Update MachineSSAUpdater with the same changes I made for the IR-level
SSAUpdater. I'm going to try to refactor this to share most of the code between them. llvm-svn: 102353
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@ -23,22 +23,27 @@ namespace llvm {
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class TargetInstrInfo;
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class TargetInstrInfo;
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class TargetRegisterClass;
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class TargetRegisterClass;
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template<typename T> class SmallVectorImpl;
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template<typename T> class SmallVectorImpl;
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class BumpPtrAllocator;
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/// MachineSSAUpdater - This class updates SSA form for a set of virtual
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/// MachineSSAUpdater - This class updates SSA form for a set of virtual
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/// registers defined in multiple blocks. This is used when code duplication
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/// registers defined in multiple blocks. This is used when code duplication
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/// or another unstructured transformation wants to rewrite a set of uses of one
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/// or another unstructured transformation wants to rewrite a set of uses of one
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/// vreg with uses of a set of vregs.
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/// vreg with uses of a set of vregs.
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class MachineSSAUpdater {
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class MachineSSAUpdater {
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public:
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class BBInfo;
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typedef SmallVectorImpl<BBInfo*> BlockListTy;
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private:
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/// AvailableVals - This keeps track of which value to use on a per-block
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/// AvailableVals - This keeps track of which value to use on a per-block
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/// basis. When we insert PHI nodes, we keep track of them here.
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/// basis. When we insert PHI nodes, we keep track of them here.
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//typedef DenseMap<MachineBasicBlock*, unsigned > AvailableValsTy;
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//typedef DenseMap<MachineBasicBlock*, unsigned > AvailableValsTy;
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void *AV;
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void *AV;
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/// IncomingPredInfo - We use this as scratch space when doing our recursive
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/// BBMap - The GetValueAtEndOfBlock method maintains this mapping from
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/// walk. This should only be used in GetValueInBlockInternal, normally it
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/// basic blocks to BBInfo structures.
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/// should be empty.
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/// typedef DenseMap<MachineBasicBlock*, BBInfo*> BBMapTy;
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//std::vector<std::pair<MachineBasicBlock*, unsigned > > IncomingPredInfo;
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void *BM;
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void *IPI;
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/// VR - Current virtual register whose uses are being updated.
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/// VR - Current virtual register whose uses are being updated.
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unsigned VR;
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unsigned VR;
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@ -106,6 +111,15 @@ public:
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private:
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private:
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void ReplaceRegWith(unsigned OldReg, unsigned NewReg);
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void ReplaceRegWith(unsigned OldReg, unsigned NewReg);
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unsigned GetValueAtEndOfBlockInternal(MachineBasicBlock *BB);
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unsigned GetValueAtEndOfBlockInternal(MachineBasicBlock *BB);
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void BuildBlockList(MachineBasicBlock *BB, BlockListTy *BlockList,
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BumpPtrAllocator *Allocator);
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void FindDominators(BlockListTy *BlockList);
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void FindPHIPlacement(BlockListTy *BlockList);
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void FindAvailableVals(BlockListTy *BlockList);
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void FindExistingPHI(MachineBasicBlock *BB, BlockListTy *BlockList);
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bool CheckIfPHIMatches(MachineInstr *PHI);
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void RecordMatchingPHI(MachineInstr *PHI);
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void operator=(const MachineSSAUpdater&); // DO NOT IMPLEMENT
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void operator=(const MachineSSAUpdater&); // DO NOT IMPLEMENT
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MachineSSAUpdater(const MachineSSAUpdater&); // DO NOT IMPLEMENT
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MachineSSAUpdater(const MachineSSAUpdater&); // DO NOT IMPLEMENT
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};
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};
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@ -21,34 +21,50 @@
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#include "llvm/Target/TargetRegisterInfo.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/DenseMap.h"
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#include "llvm/ADT/SmallVector.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/Debug.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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using namespace llvm;
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typedef DenseMap<MachineBasicBlock*, unsigned> AvailableValsTy;
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/// BBInfo - Per-basic block information used internally by MachineSSAUpdater.
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typedef std::vector<std::pair<MachineBasicBlock*, unsigned> >
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class MachineSSAUpdater::BBInfo {
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IncomingPredInfoTy;
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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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static AvailableValsTy &getAvailableVals(void *AV) {
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return *static_cast<AvailableValsTy*>(AV);
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return *static_cast<AvailableValsTy*>(AV);
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}
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}
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static IncomingPredInfoTy &getIncomingPredInfo(void *IPI) {
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static BBMapTy *getBBMap(void *BM) {
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return *static_cast<IncomingPredInfoTy*>(IPI);
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return static_cast<BBMapTy*>(BM);
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}
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}
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MachineSSAUpdater::MachineSSAUpdater(MachineFunction &MF,
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MachineSSAUpdater::MachineSSAUpdater(MachineFunction &MF,
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SmallVectorImpl<MachineInstr*> *NewPHI)
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SmallVectorImpl<MachineInstr*> *NewPHI)
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: AV(0), IPI(0), InsertedPHIs(NewPHI) {
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: AV(0), BM(0), InsertedPHIs(NewPHI) {
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TII = MF.getTarget().getInstrInfo();
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TII = MF.getTarget().getInstrInfo();
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MRI = &MF.getRegInfo();
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MRI = &MF.getRegInfo();
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}
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}
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MachineSSAUpdater::~MachineSSAUpdater() {
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MachineSSAUpdater::~MachineSSAUpdater() {
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delete &getAvailableVals(AV);
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delete &getAvailableVals(AV);
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delete &getIncomingPredInfo(IPI);
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}
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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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/// Initialize - Reset this object to get ready for a new set of SSA
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@ -59,11 +75,6 @@ void MachineSSAUpdater::Initialize(unsigned V) {
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else
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else
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getAvailableVals(AV).clear();
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getAvailableVals(AV).clear();
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if (IPI == 0)
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IPI = new IncomingPredInfoTy();
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else
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getIncomingPredInfo(IPI).clear();
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VR = V;
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VR = V;
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VRC = MRI->getRegClass(VR);
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VRC = MRI->getRegClass(VR);
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}
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}
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@ -127,7 +138,7 @@ MachineInstr *InsertNewDef(unsigned Opcode,
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unsigned NewVR = MRI->createVirtualRegister(RC);
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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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return BuildMI(*BB, I, DebugLoc(), TII->get(Opcode), NewVR);
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}
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}
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/// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that
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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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/// is live in the middle of the specified block.
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///
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///
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@ -150,7 +161,7 @@ MachineInstr *InsertNewDef(unsigned Opcode,
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unsigned MachineSSAUpdater::GetValueInMiddleOfBlock(MachineBasicBlock *BB) {
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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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// 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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// GetValueAtEndOfBlock to do our work.
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if (!getAvailableVals(AV).count(BB))
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if (!HasValueForBlock(BB))
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return GetValueAtEndOfBlockInternal(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 there are no predecessors, just return undef.
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@ -254,141 +265,436 @@ void MachineSSAUpdater::ReplaceRegWith(unsigned OldReg, unsigned NewReg) {
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/// GetValueAtEndOfBlockInternal - Check to see if AvailableVals has an entry
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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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/// for the specified BB and if so, return it. If not, construct SSA form by
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/// walking predecessors inserting PHI nodes as needed until we get to a block
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/// first calculating the required placement of PHIs and then inserting new
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/// where the value is available.
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/// PHIs where needed.
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///
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unsigned MachineSSAUpdater::GetValueAtEndOfBlockInternal(MachineBasicBlock *BB){
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unsigned MachineSSAUpdater::GetValueAtEndOfBlockInternal(MachineBasicBlock *BB){
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AvailableValsTy &AvailableVals = getAvailableVals(AV);
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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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// Query AvailableVals by doing an insertion of null.
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// Pool allocation used internally by GetValueAtEndOfBlock.
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std::pair<AvailableValsTy::iterator, bool> InsertRes =
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BumpPtrAllocator Allocator;
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AvailableVals.insert(std::make_pair(BB, 0));
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BBMapTy BBMapObj;
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BM = &BBMapObj;
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// Handle the case when the insertion fails because we have already seen BB.
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SmallVector<BBInfo*, 100> BlockList;
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if (!InsertRes.second) {
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BuildBlockList(BB, &BlockList, &Allocator);
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// If the insertion failed, there are two cases. The first case is that the
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// value is already available for the specified block. If we get this, just
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// return the value.
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if (InsertRes.first->second != 0)
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return InsertRes.first->second;
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// Otherwise, if the value we find is null, then this is the value is not
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// Special case: bail out if BB is unreachable.
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// known but it is being computed elsewhere in our recursion. This means
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if (BlockList.size() == 0) {
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// that we have a cycle. Handle this by inserting a PHI node and returning
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BM = 0;
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// it. When we get back to the first instance of the recursion we will fill
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// in the PHI node.
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MachineBasicBlock::iterator Loc = BB->empty() ? BB->end() : BB->front();
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MachineInstr *NewPHI = InsertNewDef(TargetOpcode::PHI, BB, Loc,
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VRC, MRI,TII);
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unsigned NewVR = NewPHI->getOperand(0).getReg();
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InsertRes.first->second = NewVR;
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return NewVR;
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}
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// If there are no predecessors, then we must have found an unreachable block
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// just return 'undef'. Since there are no predecessors, InsertRes must not
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// be invalidated.
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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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// Insert an implicit_def to represent an undef value.
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MachineInstr *NewDef = InsertNewDef(TargetOpcode::IMPLICIT_DEF,
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MachineInstr *NewDef = InsertNewDef(TargetOpcode::IMPLICIT_DEF,
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BB, BB->getFirstTerminator(),
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BB, BB->getFirstTerminator(),
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VRC, MRI, TII);
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VRC, MRI, TII);
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return InsertRes.first->second = NewDef->getOperand(0).getReg();
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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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}
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// Okay, the value isn't in the map and we just inserted a null in the entry
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FindDominators(&BlockList);
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// to indicate that we're processing the block. Since we have no idea what
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FindPHIPlacement(&BlockList);
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// value is in this block, we have to recurse through our predecessors.
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FindAvailableVals(&BlockList);
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//
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// While we're walking our predecessors, we keep track of them in a vector,
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// then insert a PHI node in the end if we actually need one. We could use a
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// smallvector here, but that would take a lot of stack space for every level
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// of the recursion, just use IncomingPredInfo as an explicit stack.
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IncomingPredInfoTy &IncomingPredInfo = getIncomingPredInfo(IPI);
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unsigned FirstPredInfoEntry = IncomingPredInfo.size();
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// As we're walking the predecessors, keep track of whether they are all
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BM = 0;
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// producing the same value. If so, this value will capture it, if not, it
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return BBMapObj[BB]->DefBB->AvailableVal;
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// will get reset to null. We distinguish the no-predecessor case explicitly
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}
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// below.
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unsigned SingularValue = 0;
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/// FindPredecessorBlocks - Put the predecessors of Info->BB into the Preds
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bool isFirstPred = true;
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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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for (MachineBasicBlock::pred_iterator PI = BB->pred_begin(),
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E = BB->pred_end(); PI != E; ++PI) {
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E = BB->pred_end(); PI != E; ++PI)
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MachineBasicBlock *PredBB = *PI;
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Preds->push_back(*PI);
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unsigned PredVal = GetValueAtEndOfBlockInternal(PredBB);
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IncomingPredInfo.push_back(std::make_pair(PredBB, PredVal));
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// Compute SingularValue.
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Info->NumPreds = Preds->size();
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if (isFirstPred) {
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Info->Preds = static_cast<MachineSSAUpdater::BBInfo**>
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SingularValue = PredVal;
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(Allocator->Allocate(Info->NumPreds * sizeof(MachineSSAUpdater::BBInfo*),
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isFirstPred = false;
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AlignOf<MachineSSAUpdater::BBInfo*>::Alignment));
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} else if (PredVal != SingularValue)
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}
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SingularValue = 0;
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}
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/// Look up BB's entry in AvailableVals. 'InsertRes' may be invalidated. If
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/// BuildBlockList - Starting from the specified basic block, traverse back
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/// this block is involved in a loop, a no-entry PHI node will have been
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/// through its predecessors until reaching blocks with known values. Create
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/// inserted as InsertedVal. Otherwise, we'll still have the null we inserted
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/// BBInfo structures for the blocks and append them to the block list.
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/// above.
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void MachineSSAUpdater::BuildBlockList(MachineBasicBlock *BB,
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unsigned &InsertedVal = AvailableVals[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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// If all the predecessor values are the same then we don't need to insert a
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BBInfo *Info = new (*Allocator) BBInfo(BB, 0);
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// PHI. This is the simple and common case.
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(*BBMap)[BB] = Info;
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if (SingularValue) {
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WorkList.push_back(Info);
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// If a PHI node got inserted, replace it with the singlar value and delete
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// it.
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// Search backward from BB, creating BBInfos along the way and stopping when
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if (InsertedVal) {
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// reaching blocks that define the value. Record those defining blocks on
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MachineInstr *OldVal = MRI->getVRegDef(InsertedVal);
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// the RootList.
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// Be careful about dead loops. These RAUW's also update InsertedVal.
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SmallVector<MachineBasicBlock*, 10> Preds;
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assert(InsertedVal != SingularValue && "Dead loop?");
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while (!WorkList.empty()) {
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ReplaceRegWith(InsertedVal, SingularValue);
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Info = WorkList.pop_back_val();
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OldVal->eraseFromParent();
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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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}
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InsertedVal = SingularValue;
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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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// Drop the entries we added in IncomingPredInfo to restore the stack.
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// Create a new BBInfo for the predecessor.
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IncomingPredInfo.erase(IncomingPredInfo.begin()+FirstPredInfoEntry,
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unsigned PredVal = AvailableVals.lookup(Pred);
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IncomingPredInfo.end());
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BBInfo *PredInfo = new (*Allocator) BBInfo(Pred, PredVal);
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return InsertedVal;
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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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}
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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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|
||||||
// Otherwise, we do need a PHI: insert one now if we don't already have one.
|
// Initialize the worklist with the roots from the backward traversal.
|
||||||
MachineInstr *InsertedPHI;
|
while (!RootList.empty()) {
|
||||||
if (InsertedVal == 0) {
|
Info = RootList.pop_back_val();
|
||||||
MachineBasicBlock::iterator Loc = BB->empty() ? BB->end() : BB->front();
|
Info->IDom = PseudoEntry;
|
||||||
InsertedPHI = InsertNewDef(TargetOpcode::PHI, BB, Loc,
|
Info->BlkNum = -1;
|
||||||
VRC, MRI, TII);
|
WorkList.push_back(Info);
|
||||||
InsertedVal = InsertedPHI->getOperand(0).getReg();
|
|
||||||
} else {
|
|
||||||
InsertedPHI = MRI->getVRegDef(InsertedVal);
|
|
||||||
}
|
}
|
||||||
|
|
||||||
// Fill in all the predecessors of the PHI.
|
while (!WorkList.empty()) {
|
||||||
MachineInstrBuilder MIB(InsertedPHI);
|
Info = WorkList.back();
|
||||||
for (IncomingPredInfoTy::iterator I =
|
|
||||||
IncomingPredInfo.begin()+FirstPredInfoEntry,
|
|
||||||
E = IncomingPredInfo.end(); I != E; ++I)
|
|
||||||
MIB.addReg(I->second).addMBB(I->first);
|
|
||||||
|
|
||||||
// Drop the entries we added in IncomingPredInfo to restore the stack.
|
if (Info->BlkNum == -2) {
|
||||||
IncomingPredInfo.erase(IncomingPredInfo.begin()+FirstPredInfoEntry,
|
// All the successors have been handled; assign the postorder number.
|
||||||
IncomingPredInfo.end());
|
Info->BlkNum = BlkNum++;
|
||||||
|
// If not a root, put it on the BlockList.
|
||||||
|
if (!Info->AvailableVal)
|
||||||
|
BlockList->push_back(Info);
|
||||||
|
WorkList.pop_back();
|
||||||
|
continue;
|
||||||
|
}
|
||||||
|
|
||||||
|
// Leave this entry on the worklist, but set its BlkNum to mark that its
|
||||||
|
// successors have been put on the worklist. When it returns to the top
|
||||||
|
// the list, after handling its successors, it will be assigned a number.
|
||||||
|
Info->BlkNum = -2;
|
||||||
|
|
||||||
|
// Add unvisited successors to the work list.
|
||||||
|
for (MachineBasicBlock::succ_iterator SI = Info->BB->succ_begin(),
|
||||||
|
E = Info->BB->succ_end(); SI != E; ++SI) {
|
||||||
|
BBInfo *SuccInfo = (*BBMap)[*SI];
|
||||||
|
if (!SuccInfo || SuccInfo->BlkNum)
|
||||||
|
continue;
|
||||||
|
SuccInfo->BlkNum = -1;
|
||||||
|
WorkList.push_back(SuccInfo);
|
||||||
|
}
|
||||||
|
}
|
||||||
|
PseudoEntry->BlkNum = BlkNum;
|
||||||
|
}
|
||||||
|
|
||||||
|
/// IntersectDominators - This is the dataflow lattice "meet" operation for
|
||||||
|
/// finding dominators. Given two basic blocks, it walks up the dominator
|
||||||
|
/// tree until it finds a common dominator of both. It uses the postorder
|
||||||
|
/// number of the blocks to determine how to do that.
|
||||||
|
static MachineSSAUpdater::BBInfo *
|
||||||
|
IntersectDominators(MachineSSAUpdater::BBInfo *Blk1,
|
||||||
|
MachineSSAUpdater::BBInfo *Blk2) {
|
||||||
|
while (Blk1 != Blk2) {
|
||||||
|
while (Blk1->BlkNum < Blk2->BlkNum) {
|
||||||
|
Blk1 = Blk1->IDom;
|
||||||
|
if (!Blk1)
|
||||||
|
return Blk2;
|
||||||
|
}
|
||||||
|
while (Blk2->BlkNum < Blk1->BlkNum) {
|
||||||
|
Blk2 = Blk2->IDom;
|
||||||
|
if (!Blk2)
|
||||||
|
return Blk1;
|
||||||
|
}
|
||||||
|
}
|
||||||
|
return Blk1;
|
||||||
|
}
|
||||||
|
|
||||||
|
/// FindDominators - Calculate the dominator tree for the subset of the CFG
|
||||||
|
/// corresponding to the basic blocks on the BlockList. This uses the
|
||||||
|
/// algorithm from: "A Simple, Fast Dominance Algorithm" by Cooper, Harvey and
|
||||||
|
/// Kennedy, published in Software--Practice and Experience, 2001, 4:1-10.
|
||||||
|
/// Because the CFG subset does not include any edges leading into blocks that
|
||||||
|
/// define the value, the results are not the usual dominator tree. The CFG
|
||||||
|
/// subset has a single pseudo-entry node with edges to a set of root nodes
|
||||||
|
/// for blocks that define the value. The dominators for this subset CFG are
|
||||||
|
/// not the standard dominators but they are adequate for placing PHIs within
|
||||||
|
/// the subset CFG.
|
||||||
|
void MachineSSAUpdater::FindDominators(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;
|
||||||
|
|
||||||
|
// 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);
|
||||||
|
}
|
||||||
|
|
||||||
// See if the PHI node can be merged to a single value. This can happen in
|
|
||||||
// loop cases when we get a PHI of itself and one other value.
|
|
||||||
if (unsigned ConstVal = InsertedPHI->isConstantValuePHI()) {
|
|
||||||
MRI->replaceRegWith(InsertedVal, ConstVal);
|
|
||||||
InsertedPHI->eraseFromParent();
|
|
||||||
InsertedVal = ConstVal;
|
|
||||||
} else {
|
|
||||||
DEBUG(dbgs() << " Inserted PHI: " << *InsertedPHI << "\n");
|
DEBUG(dbgs() << " Inserted PHI: " << *InsertedPHI << "\n");
|
||||||
|
|
||||||
// If the client wants to know about all new instructions, tell it.
|
// If the client wants to know about all new instructions, tell it.
|
||||||
if (InsertedPHIs) InsertedPHIs->push_back(InsertedPHI);
|
if (InsertedPHIs) InsertedPHIs->push_back(InsertedPHI);
|
||||||
}
|
}
|
||||||
|
}
|
||||||
return InsertedVal;
|
|
||||||
|
/// 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);
|
||||||
|
}
|
||||||
|
}
|
||||||
}
|
}
|
||||||
|
|
Loading…
Reference in New Issue