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SSAUpdater. I'm going to try to refactor this to share most of the code between them. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@102353 91177308-0d34-0410-b5e6-96231b3b80d8
701 lines
25 KiB
C++
701 lines
25 KiB
C++
//===- MachineSSAUpdater.cpp - Unstructured SSA Update Tool ---------------===//
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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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// This file implements the MachineSSAUpdater class. It's based on SSAUpdater
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// class in lib/Transforms/Utils.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/MachineSSAUpdater.h"
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#include "llvm/CodeGen/MachineInstr.h"
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#include "llvm/CodeGen/MachineInstrBuilder.h"
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#include "llvm/CodeGen/MachineRegisterInfo.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/Target/TargetRegisterInfo.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/Support/AlignOf.h"
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#include "llvm/Support/Allocator.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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/// BBInfo - Per-basic block information used internally by MachineSSAUpdater.
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class MachineSSAUpdater::BBInfo {
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public:
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MachineBasicBlock *BB; // Back-pointer to the corresponding block.
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unsigned AvailableVal; // Value to use in this block.
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BBInfo *DefBB; // Block that defines the available value.
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int BlkNum; // Postorder number.
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BBInfo *IDom; // Immediate dominator.
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unsigned NumPreds; // Number of predecessor blocks.
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BBInfo **Preds; // Array[NumPreds] of predecessor blocks.
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MachineInstr *PHITag; // Marker for existing PHIs that match.
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BBInfo(MachineBasicBlock *ThisBB, unsigned V)
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: BB(ThisBB), AvailableVal(V), DefBB(V ? this : 0), BlkNum(0), IDom(0),
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NumPreds(0), Preds(0), PHITag(0) { }
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};
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typedef DenseMap<MachineBasicBlock*, MachineSSAUpdater::BBInfo*> BBMapTy;
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typedef DenseMap<MachineBasicBlock*, unsigned> AvailableValsTy;
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static AvailableValsTy &getAvailableVals(void *AV) {
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return *static_cast<AvailableValsTy*>(AV);
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}
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static BBMapTy *getBBMap(void *BM) {
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return static_cast<BBMapTy*>(BM);
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}
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MachineSSAUpdater::MachineSSAUpdater(MachineFunction &MF,
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SmallVectorImpl<MachineInstr*> *NewPHI)
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: AV(0), BM(0), InsertedPHIs(NewPHI) {
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TII = MF.getTarget().getInstrInfo();
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MRI = &MF.getRegInfo();
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}
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MachineSSAUpdater::~MachineSSAUpdater() {
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delete &getAvailableVals(AV);
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}
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/// Initialize - Reset this object to get ready for a new set of SSA
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/// updates. ProtoValue is the value used to name PHI nodes.
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void MachineSSAUpdater::Initialize(unsigned V) {
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if (AV == 0)
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AV = new AvailableValsTy();
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else
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getAvailableVals(AV).clear();
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VR = V;
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VRC = MRI->getRegClass(VR);
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}
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/// HasValueForBlock - Return true if the MachineSSAUpdater already has a value for
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/// the specified block.
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bool MachineSSAUpdater::HasValueForBlock(MachineBasicBlock *BB) const {
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return getAvailableVals(AV).count(BB);
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}
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/// AddAvailableValue - Indicate that a rewritten value is available in the
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/// specified block with the specified value.
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void MachineSSAUpdater::AddAvailableValue(MachineBasicBlock *BB, unsigned V) {
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getAvailableVals(AV)[BB] = V;
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}
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/// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is
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/// live at the end of the specified block.
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unsigned MachineSSAUpdater::GetValueAtEndOfBlock(MachineBasicBlock *BB) {
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return GetValueAtEndOfBlockInternal(BB);
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}
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static
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unsigned LookForIdenticalPHI(MachineBasicBlock *BB,
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SmallVector<std::pair<MachineBasicBlock*, unsigned>, 8> &PredValues) {
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if (BB->empty())
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return 0;
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MachineBasicBlock::iterator I = BB->front();
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if (!I->isPHI())
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return 0;
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AvailableValsTy AVals;
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for (unsigned i = 0, e = PredValues.size(); i != e; ++i)
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AVals[PredValues[i].first] = PredValues[i].second;
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while (I != BB->end() && I->isPHI()) {
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bool Same = true;
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for (unsigned i = 1, e = I->getNumOperands(); i != e; i += 2) {
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unsigned SrcReg = I->getOperand(i).getReg();
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MachineBasicBlock *SrcBB = I->getOperand(i+1).getMBB();
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if (AVals[SrcBB] != SrcReg) {
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Same = false;
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break;
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}
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}
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if (Same)
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return I->getOperand(0).getReg();
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++I;
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}
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return 0;
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}
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/// InsertNewDef - Insert an empty PHI or IMPLICIT_DEF instruction which define
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/// a value of the given register class at the start of the specified basic
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/// block. It returns the virtual register defined by the instruction.
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static
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MachineInstr *InsertNewDef(unsigned Opcode,
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MachineBasicBlock *BB, MachineBasicBlock::iterator I,
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const TargetRegisterClass *RC,
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MachineRegisterInfo *MRI, const TargetInstrInfo *TII) {
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unsigned NewVR = MRI->createVirtualRegister(RC);
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return BuildMI(*BB, I, DebugLoc(), TII->get(Opcode), NewVR);
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}
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/// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that
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/// is live in the middle of the specified block.
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///
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/// GetValueInMiddleOfBlock is the same as GetValueAtEndOfBlock except in one
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/// important case: if there is a definition of the rewritten value after the
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/// 'use' in BB. Consider code like this:
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///
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/// X1 = ...
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/// SomeBB:
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/// use(X)
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/// X2 = ...
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/// br Cond, SomeBB, OutBB
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///
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/// In this case, there are two values (X1 and X2) added to the AvailableVals
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/// set by the client of the rewriter, and those values are both live out of
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/// their respective blocks. However, the use of X happens in the *middle* of
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/// a block. Because of this, we need to insert a new PHI node in SomeBB to
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/// merge the appropriate values, and this value isn't live out of the block.
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///
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unsigned MachineSSAUpdater::GetValueInMiddleOfBlock(MachineBasicBlock *BB) {
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// If there is no definition of the renamed variable in this block, just use
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// GetValueAtEndOfBlock to do our work.
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if (!HasValueForBlock(BB))
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return GetValueAtEndOfBlockInternal(BB);
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// If there are no predecessors, just return undef.
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if (BB->pred_empty()) {
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// Insert an implicit_def to represent an undef value.
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MachineInstr *NewDef = InsertNewDef(TargetOpcode::IMPLICIT_DEF,
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BB, BB->getFirstTerminator(),
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VRC, MRI, TII);
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return NewDef->getOperand(0).getReg();
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}
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// Otherwise, we have the hard case. Get the live-in values for each
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// predecessor.
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SmallVector<std::pair<MachineBasicBlock*, unsigned>, 8> PredValues;
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unsigned SingularValue = 0;
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bool isFirstPred = true;
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for (MachineBasicBlock::pred_iterator PI = BB->pred_begin(),
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E = BB->pred_end(); PI != E; ++PI) {
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MachineBasicBlock *PredBB = *PI;
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unsigned PredVal = GetValueAtEndOfBlockInternal(PredBB);
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PredValues.push_back(std::make_pair(PredBB, PredVal));
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// Compute SingularValue.
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if (isFirstPred) {
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SingularValue = PredVal;
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isFirstPred = false;
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} else if (PredVal != SingularValue)
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SingularValue = 0;
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}
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// Otherwise, if all the merged values are the same, just use it.
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if (SingularValue != 0)
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return SingularValue;
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// If an identical PHI is already in BB, just reuse it.
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unsigned DupPHI = LookForIdenticalPHI(BB, PredValues);
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if (DupPHI)
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return DupPHI;
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// Otherwise, we do need a PHI: insert one now.
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MachineBasicBlock::iterator Loc = BB->empty() ? BB->end() : BB->front();
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MachineInstr *InsertedPHI = InsertNewDef(TargetOpcode::PHI, BB,
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Loc, VRC, MRI, TII);
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// Fill in all the predecessors of the PHI.
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MachineInstrBuilder MIB(InsertedPHI);
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for (unsigned i = 0, e = PredValues.size(); i != e; ++i)
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MIB.addReg(PredValues[i].second).addMBB(PredValues[i].first);
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// See if the PHI node can be merged to a single value. This can happen in
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// loop cases when we get a PHI of itself and one other value.
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if (unsigned ConstVal = InsertedPHI->isConstantValuePHI()) {
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InsertedPHI->eraseFromParent();
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return ConstVal;
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}
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// If the client wants to know about all new instructions, tell it.
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if (InsertedPHIs) InsertedPHIs->push_back(InsertedPHI);
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DEBUG(dbgs() << " Inserted PHI: " << *InsertedPHI << "\n");
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return InsertedPHI->getOperand(0).getReg();
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}
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static
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MachineBasicBlock *findCorrespondingPred(const MachineInstr *MI,
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MachineOperand *U) {
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for (unsigned i = 1, e = MI->getNumOperands(); i != e; i += 2) {
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if (&MI->getOperand(i) == U)
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return MI->getOperand(i+1).getMBB();
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}
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llvm_unreachable("MachineOperand::getParent() failure?");
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return 0;
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}
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/// RewriteUse - Rewrite a use of the symbolic value. This handles PHI nodes,
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/// which use their value in the corresponding predecessor.
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void MachineSSAUpdater::RewriteUse(MachineOperand &U) {
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MachineInstr *UseMI = U.getParent();
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unsigned NewVR = 0;
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if (UseMI->isPHI()) {
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MachineBasicBlock *SourceBB = findCorrespondingPred(UseMI, &U);
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NewVR = GetValueAtEndOfBlockInternal(SourceBB);
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} else {
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NewVR = GetValueInMiddleOfBlock(UseMI->getParent());
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}
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U.setReg(NewVR);
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}
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void MachineSSAUpdater::ReplaceRegWith(unsigned OldReg, unsigned NewReg) {
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MRI->replaceRegWith(OldReg, NewReg);
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AvailableValsTy &AvailableVals = getAvailableVals(AV);
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for (DenseMap<MachineBasicBlock*, unsigned>::iterator
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I = AvailableVals.begin(), E = AvailableVals.end(); I != E; ++I)
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if (I->second == OldReg)
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I->second = NewReg;
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}
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/// GetValueAtEndOfBlockInternal - Check to see if AvailableVals has an entry
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/// for the specified BB and if so, return it. If not, construct SSA form by
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/// first calculating the required placement of PHIs and then inserting new
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/// PHIs where needed.
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unsigned MachineSSAUpdater::GetValueAtEndOfBlockInternal(MachineBasicBlock *BB){
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AvailableValsTy &AvailableVals = getAvailableVals(AV);
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if (unsigned V = AvailableVals[BB])
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return V;
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// Pool allocation used internally by GetValueAtEndOfBlock.
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BumpPtrAllocator Allocator;
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BBMapTy BBMapObj;
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BM = &BBMapObj;
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SmallVector<BBInfo*, 100> BlockList;
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BuildBlockList(BB, &BlockList, &Allocator);
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// Special case: bail out if BB is unreachable.
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if (BlockList.size() == 0) {
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BM = 0;
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// Insert an implicit_def to represent an undef value.
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MachineInstr *NewDef = InsertNewDef(TargetOpcode::IMPLICIT_DEF,
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BB, BB->getFirstTerminator(),
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VRC, MRI, TII);
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unsigned V = NewDef->getOperand(0).getReg();
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AvailableVals[BB] = V;
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return V;
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}
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FindDominators(&BlockList);
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FindPHIPlacement(&BlockList);
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FindAvailableVals(&BlockList);
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BM = 0;
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return BBMapObj[BB]->DefBB->AvailableVal;
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}
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/// FindPredecessorBlocks - Put the predecessors of Info->BB into the Preds
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/// vector, set Info->NumPreds, and allocate space in Info->Preds.
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static void FindPredecessorBlocks(MachineSSAUpdater::BBInfo *Info,
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SmallVectorImpl<MachineBasicBlock*> *Preds,
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BumpPtrAllocator *Allocator) {
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MachineBasicBlock *BB = Info->BB;
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for (MachineBasicBlock::pred_iterator PI = BB->pred_begin(),
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E = BB->pred_end(); PI != E; ++PI)
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Preds->push_back(*PI);
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Info->NumPreds = Preds->size();
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Info->Preds = static_cast<MachineSSAUpdater::BBInfo**>
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(Allocator->Allocate(Info->NumPreds * sizeof(MachineSSAUpdater::BBInfo*),
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AlignOf<MachineSSAUpdater::BBInfo*>::Alignment));
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}
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/// BuildBlockList - Starting from the specified basic block, traverse back
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/// through its predecessors until reaching blocks with known values. Create
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/// BBInfo structures for the blocks and append them to the block list.
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void MachineSSAUpdater::BuildBlockList(MachineBasicBlock *BB,
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BlockListTy *BlockList,
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BumpPtrAllocator *Allocator) {
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AvailableValsTy &AvailableVals = getAvailableVals(AV);
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BBMapTy *BBMap = getBBMap(BM);
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SmallVector<BBInfo*, 10> RootList;
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SmallVector<BBInfo*, 64> WorkList;
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BBInfo *Info = new (*Allocator) BBInfo(BB, 0);
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(*BBMap)[BB] = Info;
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WorkList.push_back(Info);
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// Search backward from BB, creating BBInfos along the way and stopping when
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// reaching blocks that define the value. Record those defining blocks on
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// the RootList.
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SmallVector<MachineBasicBlock*, 10> Preds;
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while (!WorkList.empty()) {
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Info = WorkList.pop_back_val();
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Preds.clear();
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FindPredecessorBlocks(Info, &Preds, Allocator);
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// Treat an unreachable predecessor as a definition with 'undef'.
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if (Info->NumPreds == 0) {
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// Insert an implicit_def to represent an undef value.
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MachineInstr *NewDef = InsertNewDef(TargetOpcode::IMPLICIT_DEF,
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Info->BB,
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Info->BB->getFirstTerminator(),
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VRC, MRI, TII);
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Info->AvailableVal = NewDef->getOperand(0).getReg();
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Info->DefBB = Info;
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RootList.push_back(Info);
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continue;
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}
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for (unsigned p = 0; p != Info->NumPreds; ++p) {
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MachineBasicBlock *Pred = Preds[p];
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// Check if BBMap already has a BBInfo for the predecessor block.
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BBMapTy::value_type &BBMapBucket = BBMap->FindAndConstruct(Pred);
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if (BBMapBucket.second) {
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Info->Preds[p] = BBMapBucket.second;
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continue;
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}
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// Create a new BBInfo for the predecessor.
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unsigned PredVal = AvailableVals.lookup(Pred);
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BBInfo *PredInfo = new (*Allocator) BBInfo(Pred, PredVal);
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BBMapBucket.second = PredInfo;
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Info->Preds[p] = PredInfo;
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if (PredInfo->AvailableVal) {
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RootList.push_back(PredInfo);
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continue;
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}
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WorkList.push_back(PredInfo);
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}
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}
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// Now that we know what blocks are backwards-reachable from the starting
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// block, do a forward depth-first traversal to assign postorder numbers
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// to those blocks.
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BBInfo *PseudoEntry = new (*Allocator) BBInfo(0, 0);
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unsigned BlkNum = 1;
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// Initialize the worklist with the roots from the backward traversal.
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while (!RootList.empty()) {
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Info = RootList.pop_back_val();
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Info->IDom = PseudoEntry;
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Info->BlkNum = -1;
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WorkList.push_back(Info);
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}
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while (!WorkList.empty()) {
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Info = WorkList.back();
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if (Info->BlkNum == -2) {
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// All the successors have been handled; assign the postorder number.
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Info->BlkNum = BlkNum++;
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// If not a root, put it on the BlockList.
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if (!Info->AvailableVal)
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BlockList->push_back(Info);
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WorkList.pop_back();
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continue;
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}
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// Leave this entry on the worklist, but set its BlkNum to mark that its
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// successors have been put on the worklist. When it returns to the top
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// the list, after handling its successors, it will be assigned a number.
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Info->BlkNum = -2;
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// Add unvisited successors to the work list.
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for (MachineBasicBlock::succ_iterator SI = Info->BB->succ_begin(),
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E = Info->BB->succ_end(); SI != E; ++SI) {
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BBInfo *SuccInfo = (*BBMap)[*SI];
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if (!SuccInfo || SuccInfo->BlkNum)
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continue;
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SuccInfo->BlkNum = -1;
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WorkList.push_back(SuccInfo);
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}
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}
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PseudoEntry->BlkNum = BlkNum;
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}
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/// IntersectDominators - This is the dataflow lattice "meet" operation for
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/// finding dominators. Given two basic blocks, it walks up the dominator
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/// tree until it finds a common dominator of both. It uses the postorder
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/// number of the blocks to determine how to do that.
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static MachineSSAUpdater::BBInfo *
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IntersectDominators(MachineSSAUpdater::BBInfo *Blk1,
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MachineSSAUpdater::BBInfo *Blk2) {
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while (Blk1 != Blk2) {
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while (Blk1->BlkNum < Blk2->BlkNum) {
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Blk1 = Blk1->IDom;
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if (!Blk1)
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return Blk2;
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}
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while (Blk2->BlkNum < Blk1->BlkNum) {
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Blk2 = Blk2->IDom;
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if (!Blk2)
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return Blk1;
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}
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}
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return Blk1;
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}
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/// FindDominators - Calculate the dominator tree for the subset of the CFG
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/// corresponding to the basic blocks on the BlockList. This uses the
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/// algorithm from: "A Simple, Fast Dominance Algorithm" by Cooper, Harvey and
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/// Kennedy, published in Software--Practice and Experience, 2001, 4:1-10.
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/// Because the CFG subset does not include any edges leading into blocks that
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/// define the value, the results are not the usual dominator tree. The CFG
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/// subset has a single pseudo-entry node with edges to a set of root nodes
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/// for blocks that define the value. The dominators for this subset CFG are
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/// not the standard dominators but they are adequate for placing PHIs within
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/// the subset CFG.
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void MachineSSAUpdater::FindDominators(BlockListTy *BlockList) {
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bool Changed;
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do {
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Changed = false;
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// Iterate over the list in reverse order, i.e., forward on CFG edges.
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for (BlockListTy::reverse_iterator I = BlockList->rbegin(),
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E = BlockList->rend(); I != E; ++I) {
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BBInfo *Info = *I;
|
|
|
|
// Start with the first predecessor.
|
|
assert(Info->NumPreds > 0 && "unreachable block");
|
|
BBInfo *NewIDom = Info->Preds[0];
|
|
|
|
// Iterate through the block's other predecessors.
|
|
for (unsigned p = 1; p != Info->NumPreds; ++p) {
|
|
BBInfo *Pred = Info->Preds[p];
|
|
NewIDom = IntersectDominators(NewIDom, Pred);
|
|
}
|
|
|
|
// Check if the IDom value has changed.
|
|
if (NewIDom != Info->IDom) {
|
|
Info->IDom = NewIDom;
|
|
Changed = true;
|
|
}
|
|
}
|
|
} while (Changed);
|
|
}
|
|
|
|
/// IsDefInDomFrontier - Search up the dominator tree from Pred to IDom for
|
|
/// any blocks containing definitions of the value. If one is found, then the
|
|
/// successor of Pred is in the dominance frontier for the definition, and
|
|
/// this function returns true.
|
|
static bool IsDefInDomFrontier(const MachineSSAUpdater::BBInfo *Pred,
|
|
const MachineSSAUpdater::BBInfo *IDom) {
|
|
for (; Pred != IDom; Pred = Pred->IDom) {
|
|
if (Pred->DefBB == Pred)
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// FindPHIPlacement - PHIs are needed in the iterated dominance frontiers of
|
|
/// the known definitions. Iteratively add PHIs in the dom frontiers until
|
|
/// nothing changes. Along the way, keep track of the nearest dominating
|
|
/// definitions for non-PHI blocks.
|
|
void MachineSSAUpdater::FindPHIPlacement(BlockListTy *BlockList) {
|
|
bool Changed;
|
|
do {
|
|
Changed = false;
|
|
// Iterate over the list in reverse order, i.e., forward on CFG edges.
|
|
for (BlockListTy::reverse_iterator I = BlockList->rbegin(),
|
|
E = BlockList->rend(); I != E; ++I) {
|
|
BBInfo *Info = *I;
|
|
|
|
// If this block already needs a PHI, there is nothing to do here.
|
|
if (Info->DefBB == Info)
|
|
continue;
|
|
|
|
// Default to use the same def as the immediate dominator.
|
|
BBInfo *NewDefBB = Info->IDom->DefBB;
|
|
for (unsigned p = 0; p != Info->NumPreds; ++p) {
|
|
if (IsDefInDomFrontier(Info->Preds[p], Info->IDom)) {
|
|
// Need a PHI here.
|
|
NewDefBB = Info;
|
|
break;
|
|
}
|
|
}
|
|
|
|
// Check if anything changed.
|
|
if (NewDefBB != Info->DefBB) {
|
|
Info->DefBB = NewDefBB;
|
|
Changed = true;
|
|
}
|
|
}
|
|
} while (Changed);
|
|
}
|
|
|
|
/// FindAvailableVal - If this block requires a PHI, first check if an existing
|
|
/// PHI matches the PHI placement and reaching definitions computed earlier,
|
|
/// and if not, create a new PHI. Visit all the block's predecessors to
|
|
/// calculate the available value for each one and fill in the incoming values
|
|
/// for a new PHI.
|
|
void MachineSSAUpdater::FindAvailableVals(BlockListTy *BlockList) {
|
|
AvailableValsTy &AvailableVals = getAvailableVals(AV);
|
|
|
|
// Go through the worklist in forward order (i.e., backward through the CFG)
|
|
// and check if existing PHIs can be used. If not, create empty PHIs where
|
|
// they are needed.
|
|
for (BlockListTy::iterator I = BlockList->begin(), E = BlockList->end();
|
|
I != E; ++I) {
|
|
BBInfo *Info = *I;
|
|
// Check if there needs to be a PHI in BB.
|
|
if (Info->DefBB != Info)
|
|
continue;
|
|
|
|
// Look for an existing PHI.
|
|
FindExistingPHI(Info->BB, BlockList);
|
|
if (Info->AvailableVal)
|
|
continue;
|
|
|
|
MachineBasicBlock::iterator Loc =
|
|
Info->BB->empty() ? Info->BB->end() : Info->BB->front();
|
|
MachineInstr *InsertedPHI = InsertNewDef(TargetOpcode::PHI, Info->BB, Loc,
|
|
VRC, MRI, TII);
|
|
unsigned PHI = InsertedPHI->getOperand(0).getReg();
|
|
Info->AvailableVal = PHI;
|
|
AvailableVals[Info->BB] = PHI;
|
|
}
|
|
|
|
// Now go back through the worklist in reverse order to fill in the arguments
|
|
// for any new PHIs added in the forward traversal.
|
|
for (BlockListTy::reverse_iterator I = BlockList->rbegin(),
|
|
E = BlockList->rend(); I != E; ++I) {
|
|
BBInfo *Info = *I;
|
|
|
|
if (Info->DefBB != Info) {
|
|
// Record the available value at join nodes to speed up subsequent
|
|
// uses of this SSAUpdater for the same value.
|
|
if (Info->NumPreds > 1)
|
|
AvailableVals[Info->BB] = Info->DefBB->AvailableVal;
|
|
continue;
|
|
}
|
|
|
|
// Check if this block contains a newly added PHI.
|
|
unsigned PHI = Info->AvailableVal;
|
|
MachineInstr *InsertedPHI = MRI->getVRegDef(PHI);
|
|
if (!InsertedPHI->isPHI() || InsertedPHI->getNumOperands() > 1)
|
|
continue;
|
|
|
|
// Iterate through the block's predecessors.
|
|
MachineInstrBuilder MIB(InsertedPHI);
|
|
for (unsigned p = 0; p != Info->NumPreds; ++p) {
|
|
BBInfo *PredInfo = Info->Preds[p];
|
|
MachineBasicBlock *Pred = PredInfo->BB;
|
|
// Skip to the nearest preceding definition.
|
|
if (PredInfo->DefBB != PredInfo)
|
|
PredInfo = PredInfo->DefBB;
|
|
MIB.addReg(PredInfo->AvailableVal).addMBB(Pred);
|
|
}
|
|
|
|
DEBUG(dbgs() << " Inserted PHI: " << *InsertedPHI << "\n");
|
|
|
|
// If the client wants to know about all new instructions, tell it.
|
|
if (InsertedPHIs) InsertedPHIs->push_back(InsertedPHI);
|
|
}
|
|
}
|
|
|
|
/// FindExistingPHI - Look through the PHI nodes in a block to see if any of
|
|
/// them match what is needed.
|
|
void MachineSSAUpdater::FindExistingPHI(MachineBasicBlock *BB,
|
|
BlockListTy *BlockList) {
|
|
for (MachineBasicBlock::iterator BBI = BB->begin(), BBE = BB->end();
|
|
BBI != BBE && BBI->isPHI(); ++BBI) {
|
|
if (CheckIfPHIMatches(BBI)) {
|
|
RecordMatchingPHI(BBI);
|
|
break;
|
|
}
|
|
// Match failed: clear all the PHITag values.
|
|
for (BlockListTy::iterator I = BlockList->begin(), E = BlockList->end();
|
|
I != E; ++I)
|
|
(*I)->PHITag = 0;
|
|
}
|
|
}
|
|
|
|
/// CheckIfPHIMatches - Check if a PHI node matches the placement and values
|
|
/// in the BBMap.
|
|
bool MachineSSAUpdater::CheckIfPHIMatches(MachineInstr *PHI) {
|
|
BBMapTy *BBMap = getBBMap(BM);
|
|
SmallVector<MachineInstr*, 20> WorkList;
|
|
WorkList.push_back(PHI);
|
|
|
|
// Mark that the block containing this PHI has been visited.
|
|
(*BBMap)[PHI->getParent()]->PHITag = PHI;
|
|
|
|
while (!WorkList.empty()) {
|
|
PHI = WorkList.pop_back_val();
|
|
|
|
// Iterate through the PHI's incoming values.
|
|
for (unsigned i = 1, e = PHI->getNumOperands(); i != e; i += 2) {
|
|
unsigned IncomingVal = PHI->getOperand(i).getReg();
|
|
BBInfo *PredInfo = (*BBMap)[PHI->getOperand(i+1).getMBB()];
|
|
// Skip to the nearest preceding definition.
|
|
if (PredInfo->DefBB != PredInfo)
|
|
PredInfo = PredInfo->DefBB;
|
|
|
|
// Check if it matches the expected value.
|
|
if (PredInfo->AvailableVal) {
|
|
if (IncomingVal == PredInfo->AvailableVal)
|
|
continue;
|
|
return false;
|
|
}
|
|
|
|
// Check if the value is a PHI in the correct block.
|
|
MachineInstr *IncomingPHIVal = MRI->getVRegDef(IncomingVal);
|
|
if (!IncomingPHIVal->isPHI() ||
|
|
IncomingPHIVal->getParent() != PredInfo->BB)
|
|
return false;
|
|
|
|
// If this block has already been visited, check if this PHI matches.
|
|
if (PredInfo->PHITag) {
|
|
if (IncomingPHIVal == PredInfo->PHITag)
|
|
continue;
|
|
return false;
|
|
}
|
|
PredInfo->PHITag = IncomingPHIVal;
|
|
|
|
WorkList.push_back(IncomingPHIVal);
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/// RecordMatchingPHI - For a PHI node that matches, record it and its input
|
|
/// PHIs in both the BBMap and the AvailableVals mapping.
|
|
void MachineSSAUpdater::RecordMatchingPHI(MachineInstr *PHI) {
|
|
BBMapTy *BBMap = getBBMap(BM);
|
|
AvailableValsTy &AvailableVals = getAvailableVals(AV);
|
|
SmallVector<MachineInstr*, 20> WorkList;
|
|
WorkList.push_back(PHI);
|
|
|
|
// Record this PHI.
|
|
MachineBasicBlock *BB = PHI->getParent();
|
|
AvailableVals[BB] = PHI->getOperand(0).getReg();
|
|
(*BBMap)[BB]->AvailableVal = PHI->getOperand(0).getReg();
|
|
|
|
while (!WorkList.empty()) {
|
|
PHI = WorkList.pop_back_val();
|
|
|
|
// Iterate through the PHI's incoming values.
|
|
for (unsigned i = 1, e = PHI->getNumOperands(); i != e; i += 2) {
|
|
unsigned IncomingVal = PHI->getOperand(i).getReg();
|
|
MachineInstr *IncomingPHIVal = MRI->getVRegDef(IncomingVal);
|
|
if (!IncomingPHIVal->isPHI()) continue;
|
|
BB = IncomingPHIVal->getParent();
|
|
BBInfo *Info = (*BBMap)[BB];
|
|
if (!Info || Info->AvailableVal)
|
|
continue;
|
|
|
|
// Record the PHI and add it to the worklist.
|
|
AvailableVals[BB] = IncomingVal;
|
|
Info->AvailableVal = IncomingVal;
|
|
WorkList.push_back(IncomingPHIVal);
|
|
}
|
|
}
|
|
}
|