//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "ssaupdater"
+#include "llvm/Constants.h"
#include "llvm/Instructions.h"
+#include "llvm/IntrinsicInst.h"
#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/TinyPtrVector.h"
+#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Support/AlignOf.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/SSAUpdater.h"
#include "llvm/Transforms/Utils/SSAUpdaterImpl.h"
+
using namespace llvm;
typedef DenseMap<BasicBlock*, Value*> AvailableValsTy;
}
SSAUpdater::SSAUpdater(SmallVectorImpl<PHINode*> *NewPHI)
- : AV(0), PrototypeValue(0), InsertedPHIs(NewPHI) {}
+ : AV(0), ProtoType(0), ProtoName(), InsertedPHIs(NewPHI) {}
SSAUpdater::~SSAUpdater() {
delete &getAvailableVals(AV);
}
/// Initialize - Reset this object to get ready for a new set of SSA
-/// updates. ProtoValue is the value used to name PHI nodes.
-void SSAUpdater::Initialize(Value *ProtoValue) {
+/// updates with type 'Ty'. PHI nodes get a name based on 'Name'.
+void SSAUpdater::Initialize(Type *Ty, StringRef Name) {
if (AV == 0)
AV = new AvailableValsTy();
else
getAvailableVals(AV).clear();
- PrototypeValue = ProtoValue;
+ ProtoType = Ty;
+ ProtoName = Name;
}
/// HasValueForBlock - Return true if the SSAUpdater already has a value for
/// AddAvailableValue - Indicate that a rewritten value is available in the
/// specified block with the specified value.
void SSAUpdater::AddAvailableValue(BasicBlock *BB, Value *V) {
- assert(PrototypeValue != 0 && "Need to initialize SSAUpdater");
- assert(PrototypeValue->getType() == V->getType() &&
+ assert(ProtoType != 0 && "Need to initialize SSAUpdater");
+ assert(ProtoType == V->getType() &&
"All rewritten values must have the same type");
getAvailableVals(AV)[BB] = V;
}
// If there are no predecessors, just return undef.
if (PredValues.empty())
- return UndefValue::get(PrototypeValue->getType());
+ return UndefValue::get(ProtoType);
// Otherwise, if all the merged values are the same, just use it.
if (SingularValue != 0)
}
// Ok, we have no way out, insert a new one now.
- PHINode *InsertedPHI = PHINode::Create(PrototypeValue->getType(),
- PrototypeValue->getName(),
- &BB->front());
- InsertedPHI->reserveOperandSpace(PredValues.size());
+ PHINode *InsertedPHI = PHINode::Create(ProtoType, PredValues.size(),
+ ProtoName, &BB->front());
// Fill in all the predecessors of the PHI.
for (unsigned i = 0, e = PredValues.size(); i != e; ++i)
// 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 (Value *ConstVal = InsertedPHI->hasConstantValue()) {
+ if (Value *V = SimplifyInstruction(InsertedPHI)) {
InsertedPHI->eraseFromParent();
- return ConstVal;
+ return V;
}
+ // Set DebugLoc.
+ InsertedPHI->setDebugLoc(GetFirstDebugLocInBasicBlock(BB));
+
// If the client wants to know about all new instructions, tell it.
if (InsertedPHIs) InsertedPHIs->push_back(InsertedPHI);
/// GetUndefVal - Get an undefined value of the same type as the value
/// being handled.
static Value *GetUndefVal(BasicBlock *BB, SSAUpdater *Updater) {
- return UndefValue::get(Updater->PrototypeValue->getType());
+ return UndefValue::get(Updater->ProtoType);
}
/// CreateEmptyPHI - Create a new PHI instruction in the specified block.
/// Reserve space for the operands but do not fill them in yet.
static Value *CreateEmptyPHI(BasicBlock *BB, unsigned NumPreds,
SSAUpdater *Updater) {
- PHINode *PHI = PHINode::Create(Updater->PrototypeValue->getType(),
- Updater->PrototypeValue->getName(),
- &BB->front());
- PHI->reserveOperandSpace(NumPreds);
+ PHINode *PHI = PHINode::Create(Updater->ProtoType, NumPreds,
+ Updater->ProtoName, &BB->front());
return PHI;
}
SSAUpdaterImpl<SSAUpdater> Impl(this, &AvailableVals, InsertedPHIs);
return Impl.GetValue(BB);
}
+
+//===----------------------------------------------------------------------===//
+// LoadAndStorePromoter Implementation
+//===----------------------------------------------------------------------===//
+
+LoadAndStorePromoter::
+LoadAndStorePromoter(const SmallVectorImpl<Instruction*> &Insts,
+ SSAUpdater &S, StringRef BaseName) : SSA(S) {
+ if (Insts.empty()) return;
+
+ Value *SomeVal;
+ if (LoadInst *LI = dyn_cast<LoadInst>(Insts[0]))
+ SomeVal = LI;
+ else
+ SomeVal = cast<StoreInst>(Insts[0])->getOperand(0);
+
+ if (BaseName.empty())
+ BaseName = SomeVal->getName();
+ SSA.Initialize(SomeVal->getType(), BaseName);
+}
+
+
+void LoadAndStorePromoter::
+run(const SmallVectorImpl<Instruction*> &Insts) const {
+
+ // First step: bucket up uses of the alloca by the block they occur in.
+ // This is important because we have to handle multiple defs/uses in a block
+ // ourselves: SSAUpdater is purely for cross-block references.
+ DenseMap<BasicBlock*, TinyPtrVector<Instruction*> > UsesByBlock;
+
+ for (unsigned i = 0, e = Insts.size(); i != e; ++i) {
+ Instruction *User = Insts[i];
+ UsesByBlock[User->getParent()].push_back(User);
+ }
+
+ // Okay, now we can iterate over all the blocks in the function with uses,
+ // processing them. Keep track of which loads are loading a live-in value.
+ // Walk the uses in the use-list order to be determinstic.
+ SmallVector<LoadInst*, 32> LiveInLoads;
+ DenseMap<Value*, Value*> ReplacedLoads;
+
+ for (unsigned i = 0, e = Insts.size(); i != e; ++i) {
+ Instruction *User = Insts[i];
+ BasicBlock *BB = User->getParent();
+ TinyPtrVector<Instruction*> &BlockUses = UsesByBlock[BB];
+
+ // If this block has already been processed, ignore this repeat use.
+ if (BlockUses.empty()) continue;
+
+ // Okay, this is the first use in the block. If this block just has a
+ // single user in it, we can rewrite it trivially.
+ if (BlockUses.size() == 1) {
+ // If it is a store, it is a trivial def of the value in the block.
+ if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
+ updateDebugInfo(SI);
+ SSA.AddAvailableValue(BB, SI->getOperand(0));
+ } else
+ // Otherwise it is a load, queue it to rewrite as a live-in load.
+ LiveInLoads.push_back(cast<LoadInst>(User));
+ BlockUses.clear();
+ continue;
+ }
+
+ // Otherwise, check to see if this block is all loads.
+ bool HasStore = false;
+ for (unsigned i = 0, e = BlockUses.size(); i != e; ++i) {
+ if (isa<StoreInst>(BlockUses[i])) {
+ HasStore = true;
+ break;
+ }
+ }
+
+ // If so, we can queue them all as live in loads. We don't have an
+ // efficient way to tell which on is first in the block and don't want to
+ // scan large blocks, so just add all loads as live ins.
+ if (!HasStore) {
+ for (unsigned i = 0, e = BlockUses.size(); i != e; ++i)
+ LiveInLoads.push_back(cast<LoadInst>(BlockUses[i]));
+ BlockUses.clear();
+ continue;
+ }
+
+ // Otherwise, we have mixed loads and stores (or just a bunch of stores).
+ // Since SSAUpdater is purely for cross-block values, we need to determine
+ // the order of these instructions in the block. If the first use in the
+ // block is a load, then it uses the live in value. The last store defines
+ // the live out value. We handle this by doing a linear scan of the block.
+ Value *StoredValue = 0;
+ for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) {
+ if (LoadInst *L = dyn_cast<LoadInst>(II)) {
+ // If this is a load from an unrelated pointer, ignore it.
+ if (!isInstInList(L, Insts)) continue;
+
+ // If we haven't seen a store yet, this is a live in use, otherwise
+ // use the stored value.
+ if (StoredValue) {
+ replaceLoadWithValue(L, StoredValue);
+ L->replaceAllUsesWith(StoredValue);
+ ReplacedLoads[L] = StoredValue;
+ } else {
+ LiveInLoads.push_back(L);
+ }
+ continue;
+ }
+
+ if (StoreInst *SI = dyn_cast<StoreInst>(II)) {
+ // If this is a store to an unrelated pointer, ignore it.
+ if (!isInstInList(SI, Insts)) continue;
+ updateDebugInfo(SI);
+
+ // Remember that this is the active value in the block.
+ StoredValue = SI->getOperand(0);
+ }
+ }
+
+ // The last stored value that happened is the live-out for the block.
+ assert(StoredValue && "Already checked that there is a store in block");
+ SSA.AddAvailableValue(BB, StoredValue);
+ BlockUses.clear();
+ }
+
+ // Okay, now we rewrite all loads that use live-in values in the loop,
+ // inserting PHI nodes as necessary.
+ for (unsigned i = 0, e = LiveInLoads.size(); i != e; ++i) {
+ LoadInst *ALoad = LiveInLoads[i];
+ Value *NewVal = SSA.GetValueInMiddleOfBlock(ALoad->getParent());
+ replaceLoadWithValue(ALoad, NewVal);
+
+ // Avoid assertions in unreachable code.
+ if (NewVal == ALoad) NewVal = UndefValue::get(NewVal->getType());
+ ALoad->replaceAllUsesWith(NewVal);
+ ReplacedLoads[ALoad] = NewVal;
+ }
+
+ // Allow the client to do stuff before we start nuking things.
+ doExtraRewritesBeforeFinalDeletion();
+
+ // Now that everything is rewritten, delete the old instructions from the
+ // function. They should all be dead now.
+ for (unsigned i = 0, e = Insts.size(); i != e; ++i) {
+ Instruction *User = Insts[i];
+
+ // If this is a load that still has uses, then the load must have been added
+ // as a live value in the SSAUpdate data structure for a block (e.g. because
+ // the loaded value was stored later). In this case, we need to recursively
+ // propagate the updates until we get to the real value.
+ if (!User->use_empty()) {
+ Value *NewVal = ReplacedLoads[User];
+ assert(NewVal && "not a replaced load?");
+
+ // Propagate down to the ultimate replacee. The intermediately loads
+ // could theoretically already have been deleted, so we don't want to
+ // dereference the Value*'s.
+ DenseMap<Value*, Value*>::iterator RLI = ReplacedLoads.find(NewVal);
+ while (RLI != ReplacedLoads.end()) {
+ NewVal = RLI->second;
+ RLI = ReplacedLoads.find(NewVal);
+ }
+
+ replaceLoadWithValue(cast<LoadInst>(User), NewVal);
+ User->replaceAllUsesWith(NewVal);
+ }
+
+ instructionDeleted(User);
+ User->eraseFromParent();
+ }
+}
+
+bool
+LoadAndStorePromoter::isInstInList(Instruction *I,
+ const SmallVectorImpl<Instruction*> &Insts)
+ const {
+ return std::find(Insts.begin(), Insts.end(), I) != Insts.end();
+}
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