->isLayoutSuccessor(this))
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return false;
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// If the block is completely empty, then it definitely does fall through.
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if (Pred->empty())
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return true;
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// Otherwise, check the last instruction.
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const MachineInstr &LastInst = Pred->back();
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return !LastInst.getDesc().isBarrier();
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}
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void MachineBasicBlock::dump() const {
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print(errs());
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}
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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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if (TRI)
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os << " %" << TRI->get(RegNo).Name;
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else
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os << " %physreg" << RegNo;
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} else
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os << " %reg" << RegNo;
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}
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void MachineBasicBlock::print(raw_ostream &OS) const {
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const MachineFunction *MF = getParent();
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if (!MF) {
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OS << "Can't print out MachineBasicBlock because parent MachineFunction"
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<< " is null\n";
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return;
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}
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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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Comma = ", ";
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}
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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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OS << '\n';
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const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo();
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if (!livein_empty()) {
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OS << " Live Ins:";
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for (const_livein_iterator I = livein_begin(),E = livein_end(); I != E; ++I)
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OutputReg(OS, *I, TRI);
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OS << '\n';
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}
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// Print the preds of this block according to the CFG.
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if (!pred_empty()) {
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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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OS << '\n';
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}
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for (const_iterator I = begin(); I != end(); ++I) {
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OS << '\t';
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I->print(OS, &getParent()->getTarget());
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}
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// Print the successors of this block according to the CFG.
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if (!succ_empty()) {
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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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OS << '\n';
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}
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}
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void MachineBasicBlock::removeLiveIn(unsigned Reg) {
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livein_iterator I = std::find(livein_begin(), livein_end(), Reg);
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assert(I != livein_end() && "Not a live in!");
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LiveIns.erase(I);
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}
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bool MachineBasicBlock::isLiveIn(unsigned Reg) const {
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const_livein_iterator I = std::find(livein_begin(), livein_end(), Reg);
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return I != livein_end();
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}
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void MachineBasicBlock::moveBefore(MachineBasicBlock *NewAfter) {
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getParent()->splice(NewAfter, this);
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}
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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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}
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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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}
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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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Successors.erase(I);
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}
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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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}
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void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) {
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Predecessors.push_back(pred);
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}
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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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}
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void MachineBasicBlock::transferSuccessors(MachineBasicBlock *fromMBB) {
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if (this == fromMBB)
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return;
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for (MachineBasicBlock::succ_iterator I = fromMBB->succ_begin(),
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E = fromMBB->succ_end(); I != E; ++I)
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addSuccessor(*I);
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while (!fromMBB->succ_empty())
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fromMBB->removeSuccessor(fromMBB->succ_begin());
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}
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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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}
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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 next(I) == MachineFunction::const_iterator(MBB);
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}
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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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return this;
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}
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/// eraseFromParent - This method unlinks 'this' from the containing function,
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/// and deletes it.
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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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}
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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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--I;
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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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// with New.
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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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}
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// Update the successor information.
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removeSuccessor(Old);
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addSuccessor(New);
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}
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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
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/// be null.
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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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bool isCond) {
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bool MadeChange = false;
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bool AddedFallThrough = false;
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MachineFunction::iterator FallThru = next(MachineFunction::iterator(this));
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// If this block ends with a conditional branch that falls through to its
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// successor, set DestB as the successor.
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if (isCond) {
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if (DestB == 0 && FallThru != getParent()->end()) {
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DestB = FallThru;
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AddedFallThrough = true;
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}
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} else {
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// If this is an unconditional branch with no explicit dest, it must just be
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// a fallthrough into DestB.
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if (DestA == 0 && FallThru != getParent()->end()) {
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DestA = FallThru;
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AddedFallThrough = true;
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}
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}
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MachineBasicBlock::succ_iterator SI = succ_begin();
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MachineBasicBlock *OrigDestA = DestA, *OrigDestB = DestB;
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while (SI != succ_end()) {
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if (*SI == DestA && DestA == DestB) {
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DestA = DestB = 0;
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++SI;
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} else if (*SI == DestA) {
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DestA = 0;
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++SI;
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} else if (*SI == DestB) {
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DestB = 0;
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++SI;
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} else if ((*SI)->isLandingPad() &&
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*SI!=OrigDestA && *SI!=OrigDestB) {
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++SI;
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} else {
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// Otherwise, this is a superfluous edge, remove it.
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SI = removeSuccessor(SI);
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MadeChange = true;
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}
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}
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if (!AddedFallThrough) {
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assert(DestA == 0 && DestB == 0 &&
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"MachineCFG is missing edges!");
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} else if (isCond) {
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assert(DestA == 0 && "MachineCFG is missing edges!");
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}
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return MadeChange;
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}
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